ClpDualRowDantzig.cpp

// Copyright (C) 2002, International Business Machines
// Corporation and others.  All Rights Reserved.

#include "CoinPragma.hpp"
#include "ClpSimplex.hpp"
#include "ClpDualRowDantzig.hpp"
#include "CoinIndexedVector.hpp"

//#############################################################################
// Constructors / Destructor / Assignment
//#############################################################################

//-------------------------------------------------------------------
// Default Constructor 
//-------------------------------------------------------------------
ClpDualRowDantzig::ClpDualRowDantzig () 
: ClpDualRowPivot()
{
  type_=1;
}

//-------------------------------------------------------------------
// Copy constructor 
//-------------------------------------------------------------------
ClpDualRowDantzig::ClpDualRowDantzig (const ClpDualRowDantzig & source) 
: ClpDualRowPivot(source)
{  

}

//-------------------------------------------------------------------
// Destructor 
//-------------------------------------------------------------------
ClpDualRowDantzig::~ClpDualRowDantzig ()
{

}

//----------------------------------------------------------------
// Assignment operator 
//-------------------------------------------------------------------
ClpDualRowDantzig &
ClpDualRowDantzig::operator=(const ClpDualRowDantzig& rhs)
{
  if (this != &rhs) {
    ClpDualRowPivot::operator=(rhs);
  }
  return *this;
}

// Returns pivot row, -1 if none
int 
ClpDualRowDantzig::pivotRow()
{
  assert(model_);
  int iRow;
  const int * pivotVariable = model_->pivotVariable();
  double largest=model_->currentPrimalTolerance();
  // we can't really trust infeasibilities if there is primal error
  if (model_->largestPrimalError()>1.0e-8)
    largest *= model_->largestPrimalError()/1.0e-8;
  int chosenRow=-1;
  for (iRow=0;iRow<model_->numberRows();iRow++) {
    int iPivot=pivotVariable[iRow];
    double value = model_->solution(iPivot);
    double lower = model_->lower(iPivot);
    double upper = model_->upper(iPivot);
    if (max(value-upper,lower-value)>largest) {
      int iSequence = pivotVariable[iRow];
      if (!model_->flagged(iSequence)) {
        chosenRow=iRow;
        largest=max(value-upper,lower-value);
      }
    }
  }
  return chosenRow;
}
// Returns pivot alpha
double
ClpDualRowDantzig::updateWeights(CoinIndexedVector * input,
                                  CoinIndexedVector * spare,
                                  CoinIndexedVector * updatedColumn)
{
  // pivot element
  double alpha=0.0;
  // look at updated column
  double * work = updatedColumn->denseVector();
  int number = updatedColumn->getNumElements();
  int * which = updatedColumn->getIndices();
  int i;
  int pivotRow = model_->pivotRow();

  if (updatedColumn->packedMode()) {
    for (i =0; i < number; i++) {
      int iRow = which[i];
      if (iRow==pivotRow) {
        alpha = work[i];
        break;
      }
    }
  } else {
    alpha = work[pivotRow];
  }
  return alpha;
}
  
/* Updates primal solution (and maybe list of candidates)
   Uses input vector which it deletes
   Computes change in objective function
*/
void 
ClpDualRowDantzig::updatePrimalSolution(CoinIndexedVector * primalUpdate,
                                        double primalRatio,
                                        double & objectiveChange)
{
  double * work = primalUpdate->denseVector();
  int number = primalUpdate->getNumElements();
  int * which = primalUpdate->getIndices();
  int i;
  double changeObj=0.0;
  const int * pivotVariable = model_->pivotVariable();
  if (primalUpdate->packedMode()) {
    for (i=0;i<number;i++) {
      int iRow=which[i];
      int iPivot=pivotVariable[iRow];
      double & value = model_->solutionAddress(iPivot);
      double cost = model_->cost(iPivot);
      double change = primalRatio*work[i];
      value -= change;
      changeObj -= change*cost;
      work[i]=0.0;
    }
  } else {
    for (i=0;i<number;i++) {
      int iRow=which[i];
      int iPivot=pivotVariable[iRow];
      double & value = model_->solutionAddress(iPivot);
      double cost = model_->cost(iPivot);
      double change = primalRatio*work[iRow];
      value -= change;
      changeObj -= change*cost;
      work[iRow]=0.0;
    }
  }
  primalUpdate->setNumElements(0);
  objectiveChange += changeObj;
}
//-------------------------------------------------------------------
// Clone
//-------------------------------------------------------------------
ClpDualRowPivot * ClpDualRowDantzig::clone(bool CopyData) const
{
  if (CopyData) {
    return new ClpDualRowDantzig(*this);
  } else {
    return new ClpDualRowDantzig();
  }
}

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