Modify hash probing code to pvs
Posted: Mon Dec 05, 2016 1:51 pm
Hello all,
My first engine Tunguska is playing at 2100 ELO I believe, but before releasing it here, I want to try PVS + aspiration (and some tweaks to the eval, which is very simple by now).
To do this, I'm looking at the CPW code at https://github.com/nescitus/cpw-engine/ ... search.cpp.
Since I don't fully understand some details, I got confused at the hash probing code.
Here's my current code:
And here's CPW code:
How do I modify my code? I don't get that !is_pv part.
Note: my search and hashtable code are taken fron the 'Vice' engine. I'm still absorving how all this works!
Thank you!
My first engine Tunguska is playing at 2100 ELO I believe, but before releasing it here, I want to try PVS + aspiration (and some tweaks to the eval, which is very simple by now).
To do this, I'm looking at the CPW code at https://github.com/nescitus/cpw-engine/ ... search.cpp.
Since I don't fully understand some details, I got confused at the hash probing code.
Here's my current code:
Code: Select all
//calling the hashprobe
int score = -INFINITE;
int pvMove = Move::NO_MOVE;
if( HashTable::probeHashEntry(board, &pvMove, &score, alpha, beta, depth)){
board.hashTable->cut++;
return score;
}Code: Select all
//Hash probe implementation
bool HashTable::probeHashEntry(Board& board, int *move, int *score, int alpha, int beta, int depth) {
int index = (int)(board.zKey & board.hashTable->numEntries_1);
if(board.hashTable->table[index].zKey == board.zKey) {
*move = board.hashTable->table[index].move;
if(board.hashTable->table[index].depth >= depth){
board.hashTable->hit++;
*score = board.hashTable->table[index].score;
if(*score > ISMATE)
*score -= board.ply;
else if(*score < -ISMATE)
*score += board.ply;
switch(board.hashTable->table[index].flags) {
assert(*score >= -Search::INFINITE && *score <= Search::INFINITE);
case HFALPHA:
if(*score <= alpha) {
*score = alpha;
return true;
}
break;
case HFBETA:
if(*score >= beta) {
*score = beta;
return true;
}
break;
case HFEXACT:
return true;
break;
default: assert(false);
break;
}
}
}
return false;
}Code: Select all
// in pv nodes we return only in case of an exact hash hit
if ((val = tt_probe(depth, alpha, beta, &tt_move_index)) != INVALID) {
if (!is_pv || (val > alpha && val < beta)) {
//mate val correction ommited
return val;
}
}Note: my search and hashtable code are taken fron the 'Vice' engine. I'm still absorving how all this works!
Thank you!