// 5-6. Halfmove clock and fullmove number
ss >> std::skipws >> st->rule50 >> gamePly;
- // Convert from fullmove starting from 1 to ply starting from 0,
+ // Convert from fullmove starting from 1 to gamePly starting from 0,
// handle also common incorrect FEN with fullmove = 0.
gamePly = std::max(2 * (gamePly - 1), 0) + (sideToMove == BLACK);
{
stp = stp->previous->previous;
- // At root position ply is 1, so return a draw score if a position
- // repeats once earlier but strictly after the root, or repeats twice
- // before or at the root.
+ // Return a draw score if a position repeats once earlier but strictly
+ // after the root, or repeats twice before or at the root.
if ( stp->key == st->key
- && ++cnt + (ply - 1 > i) == 2)
+ && ++cnt + (ply > i) == 2)
return true;
}
void Thread::search() {
- Stack stack[MAX_PLY+7], *ss = stack+4; // To allow referencing (ss-4) and (ss+2)
+ Stack stack[MAX_PLY+7], *ss = stack+4; // To reference from (ss-4) to (ss+2)
Value bestValue, alpha, beta, delta;
Move easyMove = MOVE_NONE;
MainThread* mainThread = (this == Threads.main() ? Threads.main() : nullptr);
Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning) {
const bool PvNode = NT == PV;
- const bool rootNode = PvNode && (ss-1)->ply == 0;
+ const bool rootNode = PvNode && ss->ply == 0;
assert(-VALUE_INFINITE <= alpha && alpha < beta && beta <= VALUE_INFINITE);
assert(PvNode || (alpha == beta - 1));
moveCount = quietCount = ss->moveCount = 0;
ss->statScore = 0;
bestValue = -VALUE_INFINITE;
- ss->ply = (ss-1)->ply + 1;
// Check for the available remaining time
if (thisThread == Threads.main())
static_cast<MainThread*>(thisThread)->check_time();
- // Used to send selDepth info to GUI
- if (PvNode && thisThread->selDepth < ss->ply)
- thisThread->selDepth = ss->ply;
+ // Used to send selDepth info to GUI (selDepth counts from 1, ply from 0)
+ if (PvNode && thisThread->selDepth < ss->ply + 1)
+ thisThread->selDepth = ss->ply + 1;
if (!rootNode)
{
assert(0 <= ss->ply && ss->ply < MAX_PLY);
+ (ss+1)->ply = ss->ply + 1;
ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
ss->contHistory = &thisThread->contHistory[NO_PIECE][0];
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
int drawScore = TB::UseRule50 ? 1 : 0;
- value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply
- : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply
+ value = v < -drawScore ? -VALUE_MATE + MAX_PLY + ss->ply + 1
+ : v > drawScore ? VALUE_MATE - MAX_PLY - ss->ply - 1
: VALUE_DRAW + 2 * v * drawScore;
tte->save(posKey, value_to_tt(value, ss->ply), BOUND_EXACT,
}
ss->currentMove = bestMove = MOVE_NONE;
- ss->ply = (ss-1)->ply + 1;
+ (ss+1)->ply = ss->ply + 1;
moveCount = 0;
// Check for an instant draw or if the maximum ply has been reached
// only two types of depth in TT: DEPTH_QS_CHECKS or DEPTH_QS_NO_CHECKS.
ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
: DEPTH_QS_NO_CHECKS;
-
// Transposition table lookup
posKey = pos.key();
tte = TT.probe(posKey, ttHit);