Sbb: SbbBranchDefaultDecision class Reference

Compare two branching objects. Return nonzero if thisOne is better than bestSoFar.

The routine compares branches using the values supplied in numInfUp and numInfDn until a solution is found by search, after which it uses the values supplied in changeUp and changeDn. The best branching object seen so far and the associated parameter values are remembered in the SbbBranchDefaultDecision object. The nonzero return value is +1 if the up branch is preferred, -1 if the down branch is preferred.

As the names imply, the assumption is that the values supplied for numInfUp and numInfDn will be the number of infeasibilities reported by the branching object, and changeUp and changeDn will be the estimated change in objective. Other measures can be used if desired.

Because an SbbBranchDefaultDecision object remembers the current best branching candidate (bestObject_) as well as the values used in the comparison, the parameter bestSoFar is redundant, hence unused.

00970 {
00971   bool beforeSolution = thisOne->model()->getSolutionCount()==
00972     thisOne->model()->getNumberHeuristicSolutions();;
00973   int betterWay=0;
00974   if (beforeSolution) {
00975     if (!bestObject_) {
00976       bestNumberUp_=INT_MAX;
00977       bestNumberDown_=INT_MAX;
00978     }
00979     // before solution - choose smallest number 
00980     // could add in depth as well
00981     int bestNumber = min(bestNumberUp_,bestNumberDown_);
00982     if (numInfUp<numInfDn) {
00983       if (numInfUp<bestNumber) {
00984         betterWay = 1;
00985       } else if (numInfUp==bestNumber) {
00986         if (changeUp<bestCriterion_)
00987           betterWay=1;
00988       }
00989     } else if (numInfUp>numInfDn) {
00990       if (numInfDn<bestNumber) {
00991         betterWay = -1;
00992       } else if (numInfDn==bestNumber) {
00993         if (changeDn<bestCriterion_)
00994           betterWay=-1;
00995       }
00996     } else {
00997       // up and down have same number
00998       bool better=false;
00999       if (numInfUp<bestNumber) {
01000         better=true;
01001       } else if (numInfUp==bestNumber) {
01002         if (min(changeUp,changeDn)<bestCriterion_)
01003           better=true;;
01004       }
01005       if (better) {
01006         // see which way
01007         if (changeUp<=changeDn)
01008           betterWay=1;
01009         else
01010           betterWay=-1;
01011       }
01012     }
01013   } else {
01014     if (!bestObject_) {
01015       bestCriterion_=-1.0;
01016     }
01017     // got a solution
01018     if (changeUp<=changeDn) {
01019       if (changeUp>bestCriterion_)
01020         betterWay=1;
01021     } else {
01022       if (changeDn>bestCriterion_)
01023         betterWay=-1;
01024     }
01025   }
01026   if (betterWay) {
01027     bestCriterion_ = min(changeUp,changeDn);
01028     bestChangeUp_ = changeUp;
01029     bestNumberUp_ = numInfUp;
01030     bestChangeDown_ = changeDn;
01031     bestNumberDown_ = numInfDn;
01032     bestObject_=thisOne;
01033   }
01034   return betterWay;
01035 }


Public Member Functions
	SbbBranchDefaultDecision (const SbbBranchDefaultDecision &)
virtual SbbBranchDecision *	clone () const
	Clone.
virtual void	initialize (SbbModel *model)
	Initialize, e.g. before the start of branch selection at a node.
virtual int	betterBranch (SbbBranchingObject thisOne, SbbBranchingObject bestSoFar, double changeUp, int numInfUp, double changeDn, int numInfDn)
	Compare two branching objects. Return nonzero if `thisOne` is better than `bestSoFar`.
Private Member Functions
SbbBranchDefaultDecision &	operator= (const SbbBranchDefaultDecision &rhs)
	Illegal Assignment operator.
Private Attributes
double	bestCriterion_
	data "best" so far
double	bestChangeUp_
	Change up for best.
int	bestNumberUp_
	Number of infeasibilities for up.
double	bestChangeDown_
	Change down for best.
int	bestNumberDown_
	Number of infeasibilities for down.
SbbBranchingObject *	bestObject_
	Pointer to best branching object.

SbbBranchDefaultDecision Class Reference

Public Member Functions

Private Member Functions

Private Attributes

Detailed Description

Member Function Documentation