File: CbcHeuristicDiveFractional.cpp

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/* $Id: CbcHeuristicDiveFractional.cpp 2093 2014-11-06 16:17:38Z forrest $ */
// Copyright (C) 2008, International Business Machines
// Corporation and others.  All Rights Reserved.
// This code is licensed under the terms of the Eclipse Public License (EPL).

#if defined(_MSC_VER)
// Turn off compiler warning about long names
#  pragma warning(disable:4786)
#endif

#include "CbcHeuristicDiveFractional.hpp"
#include "CbcStrategy.hpp"

// Default Constructor
CbcHeuristicDiveFractional::CbcHeuristicDiveFractional()
        : CbcHeuristicDive()
{
}

// Constructor from model
CbcHeuristicDiveFractional::CbcHeuristicDiveFractional(CbcModel & model)
        : CbcHeuristicDive(model)
{
}

// Destructor
CbcHeuristicDiveFractional::~CbcHeuristicDiveFractional ()
{
}

// Clone
CbcHeuristicDiveFractional *
CbcHeuristicDiveFractional::clone() const
{
    return new CbcHeuristicDiveFractional(*this);
}

// Create C++ lines to get to current state
void
CbcHeuristicDiveFractional::generateCpp( FILE * fp)
{
    CbcHeuristicDiveFractional other;
    fprintf(fp, "0#include \"CbcHeuristicDiveFractional.hpp\"\n");
    fprintf(fp, "3  CbcHeuristicDiveFractional heuristicDiveFractional(*cbcModel);\n");
    CbcHeuristic::generateCpp(fp, "heuristicDiveFractional");
    fprintf(fp, "3  cbcModel->addHeuristic(&heuristicDiveFractional);\n");
}

// Copy constructor
CbcHeuristicDiveFractional::CbcHeuristicDiveFractional(const CbcHeuristicDiveFractional & rhs)
        :
        CbcHeuristicDive(rhs)
{
}

// Assignment operator
CbcHeuristicDiveFractional &
CbcHeuristicDiveFractional::operator=( const CbcHeuristicDiveFractional & rhs)
{
    if (this != &rhs) {
        CbcHeuristicDive::operator=(rhs);
    }
    return *this;
}

bool
CbcHeuristicDiveFractional::selectVariableToBranch(OsiSolverInterface* solver,
        const double* newSolution,
        int& bestColumn,
        int& bestRound)
{
    int numberIntegers = model_->numberIntegers();
    const int * integerVariable = model_->integerVariable();
    double integerTolerance = model_->getDblParam(CbcModel::CbcIntegerTolerance);

    bestColumn = -1;
    bestRound = -1; // -1 rounds down, +1 rounds up
    double bestFraction = COIN_DBL_MAX;
    bool allTriviallyRoundableSoFar = true;
    int bestPriority = COIN_INT_MAX;
    for (int i = 0; i < numberIntegers; i++) {
        int iColumn = integerVariable[i];
        double value = newSolution[iColumn];
        double fraction = value - floor(value);
        int round = 0;
        if (fabs(floor(value + 0.5) - value) > integerTolerance) {
            if (allTriviallyRoundableSoFar || (downLocks_[i] > 0 && upLocks_[i] > 0)) {

                if (allTriviallyRoundableSoFar && downLocks_[i] > 0 && upLocks_[i] > 0) {
                    allTriviallyRoundableSoFar = false;
                    bestFraction = COIN_DBL_MAX;
                }

                // the variable cannot be rounded
                if (fraction < 0.5)
                    round = -1;
                else {
                    round = 1;
                    fraction = 1.0 - fraction;
                }

                // if variable is not binary, penalize it
                if (!solver->isBinary(iColumn))
                    fraction *= 1000.0;

		// if priorities then use
		if (priority_) {
		  int thisRound=static_cast<int>(priority_[i].direction);
		  if ((thisRound&1)!=0) 
		    round = ((thisRound&2)==0) ? -1 : +1;
		  if (priority_[i].priority>bestPriority) {
		    fraction=COIN_DBL_MAX;
		  } else if (priority_[i].priority<bestPriority) {
		    bestPriority=static_cast<int>(priority_[i].priority);
		    bestFraction=COIN_DBL_MAX;
		  }
		}
                if (fraction < bestFraction) {
                    bestColumn = iColumn;
                    bestFraction = fraction;
                    bestRound = round;
                }
            }
        }
    }
    return allTriviallyRoundableSoFar;
}