int main(int ununsed, char **alsoUnused)
{
TestHashTable();
return 0;
}
int AlphaBeta(board_t *brd, int alpha, int beta, int depth, searchinfo_t *sinfo, int null)
{
if(depth == 0){
//return Eval(brd);
return Quiece(brd, alpha, beta, sinfo);
}
if(!(sinfo->nodes & 0xfff)) CheckUp(sinfo);
sinfo->nodes++;
ASSERT(CheckBrd(brd));
// if we are not the root of the tree and we have a repetition
// or we exceeded the fifty move rule, then we have a draw and return 0
if((IsRep(brd) || brd->fifty >= 100) && brd->ply) return 0;
if(brd->ply >= MAXDEPTH-1) return Eval(brd); // if we are too deep, we return
// test if we are in check
int check = SqAttacked(brd, LOCATEBIT(brd->bb[brd->side][King]), brd->side^1);
if(check) depth++;
int score = -INFINITE;
int pvMain = NO_MOVE;
// check the transposition table if we have searched the current position before
// if so, return what we found
if(TestHashTable(brd, &pvMain, &score, alpha, beta, depth)) return score;
// Before we search, we try how we do if we don't make a move
// i.e. make a null move
if( null && !check && brd->ply && depth >= 4 &&
(brd->all[brd->side]^brd->bb[brd->side][Pawn]^brd->bb[brd->side][King]) )
{
MakeMoveNull(brd);
// We cannot do two null moves in a row so we set the null argument here to false
score = -AlphaBeta(brd, -beta, -beta + 1, depth-4, sinfo, false);
TakeBackNull(brd);
if(sinfo->stop){
return 0;
}
if(score >= beta){
return beta;
}
}
mlist_t list;
int i;
int legal = 0;
int bestMove = NO_MOVE;
int bestScore = -INFINITE;
int oldAlpha = alpha;
score = -INFINITE;
GenMoves(brd, &list);
// we tested our transposition table for the best move 'pvMain'
// if it exists we will set this move as the first move to be searched
if(pvMain != NO_MOVE){
if(MakeMove(brd, pvMain)){
score = -AlphaBeta(brd, -beta, -alpha, depth-1, sinfo, true);
TakeBack(brd);
bestScore = score;
if(score > alpha){
if(score >= beta){
if(!(pvMain & FLAGCAP)){
brd->betaMoves[1][brd->ply] = brd->betaMoves[0][brd->ply];
brd->betaMoves[0][brd->ply] = pvMain;
}
return beta;
}
alpha = score;
bestMove = pvMain;
}
}
/*/
for(i = 0; i < list.len; i++){
if(list.move[i].move == pvMain){
list.move[i].score = 5000000;
break;
}
}//*/
}
for(i = 0; i < list.len; i++) // Loop through all moves
{
if(sinfo->stop) return 0;
SelectNextMove(&list, i);
if(!MakeMove(brd, list.move[i].move)) continue;
legal++; // we have found a legal move so we need not check for mate afterwards
// call AlphaBeta in a negamax fashion
score = -AlphaBeta(brd, -beta, -alpha, depth-1, sinfo, true);
TakeBack(brd);
if(score > bestScore){
bestScore = score;
if(score > alpha){
if(score >= beta){
if(legal==1) sinfo->fhf++; // count the number of beta cutoffs searched first
sinfo->fh++; // compared to all beta cutoffs (measure of efficiency)
if(!(list.move[i].move & FLAGCAP)){
brd->betaMoves[1][brd->ply] = brd->betaMoves[0][brd->ply];
brd->betaMoves[0][brd->ply] = list.move[i].move;
}
// Store the move in the transposition table as a beta (killer) move
StorePvMove(brd, bestMove, depth, beta, HFBETA);
return beta;
}
alpha = score;
bestMove = list.move[i].move;
}
}
}
if(legal == 0){ // We havn't found a legal move
if(check){
// if we are in check it is mate; but we want the shortest path
// to it so we'll subtract the path length
return -MATE + brd->ply;
}
return 0; // Stalemate
}
if(oldAlpha != alpha){
// Store exact (normal) transposition entry
StorePvMove(brd, bestMove, depth, bestScore, HFEXACT);
}
else {
// Store alpha cutoff transposition entry
StorePvMove(brd, bestMove, depth, alpha, HFALPHA);
}
return alpha;
}