CV


Education

  • Cornell University, Ithaca, NY
    • Ph.D. in Operations Research: May 1995
    • Major: Optimization
    • Minors: Computer Science; Statistics
    • Thesis: Parallel Branch and Cut for Vehicle Routing
    • Thesis advisor: Dr. Leslie E. Trotter, Jr.
  • Carnegie Mellon University, Pittsburgh, PA
    • M.S. in Mathematics and B.S. in Applied Mathematics (with University Honors): May 1991
    • Concentration: Operations Research

Current Positions

Previous Positions

Research Funding

Honors and Awards

  • Ph.D Faculty of the Year, Department of Industrial and Systems Engineering, Lehigh University, 2021.
  • Outstanding Doctoral Student Advising Award, Rossin College of Engineering and Applied Science, 2021.
  • INFORMS Impact Prize, November 2014.
  • Meritorious Service Award for Exceptional Contribution to the Journal Operations Research, August 2013.
  • Visiting Lecturer, Operations Research Society of New Zealand, Spring 2009
  • Senior Fellow, The Institute of Advanced Studies, Università di Bologna, Fall 2008
  • Hillman Award for Excellence in Graduate Advising, May 2008
  • First Open Contest of Parallel Programming, First Place, October 2007
  • Sigma Xi Scientific Research Society, member, May 2003 – present
  • Lehigh Engineering Ingenuity Award for Exceptional Accomplishment in Teaching and/or Research by Junior Faculty, April 2003
  • IBM Faculty Partnership Award (three times), August 2001 – August 2004
  • Rossin Assistant Professorship, June 2001 – June 2003

Refereed Publications

  • S. Fallah, T. K. Ralphs, and N. Boland, “On the relationship between the value function and the efficient frontier of a mixed integer linear optimization problem,” Mathematical methods of operations research, 2024. [PDF] [DOI] [Bibtex] 
    @Article{ FalRalBol24,
title = {On the Relationship between the Value Function and the
Efficient Frontier of a Mixed Integer Linear Optimization
Problem},
author  = {Fallah, Samira and Ralphs, Ted K. and Boland, Natashia
L.},
year = {2024},
journal  = {Mathematical Methods of Operations Research},
publisher  = {COR@L Laboratory, Lehigh University},
issn = {1432-2994},
doi = {10.1007/s00186-024-00871-2},
url = {https://arxiv.org/abs/2303.00785},
abstract  = {In this study, we investigate the connection between the
efficient frontier (EF) of a general multiobjective mixed
integer linear optimization problem (MILP) and the
so-called restricted value function (RVF) of a closely
related single-objective MILP. In the first part of the
paper, we detail the mathematical structure of the RVF,
including characterizing the set of points at which it is
differentiable, the gradients at such points, and the
subdifferential at all nondifferentiable points. We then
show that the EF of the multiobjective MILP is comprised of
points on the boundary of the epigraph of the RVF and that
any description of the EF suffices to describe the RVF and
vice versa. Because of the close relationship of the RVF to
the EF, we observe that methods for constructing the
so-called value function (VF) of an MILP and methods for
constructing the EF of a multiobjective optimization
problem are effectively interchangeable. Exploiting this
observation, we propose a generalized cutting-plane
algorithm for constructing the EF of a multiobjective MILP
that arises from an existing algorithm for constructing the
classical MILP VF. The algorithm identifies the set of all
integer parts of solutions on the EF. We prove that the
algorithm converges finitely under a standard boundedness
assumption and comes with a performance guarantee if
terminated early.},
note = {Appeared on-line only}
}
  • S. Bolusani and T. K. Ralphs, “A framework for generalized benders’ decomposition and its application to multilevel optimization,” Mathematical programming series b, vol. 196, p. 389–426, 2022. [PDF] [DOI] [Bibtex] 
    @Article{ BolRal22,
title = {A Framework for Generalized Benders' Decomposition and Its
Application to Multilevel Optimization},
author  = {Bolusani, S. and Ralphs, T.K.},
year = {2022},
journal  = {Mathematical Programming Series B},
volume  = {196},
pages = {389--426},
publisher  = {COR@L Laboratory Report 20T-001-R2, Lehigh University},
doi = {10.1007/s10107-021-01763-7},
url = {https://arxiv.org/abs/2104.06496}
}
  • S. Xueyu, O. A. Prokopyev, and T. K. Ralphs, “Mixed integer bilevel optimization with a k-optimal follower: a hierarchy of bounds,” Mathematical programming computation, vol. 15, p. 1–51, 2022. [PDF] [DOI] [Bibtex] 
    @Article{ XueProRal22,
title = {Mixed Integer Bilevel Optimization with a K-Optimal
Follower: A Hierarchy of Bounds},
author  = {Xueyu, Shi and Prokopyev, Oleg A. and Ralphs, Ted K.},
year = {2022},
journal  = {Mathematical Programming Computation},
volume  = {15},
pages = {1--51},
publisher  = {COR@L Laboratory, Lehigh University},
doi = {10.1007/s12532-022-00227-z},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/HierarchyOfBounds20.pdf}
}
  • A. Gleixner, G. Hendel, G. Gamrath, T. Achterberg, M. Bastubbe, T. Berthold, P. Christophel, K. Jarck, T. Koch, J. Linderoth, M. Luebbecke, H. D. Mittelmann, D. Ozyurt, T. K. Ralphs, Y. Shinano, and D. Salvagnin, “MIPLIB 2017: Data-driven compilation of the 6th mixed-integer programming library,” Mathematical programming computation, vol. 13, p. 443–490, 2021. [PDF] [DOI] [Bibtex] 
    @Article{ GleHenGamAchBasBerChrJarKocLin.ea21,
title = {{{MIPLIB}} 2017: {{Data-driven}} Compilation of the 6th
Mixed-Integer Programming Library},
author  = {Gleixner, Ambros and Hendel, Gregor and Gamrath, Gerald
and Achterberg, Tobias and Bastubbe, Michael and Berthold,
Timo and Christophel, Philipp and Jarck, Kati and Koch,
Thorsten and Linderoth, Jeffrey and Luebbecke, Marco and
Mittelmann, Hans D. and Ozyurt, Derya and Ralphs, Ted K.
and Shinano, Yuji and Salvagnin, Domenico},
year = {2021},
journal  = {Mathematical Programming Computation},
volume  = {13},
pages = {443--490},
publisher  = {Zuse Institute Berlin},
doi = {10.1007/s12532-020-00194-3},
url = {http://www.optimization-online.org/DB_FILE/2019/07/7285.pdf}
}
  • A. Bulut and T. K. Ralphs, “On the complexity of inverse mixed integer linear optimization,” Siam journal on optimization, vol. 31, p. 3014–3043, 2021. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ BulRal21,
title = {On the Complexity of Inverse Mixed Integer Linear
Optimization},
author  = {Bulut, A. and Ralphs, T.K.},
year = {2021},
journal  = {SIAM Journal on Optimization},
volume  = {31},
pages = {3014--3043},
publisher  = {COR@L Laboratory Report 15T-001-R5, Lehigh University},
doi = {10.1137/20M1377369},
url = {https://arxiv.org/abs/2104.09002},
software  = {https://github.com/tkralphs/CuPPy}
}
  • S. Bolusani, S. Coniglio, T. K. Ralphs, and S. Tahernejad, “A unified framework for multistage mixed integer linear optimization,” in Bilevel Optimization: Advances and Next Challenges, S. Dempe and A. Zemkoho, Eds., Springer, 2020, p. 513–560. [PDF] [DOI] [Bibtex] 
    @InCollection{ BolConRalTah20,
title = {A Unified Framework for Multistage Mixed Integer Linear
Optimization},
booktitle  = {Bilevel {{Optimization}}: {{Advances}} and {{Next
Challenges}}},
author  = {Bolusani, S. and Coniglio, S. and Ralphs, T.K. and
Tahernejad, S.},
editor  = {Dempe, S. and Zemkoho, A.},
year = {2020},
pages = {513--560},
publisher  = {Springer},
doi = {10.1007/978-3-030-52119-6},
url = {https://arxiv.org/abs/2104.09003},
isbn = {978-3-030-52118-9}
}
  • S. Tahernejad, T. K. Ralphs, and S. T. DeNegre, “A branch-and-cut algorithm for mixed integer bilevel linear optimization problems and its implementation,” Mathematical programming computation, vol. 12, p. 529–568, 2020. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ TahRalDeN20,
title = {A Branch-and-Cut Algorithm for Mixed Integer Bilevel
Linear Optimization Problems and Its Implementation},
author  = {Tahernejad, S. and Ralphs, T.K. and DeNegre, S.T.},
year = {2020},
journal  = {Mathematical Programming Computation},
volume  = {12},
pages = {529--568},
doi = {10.1007/s12532-020-00183-6},
url = {https://arxiv.org/abs/2104.09010},
software  = {https://github.com/coin-or/MibS}
}
  • T. K. Ralphs, Y. Shinano, T. Berthold, and T. Koch, “Parallel solvers for mixed integer linear programing,” in Handbook of Parallel Constraint Reasoning, Y. Hamadi and L. Sais, Eds., Springer berlin / heidelberg / cor@l laboratory, lehigh university, 2018, p. 283–336. [PDF] [DOI] [Bibtex] 
    @InCollection{ RalShiBerKoc18,
title = {Parallel Solvers for Mixed Integer Linear Programing},
booktitle  = {Handbook of {{Parallel Constraint Reasoning}}},
author  = {Ralphs, T.K. and Shinano, Y. and Berthold, T. and Koch,
T.},
editor  = {Hamadi, Y and Sais, L},
year = {2018},
pages = {283--336},
publisher  = {Springer Berlin / Heidelberg / COR@L Laboratory, Lehigh
University},
doi = {10.1007/978-3-319-63516-3_8},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ParallelMILPSurvey16.pdf}
}
  • M. Miltenberger, T. K. Ralphs, and D. Steffy, “Exploring the numerics of branch-and-cut for mixed integer linear optimization,” in Operations research proceedings: 2017, 2017. [PDF] [Bibtex] 
    @InProceedings{ MilRalSte17,
title = {Exploring the Numerics of Branch-and-Cut for Mixed Integer
Linear Optimization},
booktitle  = {Operations Research Proceedings: 2017},
author  = {Miltenberger, M. and Ralphs, T.K. and Steffy, D.},
year = {2017},
publisher  = {Springer Berlin / Heidelberg},
url = {https://opus4.kobv.de/opus4-zib/files/6464/numerics_in_mip.pdf}
}
  • Y. Zhang, L. V. Snyder, T. K. Ralphs, and Z. Xue, “The competitive facility location problem under disruption risks,” Transportation research part e: logistics and transportation review, vol. 93, 2016. [PDF] [DOI] [Bibtex] 
    @Article{ ZhaSnyRalXue16,
title = {The Competitive Facility Location Problem under Disruption
Risks},
author  = {Zhang, Y. and Snyder, L.V. and Ralphs, T.K. and Xue, Z.},
year = {2016},
journal  = {Transportation Research Part E: Logistics and
Transportation Review},
volume  = {93},
issn = {13665545},
doi = {10.1016/j.tre.2016.07.002},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/CFLPD16.pdf},
abstract  = {{\copyright} 2016 Elsevier Ltd Two players sequentially
locate a fixed number of facilities, competing to capture
market share. Facilities face disruption risks, and each
customer patronizes the nearest operational facility,
regardless of who operates it. The problem therefore
combines competitive location and location with
disruptions. This combination has been absent from the
literature. We model the problem as a Stackelberg game in
which the leader locates facilities first, followed by the
follower, and formulate the leader's decision problem as a
bilevel optimization problem. A variable neighborhood
decomposition search heuristic which includes variable
fixing and cut generation is developed. Computational
results suggest that high quality solutions can be found
quickly. Interesting managerial insights are drawn.},
keywords  = {Bilevel optimization,Competitive location,Facility
disruptions,Local search,Variable neighborhood search}
}
  • P. Belotti, J. C. Góez, I. Pólik, T. K. Ralphs, and T. Terlaky, “A complete characterization of disjunctive conic cuts for mixed integer second order cone optimization,” Discrete optimization, vol. 24, 2016. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ BelGoePolRalTer16,
title = {A Complete Characterization of Disjunctive Conic Cuts for
Mixed Integer Second Order Cone Optimization},
author  = {Belotti, P. and G{\'o}ez, J.C. and P{\'o}lik, I. and
Ralphs, T.K. and Terlaky, T.},
year = {2016},
journal  = {Discrete Optimization},
volume  = {24},
issn = {15725286},
doi = {10.1016/j.disopt.2016.10.001},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ConicCuts14.pdf},
abstract  = {{\copyright} 2016 Elsevier B.V. We study the convex hull
of the intersection of a disjunctive set defined by
parallel hyperplanes and the feasible set of a mixed
integer second order cone optimization (MISOCO) problem. We
extend our prior work on disjunctive conic cuts (DCCs),
which has thus far been restricted to the case in which the
intersection of the hyperplanes and the feasible set is
bounded. Using a similar technique, we show that one can
extend our previous results to the case in which that
intersection is unbounded. We provide a complete
characterization in closed form of the conic inequalities
required to describe the convex hull when the hyperplanes
defining the disjunction are parallel.},
keywords  = {Disjunctive conic cuts,Disjunctive programming,Mixed
integer optimization,Second order cone optimization},
software  = {https://github.com/aykutbulut/CGL-CONIC}
}
  • P. Belotti, J. C. Góez, I. Pólik, T. K. Ralphs, and T. Terlaky, “A conic representation of the convex hull of disjunctive sets and conic cuts for integer second order cone optimization,” in Numerical analysis and optimization, 2015. [PDF] [DOI] [Bibtex] 
    @InProceedings{ BelGoePolRalTer15,
title = {A Conic Representation of the Convex Hull of Disjunctive
Sets and Conic Cuts for Integer Second Order Cone
Optimization},
booktitle  = {Numerical Analysis and Optimization},
author  = {Belotti, P. and G{\'o}ez, J.C. and P{\'o}lik, I. and
Ralphs, T.K. and Terlaky, T.},
year = {2015},
volume  = {134},
issn = {21941017},
doi = {10.1007/978-3-319-17689-5_1},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ConicCuts12.pdf},
abstract  = {{\copyright} Springer International Publishing Switzerland
2015. We study the convex hull of the intersection of a
convex set E and a disjunctive set. This intersection is at
the core of solution techniques for Mixed Integer Convex
Optimization.We prove that if there exists a cone K (resp.,
a cylinder C) that has the same intersection with the
boundary of the disjunction as E, then the convex hull is
the intersection of E with K (resp., C). The existence of
such a cone (resp., a cylinder) is difficult to prove for
general conic optimization. We prove existence and unicity
of a second order cone (resp., a cylinder), when E is the
intersection of an affine space and a second order cone
(resp., a cylinder). We also provide a method for finding
that cone, and hence the convex hull, for the continuous
relaxation of the feasible set of a Mixed Integer Second
Order Cone Optimization (MISOCO) problem, assumed to be the
intersection of an ellipsoid with a general linear
disjunction. This cone provides a new conic cut for MISOCO
that can be used in branch-and-cut algorithms for MISOCO
problems.},
isbn = {978-3-319-17688-8},
keywords  = {Conic cuts,Mixed integer optimization,Second order cone
Optimization}
}
  • A. Lodi, T. K. Ralphs, and G. Woeginger, “Bilevel programming and the separation problem,” Mathematical programming, vol. 148, p. 437–458, 2014. [PDF] [DOI] [Bibtex] 
    @Article{ LodRalWoe14,
title = {Bilevel Programming and the Separation Problem},
author  = {Lodi, A. and Ralphs, T.K. and Woeginger, G.},
year = {2014},
journal  = {Mathematical Programming},
volume  = {148},
pages = {437--458},
doi = {10.1007/s10107-013-0700-x},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/BilevelSeparation12.pdf}
}
  • J. Wang and T. K. Ralphs, “Computational experience with hypergraph-based methods for automatic decomposition in discrete optimization,” in Proceedings of the conference on constraint programming, artificial intelligence, and operations research, 2013, p. 394–402. [Software] [PDF] [DOI] [Bibtex] 
    @InProceedings{ WanRal13,
title = {Computational Experience with Hypergraph-Based Methods for
Automatic Decomposition in Discrete Optimization},
booktitle  = {Proceedings of the Conference on Constraint Programming,
Artificial Intelligence, and Operations Research},
author  = {Wang, J. and Ralphs, T.K.},
year = {2013},
pages = {394--402},
issn = {03029743},
doi = {10.1007/978-3-642-38171-3_31},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/CPAIOR12.pdf},
abstract  = {Branch-and-price (BAP) algorithms based on Dantzig-Wolfe
decomposition have shown great success in solving mixed
integer linear optimization problems (MILPs) with specific
identifiable structure. Only recently has there been
investigation into the development of a "generic" version
of BAP for unstructured MILPs. One of the most important
elements required for such a generic BAP algorithm is an
automatic method of decomposition. In this paper, we report
on preliminary experiments using hypergraph partitioning as
a means of performing such automatic decomposition.
{\copyright} Springer-Verlag 2013.},
isbn = {978-3-642-38170-6},
software  = {https://github.com/coin-or/Dip}
}
  • K. L. Hoffman and T. K. Ralphs, “Integer and combinatorial optimization,” in Encyclopedia of Operations Research and Management Science, Springer, 2013, p. 771–783. [PDF] [DOI] [Bibtex] 
    @InCollection{ HofRal13,
title = {Integer and Combinatorial Optimization},
booktitle  = {Encyclopedia of {{Operations Research}} and {{Management
Science}}},
author  = {Hoffman, K.L. and Ralphs, T.K.},
year = {2013},
pages = {771--783},
publisher  = {Springer},
doi = {10.1007/978-1-4419-1153-7_129},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ICO-EORMS11.pdf}
}
  • P. Belotti, J. C. Goez, I. Polik, T. K. Ralphs, and T. Terlaky, “On families of quadratic surfaces having fixed intersection with two hyperplanes,” Discrete applied mathematics, vol. 161, p. 2778–2793, 2013. [PDF] [DOI] [Bibtex] 
    @Article{ BelGoePolRalTer13,
title = {On Families of Quadratic Surfaces Having Fixed
Intersection with Two Hyperplanes},
author  = {Belotti, P. and Goez, J.C. and Polik, I. and Ralphs, T.K.
and Terlaky, T.},
year = {2013},
journal  = {Discrete Applied Mathematics},
volume  = {161},
pages = {2778--2793},
doi = {10.1016/j.dam.2013.05.017},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/Quadratic11.pdf}
}
  • M. V. Galati, T. K. Ralphs, and J. Wang, “Computational experience with generic decomposition using the DIP framework,” in Proceedings of RAMP 2012, 2012. [Software] [PDF] [Bibtex] 
    @InProceedings{ GalRalWan12,
title = {Computational Experience with Generic Decomposition Using
the {{DIP}} Framework},
booktitle  = {Proceedings of {{RAMP}} 2012},
author  = {Galati, M.V. and Ralphs, T.K. and Wang, J.},
year = {2012},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/RAMP12.pdf},
software  = {https://github.com/coin-or/Dip}
}
  • T. Koch, T. K. Ralphs, and Y. Shinano, “Could we use a million cores to solve an integer program?,” Mathematical methods of operations research, vol. 76, p. 67–93, 2012. [PDF] [DOI] [Bibtex] 
    @Article{ KocRalShi12,
title = {Could We Use a Million Cores to Solve an Integer
Program?},
author  = {Koch, T. and Ralphs, T.K. and Shinano, Y.},
year = {2012},
journal  = {Mathematical Methods of Operations Research},
volume  = {76},
pages = {67--93},
doi = {10.1007/s00186-012-0390-9},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/Million11.pdf}
}
  • T. Koch, T. Achterburg, E. Andersen, O. Bastert, T. Berthold, R. E. Bixby, E. Danna, G. Gamrath, A. Gleixner, S. Heinz, A. Lodi, H. Mittelmann, T. K. Ralphs, D. Salvagnin, D. Steffy, and K. Wolter, “Miplib 2010,” Mathematical programming computation, vol. 3, p. 103–163, 2011. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ KocAchAndBasBerBixDanGamGleHei.ea11,
title = {Miplib 2010},
author  = {Koch, T. and Achterburg, T. and Andersen, E. and Bastert,
O. and Berthold, T. and Bixby, R.E. and Danna, E. and
Gamrath, G. and Gleixner, A. and Heinz, S. and Lodi, A. and
Mittelmann, H. and Ralphs, T.K. and Salvagnin, D. and
Steffy, D. and Wolter, K.},
year = {2011},
journal  = {Mathematical Programming Computation},
volume  = {3},
pages = {103--163},
doi = {10.1007/s12532-011-0025-9},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/miplib5.pdf},
software  = {http://miplib.zib.de/download/scriptversions/}
}
  • A. Mahajan and T. K. Ralphs, “On the complexity of selecting disjunctions in integer programming,” Siam journal on optimization, vol. 20, iss. 5, p. 2181–2198, 2010. [PDF] [DOI] [Bibtex] 
    @Article{ MahRal10,
title = {On the Complexity of Selecting Disjunctions in Integer
Programming},
author  = {Mahajan, A. and Ralphs, T.K.},
year = {2010},
journal  = {SIAM Journal on Optimization},
volume  = {20},
number  = {5},
pages = {2181--2198},
doi = {10.1137/080737587},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/Branching08.pdf}
}
  • M. Güzelsoy and T. K. Ralphs, “Integer programming duality,” in Encyclopedia of Operations Research and Management Science, J. Cochran, Ed., Wiley, 2010. [PDF] [DOI] [Bibtex] 
    @InCollection{ GuzRal10,
title = {Integer Programming Duality},
booktitle  = {Encyclopedia of {{Operations Research}} and {{Management
Science}}},
author  = {G{\"u}zelsoy, M. and Ralphs, T.K.},
editor  = {Cochran, J.},
year = {2010},
publisher  = {Wiley},
doi = {10.1002/9780470400531},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/Duality-EOR10.pdf}
}
  • T. K. Ralphs and M. V. Galati, “Decomposition methods,” in Encyclopedia of Operations Research and Management Science, J. Cochran, Ed., Wiley, 2010. [PDF] [DOI] [Bibtex] 
    @InCollection{ RalGal10,
title = {Decomposition Methods},
booktitle  = {Encyclopedia of {{Operations Research}} and {{Management
Science}}},
author  = {Ralphs, T.K. and Galati, M.V.},
editor  = {Cochran, J.},
year = {2010},
publisher  = {Wiley},
doi = {10.1002/9780470400531},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/Decomp-EOR10.pdf}
}
  • Y. Xu, T. K. Ralphs, L. Ladányi, and M. J. Saltzman, “Computational experience with a software framework for parallel integer programming,” The informs journal on computing, vol. 21, p. 383–397, 2009. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ XuRalLadSal09,
title = {Computational Experience with a Software Framework for
Parallel Integer Programming},
author  = {Xu, Y. and Ralphs, T.K. and Lad{\'a}nyi, L. and Saltzman,
M.J.},
year = {2009},
journal  = {The INFORMS Journal on Computing},
volume  = {21},
pages = {383--397},
doi = {10.1287/ijoc.1090.0347},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/CHiPPS-Rev.pdf},
software  = {https://github.com/coin-or/CHiPPS-ALPS}
}
  • Z. Akca, R. T. Berger, and T. K. Ralphs, “A branch-and-price algorithm for combined location and routing problems under capacity restrictions,” in Proceedings of the eleventh INFORMS computing society meeting, 2009, p. 309–330. [PDF] [DOI] [Bibtex] 
    @InProceedings{ AkcBerRal09,
title = {A Branch-and-Price Algorithm for Combined Location and
Routing Problems under Capacity Restrictions},
booktitle  = {Proceedings of the Eleventh {{INFORMS}} Computing Society
Meeting},
author  = {Akca, Z. and Berger, R.T. and Ralphs, T.K.},
year = {2009},
pages = {309--330},
doi = {10.1007/978-0-387-88843-9_16},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/LRP08.pdf}
}
  • A. Lodi and T. K. Ralphs, “Bilevel programming and maximally violated valid inequalities,” in Proceedings of the cologne twente workshop on graphs and combinatorial optimization, 2009, p. 125–134. [PDF] [Bibtex] 
    @InProceedings{ LodRal09,
title = {Bilevel Programming and Maximally Violated Valid
Inequalities},
booktitle  = {Proceedings of the Cologne Twente Workshop on Graphs and
Combinatorial Optimization},
author  = {Lodi, A. and Ralphs, T.K.},
year = {2009},
pages = {125--134},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/CTW09.pdf}
}
  • S. DeNegre and T. K. Ralphs, “A branch-and-cut algorithm for bilevel integer programming,” in Proceedings of the eleventh INFORMS computing society meeting, 2009, p. 65–78. [Software] [PDF] [DOI] [Bibtex] 
    @InProceedings{ DeNRal09,
title = {A Branch-and-Cut Algorithm for Bilevel Integer
Programming},
booktitle  = {Proceedings of the Eleventh {{INFORMS}} Computing Society
Meeting},
author  = {DeNegre, S. and Ralphs, T.K.},
year = {2009},
pages = {65--78},
doi = {10.1007/978-0-387-88843-9_4},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/BILEVEL08.pdf},
software  = {https://github.com/coin-or/MibS}
}
  • A. Mahajan and T. K. Ralphs, “Experiments with branching using general disjunctions,” in Proceedings of the eleventh INFORMS computing society meeting, 2009, p. 101–118. [PDF] [DOI] [Bibtex] 
    @InProceedings{ MahRal09,
title = {Experiments with Branching Using General Disjunctions},
booktitle  = {Proceedings of the Eleventh {{INFORMS}} Computing Society
Meeting},
author  = {Mahajan, A. and Ralphs, T.K.},
year = {2009},
pages = {101--118},
doi = {10.1007/978-0-387-88843-9_6},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/CompBranching08.pdf}
}
  • M. Güzelsoy and T. K. Ralphs, “Duality for mixed-integer linear programs,” International journal of operations research, vol. 4, p. 118–137, 2007. [PDF] [Bibtex] 
    @Article{ GuzRal07,
title = {Duality for Mixed-Integer Linear Programs},
author  = {G{\"u}zelsoy, M. and Ralphs, T.K.},
year = {2007},
journal  = {International Journal of Operations Research},
volume  = {4},
pages = {118--137},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/MILPD06.pdf}
}
  • T. K. Ralphs and M. V. Galati, “Decomposition and dynamic cut generation in integer programming,” Mathematical programming, vol. 106, p. 261–285, 2006. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ RalGal06,
title = {Decomposition and Dynamic Cut Generation in Integer
Programming},
author  = {Ralphs, T.K. and Galati, M.V.},
year = {2006},
journal  = {Mathematical Programming},
volume  = {106},
pages = {261--285},
doi = {10.1007/s10107-005-0606-3},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/DECOMP.pdf},
software  = {https://github.com/coin-or/Dip}
}
  • T. K. Ralphs and M. Güzelsoy, “Duality and warm starting in integer programming,” in The proceedings of the 2006 NSF design, service, and manufacturing grantees and research conference, 2006. [Software] [PDF] [Bibtex] 
    @InProceedings{ RalGuz06,
title = {Duality and Warm Starting in Integer Programming},
booktitle  = {The Proceedings of the 2006 {{NSF}} Design, Service, and
Manufacturing Grantees and Research Conference},
author  = {Ralphs, T.K. and G{\"u}zelsoy, M.},
year = {2006},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/DMII06.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, “Parallel branch and cut,” in Parallel Combinatorial Optimization, E. Talbi, Ed., Wiley, 2006, p. 53–101. [Software] [PDF] [Bibtex] 
    @InCollection{ Ral06,
title = {Parallel Branch and Cut},
booktitle  = {Parallel {{Combinatorial Optimization}}},
author  = {Ralphs, T.K.},
editor  = {Talbi, E.},
year = {2006},
pages = {53--101},
publisher  = {Wiley},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/PBandC.pdf},
city = {New York},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, M. J. Saltzman, and M. M. Wiecek, “An improved algorithm for biobjective integer programming,” Annals of operations research, vol. 147, p. 43–70, 2006. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ RalSalWie06,
title = {An Improved Algorithm for Biobjective Integer
Programming},
author  = {Ralphs, T.K. and Saltzman, M.J. and Wiecek, M.M.},
year = {2006},
journal  = {Annals of Operations Research},
volume  = {147},
pages = {43--70},
doi = {10.1007/s10479-006-0058-z},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/BICRIT2.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • J. T. Linderoth and T. K. Ralphs, “Noncommercial software for mixed-integer linear programming,” in Integer Programming: Theory and Practice, J. Karlof, Ed., Crc press, 2005, p. 253–303. [PDF] [Bibtex] 
    @InCollection{ LinRal05,
title = {Noncommercial Software for Mixed-Integer Linear
Programming},
booktitle  = {Integer {{Programming}}: {{Theory}} and {{Practice}}},
author  = {Linderoth, J.T. and Ralphs, T.K.},
editor  = {Karlof, J},
year = {2005},
pages = {253--303},
publisher  = {CRC Press},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/MILP04.pdf}
}
  • T. K. Ralphs and M. Güzelsoy, “The SYMPHONY callable library for mixed integer programming,” in Proceedings of the ninth INFORMS computing society conference, 2005, p. 61–76. [Software] [PDF] [DOI] [Bibtex] 
    @InProceedings{ RalGuz05,
title = {The {{SYMPHONY}} Callable Library for Mixed Integer
Programming},
booktitle  = {Proceedings of the Ninth {{INFORMS}} Computing Society
Conference},
author  = {Ralphs, T.K. and G{\"u}zelsoy, M.},
year = {2005},
pages = {61--76},
issn = {1387666X},
doi = {10.1007/0-387-23529-9_5},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/SYMPHONY04.pdf},
abstract  = {SYMPHONY is a customizable, open-source library for
solving mixed-integer linear programs (MILP) by branch,
cut, and price. With its large assortment of parameter
settings, user callback functions, and compile-time
options, SYMPHONY can be configured as a generic MILP
solver or an engine for solving difficult MILPs by means of
a fully customized algorithm. SYMPHONY can run on a variety
of architectures, including single-processor,
distributed-memory parallel, and shared-memory parallel
architectures under MS Windows, Linux, and other Unix
operating systems. The latest version is implemented as a
callable library that can be accessed either through calls
to the native C application program interface, or through a
C++ interface class derived from the COIN-OR Open Solver
Interface. Among its new features are the ability to solve
bicriteria MILPs, the ability to stop and warm start MILP
computations after modifying parameters or problem data,
the ability to create persistent cut pools, and the ability
to perform rudimentary sensitivity analysis on MILPs.
{\copyright} 2005 Springer Science+Business Media, Inc.},
keywords  = {Branch and bound,Branch and cut,Integer
programming,Sensitivity analysis,Software},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • Y. Xu, T. K. Ralphs, L. Ladányi, and M. J. Saltzman, “ALPS: a framework for implementing parallel tree search algorithms,” in The proceedings of the ninth INFORMS computing society conference, 2005, p. 319–334. [Software] [PDF] [DOI] [Bibtex] 
    @InProceedings{ XuRalLadSal05,
title = {{{ALPS}}: A Framework for Implementing Parallel Tree
Search Algorithms},
booktitle  = {The Proceedings of the Ninth {{INFORMS}} Computing Society
Conference},
author  = {Xu, Y. and Ralphs, T.K. and Lad{\'a}nyi, L. and Saltzman,
M.J.},
year = {2005},
volume  = {29},
pages = {319--334},
issn = {1387666X},
doi = {10.1007/0-387-23529-9_21},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ALPS04.pdf},
abstract  = {ALPS is a framework for implementing and parallelizing
tree search algorithms. It employs a number of features to
improve scalability and is designed specifically to support
the implementation of data intensive algorithms, in which
large amounts of knowledge are generated and must be
maintained and shared during the search. Implementing such
algorithms in a scalable manner is challenging both because
of storage requirements and because of communications
overhead incurred in the sharing of data. In this abstract,
we describe the design of ALPS and how the design addresses
these challenges. We present two sample applications built
with ALPS and preliminary computational results.
{\copyright} 2005 Springer Science+Business Media, Inc.},
keywords  = {Branch and bound,Integer programming,Parallel
algorithm,Software},
software  = {https://github.com/coin-or/CHiPPS-ALPS}
}
  • T. K. Ralphs and M. V. Galati, “Decomposition in integer programming,” in Integer Programming: Theory and Practice, J. Karlof, Ed., Crc press, 2005, p. 57–110. [Software] [PDF] [Bibtex] 
    @InCollection{ RalGal05,
title = {Decomposition in Integer Programming},
booktitle  = {Integer {{Programming}}: {{Theory}} and {{Practice}}},
author  = {Ralphs, T.K. and Galati, M.V.},
editor  = {Karlof, J},
year = {2005},
pages = {57--110},
publisher  = {CRC Press},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/DECOMP04.pdf},
software  = {https://github.com/coin-or/Dip}
}
  • T. K. Ralphs, L. Ladányi, and M. J. Saltzman, “A library hierarchy for implementing scalable parallel search algorithms,” Journal of supercomputing, vol. 28, p. 215–234, 2004. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ RalLadSal04,
title = {A Library Hierarchy for Implementing Scalable Parallel
Search Algorithms},
author  = {Ralphs, T.K. and Lad{\'a}nyi, L. and Saltzman, M.J.},
year = {2004},
journal  = {Journal of Supercomputing},
volume  = {28},
pages = {215--234},
doi = {10.1023/B:SUPE.0000020179.55383.ad},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/JSC02.pdf},
software  = {https://github.com/coin-or/CHiPPS-ALPS}
}
  • T. K. Ralphs, L. Ladányi, and M. J. Saltzman, “Parallel branch, cut, and price for large-scale discrete optimization,” Mathematical programming, vol. 98, p. 253–280, 2003. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ RalLadSal03,
title = {Parallel Branch, Cut, and Price for Large-Scale Discrete
Optimization},
author  = {Ralphs, T.K. and Lad{\'a}nyi, L. and Saltzman, M.J.},
year = {2003},
journal  = {Mathematical Programming},
volume  = {98},
pages = {253--280},
doi = {10.1007/s10107-003-0404-8},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/PBCP.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, “Parallel branch and cut for capacitated vehicle routing,” Parallel computing, vol. 29, p. 607–629, 2003. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ Ral03,
title = {Parallel Branch and Cut for Capacitated Vehicle Routing},
author  = {Ralphs, T.K.},
year = {2003},
journal  = {Parallel Computing},
volume  = {29},
pages = {607--629},
doi = {10.1016/S0167-8191(03)00045-0},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/PVRP.pdf},
annotation  = {Software: https://github.com/coin-or/SYMPHONY},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, L. Kopman, W. R. Pulleyblank, and T. L. E. Jr., “On the capacitated vehicle routing problem,” Mathematical programming, vol. 94, p. 343–359, 2003. [Software] [PDF] [DOI] [Bibtex] 
    @Article{ RalKopPulJr03,
title = {On the Capacitated Vehicle Routing Problem},
author  = {Ralphs, T.K. and Kopman, L. and Pulleyblank, W.R. and Jr.,
L.E. Trotter},
year = {2003},
journal  = {Mathematical Programming},
volume  = {94},
pages = {343--359},
doi = {10.1007/s10107-002-0323-0},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/VRP.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • L. Ladányi, T. K. Ralphs, and M. J. Saltzman, “Implementing scalable parallel search algorithms for data-intensive applications,” in Proceedings of the international conference on computational science, 2002, p. 592–602. [Software] [PDF] [DOI] [Bibtex] 
    @InProceedings{ LadRalSal02,
title = {Implementing Scalable Parallel Search Algorithms for
Data-Intensive Applications},
booktitle  = {Proceedings of the International Conference on
Computational Science},
author  = {Lad{\'a}nyi, L. and Ralphs, T.K. and Saltzman, M.J.},
year = {2002},
pages = {592--602},
issn = {03029743},
doi = {10.1007/3-540-46043-8_60},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ICCS02.pdf},
abstract  = {Scalability is a critical issue in the design of parallel
software for large-scale search problems. Previous research
has not addressed this issue for data-intensive
applications. We describe the design of a library for
parallel search that focuses on efficient data and search
tree management for such applications in distributed
computing environments. {\copyright} 2002 Springer-Verlag
Berlin Heidelberg.},
isbn = {3-540-43591-3},
software  = {https://github.com/coin-or/CHiPPS-ALPS}
}
  • L. Ladányi, T. K. Ralphs, and T. L. E. Jr., “Branch, cut, and price: Sequential and parallel,” in Computational Combinatorial Optimization, D. Naddef and M. Juenger, Eds., Springer, 2001, p. 223–260. [PDF] [DOI] [Bibtex] 
    @InCollection{ LadRalJr01,
title = {Branch, Cut, and Price: {{Sequential}} and Parallel},
booktitle  = {Computational {{Combinatorial Optimization}}},
author  = {Lad{\'a}nyi, L. and Ralphs, T.K. and Jr., L.E. Trotter},
editor  = {Naddef, D and Juenger, M},
year = {2001},
pages = {223--260},
publisher  = {Springer},
doi = {10.1007/3-540-45586-8_6},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/LNCS.pdf},
city = {Berlin}
}
  • M. Esö, L. Ladányi, T. K. Ralphs, and T. L. E. Jr., “Fully parallel generic branch-and-cut framework,” in Proceedings of the eighth \\vphantom\SIAM\vphantom\\ conference on parallel processing for scientific computing, 1997. [Software] [Bibtex] 
    @InProceedings{ EsoLadRalJr97,
title = {Fully Parallel Generic Branch-and-Cut Framework},
booktitle  = {Proceedings of the Eighth
\{\vphantom\}{{SIAM}}\vphantom\{\} Conference on Parallel
Processing for Scientific Computing},
author  = {Es{\"o}, M. and Lad{\'a}nyi, L. and Ralphs, T.K. and Jr.,
L.E. Trotter},
year = {1997},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, “On the mixed chinese postman problem,” Operations research letters, vol. 14, p. 123–127, 1993. [PDF] [DOI] [Bibtex] 
    @Article{ Ral93,
title = {On the Mixed Chinese Postman Problem},
author  = {Ralphs, T.K.},
year = {1993},
journal  = {Operations Research Letters},
volume  = {14},
pages = {123--127},
doi = {10.1016/0167-6377(93)90021-8},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/MPP.pdf}
}

Technical Reports and Publications In Review

  • O. A. Prokopyev and T. K. Ralphs, “On the complexity of finding locally optimal solutions in bilevel linear programming,” COR@L Laboratory, Lehigh University, 24T-015, 2024. [PDF] [Bibtex] 
    @TechReport{ ProRal24,
title = {On the Complexity of Finding Locally Optimal Solutions in
Bilevel Linear Programming},
author  = {Prokopyev, O.A. and Ralphs, T.K.},
year = {2024},
number  = {24T-015},
institution  = {COR@L Laboratory, Lehigh University},
url = {https://coral.ise.lehigh.edu/~ted/files/papers/BLPLocal24.pdf}
}
  • Y. Xie, T. K. Ralphs, and O. A. Prokopyev, “A branch-and-cut algorithm for mixed integer bilevel optimization with bounded rationality,” Working Paper, COR@L Laboratory, Lehigh University 2024. [Bibtex] 
    @TechReport{ XieRalPro24,
title = {A Branch-and-Cut Algorithm for Mixed Integer Bilevel
Optimization with Bounded Rationality},
author  = {Xie, Yu and Ralphs, Ted K. and Prokopyev, Oleg A.},
year = {2024},
institution  = {Working Paper, COR@L Laboratory, Lehigh University}
}
  • F. Battista and T. K. Ralphs, “A branch-and-cut algorithm for bilevel linear optimization based on improving directions,” Working Paper, COR@L Laboratory, Lehigh University 2024. [Bibtex] 
    @TechReport{ BatRal24,
title = {A Branch-and-Cut Algorithm for Bilevel Linear Optimization
Based on Improving Directions},
author  = {Battista, F. and Ralphs, T.K.},
year = {2024},
institution  = {Working Paper, COR@L Laboratory, Lehigh University}
}
  • T. K. Ralphs, “Duality, branch and bound, and parametric valid inequalities,” Working Paper, COR@L Laboratory, Lehigh University 2024. [PDF] [Bibtex] 
    @TechReport{ Ral24,
title = {Duality, Branch and Bound, and Parametric Valid
Inequalities},
author  = {Ralphs, T.K.},
year = {2024},
institution  = {Working Paper, COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/talks/ParametricInequalities-INFORMS17.pdf}
}
  • S. Coniglio and T. K. Ralphs, “Bound-optimal cuts: On the generation of cuts which maximize the bound improvement,” Working Paper, COR@L Laboratory, Lehigh University 2024. [Bibtex] 
    @TechReport{ ConRal24,
title = {Bound-Optimal Cuts: {{On}} the Generation of Cuts Which
Maximize the Bound Improvement},
author  = {Coniglio, S. and Ralphs, T.K.},
year = {2024},
institution  = {Working Paper, COR@L Laboratory, Lehigh University}
}
  • J. Thürauf, T. Kleinert, I. Ljubić, T. K. Ralphs, and M. Schmidt, “BOBILib: Bilevel optimization (benchmark) instance library,” 2024. [PDF] [Bibtex] 
    @TechReport{ ThuKleLjuRalSch24,
title = {{{BOBILib}}: {{Bilevel}} Optimization (Benchmark) Instance
Library},
author  = {Th{\"u}rauf, J. and Kleinert, T. and Ljubi{\'c}, I. and
Ralphs, T.K. and Schmidt, M.},
year = {2024},
url = {https://optimization-online.org/2024/07/bobilib-bilevel-optimization-benchmark-instance-library/}
}
  • S. P. Kelley, A. M. Kazachkov, and T. K. Ralphs, “Warm starting of mixed integer linear optimization problems via parametric disjunctive cuts,” Working Paper, COR@L Laboratory, Lehigh University 2023. [Bibtex] 
    @TechReport{ KelKazRal23,
title = {Warm Starting of Mixed Integer Linear Optimization
Problems via Parametric Disjunctive Cuts},
author  = {Kelley, S.P. and Kazachkov, A.M. and Ralphs, T.K.},
year = {2023},
institution  = {Working Paper, COR@L Laboratory, Lehigh University}
}
  • T. K. Ralphs, M. Guzelsoy, and A. Mahajan, “SYMPHONY version 5.7 user’s manual,” COR@L Laboratory, Lehigh University 2023. [PDF] [Bibtex] 
    @TechReport{ RalGuzMah23,
title = {{{SYMPHONY}} Version 5.7 User's Manual},
author  = {Ralphs, T.K. and Guzelsoy, M. and Mahajan, A.},
year = {2023},
institution  = {COR@L Laboratory, Lehigh University},
url = {https://coin-or.github.io/SYMPHONY/doc/SYMPHONY-5.7.1-Manual.pdf}
}
  • T. K. Ralphs, M. Guzelsoy, and A. Mahajan, “SYMPHONY version 5.6 user’s manual,” COR@L Laboratory, Lehigh University 2022. [Software] [PDF] [Bibtex] 
    @TechReport{ RalGuzMah22,
title = {{{SYMPHONY}} Version 5.6 User's Manual},
author  = {Ralphs, T.K. and Guzelsoy, M. and Mahajan, A.},
year = {2022},
institution  = {COR@L Laboratory, Lehigh University},
url = {https://coin-or.github.io/SYMPHONY/doc/SYMPHONY-5.6.19-Manual.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, “Separation, inverse optimization, and decomposition,” Working Paper, COR@L Laboratory, Lehigh University 2021. [PDF] [Bibtex] 
    @TechReport{ Ral21,
title = {Separation, Inverse Optimization, and Decomposition},
author  = {Ralphs, T.K.},
year = {2021},
institution  = {Working Paper, COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/talks/InversePrimalSeparation-PKU18.pdf}
}
  • S. Tahernejad and T. K. Ralphs, “Valid inequalities for mixed integer bilevel optimization problems,” COR@L Laboratory, Lehigh University, 20T-013, 2020. [Software] [PDF] [Bibtex] 
    @TechReport{ TahRal20,
title = {Valid Inequalities for Mixed Integer Bilevel Optimization
Problems},
author  = {Tahernejad, S. and Ralphs, T.K.},
year = {2020},
number  = {20T-013},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/MibSCuts20.pdf},
software  = {https://github.com/coin-or/MibS}
}
  • S. J. Maher, T. K. Ralphs, and Y. Shinano, “Assessing the effectiveness of (parallel) branch-and-bound algorithms,” COR@L Laboratory, Lehigh University, 19T-017, 2019. [PDF] [Bibtex] 
    @TechReport{ MahRalShi19,
title = {Assessing the Effectiveness of (Parallel) Branch-and-Bound
Algorithms},
author  = {Maher, S.J. and Ralphs, T.K. and Shinano, Y.},
year = {2019},
number  = {19T-017},
institution  = {COR@L Laboratory, Lehigh University},
url = {https://arxiv.org/abs/2104.10025}
}
  • M. Walter and T. K. Ralphs, “Algorithms for inverse mixed integer programming,” Working Paper, COR@L Laboratory, Lehigh University 2018. [Bibtex] 
    @TechReport{ WalRal18,
title = {Algorithms for Inverse Mixed Integer Programming},
author  = {Walter, M. and Ralphs, T.K.},
year = {2018},
institution  = {Working Paper, COR@L Laboratory, Lehigh University}
}
  • M. V. Galati and T. K. Ralphs, “DIP: a framework for decomposition in integer programming,” Working Paper, COR@L Laboratory, Lehigh University 2017. [Software] [PDF] [Bibtex] 
    @TechReport{ GalRal17,
title = {{{DIP}}: A Framework for Decomposition in Integer
Programming},
author  = {Galati, M.V. and Ralphs, T.K.},
year = {2017},
institution  = {Working Paper, COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/talks/DecompCSIRO11.pdf},
software  = {https://github.com/coin-or/Dip}
}
  • S. T. DeNegre and T. K. Ralphs, “Computational experience solving mixed integer interdiction problems,” Working Paper, COR@L Laboratory, Lehigh University 2017. [Bibtex] 
    @TechReport{ DeNRal17,
title = {Computational Experience Solving Mixed Integer
Interdiction Problems},
author  = {DeNegre, S.T. and Ralphs, T.K.},
year = {2017},
institution  = {Working Paper, COR@L Laboratory, Lehigh University}
}
  • A. Bulut and T. K. Ralphs, “DisCO: An open source solver for discrete conic optimization,” Working Paper, COR@L Laboratory, Lehigh University 2017. [Software] [PDF] [Bibtex] 
    @TechReport{ BulRal17a,
title = {{{DisCO}}: {{An}} Open Source Solver for Discrete Conic
Optimization},
author  = {Bulut, A. and Ralphs, T.K.},
year = {2017},
institution  = {Working Paper, COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/talks/DisCO-INFORMS17.pdf},
software  = {https://github.com/aykutbulut/DisCO}
}
  • A. Bulut and T. K. Ralphs, “Complexity for mathematical programs,” Working Paper, COR@L Laboratory, Lehigh University 2017. [PDF] [Bibtex] 
    @TechReport{ BulRal17,
title = {Complexity for Mathematical Programs},
author  = {Bulut, A. and Ralphs, T.K.},
year = {2017},
institution  = {Working Paper, COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/talks/MIP12.pdf}
}
  • M. E. Pfetsch and T. K. Ralphs, “Towards more “scientific” computations in mathematical optimization,” Working Paper, COR@L Laboratory, Lehigh University 2017. [Bibtex] 
    @TechReport{ PfeRal17,
title = {Towards More "Scientific" Computations in Mathematical
Optimization},
author  = {Pfetsch, M.E. and Ralphs, T.K.},
year = {2017},
institution  = {Working Paper, COR@L Laboratory, Lehigh University}
}
  • T. K. Ralphs, “Data science and analytics,” {Industrial and Systems Engineering Report 15T-009, Lehigh University} 2015. [PDF] [Bibtex] 
    @TechReport{ Ral15,
title = {Data Science and Analytics},
author  = {Ralphs, T.K.},
year = {2015},
institution  = {{Industrial and Systems Engineering Report 15T-009, Lehigh
University}},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/dataScience.pdf}
}
  • A. Hassanzadeh and T. K. Ralphs, “A generalization of benders’ algorithm for two-stage stochastic optimization problems with mixed integer recourse,” COR@L Laboratory, Lehigh University, 14T-005, 2014. [Software] [PDF] [Bibtex] 
    @TechReport{ HasRal14a,
title = {A Generalization of Benders' Algorithm for Two-Stage
Stochastic Optimization Problems with Mixed Integer
Recourse},
author  = {Hassanzadeh, A. and Ralphs, T.K.},
year = {2014},
number  = {14T-005},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/SMILPGenBenders14.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • A. Hassanzadeh and T. K. Ralphs, “On the value function of a mixed integer linear optimization problem and an algorithm for its construction,” COR@L Laboratory, Lehigh University, 14T-004, 2014. [Software] [PDF] [Bibtex] 
    @TechReport{ HasRal14,
title = {On the Value Function of a Mixed Integer Linear
Optimization Problem and an Algorithm for Its
Construction},
author  = {Hassanzadeh, A. and Ralphs, T.K.},
year = {2014},
number  = {14T-004},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/MILPValueFunction14.pdf},
software  = {https://github.com/tkralphs/ValueFunction}
}
  • T. K. Ralphs, M. Güzelsoy, and A. Mahajan, “SYMPHONY version 5.5 user’s manual,” COR@L Laboratory, Lehigh University 2013. [Software] [PDF] [Bibtex] 
    @TechReport{ RalGuzMah13,
title = {{{SYMPHONY}} Version 5.5 User's Manual},
author  = {Ralphs, T.K. and G{\"u}zelsoy, M. and Mahajan, A.},
year = {2013},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://www.coin-or.org/SYMPHONY/doc/SYMPHONY-5.5.0-Manual.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • A. Lodi, T. K. Ralphs, F. Rossi, and S. Smriglio, “Interdiction branching,” COR@L Laboratory, Lehigh University, 11T-012-R2, 2011. [Software] [PDF] [Bibtex] 
    @TechReport{ LodRalRosSmr11,
title = {Interdiction Branching},
author  = {Lodi, A. and Ralphs, T.K. and Rossi, F. and Smriglio, S.},
year = {2011},
number  = {11T-012-R2},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/BilevelBranching.pdf},
software  = {https://github.com/tkralphs/InterdictionBranch}
}
  • M. Güzelsoy and T. K. Ralphs, “Warm-starting for real-time vehicle routing,” COR@L Laboratory, Lehigh University 2011. [Software] [Bibtex] 
    @TechReport{ GuzRal11,
title = {Warm-Starting for Real-Time Vehicle Routing},
author  = {G{\"u}zelsoy, M. and Ralphs, T.K.},
year = {2011},
institution  = {COR@L Laboratory, Lehigh University},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, M. Güzelsoy, and A. Mahajan, “SYMPHONY version 5.3 user’s manual,” COR@L Laboratory, Lehigh University 2011. [Software] [PDF] [Bibtex] 
    @TechReport{ RalGuzMah11,
title = {{{SYMPHONY}} Version 5.3 User's Manual},
author  = {Ralphs, T.K. and G{\"u}zelsoy, M. and Mahajan, A.},
year = {2011},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://www.coin-or.org/SYMPHONY/doc/SYMPHONY-5.3.4-Manual.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, M. Güzelsoy, and A. Mahajan, “SYMPHONY version 5.4 user’s manual,” COR@L Laboratory, Lehigh University 2011. [Software] [PDF] [Bibtex] 
    @TechReport{ RalGuzMah11a,
title = {{{SYMPHONY}} Version 5.4 User's Manual},
author  = {Ralphs, T.K. and G{\"u}zelsoy, M. and Mahajan, A.},
year = {2011},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://www.coin-or.org/SYMPHONY/doc/SYMPHONY-5.4.0-Manual.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, A. Mahajan, and M. Güzelsoy, “SYMPHONY version 5.2 user’s manual,” COR@L Laboratory, Lehigh University 2010. [Software] [PDF] [Bibtex] 
    @TechReport{ RalMahGuz10,
title = {{{SYMPHONY}} Version 5.2 User's Manual},
author  = {Ralphs, T.K. and Mahajan, A. and G{\"u}zelsoy, M.},
year = {2010},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://www.coin-or.org/SYMPHONY/doc/SYMPHONY-5.2.3-Manual.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • Z. Akca, R. T. Berger, and T. K. Ralphs, “Solution methods for the multi-trip elementary shortest path problem with resource constraints,” COR@L Laboratory, Lehigh University 2010. [PDF] [Bibtex] 
    @TechReport{ AkcBerRal10,
title = {Solution Methods for the Multi-Trip Elementary Shortest
Path Problem with Resource Constraints},
author  = {Akca, Z. and Berger, R.T. and Ralphs, T.K.},
year = {2010},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/MESPPRC10.pdf}
}
  • Z. Akca, R. T. Berger, and T. K. Ralphs, “Modeling and solving location, routing, and scheduling problems,” COR@L Laboratory, Lehigh University, 08T-009, 2008. [PDF] [Bibtex] 
    @TechReport{ AkcBerRal08,
title = {Modeling and Solving Location, Routing, and Scheduling
Problems},
author  = {Akca, Z. and Berger, R.T. and Ralphs, T.K.},
year = {2008},
number  = {08T-009},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/LRSP08.pdf}
}
  • T. K. Ralphs, “SYMPHONY version 5.1 user’s manual,” COR@L Laboratory, Lehigh University 2008. [Software] [PDF] [Bibtex] 
    @TechReport{ Ral08,
title = {{{SYMPHONY}} Version 5.1 User's Manual},
author  = {Ralphs, T.K.},
year = {2008},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://www.coin-or.org/SYMPHONY/SYMPHONY-5.1.8-Manual.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • M. Güzelsoy and T. K. Ralphs, “The value function of a mixed-integer linear program with a single constraint,” COR@L Laboratory, Lehigh University 2008. [PDF] [Bibtex] 
    @TechReport{ GuzRal08,
title = {The Value Function of a Mixed-Integer Linear Program with
a Single Constraint},
author  = {G{\"u}zelsoy, M. and Ralphs, T.K.},
year = {2008},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ValueFunction.pdf}
}
  • O. Osaltyn, B. Hunsaker, and T. K. Ralphs, “Visualizing branch-and-bound algorithms,” COR@L Laboratory, Lehigh Univesity 2007. [Software] [PDF] [Bibtex] 
    @TechReport{ OsaHunRal07,
title = {Visualizing Branch-and-Bound Algorithms},
author  = {Osaltyn, O. and Hunsaker, B. and Ralphs, T.K.},
year = {2007},
institution  = {COR@L Laboratory, Lehigh Univesity},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/BBVis.pdf},
software  = {http://github.com/coin-or/GrUMPy}
}
  • Y. Xu, T. K. Ralphs, L. Ladányi, and M. J. Saltzman, “Computational experience with a framework for parallel integer programming,” COR@L Laboratory, Lehigh University 2007. [Software] [PDF] [Bibtex] 
    @TechReport{ XuRalLadSal07,
title = {Computational Experience with a Framework for Parallel
Integer Programming},
author  = {Xu, Y. and Ralphs, T.K. and Lad{\'a}nyi, L. and Saltzman,
M.J.},
year = {2007},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/CHiPPS.pdf},
software  = {https://github.com/coin-or/CHiPPS-BLIS}
}
  • T. K. Ralphs and M. Güzelsoy, “Duality, warm starting, and sensitivity analysis in integer programming,” COR@L Laboratory, Lehigh University, 04T-022, 2004. [PDF] [Bibtex] 
    @TechReport{ RalGuz04,
title = {Duality, Warm Starting, and Sensitivity Analysis in
Integer Programming},
author  = {Ralphs, T.K. and G{\"u}zelsoy, M.},
year = {2004},
number  = {04T-022},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://ise.lehigh.edu/sites/ise.lehigh.edu/files/04t_022.pdf},
note = {Available by request}
}
  • T. K. Ralphs, M. J. Saltzman, and M. M. Wiecek, “An improved algorithm for biobjective integer programming and its application to network routing problems,” COR@L Laboratory Report, Lehigh University, 04T-004, 2004. [Software] [PDF] [Bibtex] 
    @TechReport{ RalSalWie04,
title = {An Improved Algorithm for Biobjective Integer Programming
and Its Application to Network Routing Problems},
author  = {Ralphs, T.K. and Saltzman, M.J. and Wiecek, M.M.},
year = {2004},
number  = {04T-004},
institution  = {COR@L Laboratory Report, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/BICRIT.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, “SYMPHONY version 5.0 user’s manual,” COR@L Laboratory, Lehigh University, 04T-011, 2004. [Software] [Bibtex] 
    @TechReport{ Ral04,
title = {{{SYMPHONY}} Version 5.0 User's Manual},
author  = {Ralphs, T.K.},
year = {2004},
number  = {04T-011},
institution  = {COR@L Laboratory, Lehigh University},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, “SYMPHONY version 4.0 user’s manual,” COR@L Laboratory, Lehigh University 2003. [Software] [Bibtex] 
    @TechReport{ Ral03a,
title = {{{SYMPHONY}} Version 4.0 User's Manual},
author  = {Ralphs, T.K.},
year = {2003},
institution  = {COR@L Laboratory, Lehigh University},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs and J. C. Hartman, “Capacitated network routing (a preliminary progress report),” COR@L Laboratory, Lehigh University, 01W-009, 2001. [Software] [PDF] [Bibtex] 
    @TechReport{ RalHar01,
title = {Capacitated Network Routing (a Preliminary Progress
Report)},
author  = {Ralphs, T.K. and Hartman, J.C.},
year = {2001},
number  = {01W-009},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/CNRP.pdf},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs and L. Ladányi, “COIN/BCP user’s manual,” COR@L Laboratory, Lehigh University 2001. [Software] [PDF] [Bibtex] 
    @TechReport{ RalLad01,
title = {{{COIN}}/{{BCP}} User's Manual},
author  = {Ralphs, T.K. and Lad{\'a}nyi, L.},
year = {2001},
institution  = {COR@L Laboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/BCP-Manual.pdf},
software  = {https://github.com/coin-or/Bcp}
}
  • T. K. Ralphs, L. Ladányi, and M. J. Saltzman, “A library hierarchy for implementing scalable parallel search algorithms,” COR@LLaboratory, Lehigh University 2001. [Software] [PDF] [Bibtex] 
    @TechReport{ RalLadSal01,
title = {A Library Hierarchy for Implementing Scalable Parallel
Search Algorithms},
author  = {Ralphs, T.K. and Lad{\'a}nyi, L. and Saltzman, M.J.},
year = {2001},
institution  = {COR@LLaboratory, Lehigh University},
url = {http://coral.ie.lehigh.edu/~ted/files/papers/ALPS.pdf},
software  = {https://github.com/coin-or/CHiPPS-ALPS}
}
  • T. K. Ralphs and L. Ladányi, “SYMPHONY: a parallel framework for branch, cut, and price,” Rice University 2000. [Software] [Bibtex] 
    @TechReport{ RalLad00,
title = {{{SYMPHONY}}: A Parallel Framework for Branch, Cut, and
Price},
author  = {Ralphs, T.K. and Lad{\'a}nyi, L.},
year = {2000},
institution  = {Rice University},
software  = {https://github.com/coin-or/SYMPHONY}
}
  • T. K. Ralphs, “Parallel branch and cut for vehicle routing,” PhD Thesis, 1995. [Software] [Bibtex] 
    @PhDThesis{ Ral95,
title = {Parallel Branch and Cut for Vehicle Routing},
author  = {Ralphs, T.K.},
year = {1995},
month = may,
school  = {Cornell University},
software  = {https://github.com/coin-or/SYMPHONY}
}

Software

  • SYMPHONY: Single- or Multi-Process Optimization over Networks
    An open-source, generic MILP solver, callable library, and extensible framework for implementing customized MILP solvers, SYMPHONY can be built in various sequential and parallel configurations for either distributed or shared memory architectures. SYMPHONY has a number of advanced capabilities stemming from the research projects discussed above, including the ability to solve multi-objective MILPs, the ability to warm start its solution procedure, and the ability to perform basic sensitivity analyses. SYMPHONY has an active user community and has been deployed in a variety of application areas, including computational biology, wireless telecommunications, supply chain management, transportation services, and air transportation. It can be used “out of the box” as a solver for generic mixed-integer linear programs or customized for a particular application through the use of numerous callback functions.
  • CHiPPS: The COIN High Performance Parallel Search Framework
    This C++ class library and framework for implementing parallel search algorithms for large-scale, data-intensive applications consist of three layers.

    • ALPS: Abstract Library for Parallel Search
      ALPS provides the base infrastructure for implementing a variety of search algorithms, such as branch and bound or constraint logic programming. Two prototype solvers, a vanilla branch-and-cut solver and a knapsack problem solver, have been derived from ALPS to demonstrate its use.
    • BiCePS: Branch, Constrain, and Price Software
      Built on top of ALPS, BiCePS provides the data layer for implementing relaxation-based optimization algorithms, such as LP-based branch and bound. Scalability is maintained through the use of compact data structures for storage and communication of problem data.
    • BLIS: BiCePS Linear Integer Solver
      This C++ class library is a concretization of BiCePS for the case of mixed-integer linear programming based on LP relaxation. From BLIS, one can easily derive custom solver applications. A number of such applications have already been developed, including a solver for various types of routing problems and a solver for mixed integer bilevel programs.
  • DIP
    A software framework for implementing bounding methods for integer programs based on the integration of traditional decomposition methods with polyhedral methods. The framework has been integrated with CHiPPS to provide a complete solver framework.
  • GiMPy
    This package began as a tool for visualizing various graph algorithms that I used in both ISE 172 and ISE 411. It has now been expanded out into a full-featured graph class that is useful as a research code due to its clarity of implementation and display capabilities. It is the basis for the GrUMPy project, which is a class for visualizing mathematical programming algorithms, such as branch and bound and the cutting plane method.
  • GruMPy
    GruMPy is based on an earlier project called the Branch-and-Bound Analysis Kit (BAK), which was a tool for visualizing and monitoring the progress of branch-and-bound algorithms. It has now been re-implemented on top of GiMPy to take advantage of the capabilities of that class.
  • CuPPy
    This package is a collection of implementations of cutting plane algorithms written in Python. It is intended both as a tool for use in the classroom in teaching discrete optimization and as a research tool. It includes some experimental methods for generating and visualizing some new classes of cutting planes not yet described in the literature.
  • BLImPy
    BLIMPy is a collection of basic list data structures, such as the linked list that I use in ISE 172 and is also used in GiMPy.
  • COLA
    A software project being developed as part a recently awarded NSF grant on conic Optimization. It is a solver for second order cone optimization problems that uses outer approximation of the second order cones.
  • DietCOLA
    A solver for second order cone optimization problems that have integrality restrictions on some of the variables. DisCO is built on top of the CHiPPS tree search framework and is a proof-of-concept for the development of DisCO (see below). It solves the SOCPs with COLA.
  • DisCO
    A solver for second order cone optimization problems that have integrality restrictions on some of the variables. It is a generalization of the BLIS solver from CHiPPs and replaces the simplex-based LP solver for solving the continuous relaxation problems there with a more general conic solver.
  • OSI-Conic
    A generic solver API for conic optimization solvers that is used to provide an interface to various solvers that can be used to solve the continuous relaxations required in DisCO.
  • CGL-Conic
    A library of constraint generators for discrete conic optimization problems the be used within the DisCO framework.
  • MibS: Mixed Integer Bilevel Solver
    A software package for solving mixed integer bilevel programs. Such programs arise in the analysis of hierarchical decision systems with multiple, independent decision-makers whose interests are not necessarily aligned. The solver implements a rudimentary branch-and-cut algorithm for solving integer bilevel linear programs that extends existing techniques for standard integer linear programs. It uses cutting plane techniques to produce improved bounds, does not require specialized branching strategies, and can be implemented in a straightforward way using only linear solvers. Our implementation is built using software components available in the COIN-OR software repository.
  • COIN-OR Optimization Suite
    I maintain a build harness and installers for the interoperable suite of tools available in COIN for solving optimization problems. This includes a broad range of solvers and the suite is perhaps the most capable such suite available overall, including commercial offerings. It is very widely used and has been embedded in or can be accessed from all the top modeling and analysis
    environments, including the Excel and OpenOffice spreadsheets, Matlab, Sage, R, Python, and all major modeling languages.

Plenaries, Keynotes, Tutorials, and Short Courses

  • T.K. Ralphs, Branch and Cut for Integer Bilevel Optimization (Plenary), Third International Workshop on Bilevel Optimization, Rancagua, Chile, January 2024 (Slides)
  • T.K. Ralphs, Multilevel and Multistage Optimization (Short Course), University of Erlangen, Erlangen, Germany, March 2017 (Slides)
  • T.K. Ralphs, Multilevel and Multistage Optimization (Short Course), Zuse Institute Berlin, Berlin, Germany, December 2016 (Slides)
  • T.K. Ralphs, Computational Integer Programming (Short Course), International Workshop on Modern Optimization and Applications, Beijing, China, June 2016 (Slides)
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, and A. Hassanzadeh, and S. Tahernajad Multistage Discrete Optimization (Tutorial), INFORMS Optimization Society Conference, Princeton, NJ, March 2016
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, and A. Hassanzadeh, and S. Tahernajad Multistage Discrete Optimization (Plenary), First International Workshop on Bilevel Programming, Monterrey, Mexico, March 2016 (PDF)
  • T.K. Ralphs, Multilevel and Multistage Optimization (Short Course), IIT Bombay, Mumbai, India, December 2015 (Slides)
  • T.K. Ralphs, COIN Fest 2015: Workshop on Modeling and the COIN-OR Optimization Suite (Full-day Tutorial), INFORMS Computing Society Conference, Richmond, Virginia, January 2015. (Slides
  • T.K. Ralphs, Accessible Analytics: Openness and Operations Research (Keynote Address), South African Operational Research Society Conference 2014, Parys, South Africa, September 2014.
  • T.K. Ralphs, An Introduction to the COIN-OR Optimization Suite (Tutorial), South African Operational Research Society Conference 2014, Parys, South Africa, September 2014 (Slides)
  • T.K. Ralphs Tools for Modeling Optimization Problems (Tutorial), North-West University, PUK Campus, Potchefstroom, South Africa, June 2013 (Slides).
  • T.K. Ralphs An Introduction to the COIN-OR Optimization Suite: Open Source Tools for Building and Solving Optimization Models (Tutorial), Optimization Days, Montreal, May 2013 (PDF)
  • T.K. Ralphs, et. al., Decomposition Methods for Discrete Optimization (Tutorial), INFORMS Computing Society Biannual Meeting, Santa Fe, NM, January 2013 (PDF).
  • T.K. Ralphs, Computational Integer Programming (Short Course), Universidad de los Andes, August, 2010 (a href=/~ted/teaching/mip”>Course Page).
  • T.K. Ralphs and M. Guzelsoy, A Mini-Tutorial on the SYMPHONY Callable Library for Mixed-Integer Linear Programming, The Ninth INFORMS Computing Society Conference, Annapolis, MD, January 2005 (PS PDF).
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman , Tutorial: COIN-OR: Software Tools for Implementing Custom Solvers, the Institute for Operations Research and Management Science Annual Conference, Atlanta, GA, October 2003. (PS PDF).
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman, Software Tools for Implementing Branch, Cut, and Price Algorithms (Tutorial), The Institute for Operations Research and Management Science Annual Conference, San Jose, CA, November 2002 . (PS PDF).
  • L. Ladányi and T.K. Ralphs, Open-source Tool Kit for Implementing Branch, Cut, and Price Algorithms (Tutorial), The Institute for Operations Research and Management Science Annual Conference, Miami, FL, November 2001.
  • T.K. Ralphs and L. Ladányi, SYMPHONY: A Framework for Parallel Branch and Cut (Tutorial), DONET Spring School on Computation Combinatorial Optimization, Saarbrucken, Germany, May 2000 (PS PDF).

Conference Presentations

  • T.K. Ralphs, Latest Developments in the MibS Solver for Mixed Integer Bilevel Optimization, EURO Conference 2024, Copenhagen, June 2024 (PDF)
  • T.K. Ralphs, It’s Farkas All the Way Down: A Generalized Farkas Lemma and Its Implications, MIP Workshop 2024, Lexington, KY, June 2024 (PDF)
  • T.K. Ralphs, Branch and Cut for Bilevel Integer Linear Optimization, Third International Workshop on Bilevel Optimization, Rancagua, Chile, January 2024 (PDF)
  • M. Schmidt, T. Kleinert, I. Ljubic, T.K. Ralphs, J. Thurauf, BOBILib – A Bilevel Optimization Benchmark Instance Library, International Symposium on Mathematical Programming 2024, Montreal (PDF)
  • F. Battista and T.K. Ralphs, A Branch-and-Cut Algorithm for Mixed Integer Bilevel Linear Optimization Based on Improving Directions, International Symposium on Mathematical Programming 2024, Montreal (PDF)
  • T.K. Ralphs, Parametric Inequalities in Mixed Integer (Non?) Linear Optimization, Workshop on Optimization at the Second Level, Mittag Leffler Institute, Sweden, July 2023 (PDF)
  • T.K. Ralphs and S. Bolusani, Parametric Inequalities in Mixed Integer Linear Optimization, INFORMS Annual Meeting, Phoenix, AZ, October 2023 (PDF)
  • F. Battista and T.K. Ralphs, Exploiting Dual Functions in Mixed Integer Bilevel Linear Programs, INFORMS Annual Meeting, Phoenix, AZ, October 2023 (PDF)
  • T.K. Ralphs, Generalized Duality and Value Functions, Workshop on Optimization at the Second Level, Schloss Dagstuhl, Germany, November 2022 (PDF)
  • M.H. Shaelaie, T.K. Ralphs and L.V. Snyder, Towards A Unified Framework For Branch And Bound And Reinforcement
    Learning, INFORMS Computing Society Annual Meeting, Tampa, FL, 2021
  • M.H. Shaelaie, T.K. Ralphs and L.V. Snyder, Towards A Unified Framework For Branch And Bound And Reinforcement
    Learning, INFORMS Annual Meeting, Anaheim, CA, 2021
  • Y. Xie and T.K. Ralphs, Mixed Integer Bilevel Linear Optimization With Bounded Rationality, INFORMS Annual Meeting, Anaheim,
    CA, 2021
  • S. Fallah, T.K. Ralphs, and L.V. Snyder, A Method of Constructing the Efficient Frontier by Exploiting the Value Function,
    INFORMS Annual Meeting, Anaheim, CA, 2021
  • T.K. Ralphs, Duality and Meaning in Computation, INFORMS Annual Meeting, Anaheim, CA, 2021
  • T.K. Ralphs, Duality and Meaning in Computation, UG Workshop, Berlin, 2021 (PDF)
  • S. Bolusani, T.K. Ralphs, and S. Tahernejad, A Framework for Generalized Benders’ Decomposition and Its Application to
    Multilevel Optimization, INFORMS Annual Meeting, Virtual, 2020 (PDF)
  • X. Shi, O.A. Prokopyev, and T.K. Ralphs, A Scalable Bounding Approach for the Mixed Integer Bilevel Program, INFORMS
    Annual Meeting, Virtual, 2020
  • S. Fallah, T.K. Ralphs, and L.V. Snyder, A Branch-and-Price Algorithm for Integrated Location, Routing and Scheduling
    Problems, INFORMS Annual Meeting, Virtual, 2020
  • T.K. Ralphs and S. Bolusani, Parametric Valid Inequalities, INFORMS Annual Meeting, Seattle, WA, October 2019 (PDF)
  • T.K. Ralphs, S. Bolusani and S. Tahernejad, Multistage/Multilevel Discrete Optimization, International Conference on Stochastic Programming, Trondheim, Norway, July 2019 (PDF)
  • T.K. Ralphs, Duality in Integer Linear Programming, Joint Mathematics Meetings, Baltimore, MD, January 2019 (PDF)
  • T.K. Ralphs, S.J. Maher, and Y. Shinano, Assessing Performance of Parallel MILP Solvers, UG Workshop, Berlin, Germany, January 2019 (PDF)
  • T.K. Ralphs, Separation, Inverse Optimization, and Decomposition: Connecting the Dots, 23rd Workshop on Combinatorial Optimization, Aussois, France, January 2019 (PDF)
  • S. Tahernejad and T.K. Ralphs, Two-stage Mixed-integer Stochastic Bilevel Optimization Problems, INFORMS Annual Meeting, Phoenix, AZ, November 2018
  • S. Bolusani, F. Qiu, T.K. Ralphs, A. Botterud, and K. Kim, Warm Starting for Security Constrained Deterministic Unit Commitment, INFORMS Annual Meeting, Phoenix, AZ, November 2018
  • T.K. Ralphs, Introduction to COIN-OR and the Optimization Suite, COIN fORgery: Developing Open Source Tools for Operations Research, Institute for Mathematics and Its Applications, Minneapolis, MN, October 2018 (PDF)
  • T.K. Ralphs, Introduction to Project Management in COIN-OR, COIN fORgery: Developing Open Source Tools for Operations Research, Institute for Mathematics and Its Applications, Minneapolis, MN, October 2018 (PDF)
  • T.K. Ralphs, Introduction to Build and Test in COIN-OR, COIN fORgery: Developing Open Source Tools for Operations Research, Institute for Mathematics and Its Applications, Minneapolis, MN, October 2018 (PDF)
  • S. Bolusani and T.K. Ralphs, Generalized Benders’ Algorithm for Mixed Integer Bilevel Linear Optimization, MOPTA 2018, Bethlehem, PA, August 2018 (PDF)
  • T.K. Ralphs, Parallel Solution of Mixed Integer Linear Programs, New Computing-driven Opportunities for Optimization, Wuyishan, Fujian, China, August 2018 (PDF)
  • T.K. Ralphs, Separation, Inverse Optimization, and Decomposition: Some Observations, Peking University Workshop on Optimization Theory and Methods, Beijing, China, August 2018 (PDF)
  • S. Bolusani and T.K. Ralphs, Generalized Benders’ Algorithm for Mixed Integer Bilevel Linear Optimization, Second International Workshop of Bilvel Programming, Lille, France, June 2018
  • S. Tahernejad, T.K. Ralphs, Valid Inequalities for Mixed Integer Bilevel Linear Optimization (poster), Second International Workshop of Bilvel Programming, Lille, France, June 2018 (PDF)
  • S. Tahernejad, T.K. Ralphs, Valid Inequalities for Mixed Integer Bilevel Linear Optimization (poster), Mixed Integer Programming Workshop, Clemson, SC, June 2018 (PDF)
  • T.K. Ralphs, S.J. Maher, and Y. Shinano, Assessing Performance of Parallel MILP Solvers, International Symposium on Mathematical Programming, Bordeaux, France, July 2018 (PDF)
  • T.K. Ralphs, S.J. Maher, and Y. Shinano, Assessing Performance of Parallel MILP Solvers, SIAM Conference on Parallel Processing for Scientific Computing, Tokyo, Japan, March 2018
  • T.K. Ralphs, Multilevel Optimization and Game Theory: Applications and Algorithms, Tsinghua University, Beijing, China, March 2018
  • T.K. Ralphs, Parametric Valid Inequalities, INFORMS Annual Meeting, Houston, TX, October 2017 (PDF)
  • A. Bulut and T.K. Ralphs, Computational Approaches to Mixed Integer Second Order Cone Optimization, INFORMS Annual Meeting, Houston, TX, October 2017 (PDF)
  • S. Taherjejad, T.K. Ralphs, and S. DeNegre, A Branch-and-Cut Algorithm for Mixed Integer Bilevel Linear Optimization Problems and Its Implementation, INFORMS Annual Meeting, Houston, TX, October 2017 (PDF)
  • S. Bolusani and T.K. Ralphs, Generalized Benders’ Algorithm for Mixed Integer Bilevel Linear Optimization, INFORMS Annual Meeting, Houston, TX, October 2017
  • T.K. Ralphs, Open Source Tools for Optimization in Python, Sage Days, Institute for Mathematics and Its Application, Minneapolis, MN, August 2017 (PDF)
  • A. Bulut and T.K. Ralphs, Computational Approaches to Mixed Integer Second Order Cone Optimization, SIAM Conference on Optimization, Vancouver, BC, Canada, May 2017
  • T.K. Ralphs, S.J. Maher, and Y. Shinano, Assessing Performance of Parallel MILP Solvers: How Are We Doing, Really?, SIAM Conference on Optimization, Vancouver, BC, Canada, May 2017 (PDF)
  • T.K. Ralphs, Duality and Warm-starting in MILP, Meeting of the MIPLIB Steering Committee, Zuse Institute Berlin, Berlin, Germany, September 2016 (PDF)
  • T.K. Ralphs, The COIN-OR Optimization Suite: Open Source Tools for Optimization, International Congress on Mathematical Software, Berlin, Germany, July 2016
  • T.K. Ralphs, Separation, Inverse Optimization, and Decomposition: Some Observations, International Workshop on Modern Optimization and Applications, Beijing, China, June 2016 (PDF)
  • T.K. Ralphs, Separation, Inverse Optimization, and Decomposition: Some Observations, International Workshop on Column Generation 2016, Buzios, Brazil, May 2016 (PDF)
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, and A. Hassanzadeh, and S. Tahernajad Multistage Discrete Optimization (Tutorial, Part I), INFORMS Optimization Society Conference, Princeton, NJ, March 2016
  • S. Bolusani, T.K. Ralphs, M. Guzelsoy, and A. Mahajan Bilevel Optimization and the SYMPHONY MILP Solver (Tutorial, Part II), INFORMS Optimization Society Conference, Princeton, NJ, March 2016
  • S. Tahernajad, T.K. Ralphs, and S. DeNegre The MibS Solver for Bilevel Integer Optimization Problems (Tutorial, Part III), INFORMS Optimization Society Conference, Princeton, NJ, March 2016
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, and A. Hassanzadeh, and S. Tahernajad Computational Experience with Algorithms for Solving Multistage Integer Programs, Aussois Workshop on Combinatorial Optimization, Aussois, France, January 2016 (PDF)
  • T.K. Ralphs, Open Source Tools for Optimization in Python, SciPy India, IIT Bombay, Mumbai, India, December 2015 (PDF)
  • S. Tahernejad and T.K. Ralphs, Branch-and-cut Algorithm for Integer Bilevel Linear Optimization Problems, INFORMS Annual Meeting, Philadelphia, November, 2015.
  • A. Bulut and T.K. Ralphs, Computational Approaches to Mixed Integer Second Order Cone Optimization, INFORMS Annual Meeting, Philadelphia, November, 2015.
  • S. Bolusani and T.K. Ralphs, Solving Bilevel Linear Optimization Problems in Parallel, INFORMS Annual Meeting, Philadelphia, November, 2015.
  • T.K. Ralphs, M. Guzelsoy, and A. Hassanzadeh, Computational Experience with a Benders Algorithm for Two-stage Stochastic Integer Programming, INFORMS Annual Meeting, Philadelphia, November, 2015 (PDF).
  • T.K. Ralphs, Big Data Analytics: The Hype and the Hope, Mountain Talk Webinar given to Lehigh Alumni Association, October, 2015 (PDF)
  • T.K. Ralphs, S. Tahernajad, S. DeNegre, M. Guzelsoy, and A. Hassanzadeh, Bilevel Integer Optimization: Theory and Algorithms, International Symposium on Mathematical Programming 2015, Pittsburgh, PA, July 2015 (PDF)
  • A. Bulut and T.K. Ralphs, Computational Approaches to Mixed Integer Second Order Cone Optimization, International Symposium on Mathematical Programming 2015, Pittsburgh, PA, July 2015
  • M.J. Saltzman and T.K. Ralphs, COIN-OR at 15: Open Source Tools for Operations Research, International Symposium on Mathematical Programming 2015, Pittsburgh, PA, July 2015
  • A. Hassanzadeh, T.K. Ralphs, and M. Guzelsoy, A Benders’ Algorithm for Two-stage Stochastic Optimization Problems with Mixed Integer Programs, INFORMS Computing Society Biennial Meeting, Richmond, VA, January 2015 (PDF)
  • J. Wang and T.K. Ralphs, Recent Progress on the DIP Decomposition-based MILP Solver, INFORMS Computing Society Biennial Meeting, Richmond, VA, January 2015
  • T.K. Ralphs and A. Bulut, Optimization, Separation, and the Complexity of Inverse Optimization, INFORMS Annual Meeting, San Francisco, CA, November 2014 (PDF)
  • A. Bulut and T.K. Ralphs, Valid Inequalities for Mixed Integer Second Order Cone Optimization, INFORMS Annual Meeting, San Francisco, CA, November 2014
  • T.K. Ralphs, M. Galati, M. O’Sullivan, and J. Wang, DIP and DipPy: A Decomposition-based Modeling System and Solver, International Federation of Operations Research Societies Triennial Conference, Barcelona, Spain, July 2014 (PDF)
  • T.K. Ralphs, M. Guzelsoy, and A. Hassanzadeh, Generation and Representation of Piecewise Polyhedral Value Functions, MINLP 2014, Carnegie Mellon University, Pittsburgh, PA, June 2014 (PDF)
  • T. Terlaky, J. Goez, S. Cay, T.K. Ralphs, P. Belotti, and I. Polik, Mixed Integer Second-order Conic Optimization: Disjunctive Conic Cuts
    and Portfolio Models, MINLP 2014, Carnegie Mellon University, Pittsburgh, PA, June 2014.
  • A. Bulut and T.K. Ralphs, On the Complexity and Solution of Inverse Mixed Integer Linear Programs, INFORMS Annual Meeting, Minneapolis, MN, October 2013 (PDF)
  • A. Hassanzadeh, T.K. Ralphs, and M. Guzelsoy, A Generalized Benders’ Algorithm for Two-stage Stochastic Mixed Integer Linear Programs, INFORMS Annual Meeting, Minneapolis, MN, October 2013 (PDF)
  • T.K. Ralphs, J. Wang, M. Galati, and M. O’Sullivan, DIP and DipPy: A Decomposition-based Modeling System and Solver, INFORMS Annual Meeting, Minneapolis, MN, October 2013 (PDF)
  • T.K. Ralphs, A. Bulut, A. Lodi, and G. Woeginger, Multilevel and Multistage Integer Programming: Complexity and Algorithms, INFORMS Annual Meeting, Minneapolis, MN, October 2013 (PDF)
  • T.K. Ralphs and J. Wang Computational Experience with Hypergraph-based Methods for Automatic Decomposition in Integer Programming, CPAIOR 2013, IBM T.J. Watson Research Center, May 2013 (PDF)
  • T.K. Ralphs, A. Bulut, S. DeNegre, M. Guzelsoy, A. Hassanzadeh, Multilevel Integer Programming, The Polynomial Time Hierarchy, and Parallel Computing, Penn State University, March 2013 (PDF)
  • J.C. Góez, P. Belotti, I. Polik, T.K. Ralphs, and T. Terlaky, Disjunctive Conic Cuts, INFORMS Computing Society Biannual Meeting, Santa Fe, NM, January 2013 (PDF).
  • A. Bulut and T.K. Ralphs, Inverse Integer Programming: Complexity and Algorithms, INFORMS Computing Society Biannual Meeting, Santa Fe, NM, January 2013 (PDF).
  • A. Hassanzadeh, T.K. Ralphs, and M. Guzelsoy, A Value Function Approach for Solving Two-stage Stochastic Programs with Mixed Integer Recourse, INFORMS Computing Society Biannual Meeting, Santa Fe, NM, January 2013 (PDF).
  • T.K. Ralphs, A. Bulut, M. O’Sullivan, O. Ozaltin, and B. Hunsaker, GiMPy and GrUMPy: Visualization for Optimization in Python, INFORMS Computing Society Biannual Meeting, Santa Fe, NM, January 2013 (PDF).
  • J.C. Góez, P. Belotti, I. Polik, T.K. Ralphs, and T. Terlaky, Branch and Bound for Mixed Integer Second Order Cone Optimization: Impact of Disjunctive Conic Cuts, INFORMS Annual Conference, Phoenix, AZ, November 2012.
  • T.K. Ralphs, M.V. Galati, and J. Wang, DIP and DIPPy: Towards a Generic, Decomposition-based MIP Solver, INFORMS Annual Conference, Phoenix, AZ, October 2012 (PDF).
  • T.K. Ralphs and S. Yildiz, Some Experiments on Branching with General Disjunctions, INFORMS Annual Conference, Phoenix, AZ, October 2012 (PDF).
  • A. Bulut and T.K. Ralphs, An Algorithm for Solving Inverse Integer Programs, INFORMS Annual Conference, Phoenix, AZ, October 2012 (PDF).
  • A. Hassanzadeh and T.K. Ralphs, An Algorithm for Solving Two-stage Stochastic Programs with Mixed Integer Recourse, INFORMS Annual Conference, Phoenix, AZ, October 2012 (PDF).
  • T.K. Ralphs, T. Koch, and Y. Shinano, Could we Use a Million Cores to Solve a Single Integer Program?, INFORMS Annual Conference, Phoenix, AZ, October 2012 (PDF).
  • T.K. Ralphs, A. Bulut, M. O’Sullivan, O. Ozaltin, and B. Hunsaker, GiMPy and GrUMPy: Visualization for Optimization in Python, INFORMS Annual Conference, Phoenix, AZ, October 2012.
  • T.K. Ralphs, M.V. Galati, and J. Wang, Computational Experience with Generic Decomposition using the DIP framework, RAMP Symposium, Tokyo, Japan, September 2012.
  • T.K. Ralphs, M.V. Galati, and J. Wang, Generic Decomposition-based Solution Methods, International Symposium on Mathematical Programming, Berlin, Germany, August 2012 (PDF).
  • T.K. Ralphs, A. Bulut, A. Lodi, F. Rossi, S. Smriglio, and G. Woeginger, Complexity and Multilevel Optimization, Mixed Integer Programming Workshop, UC Davis, July 2012 (PDF).
  • T.K. Ralphs and Y. Xu, Computational Approaches to Solving Integer Programs in Parallel, INFORMS Annual Conference, Charlotte, NC, November 2011 (PDF).
  • T.K. Ralphs, S. DeNegre, and M. Guzelsoy, Computational Experience Solving Bilevel Programs, INFORMS Annual Conference, Charlotte, NC, November 2011 (PDF).
  • J.C. Góez, P. Belotti, I. Polik, T.K. Ralphs, and T. Terlaky, Generating the Convex Hull of Disjunctions in Mixed Integer Second Order Cone Optimization (MISOCO), INFORMS Annual Conference, Charlotte, NC, November 2011.
  • G. Gamrath et al., MIPLIB 2010, INFORMS Annual Conference, Charlotte, NC, November 2011.
  • J.C. Góez, P. Belotti, I. Polik, T.K. Ralphs, and T. Terlaky, Generating the Convex Hull of a Disjunction for Mixed Integer Second Order Cone Optimization, MOPTA, Bethlehem, PA, August 2011.
  • T.K. Ralphs and Y. Xu, Computational Approaches to Solving Integer Programs in Parallel, SIAM Conference on Optimization, Darmstadt, Germany, May 2011 (PDF).
  • T.K. Ralphs, COIN-OR: Revving Up the Engine, INFORMS Annual Conference, Austin, TX, November 2010 (PDF).
  • T.K. Ralphs, A. Lodi, F. Rossi, and S. Smriglio, Interdiction Branching, INFORMS Annual Conference, Austin, TX, November 2010 (PDF).
  • M. Galati and T.K. Ralphs, Progress Update on COIN/DIP – Decomposition for Integer Programming, INFORMS Annual Conference, Austin, TX, November 2010.
  • A. Mahajan and T.K. Ralphs, Selecting Disjunctions for Solving MILPs, INFORMS Annual Conference, Austin, TX, November 2010.
  • S. DeNegre and T.K. Ralphs, Sensor Placement in Water Networks: An Interdiction Model, INFORMS Annual Conference, Austin, TX, November 2010.
  • J.C. Góez, P. Belotti, I. Polik, T.K. Ralphs, and T. Terlaky, Disjunctive Conic Cuts for Mixed Integer Second Order Cone Optimization, INFORMS Annual Conference, Austin, TX, November 2010.
  • J.C. Góez, P. Belotti, I. Polik, T.K. Ralphs, and T. Terlaky, Disjunctive Conic Cuts for Second Order Cone Optimization, MOPTA, Bethlehem, PA, August 2010.
  • T.K. Ralphs, Benchmarking and Performance Analysis of Optimization Software, CPAIOR 2010, Bologna, Italy, June 2010 (PDF).
  • T.K. Ralphs and Y. Xu, The COIN-OR High-Performance Parallel Search Framework, CPAIOR 2010, Bologna, Italy, June 2010 (PDF).
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, A. Lodi, F. Rossi, and S. Smriglio, Bilevel Integer Linear Programming, Workshop on Combinatorial Optimization, Aussois, France, January 2010 (PDF).
  • T.K. Ralphs, Y. Xu, L. Ladanyi, and M.Saltzman, Implementing Custom Applications with CHiPPS, INFORMS Annual Conference, San Diego, October 2009 (PDF).
  • T.K. Ralphs, Y. Xu, L. Ladanyi, and M.Saltzman, Computational Experience with Parallel Integer Programming using the CHiPPS Framework, INFORMS Annual Conference, San Diego, October 2009 (PDF).
  • M. Guzelsoy, T.K. Ralphs On the Value Function of a Mixed Integer Linear Program, INFORMS Annual Conference, San Diego, October 2009.
  • S. DeNegre, T.K. Ralphs Branch and Cut for Mixed Integer Bilevel Linear Programs, INFORMS Annual Conference, San Diego, October 2009 (PDF).
  • M. Galati and T.K. Ralphs, A Framework for Decomposition in Integer Programming, INFORMS Annual Conference, San Diego, October 2009.
  • T.K. Ralphs, Introduction to COIN-OR Tools for Optimization, Combinatorial Optimization at Work, ZIB, Berlin, September 2009 (PDF).
  • A. Mahajan and T.K. Ralphs, To Branch or To Cut, International Symposium on Mathematical Programming, Chicago, August 2009 (PDF).
  • T.K. Ralphs, A. Lodi, F. Rossi, and S. Smriglio, Bilevel Branching, International Symposium on Mathematical Programming, Chicago, August 2009 (PDF).
  • T.K. Ralphs, S. DeNegre, and E. Suet Tse, A Bilevel Integer Nonlinear Programming Model for Cross-layer Network Design Optimization, International Symposium on Mathematical Programming, Chicago, August 2009 (PDF).
  • M. Galati and T.K. Ralphs, A Framework for Decomposition in Integer Programming, International Symposium on Mathematical Programming, Chicago, August 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, MOPTA 2009, Bethlehem, PA, August 2009 (PDF).
  • T.K. Ralphs and M. Galati, A Framework for Decomposition in Integer Programming, University of Newcastle, Newcastle, NSW, Australia, June 2009 (PDF).
  • T.K. Ralphs, Y. Xu, L. Ladanyi, and M.Saltzman, Doing it in Parallel (DIP) with the COIN-OR High Performance Parallel Search Framework (CHiPPS), University of Newcastle, Newcastle, NSW, Australia, May 2009 (PDF).
  • A. Mahajan and T.K. Ralphs, In Search of Optimal Disjunctions in Mixed Integer Programming, University of Newcastle, Newcastle, NSW, Australia, May 2009 (PDF).
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, University of Newcastle, Newcastle, NSW, Australia, May 2009 (PDF).
  • T.K. Ralphs and M. Guzelsoy, Duality in Mixed Integer Linear Programming, University of Newcastle, Newcastle, NSW, Australia, May 2009 (PDF).
  • T.K. Ralphs and M. Guzelsoy, Duality in Mixed Integer Linear Programming, Monash University, Melbourne, VIC, Australia, April 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, University of Melbourne, VIC, Australia, April 2009.
  • A. Mahajan and T.K. Ralphs, In Search of Optimal Disjunctions in Mixed Integer Programming, Monash University, Melbourne, VIC, Australia, April 2009.
  • T.K. Ralphs and M. Galati, A Framework for Decomposition in Integer Programming, Monash University, Melbourne, VIC, Australia, March 2009.
  • T.K. Ralphs, Y. Xu, L. Ladanyi, and M. Saltzman, Doing it in Parallel (DIP) with the COIN-OR High Performance Parallel Search Framework (CHiPPS), Monash University, Melbourne, VIC, Australia, March 2009.
  • T.K. Ralphs and M. Guzelsoy, Duality in Mixed Integer Linear Programming, University of Canterbury, Christchurch, New Zealand, February 2009.
  • T.K. Ralphs, Introduction to COIN-OR: Open Source Software for Optimization, University of Canterbury, Christchurch, New Zealand, February 2009 (PDF).
  • T.K. Ralphs and M. Guzelsoy, On the Value Function of a General Mixed Integer Linear Program, Victoria University of Wellington, New Zealand, January 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, Victoria University of Wellington, New Zealand, January 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, University of Auckland, New Zealand, January 2009.
  • A. Mahajan and T.K. Ralphs, In Search of Optimal Disjunctions in Mixed Integer Programming, Argonne National Labs, Chicago, IL, December 2008 (PDF).
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, Université Bordeaux, France, December 2008 (PDF).
  • T.K. Ralphs, Short Course in Bilevel Programming, Università di Bologna, Italy, December 2008.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, Politecnico di Milano, November 2008.
  • T.K. Ralphs, Optimization and Combinatorial Auctions, Institute for Advanced Studies, Università di Bologna, Italy, November 2008.
  • S. Denegre and T.K. Ralphs, A Mixed Integer Bilevel Programming Solver, INFORMS Annual Meeting, Washington, D.C., October, 2008.
  • M. Guzelsoy and T.K. Ralphs, Approximating the Value Function of a Mixed Integer Linear Program, INFORMS Annual Meeting, Washington, D.C., October, 2008.
  • Y. Xu, T.K. Ralphs, L. Ladanyi, and M.J. Saltzman, Developing Applications Based on CHiPPS, INFORMS Annual Meeting, Washington, D.C., October, 2008.
  • S. Denegre and T.K. Ralphs, Mixed Integer Interdiction, INFORMS Annual Meeting, Washington, D.C., October, 2008.
  • A. Mahajan and T.K. Ralphs, On Branching on General Hyperplanes for Mixed Inteer Programming, INFORMS Annual Meeting, Washington, D.C., October, 2008.
  • M. Guzelsoy, A. Mahajan, and T.K. Ralphs, The SYMPHONY MIP Solver, INFORMS Annual Meeting, Washington, D.C., October, 2008.
  • M. Guzelsoy and T.K. Ralphs, Warm Starting for Mixed Integer Linear Programming, INFORMS Annual Meeting, Washington, D.C., October, 2008.
  • T.K. Ralphs and M. Guzelsoy, On the Value Function of a General Mixed Integer Linear Program, XXXIX Annual Conference of Italian Operational Research Society, Ischia, Italy, September, 2008 (PDF).
  • Z. Akca, R. Berger, T.K. Ralphs, Optimizing Location, Routing, and Scheduling Decisions Under Capacity Restrictions, Column Generation 2008, Aussois, France, June 2008.
  • M. Galati, T.K. Ralphs, A Framework for Decomposition in Integer Programming, Column Generation 2008, Aussois, France, June 2008.
  • Y. Xu, T.K. Ralphs, M.J. Saltzman, and L. Ladányi, The CHiPPS Framework for Parallel Tree Search and Integer Programming, INFORMS Optimization Society Conference, Atlanta, GA, March, 2008.
  • M. Galati, T.K. Ralphs, DECOMP: A Framework for Decomposition in Integer Programming, INFORMS Optimization Society Conference, Atlanta, GA, March, 2008.
  • T.K. Ralphs and M. Guzelsoy, The Value Function of a Mixed Integer Program with a Single Constraint, INFORMS Optimization Society Conference, Atlanta, GA, March, 2008.
  • Y. Xu, T.K. Ralphs, M.J. Saltzman, and L. Ladányi, A Framework for Implementing Parallel Tree Search Algorithms, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • M. Galati and T.K. Ralphs, DECOMP: A Framework for Decomposition in Integer Programming, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • O. Osaltyn, B. Hunsaker, and T.K. Ralphs, Estimating Solution Time of Branch-and-bound Algorithm, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • B. Hunsaker, O. Osaltyn, and T.K. Ralphs, Visualization Tools for Branch-and-bound Algorithms, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • Z. Akca, R. Berger, and T.K. Ralphs, Solving Integrated Location, Routing and Scheduling Problems, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • S. DeNegre and T.K. Ralphs, Solution Approaches for Integer Bilevel Programs, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • Y. Xu, T.K. Ralphs, M.J. Saltzman, and L. Ladányi, The Design and Implementation of BLIS, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • M. Guzelsoy and T.K. Ralphs, The SYMPHONY Callable Library, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • M. Guzelsoy and T.K. Ralphs, The Value Function of a Mixed-integer Linear Program with a Single Constraint, INFORMS Annual Conference, Seattle, WA, November, 2007.
  • T.K. Ralphs and M. Guzelsoy, Warm Starting for Mixed Integer Linear Programs, INFORMS Annual Conference, Seattle, WA, November, 2007 (PDF).
  • S. DeNegre and T.K. Ralphs, Integer Bilevel Linear Programming: A Novel Branch-and-Cut Algorithm, INFORMS International Conference, Puerto Rico, July, 2007.
  • B. Hunsaker, O. Osaltyn, and T.K. Ralphs, Visualization Tools for Branch-and-Bound, The Tenth INFORMS Computing Society Conference, Miami, FL, January, 2007.
  • T.K. Ralphs, M. Guzelsoy, J.T. Linderoth, M.J. Saltzman, and M. Wiecek, Using Cyberinfrastructure Tools to Solve Biobjective Integer Programs, INFORMS Annual Conference, Pittsburgh, PA, November 2006 (PDF).
  • M.J. Saltzman, L. Ladányi, and T.K. Ralphs, The COIN-OR Open Solver Interface: Inside a Portable Solver API, INFORMS Annual Conference, Pittsburgh, PA, November 2006.
  • K. Martin, JP Fasano, and T.K. Ralphs, Source Code Not Required: Using the COIN-OR Binaries, INFORMS Annual Conference, Pittsburgh, PA, November 2006.
  • M.V. Galati and T.K. Ralphs, DECOMP: A Framework for Decomposition in Integer Programming, INFORMS Annual Conference, Pittsburgh, PA, November 2006.
  • Y. Xu, T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, INFORMS Annual Conference, Pittsburgh, PA, November 2006.
  • S. DeNegre and T.K. Ralphs, Multiobjective Mixed-Integer Stackelberg Games, The International Symposium on Mathematical Programming, Rio de Janeiro, Brazil, August 2006.
  • T.K. Ralphs, Y. Xu, M.J. Saltzman, and L. Ladányi, Parallel Integer Programming with ALPS, The International Symposium on Mathematical Programming, Rio de Janeiro, Brazil, August 2006 (PDF).
  • T.K. Ralphs, The SYMPHONY Framework for Mixed-Integer Linear Programming: Basic Features, DIMACS Workshop on COIN-OR, Rutgers University, July 2006 (PDF).
  • T.K. Ralphs, The SYMPHONY Framework for Mixed-Integer Linear Programming: Advanced Features, DIMACS Workshop on COIN-OR, Rutgers University, July 2006 (PDF).
  • T.K. Ralphs and S. DeNegre, Multiobjective Mixed-Integer Stackelberg Games, EURO XXI, Reykjavic, Iceland, June 2006 (PDF).
  • M.J. Saltzman, Y. Xu, T.K. Ralphs, and L. Ladányi, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, EURO XXI, Reykjavic, Iceland, June 2006.
  • T.K. Ralphs, M. Saltzman, and M. Galati, Using COIN-OR to Solve the Uncapacitated Facility Location Problem, EURO XXI, Reykjavic, Iceland, June 2006 (PDF).
  • T.K. Ralphs, M. Guzelsoy, J.T. Linderoth, M.J. Saltzman, and M. Wiecek, Biobjective Integer Programming, MIP 2006: Workshop on Mixed-Integer Programming, University of Miami, June 2006 (PS PDF).
  • T.K. Ralphs and M. Guzelsoy, The SYMPHONY Callable Library, INFORMS Annual Conference, San Francisco, CA, November 2005 (PS PDF).
  • Y. Xu, T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, INFORMS Annual Conference, San Francisco, CA, November 2005 (PS PDF).
  • M.V. Galati and T.K. Ralphs, DECOMP: A Framework for Decomposition and Dynamic Cut Generation in Integer Programming, INFORMS Annual Conference, San Francisco, CA, November 2005.
  • T.K. Ralphs and A. Pilatin, Parallel Solution of Vehicle Routing Problems, INFORMS Annual Conference, San Francisco, CA, November 2005 (PS PDF).
  • Y. Xu, T.K. Ralphs, L. Ladányi, and M.J. Saltzman, ALPS: A Framework for Implementing Parallel Tree Search Algorithms, Fourth International Workshop of the EURO Working Group on Parallel Processing in Operations Research, Mont Tremblant, Canada, January 2005.
  • T.K. Ralphs and M. Guzelsoy, The SYMPHONY Callable Library for Mixed-Integer Linear Programming, The Ninth INFORMS Computing Society Conference, Annapolis, MD, January 2005 (PS PDF).
  • M.V. Galati and T.K. Ralphs, DECOMP: A Framework for Decomposition and Dynamic Cut Generation in Integer Programming, The Ninth INFORMS Computing Society Conference, Annapolis, MD, January 2005.
  • Y. Xu, T.K. Ralphs, L. Ladányi, and M.J. Saltzman, ALPS: A Framework for Implementing Parallel Tree Search Algorithms, The Ninth INFORMS Computing Society Conference, Annapolis, MD, January 2005.
  • T.K. Ralphs and M. Guzelsoy, Duality, Warm Starting, and Sensitivity Analysis in Integer Programming, the Institute for Operations Research and Management Science Annual Conference, Denver, CO, October 2004 (PS PDF).
  • M.V. Galati and T.K. Ralphs, A Framework for Decomposition and Dynamic Cut Generation in Integer Programming, the Institute for Operations Research and Management Science Annual Conference, Denver, CO, October 2004.
  • Y. Xu, T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Framework for Implementing Parallel Tree Search Algorithms, the Institute for Operations Research and Management Science Annual Conference, Denver, CO, October 2004.
  • M.J. Saltzman, L. Ladányi, and T.K. Ralphs , The New COIN-OR Open Solver Interface, the Institute for Operations Research and Management Science Annual Conference, Denver, CO, October 2004.
  • T.K. Ralphs, Computational Infrastructure for Operations Research: The COIN-OR Project, International Conference on Continuous Optimization, Rensselaer Polytechnic Institute, August 2004 (PS PDF).
  • T.K. Ralphs et.al, COIN-OR: Software Tools for Optimization (Workshop), CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004.
  • T.K. Ralphs, M. Guzelsoy, M.J. Saltzman, and M. Wiecek, An Open Source Solver for Bicriteria Mixed Integer Programs, CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004 (PS PDF).
  • M.V. Galati and T.K. Ralphs, DECOMP: A Framework for Decomposition and Dynamic Cut Generation in Integer Programming, CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004.
  • Y. Xu, T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Framework for Scalable Parallel Tree Search, CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004 (PS PDF).
  • M.J. Saltzman, L. Ladányi, and T.K. Ralphs, The COIN-OR Open Solver Interface: Technology Overview, CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004.
  • T.K. Ralphs and M.V. Galati, Decomposition and Dynamic Cut Generation in Integer Programming, the Eighth Aussois International Workshop on Combinatorial Optimization, Aussois, France, January 2004 (PS PDF).
  • Y. Xu, T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Framework for Scalable Parallel Tree Search, the Institute for Operations Research and Management Science Annual Conference, Atlanta, GA, October 2003.
  • T.K. Ralphs and M.V. Galati, Decomposition and Dynamic Cut Generation in Integer Programming, the Institute for Operations Research and Management Science Annual Conference, Atlanta, GA, October 2003 (PS PDF).
  • M.J. Saltzman, L. Ladányi, and T.K. Ralphs , New Developments in The COIN Open Solver Interface, the Institute for Operations Research and Management Science Annual Conference, Atlanta, GA, October 2003.
  • B. Hunsaker, J. Forrest, R. Lougee-Heimer, T.K. Ralphs, and M.J. Saltzman, A Gentle Introduction to COIN-OR’s Open Solver Interface, the Institute for Operations Research and Management Science Annual Conference, Atlanta, GA, October 2003.
  • T.K. Ralphs, L. Ladányi, M.J. Saltzman, and Y. Xu, A Framework for Scalable Parallel Tree Search, the International Symposium on Mathematical Programming, Copenhagen, Denmark, August 2003. (PS PDF).
  • M. Galati and T.K. Ralphs, Decomposition and Dynamic Cut Generation in Integer Programming, the International Symposium on Mathematical Programming, Copenhagen, Denmark, August 2003. (PS PDF).
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman , COIN-OR: Software Tools for Implementing Custom Solvers, the International Symposium on Mathematical Programming, Copenhagen, Denmark, August 2003 (Workshop). (PS PDF).
  • M.J. Saltzman, L. Ladányi, and T.K. Ralphs , The COIN Open Solver Interface: A Progress Report, the International Symposium on Mathematical Programming, Copenhagen, Denmark, August 2003.
  • T.K. Ralphs and M. Galati, Decomposition and Dynamic Cut Generation in Integer Programming, Discussions on Mixed Integer Programming ’03 , Columbia University, June 2003. (PS PDF).
  • T.K. Ralphs, L. Ladányi and M.J. Saltzman, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, The Institute for Operations Research and Management Science Conference, San Jose, CA, November 2002. (PS PDF).
  • M. Galati and T.K. Ralphs, Decomposition-based Algorithms for Large-scale Discrete Optimization, The Institute for Operations Research and Management Science Annual Conference, San Jose, CA, November 2002.
  • M.J. Saltzman, T.K. Ralphs, and L. Ladányi, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, The International Federation of Operations Research Societies Conference, University of Edinburgh, July 2002.
  • T.K. Ralphs, The Common Optimization Interface for Operations Research (COIN-OR) Initiative, The International Federation of Operations Research Societies Conference, University of Edinburgh, July 2002. (PS PDF).
  • M.J. Saltzman, T.K. Ralphs, and L. Ladányi, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, The Integer Programming Conference in Honor of Egon Balas’ 80th Birthday, Carnegie-Mellon University, June 2002.
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Library Hierarchy for Scalable Parallel Tree Search, Parallel Processing in Operations Research , Guadeloupe, France, May 2002 (PS PDF).
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman, Implementing Scalable Parallel Search Algorithms for Data-intensive Applications, International Conference on Computational Science, University of Amsterdam, April 2002 (PS PDF).
  • T.K. Ralphs and J.C. Hartman, Branch and Cut for Capacitated Network Routing, The Institute for Operations Research and Management Science Annual Conference, Miami, FL, November 2001 (PS PDF).
  • L. Ladányi and T.K. Ralphs, Branch, Cut, and Price: The Next Generation, The Institute for Operations Research and Management Science Conference, Miami, FL, November 2001.
  • M. Galati and T.K. Ralphs, Valid Inequalities for the Cable Trench Problem, The Institute for Operations Research and Management Science Annual Conference, Miami, FL, November 2001.
  • T.K. Ralphs, Branch, Cut, and Price for Routing and Packing Problems , INFORMS International, Maui, HI, June 2001 (PS PDF).
  • T.K. Ralphs, Implementing Branch, Cut, and Price Algorithms , Workshop on Novel Approaches to Hard Discrete Optimization Problems, University of Waterloo, April 2001 (PS PDF).
  • T.K. Ralphs, A Branch and Cut Algorithm for the Vehicle Routing Problem, The Institute for Operations Research and Management Science Conference, San Antonio, TX, November 2000 (PS PDF).
  • T.K. Ralphs, Solving Hard Combinatorial Problems: A Research Overview, Department of Industrial and Manufacturing Systems Engineering Seminar Series, Lehigh University, Bethlehem, PA, September 2000 (PS PDF).
  • T.K. Ralphs, Parallel Branch and Cut for Dummies, International Symposium on Mathematical Programming, Atlanta, GA, August 2000 (PS PDF).
  • T.K. Ralphs, L. Kopman, W. Pulleyblank, and L.E. Trotter Jr., A Generic Separation Algorithm for Combinatorial Optimization, DONET Workshop on Combinatorial Optimization, Aussois, France, March 2000 (Instructor) (PS PDF).
  • T.K. Ralphs, W. Pulleyblank, and L.E. Trotter Jr., A New Generic Separation Algorithm and Its Application to the Vehicle Routing Problem The Institute for Operations Research and Management Science Annual Conference, Philadelphia, PA, November 1999 (PS PDF).
  • T.K. Ralphs and L. Ladányi, Computational Experience with Generic Parallel Branch and Cut, The Institute for Operations Research and Management Science Annual Conference, Seattle, WA, October 1998 (PS PDF).
  • T.K. Ralphs, W. Pulleyblank, and L. Trotter Jr., Parallel Branch and Cut for Vehicle Routing, The International Symposium on Mathematical Programming ’97, Lausanne, Switzerland, August 1997.
  • M. Eso, L. Ladányi, T.K. Ralphs, and L.E. Trotter Jr., Fully Parallel Generic Branch-and-Cut Framework, The 8th SIAM Conference on Parallel Processing for Scientific Computing, Minneapolis, MN, March 1997.

Seminar Presentations

  • T.K. Ralphs, Multilevel Optimization and Game Theory: Applications and Algorithms, Tsinghua University, Beijing, China, March 2018
  • T.K. Ralphs, Algorithms: Why and How, Guest Lecture, Introduction to Operations Research, Cal Poly, San Luis Obispo, CA, March 2017 (PDF)
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, and A. Hassanzadeh, and S. Tahernajad, Duality, Multilevel Optimization, and Game Theory: Algorithms and Applications, Virginia Tech, Blacksburg, VA, February 2017 (PDF)
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, and A. Hassanzadeh, and S. Tahernajad, Duality, Multilevel Optimization, and Game Theory: Algorithms and Applications, Norwegian School of Economics, Bergen, Norway, September 2016 (PDF)
  • T.K.R., Duality and Warm-starting in MILP, Zuse Institute Berlin, Berlin, Germany, September 2016 (PDF)
  • T.K. Ralphs, A. Bulut, S. DeNegre, M. Guzelsoy, A. Hassanzadeh, Multistage Integer Programming: Algorithms and Complexity, University of Houston, March 2014.
  • T.K. Ralphs, A. Bulut, S. DeNegre, M. Guzelsoy, A. Hassanzadeh, Multilevel and Multistage Integer Programming: Algorithms and Complexity, Oakland University, November 2013.
  • T.K. Ralphs, A. Bulut, S. DeNegre, M. Guzelsoy, A. Hassanzadeh, Multilevel and Multistage Integer Programming: Algorithms and Complexity, University of Florida, October 2013.
  • T.K. Ralphs, A. Bulut, S. DeNegre, M. Guzelsoy, A. Hassanzadeh, Multilevel Integer Programming, The Polynomial Time Hierarchy, and Parallel Computing, Penn State University, March 2013
  • T.K. Ralphs, A. Bulut, A. Lodi, F. Rossi, S. Smriglio, and G. Woeginger, Complexity and Multilevel Optimization, University of Kyoto, Kyoto, Japan, September 2012.
  • T.K. Ralphs, A. Bulut, A. Lodi, F. Rossi, S. Smriglio, and G. Woeginger, Complexity and Multilevel Optimization, Chuo University, Tokyo, Japan, September 2012.
  • T.K. Ralphs, M. Galati, and J. Wang, DIP with CHiPPS: Decomposition in Integer Linear Programming, CSIRO, Melbourne, Australia, December 2011 (PDF).
  • T.K. Ralphs Making Molehills out of Mountains: A Guided Tour of Discrete Optimization, CSIRO, Melbourne, Australia, December 2011 (PDF).
  • T.K. Ralphs, M. Galati, and J. Wang, DIP with CHiPPS: Decomposition in Integer Linear Programming, University of Michigan, Ann Arbor, MI, November 2011 (PDF).
  • T.K. Ralphs and M. Galati, DIP with CHiPPS: Decomposition in Integer Linear Programming, ExxonMobil Research, Annandale, NJ, October 2011 (PDF).
  • T.K. Ralphs, S. DeNegre, and M. Guzelsoy, Bilevel Integer Linear Programming, University of Edinburgh, Edinburgh, UK, May 2011 (PDF).
  • T.K. Ralphs and M. Galati, Decomposition in Integer Linear Programming, Cornell University, Ithaca, NY, March 2011 (PDF).
  • T.K. Ralphs, S. DeNegre, and M. Guzelsoy, Bilevel Integer Linear Programming, Northwestern University, Chicago, IL, January 2011 (PDF).
  • T.K. Ralphs, S. DeNegre, M. Guzelsoy, A. Lodi, F. Rossi, and S. Smriglio, Bilevel Integer Programming, University of Pittsburgh, Pittsburgh, PA, October 2010 (PDF).
  • T.K. Ralphs and M. Galati, DIP with ChiPPS: Decomposition Methods for Integer Linear Programming, University of Bordeaux, Bordeaux, France, June 2010 (PDF).
  • T.K. Ralphs and M. Galati, DIP with ChiPPS: Decomposition Methods for Integer Linear Programming, University of Edinburgh, Edinburgh, Scotland, June 2010.
  • T.K. Ralphs, Introduction to COIN-OR Tools for Optimization, COR@L Seminar, Lehigh University, January 2010 (PDF).
  • T.K. Ralphs and M. Guzelsoy, Duality in Mixed Integer Linear Programming, University of Newcastle, Newcastle, Australia, May 2009 (PDF).
  • T.K. Ralphs and M. Guzelsoy, Duality in Mixed Integer Linear Programming, Monash University, Melbourne, Australia, April 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, University of Melbourne, Australia, April 2009.
  • A. Mahajan and T.K. Ralphs, In Search of Optimal Disjunctions in Mixed Integer Programming, Monash University, Melbourne, Australia, April 2009.
  • T.K. Ralphs and M. Galati, A Framework for Decomposition in Integer Programming, Monash University, Melbourne, Australia, March 2009 (PDF).
  • T.K. Ralphs, Y. Xu, L. Ladanyi, and M.Saltzman, Doing it in Parallel (DIP) with the COIN-OR High Performance Parallel Search Framework (CHiPPS), Monash University, Melbourne, Australia, March 2009 (PDF).
  • T.K. Ralphs and M. Guzelsoy, Duality in Mixed Integer Linear Programming, University of Canterbury, Christchurch, New Zealand, February 2009 (PDF).
  • T.K. Ralphs, Introduction to COIN-OR: Open Source Software for Optimization, University of Canterbury, Christchurch, New Zealand, February 2009 (PDF).
  • T.K. Ralphs and M. Guzelsoy, On the Value Function of a General Mixed Integer Linear Program, Victoria University of Wellington, New Zealand, January 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, Victoria University of Wellington, New Zealand, January 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, University of Auckland, New Zealand, January 2009.
  • T.K. Ralphs and S. Denegre, Bilevel Integer Linear Programming, Università degli Studi dell’Aquila, Italy, September 2008 (PDF).
  • T.K. Ralphs, Y. Xu, L. Ladanyi, and M.Saltzman, Doing it in Parallel (DIP) with the COIN-OR High Performance Parallel Search Framework (CHiPPS), Graduate Research Seminar, Pennsylvania State University, April, 2008.
  • T.K. Ralphs and M. Guzelsoy, The Value Function of a Mixed Integer Program with a Single Constraint, COPTA Seminar, University of Wisconsin-Madison, February, 2008.
  • T.K. Ralphs, M. Guzelsoy, J.T. Linderoth, M.J. Saltzman, and M. Wiecek, Biobjective Integer Programming, SAS Institute , June 2006. (PS PDF).
  • T.K. Ralphs, M. Guzelsoy, M. Saltzman, and M. Wiecek, Bioobjective Integer Programming, Rutgers University, Department of Industrial and Systems Engineering, Piscataway, NJ, October 2005 (PS PDF).
  • T.K. Ralphs and M. Guzelsoy, Duality, Sensitivity Analysis, and Warm Starting, SAS Institute , August 2005. (PS PDF).
  • T.K. Ralphs, Making Molehills out of Mountains: A Guided Tour of Large-scale Discrete Optimization, Mathematics Department Colloquium, April 2005. (PS PDF).
  • T.K. Ralphs, Capacitated Vehicle Routing and Some Related Problems, Computer Science and Engineering Seminar Series, March 2005. (PS PDF).
  • T.K. Ralphs, Integer Programming: A Research Overview , Lehigh IGERT Seminar, September 2004. (PS PDF).
  • T.K. Ralphs, Integer Programming: A Research Overview , Lehigh IGERT Seminar, September 2003. (PS PDF).
  • T.K. Ralphs, Solving Hard Combinatorial Problems: A Research Overview , Lehigh IGERT Seminar, October 2002. (PS PDF).
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A New Framework for Scalable Parallel Tree Search, Lehigh ISE Optimization Seminar, September 2002. (PS PDF).
  • T.K. Ralphs, Solving Hard Combinatorial Problems: A Research Overview, Process Modeling and Control Seminar, Department of Chemical Engineering, Lehigh University, March 2002(PS PDF).
  • T.K. Ralphs, Decomposition-based Algorithms for Large-scale Discrete Optimization, National University of Singapore, March 2002 (PS PDF).
  • T.K. Ralphs, Capacitated Vehicle Routing and Some Related Problems, Rutgers University, Department of Industrial and Systems Engineering, Piscataway, NJ, November 2001 (PS PDF).
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, Rutgers Center for Operations Research (RUTCOR), Rutgers University, Piscataway, NJ, Sepember 2001. (PS PDF).
  • T.K. Ralphs, Branch, Cut, and Price Algorithms for Large-scale Discrete Optimization, National University of Singapore, August 2001 (PS PDF).
  • T.K. Ralphs and J.C. Hartman, Capacitated Network Routing, National University of Singapore, August 2001 (PS PDF).
  • T.K. Ralphs, L. Ladányi, and M.J. Saltzman, A Library Hierarchy for Implementing Scalable Parallel Search Algorithms, IBM T.J. Watson Research Center, Yorktown Heights, NY, August 2001 (PS PDF).
  • T.K. Ralphs, Decomposition-based Algorithms for Discrete Optimization
    , IBM T.J. Watson Research Center, Yorktown Heights, NY, August 2001. (slides available by request).
  • T.K. Ralphs and J.C. Hartman, Capacitated Network Routing , IBM T.J. Watson Research Center, Yorktown Heights, NY, July 2001 (PS PDF).
  • T.K. Ralphs, W. Pulleyblank, and L.E. Trotter Jr., A New Generic Separation Algorithm for Combinatorial Optimization, IBM T.J. Watson Research Center, Yorktown Heights, NY, November 1999 (PS PDF).
  • T.K. Ralphs, Polyhedral Aspects of the Mixed Postman Problem, Cornell Computational Optimization Project Colloquium, Ithaca, NY, February 1994.
  • T.K. Ralphs and L. Ladányi, Computational Experience with a New Heuristic for the Crew Scheduling Problem, Cornell Computational Optimization Project Colloquium, Ithaca, NY, October 1993.

Conference Sessions Chaired

  • Open Source and COIN-OR Optimization, International Federation of
    Operations Research Societies Triennial Meeting    , Barcelona, Spain, July 2014.
  • Global Optimization and Mixed-Integer Nonlinear Programming, INFORMS Annual Conference, Minneapolis, MN, October 2013
  • Multilevel Optimization, INFORMS Annual Conference, Minneapolis, MN, October 2013
  • Stochastic Optimization, INFORMS Annual Conference, Minneapolis, MN, October 2013
  • Tools and Techniques for Modeling with Python, INFORMS Annual Conference, Phoenix, AZ, October 2012
  • Panel Discussion: COIN-OR Technology Forum, INFORMS Annual Conference, Charlotte, NC, November 2011.
  • Panel Discussion: COIN-OR Technology Forum, INFORMS Annual Conference, Austin, TX, November 2010.
  • Open Source MIP Solvers, The Institute for Operations Research and Management Science Conference, Seattle, WA, November 2007.
  • Modeling Languages in the Classroom, The Institute for Operations Research and Management Science Conference, Seattle, WA, November 2007.
  • Optimization Software in the Classroom, The Institute for Operations Research and Management Science Conference, Seattle, WA, November 2007.
  • Open Source Modeling Tools, The Institute for Operations Research and Management Science Conference, San Francisco, CA, November 2005.
  • Integer Programming Software, Institute for Operations Research and Management Science Annual Conference, Denver, CO, October 2004.
  • COIN-OR: Software Tools for Optimization, CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004.
  • Computational Mixed-Integer Programming, CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004.
  • Open Source Optimization Tools, CORS/INFORMS Joint International Meeting, Banff, Alberta, Canada, May 2004.
  • COIN-OR: Software Tools for Implementing Custom Solvers , the Institute for Operations Research and Management Science Annual Conference, Atlanta, GA, October 2003.
  • Decomposition and Dynamic Cut Generation, the International Symposium on Mathematical Programming, Copenhangen, Denmark, August 2003.
  • COIN-OR: Software Tools for Implementing Custom Solvers , the International Symposium on Mathematical Programming, Copenhangen, Denmark, August 2003.
  • Standards and Interfaces in Mathematical Programming, The Institute for Operations Research and Management Science Annual Conference, San Jose, CA, November 2002.
  • Software Tools for Parallel Processing, The Institute for Operations Research and Management Science Annual Conference, San Jose, CA, November 2002.
  • Workshop: Software Tools for Implementing Branch, Cut, and Price Algorithms, The Institute for Operations Research and Management Science Annual Conference, San Jose, CA, November 2002.
  • Branch and Cut Methods , The Institute for Operations Research and Management Science Annual Conference, Miami, FL, November 2001.
  • Parallel Discrete Optimization with Applications , International Symposium on Mathematical Programming, Georgia Institute of Technology, August 2000.

Conference Organization

Conference Workshops Chaired

Student Supervision

  • Ph.D Dissertation Advisor and Committee Chair
    • Sean Kelley, ISE, TBD.
    • Hesam Shaelaie, ISE, TBD.
    • Samira Fallah, ISE, TBD.
    • Yu Xie, ISE, TBD.
    • Suresh Bolusani, ISE, TBD.
    • Jiadong Wang, ISE, Advances in Integrated Decomposition Methods for Integer Programming.
    • Sahar Tahernajad, ISE, Two-stage Mixed Integer Stochastic Bilevel Linear Optimization, December 2019.
    • Aykut Bulut, ISE, Computational Methods for Discrete Conic Optimization Problems, December 2017.
    • Anahita Hassanzadeh, ISE, Two-stage Stochastic Mixed Integer Optimization, September 2015.
    • Scott Denegre, ISE, Interdiction and Discrete Lievel Linear Programming, May 2011.
    • Matthew Galati, ISE, Decomposition in Integer Linear Programming, December 2009 (Dissertation).
    • Menal Guzelsoy, ISE, Dual Methods in Mixed Integer Linear Programming, December 2009 (Dissertation).
    • Zeliha Akca, ISE, Integrated Location, Routing, and Scheduling Problems: Models and Algorithms, December 2009 (Dissertation).
    • Ashutosh Mahajan, ISE, On Selecting Disjunctions in Mixed Integer Linear Programming, May 2009(Dissertation).
    • Yan Xu, ISE, Scalable Algorithms for Parallel Tree Search, December 2007 (Dissertation).
  • Ph.D Dissertation Committee Chair
    • Jerry Shen, ISE, Solving Multi-stage Stochastic Linear Programs on the Computational Grid.
    • Jim Ostrowski, ISE, Symmetry in Mixed Integer Programming, May 2009.
    • Wasu Glankwamdee, ISE, Branch and Bound on Computational Grids, August 2008.
    • Kumar Abhishek, ISE, Topics in Mixed Integer Nonlinear Programming, May 2008.
  • Ph.D Dissertation Committee Member
    • Sertalp Cay, ISE, TBD.
    • Sambhawa Priya, CSE, TBD.
    • Seyedalireza Yektamaram, ISE, Optimization Algorithms for Machine Learning Designed
      for Parallel and Distributed Environments      .
    • Zhengxiang Pan, CSE, Towards a Global Scale Semantic Web.
    • Xiaocun Que, ISE, Randomized Algorithms for Nonconvex Nonsmooth Optimization, May 2015.
    • Julio Goez, ISE, Mixed Integer Second Order Cone Optimization, Disjunctive Conic Cuts: Theory and Experiments, August 2013.
    • Tolga Seyhan, ISE, Network Design Under Competition, May 2012.
    • Cagri Latifoglu, ISE, Models for Production Planning and Power Procurement Portfolios, May 2012.
    • Udom Janjarassuk, ISE, Using the Computational Grid for the Effective Solution of Stochastic Programs, May 2009.
    • Qing Ye, CSE, Dynamic Multicast and Time Synchronization in Wide-area Sensor Networks, December 2007.
    • Brian Heinold, Mathematics, Sum List Coloring and Choosability, May 2006.
    • Joao Goncalves, ISE, Extensions of von Neumann’s Algorithm for Linear Programming, May 2005.
    • Lilong Huang, Chemical Engineering, Constrained Closed-loop Optimal Control, May 2005.
    • Jinlong Ban, ISE, Lehigh University, The Generalized Parallel Replacement Problem, December 2003.
  • M.S. Advisor
    • Shelley Heist, ISE, Lehigh University, Constraint Programming and Sourcing Problems, May 2003.
    • Andrew Hofmann, ISE, Lehigh University, The Mixed Postman Problem, May 2003.

Student Awards

  • Suresh Bolusani, Van Hoesen Family Best Publication Award, Industrial and Systems Engineering, Lehigh University, April 2020.
  • Sahar Tahernejad, Best Poster Award (Honorable mention), Mixed Integer Programming Workshop, Clemson University, June 2018.
  • Sahar Tahernejad, Van Hoesen Family Best Publication Award, Industrial and Systems Engineering, Lehigh University, April 2017.
  • INFORMS Transportation and Logistics Society Dissertation Prize
    • Zeliha Akca, 2010 (runner-up)
  • ISE graduate student of the year
    • Matthew Galati, 2003
    • Menal Guzelsoy, 2004
    • Suresh Bolusani, 2017
  • Lehigh Engineering Ingenuity Award for Graduate Research and Scholarship
    • Matthew Galati, 2004
    • Menal Guzelsoy, 2005
  • Computational Interface for Operations Research Open Source Coding Contest
    • Yan Xu, First Place, 2003
  • First Open Contest of Parallel Coding
    • Yan Xu and Ted Ralphs, First Place, 2007

Courses Developed and Taught

Service

  • University
    • Computational Optimization Research at Lehigh (COR@L) Laboratory, co-founder and director, September 2004 – present.
    • Lehigh Research Computing Steering Committee.
      • Co-founder and co-chairman, January 2004 – May 2016.
      • Member, May 2016 – present.
    • Manager of Research Computing Search Committee, co-chair, January 2014 – June 2014.
    • Smart Grid Cluster Hiring Search Committee, September 2011 – May 2013.
    • Cluster Hiring Proposal Development Committee: Big Analytics, Co-chair, Fall 2012 (Finalist).
    • Cluster Hiring Proposal Development Committee: Computation Science and Engineering, Co-chair, Fall 2011.
    • Working Group on Cluster Development (Strategic Planning Front-runner Initiative), March 2010 – May 2010.
    • Coordinator of university-wide IBM SUR grant application, September 2007–September 2008.
    • Mathematics Search Committee, member, September 2005 – May 2006.
    • Major Research Instrumentation Proposal review committee, September 2004 – May 2005.
  • College
    •  Joint ISE/CSE Faculty Search Committee, Chair, August 2023-present.
    • RCEAS Tenure Committee, August 2021 – present.
    • CEE Department Chair Search Committee, August 2019 – May 2021.
    • CSE Faculty Search Committee, member, September 2013 – May 2014.
    • CSE Faculty Search Committee, member, September 2009 – May 2010.
    • CSE Faculty Search Committee, member, September 2007 – May 2008.
    • RCEAS Tenure Committee, August 2009 – May 2011.
    • RCEAS committee on Computational Science and Engineering, August 2009 – June 2010.
    • ISE Department Chair Search Committee, member, April 2007 – December 2007.
    • RCEAS Dean’s Research Advisory Council, member, January 2007 – May 2008.
    • RCEAS Engineering Ingenuity Awards Committee, member, April 2005.
    • RCEAS Computational Sciences Committee, member, September 2001 – May 2003.
    • RCEAS Mathematics Curriculum Review Committee, member, September 2001 – May 2003.
    • RCEAS Freshman Advisor, September 2002 – May 2003.
    • Molecular Modeling Search Committee, member, September 2002 – May 2003.
    • Chemical Engineering Search Committee, member, September 2001 – May 2002.
  • Department
    • ISE Faculty Search Committee, Chair, August 2019 – May 2020.
    • Interim Department Chair, August 2017 – August 2018.
    • ISE Professor of Practice Search Committee, Chair, September 2015–May 2016.
    • Data Science Strategy Committee, Chair, January 2015–December 2015.
    • Undergraduate Curriculum Committee, member, September 2014 – present.
      • IT Curriculum Development Subcommittee, Chair, January 2015 – present
    • Undergraduate Advisor, September 2011 – present.
    • Doctoral Program Curriculum committee, member, December 2010 – present.
    • Doctoral Program Admissions Committee, September 2010 – present.
    • Doctoral Seminar Series (was the COR@L/INFORMS Seminar Series), founding faculty organizer, September 2002 – present.
    • Lehigh Student Chapter of the Institute for Operations Research and Management Science, founding faculty advisor, July 2005 – present.
    • Senior Faculty Search Committee, chair, September 2009 – March 2014.
    • Co-Director of Graduate Programs, September 2006 – December 2010.
    • Junior Faculty Search Committee, member, various times September 2000 – May 2010.
    • ISE Council, member, September 2001 – May 2003, September 2005 – 2008.
    • ISE Graduate Curriculum Committee, member, September 2001 – May 2008.
    • ISE Information and Systems Engineering Curriculum Development Committee, chairman, September 2001 – May 2003.

Professional Activities

  • Computational Infrastructure for Operations Research
    (COIN-OR) Foundation, September 2000–present.

    • Co-founder
    • Strategic Leadership Board, Member
    • Technical Leadership Council, Chair
    • Former Treasurer
  • Institute for Operations Research and Management Science, member, January 1997 – present.
    • Member, INFORMS Subdivisions Council, January 2013 – December 2014
    • Member, Student Affairs Committee, January 2018 – present
  • INFORMS Computing Society, member.
    • Harvey J. Greenburg Award Committee, Member, 2019.
    • Membership Committee, member, February 2008 – December 2011.
    • Board member, January 2010 – December 2011.
    • INFORMS Computing Society, Student Paper Prize Committee, Chair, May 2010 – November 2010.
  • INFORMS Optimization Society, member.
  • Mathematical Optimization Society, member, January 2000 – present
    • Founding Member of Mixed Integer Programming Society, 2022-present
    • Beale Orchard-Hayes Prize Selection Committee, Member, 2018.
  • Society of Industrial and Applied Mathematics, member, January 2011 – present.
  • MIPLIB Steering Committee, member, 2009 -present
  • External Reviewer,
    • University of New Brunswick, 2015
    • University of Auckland, 2021
  • Publication Referee
    • Annals of Operations Research
    • Computers and Operations Research
    • Computational Optimization and Applications
    • Discrete Optimization
    • Discrete Mathematics
    • European Journal of Operations Research
    • EURO Journal on Transportation and Logistics
    • EURO Journal on Computationla Optimization
    • IEEE Control Systems Society
    • IEEE Transactions on Computers
    • INFORMS Journal of Computing
    • International Journal of Operations Research
    • International Journal of Computer Mathematics
    • International Transactions in Operations Research
    • Journal of Global Optimization
    • Journal of Experimental Algorithmics
    • Management Science
    • Mathematical Methods of Operations Research
    • Mathematical Programming Series A and B
    • Mathematical Programming Computation
    • Naval Research Logistics
    • Networks
    • Operations Research
    • Operations Research Letters
    • Optimization Letters
    • Optimization Methods and Software
    • Parallel Computing
    • SIAM Journal on Optimization
    • The Open Operational Research Journal
    • Transportation Science
  • Proposal Reviewer
    • National Science Foundation
    • U.S. Civilian Research and Development Foundation
    • Australian Research Council (International Assessor)
    • Austrian Science Fund
    • National Sciences Engineering and Research Council of Canada
  • Former president of the Cornell Operations Research Graduate Association.
  • Founding member and first president of the Cornell Graduate and Professional Student Assembly.

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