/*
<moUBQPBitsIncrEval.h>
Copyright (C) DOLPHIN Project-Team, INRIA Lille - Nord Europe, 2006-2010

Sebastien Verel, Arnaud Liefooghe, Jeremie Humeau

This software is governed by the CeCILL license under French law and
abiding by the rules of distribution of free software.  You can  ue,
modify and/ or redistribute the software under the terms of the CeCILL
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*/

#ifndef _moUBQPBitsIncrEval_H
#define _moUBQPBitsIncrEval_H

#include <eval/moEval.h>
#include <eval/ubqpEval.h>

/**
 * Incremental evaluation Function for the UBQPSimple problem
 * when several bits are flipped (moBitsNeighbor)
 */
template< class Neighbor >
class moUBQPBitsIncrEval : public moEval<Neighbor>
{
public:
  typedef typename Neighbor::EOT EOT;
  
  /*
   * default constructor
   * @param _ubqpEval full evaluation of the UBQP problem
   */
  moUBQPBitsIncrEval(UbqpEval<EOT> & _ubqpEval) {
    n = _ubqpEval.getNbVar();
    Q = _ubqpEval.getQ();
  }

  /*
   * Incremental evaluation of the neighbor for the UBQP problem (complexity O(n * k) when k bits are flipped)
   * @param _solution the solution to move (bit string)
   * @param _neighbor the neighbor to consider of type moBitsNeighbor (several bits are flipped)
   */
  virtual void operator()(EOT & _solution, Neighbor & _neighbor) {
    unsigned int b;
    unsigned int j;
    int d, delta;

    delta = 0;
    for(unsigned i = 0; i < _neighbor.nBits; i++) {
      b = _neighbor.bits[i];
      d = Q[b][b]; 

      for(j = 0; j < b; j++)
	if (_solution[j] == 1)
	  d += Q[b][j];

      for(j = b+1; j < n; j++)
	if (_solution[j] == 1)
	  d += Q[j][b];

      if (_solution[b] == 0)
	delta += d;
      else
	delta -= d;

      // move the solution on this bit
      _solution[b] = !_solution[b];
    }

    // move back the solution
    for(unsigned i = 0; i < _neighbor.nBits; i++) {
      b = _neighbor.bits[i];
      _solution[b] = !_solution[b];
    }

    _neighbor.fitness(_solution.fitness() + delta);
  }

  /*
   * to get the matrix Q
   *
   * @return matrix Q
   */
  int** getQ() {
    return Q;
  }

  /*
   * to get the number of variable (bit string length)
   *
   * @return bit string length
   */
  int getNbVar() {
    return n;
  }

private:
  // number of variables
  int n;
  
  // matrix Q (supposed to be in lower triangular form)
  int ** Q;
    
};

#endif