conv-exprTrilinear.cpp

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/* $Id: conv-exprTrilinear.cpp 1069 2014-02-05 01:45:36Z pbelotti $
 *
 * Name:    conv-exprTrilinear.cpp
 * Author:  Pietro Belotti
 * Purpose: convexify trilinear terms
 *
 * This file is licensed under the Eclipse Public License (EPL)
 */

#include "CouenneTypes.hpp"
#include "CouenneExprTrilinear.hpp"
#include "CouenneExprMin.hpp"
#include "CouenneExprMax.hpp"
#include "CouenneExprClone.hpp"
#include "CouenneProblem.hpp"

using namespace Couenne;

void exprTrilinear::getBounds (expression *&lb, expression *&ub) {

  expression
    **arglistMax = new expression* [16],
    **arglistMin = new expression* [16],
    **lbA        = new expression* [3],
    **ubA        = new expression* [3];

  for (int i=0; i<3; i++)
    arglist_ [i] -> getBounds (lbA [i], ubA [i]);

  for     (int i0 = 0; i0 < 2; i0++)
    for   (int i1 = 0; i1 < 2; i1++)
      for (int i2 = 0; i2 < 2; i2++) {

        int indexTerm = i0*8 + i1*4 + i2*2;

        expression *product = new exprTrilinear (new exprClone (i0 ? ubA [0] : lbA [0]),
                                                 new exprClone (i1 ? ubA [1] : lbA [1]),
                                                 new exprClone (i2 ? ubA [2] : lbA [2]));

        arglistMax [indexTerm] = new exprCopy (product); // saves value to be retrieved later for computation

        arglistMin [indexTerm] = new exprCopy (new exprClone (product));

        arglistMax [indexTerm + 1] = new exprStore (arglistMax [indexTerm]); // evaluated at the end, safe to just copy
        arglistMin [indexTerm + 1] = new exprStore (arglistMin [indexTerm]); // evaluated at the end, safe to just copy 
      }

  lb = new exprMin (arglistMin, 16);
  ub = new exprMax (arglistMax, 16);
}



void exprTrilinear::getBounds (CouNumber &lb, CouNumber &ub) {

  CouNumber 
    lbA [3],
    ubA [3];

  for (int i=0; i<3; i++)
    arglist_ [i] -> getBounds (lbA [i], ubA [i]);

  lb =  COUENNE_INFINITY;
  ub = -COUENNE_INFINITY;

  for     (int i0 = 0; i0 < 2; i0++)
    for   (int i1 = 0; i1 < 2; i1++)
      for (int i2 = 0; i2 < 2; i2++) {

        register double curbound = 
          (i0 ? ubA [0] : lbA [0]) * 
          (i1 ? ubA [1] : lbA [1]) *
          (i2 ? ubA [2] : lbA [2]);

        if (curbound < lb) lb = curbound;
        if (curbound > ub) ub = curbound;
      }

  bool isInt = true;

  for (int i=0; i<3; i++)
    if (!(arglist_ [i] -> isInteger ())) {
      isInt = false;
      break;
    }

  if (isInt) {
    lb = ceil  (lb - COUENNE_EPS);
    ub = floor (ub + COUENNE_EPS);
  }
}