Question

int Solver::negamax(Position* pos,int alpha,int beta, int color, int depth ) {
  if(depth==0 || is_final(pos)){
    return evaluate(pos);
  }
  else{
    vector < Position* > moves = generate_moves(pos->get_board());
    vector < Position* >::iterator move;
    int min = 99999;
    for(move = moves.begin(); move < moves.end(); move++){
      int val = negamax(*move,alpha, beta, -color, depth - 1 );
      if(val <= min){
        min = val;
        delete best;
        best = NULL;
        best = (*move)->get_board();

      }
      else{
        delete *move; //So this isnt cleaning up?
        *move = NULL;
      }
     }
     min = -min;
     return min;
     }

 }

vector < Position* > TakeAwaySolver::generate_moves(Board *brd){
  TakeAwayBoard *board = static_cast<TakeAwayBoard*>(brd);
  vector < Position* > moves;
  if(board->get_data() >= 3){
     TakeAwayBoard *b = new TakeAwayBoard(board->get_data() - 3);
     Position* p = new Position(b);
     moves.push_back(p);
  }
  if(board->get_data() >= 2){
     TakeAwayBoard *b = new TakeAwayBoard(board->get_data() - 2);
     Position* p = new Position(b);
     moves.push_back(p);
  }
  TakeAwayBoard *b = new TakeAwayBoard(board->get_data() - 1);
  Position* p = new Position(b);
  moves.push_back(p);
  return moves;

}

I valgrinded my program and I’m apparently leaking memory. It seems that I’m deleting all unused objects, but perhaps I’m not understanding something. generate_moves() does allocate memory for each of the objects being pushed in. Evaluate returns 1. Does it seem possible that I’m leaking memory in any location?

Answer 1

You have an if/else in which *move is only deleted in one of the paths. I’d check there.

for(move = moves.begin(); move < moves.end(); move++){
          int val = negamax(*move,alpha, beta, -color, depth - 1 );
          if(val <= min){
            min = val;
            delete best;
            best = NULL;
            best = (*move)->get_board();
                                           //best is deleted, but *move is not
          }
          else{
            delete *move;
            *move = NULL;
          }
         }