size_t Search::perft(Position& pos, Depth depth) {
- // At the last ply just return the number of legal moves (leaf nodes)
- if (depth == ONE_PLY)
- return MoveList<LEGAL>(pos).size();
-
StateInfo st;
size_t cnt = 0;
CheckInfo ci(pos);
+ const bool leaf = depth == 2 * ONE_PLY;
for (MoveList<LEGAL> it(pos); *it; ++it)
{
pos.do_move(*it, st, ci, pos.move_gives_check(*it, ci));
- cnt += perft(pos, depth - ONE_PLY);
+ cnt += leaf ? MoveList<LEGAL>(pos).size() : perft(pos, depth - ONE_PLY);
pos.undo_move(*it);
}
-
return cnt;
}
Value bestValue, alpha, beta, delta;
memset(ss-1, 0, 4 * sizeof(Stack));
- depth = BestMoveChanges = 0;
- bestValue = delta = -VALUE_INFINITE;
(ss-1)->currentMove = MOVE_NULL; // Hack to skip update gains
+
+ depth = BestMoveChanges = 0;
+ bestValue = delta = alpha = -VALUE_INFINITE;
+ beta = VALUE_INFINITE;
+
TT.new_search();
History.clear();
Gains.clear();
// MultiPV loop. We perform a full root search for each PV line
for (PVIdx = 0; PVIdx < PVSize; PVIdx++)
{
- // Set aspiration window default width
- if (depth >= 5 && abs(RootMoves[PVIdx].prevScore) < VALUE_KNOWN_WIN)
+ // Reset aspiration window starting size
+ if (depth >= 5)
{
delta = Value(16);
- alpha = RootMoves[PVIdx].prevScore - delta;
- beta = RootMoves[PVIdx].prevScore + delta;
- }
- else
- {
- alpha = -VALUE_INFINITE;
- beta = VALUE_INFINITE;
+ alpha = std::max(RootMoves[PVIdx].prevScore - delta,-VALUE_INFINITE);
+ beta = std::min(RootMoves[PVIdx].prevScore + delta, VALUE_INFINITE);
}
// Start with a small aspiration window and, in case of fail high/low,
if (Signals.stop)
return;
- // In case of failing high/low increase aspiration window and
+ // In case of failing low/high increase aspiration window and
// research, otherwise exit the loop.
- if (bestValue > alpha && bestValue < beta)
- break;
-
- // Give some update (without cluttering the UI) before to research
- if (Time::now() - SearchTime > 3000)
- sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
-
- if (abs(bestValue) >= VALUE_KNOWN_WIN)
+ if (bestValue <= alpha)
{
- alpha = -VALUE_INFINITE;
- beta = VALUE_INFINITE;
+ alpha = std::max(bestValue - delta, -VALUE_INFINITE);
+
+ Signals.failedLowAtRoot = true;
+ Signals.stopOnPonderhit = false;
}
else if (bestValue >= beta)
- {
- beta += delta;
- delta += delta / 2;
- }
+ beta = std::min(bestValue + delta, VALUE_INFINITE);
+
else
- {
- Signals.failedLowAtRoot = true;
- Signals.stopOnPonderhit = false;
+ break;
- alpha -= delta;
- delta += delta / 2;
- }
+ delta += delta / 2;
assert(alpha >= -VALUE_INFINITE && beta <= VALUE_INFINITE);
+
+ // Give some update (without cluttering the UI) before to research
+ if (Time::now() - SearchTime > 3000)
+ sync_cout << uci_pv(pos, depth, alpha, beta) << sync_endl;
}
// Sort the PV lines searched so far and update the GUI
assert(PvNode || (alpha == beta - 1));
assert(depth > DEPTH_ZERO);
- Move movesSearched[64];
+ Move quietsSearched[64];
StateInfo st;
const TTEntry *tte;
SplitPoint* splitPoint;
Value eval, nullValue, futilityValue;
bool inCheck, givesCheck, pvMove, singularExtensionNode;
bool captureOrPromotion, dangerous, doFullDepthSearch;
- int moveCount, playedMoveCount;
+ int moveCount, quietCount;
// Step 1. Initialize node
Thread* thisThread = pos.this_thread();
- moveCount = playedMoveCount = 0;
+ moveCount = quietCount = 0;
inCheck = pos.checkers();
if (SpNode)
&& tte
&& tte->depth() >= depth
&& ttValue != VALUE_NONE // Only in case of TT access race
- && ( PvNode ? tte->type() == BOUND_EXACT
- : ttValue >= beta ? (tte->type() & BOUND_LOWER)
- : (tte->type() & BOUND_UPPER)))
+ && ( PvNode ? tte->bound() == BOUND_EXACT
+ : ttValue >= beta ? (tte->bound() & BOUND_LOWER)
+ : (tte->bound() & BOUND_UPPER)))
{
TT.refresh(tte);
ss->currentMove = ttMove; // Can be MOVE_NONE
// Step 5. Evaluate the position statically and update parent's gain statistics
if (inCheck)
+ {
ss->staticEval = ss->evalMargin = eval = VALUE_NONE;
+ goto iid_start;
+ }
else if (tte)
{
// Can ttValue be used as a better position evaluation?
if (ttValue != VALUE_NONE)
- if ( ((tte->type() & BOUND_LOWER) && ttValue > eval)
- || ((tte->type() & BOUND_UPPER) && ttValue < eval))
+ if ( ((tte->bound() & BOUND_LOWER) && ttValue > eval)
+ || ((tte->bound() & BOUND_UPPER) && ttValue < eval))
eval = ttValue;
}
else
// Update gain for the parent non-capture move given the static position
// evaluation before and after the move.
- if ( (move = (ss-1)->currentMove) != MOVE_NULL
- && (ss-1)->staticEval != VALUE_NONE
+ if ( !pos.captured_piece_type()
&& ss->staticEval != VALUE_NONE
- && !pos.captured_piece_type()
+ && (ss-1)->staticEval != VALUE_NONE
+ && (move = (ss-1)->currentMove) != MOVE_NULL
&& type_of(move) == NORMAL)
{
Square to = to_sq(move);
// Step 6. Razoring (is omitted in PV nodes)
if ( !PvNode
&& depth < 4 * ONE_PLY
- && !inCheck
&& eval + razor_margin(depth) < beta
&& ttMove == MOVE_NONE
&& abs(beta) < VALUE_MATE_IN_MAX_PLY
if ( !PvNode
&& !ss->skipNullMove
&& depth < 4 * ONE_PLY
- && !inCheck
&& eval - futility_margin(depth, (ss-1)->futilityMoveCount) >= beta
&& abs(beta) < VALUE_MATE_IN_MAX_PLY
&& abs(eval) < VALUE_KNOWN_WIN
if ( !PvNode
&& !ss->skipNullMove
&& depth > ONE_PLY
- && !inCheck
&& eval >= beta
&& abs(beta) < VALUE_MATE_IN_MAX_PLY
&& pos.non_pawn_material(pos.side_to_move()))
// prune the previous move.
if ( !PvNode
&& depth >= 5 * ONE_PLY
- && !inCheck
&& !ss->skipNullMove
&& abs(beta) < VALUE_MATE_IN_MAX_PLY)
{
}
}
+iid_start: // When in check we skip early cut tests
+
// Step 10. Internal iterative deepening
if ( depth >= (PvNode ? 5 * ONE_PLY : 8 * ONE_PLY)
&& ttMove == MOVE_NONE
&& depth >= (PvNode ? 6 * ONE_PLY : 8 * ONE_PLY)
&& ttMove != MOVE_NONE
&& !excludedMove // Recursive singular search is not allowed
- && (tte->type() & BOUND_LOWER)
+ && (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
// Step 11. Loop through moves
givesCheck = pos.move_gives_check(move, ci);
dangerous = givesCheck
|| pos.is_passed_pawn_push(move)
- || type_of(move) == CASTLE
- || ( captureOrPromotion // Entering a pawn endgame?
- && type_of(pos.piece_on(to_sq(move))) != PAWN
- && type_of(move) == NORMAL
- && ( pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK)
- - PieceValue[MG][pos.piece_on(to_sq(move))] == VALUE_ZERO));
+ || type_of(move) == CASTLE;
// Step 12. Extend checks and, in PV nodes, also dangerous moves
if (PvNode && dangerous)
pvMove = PvNode && moveCount == 1;
ss->currentMove = move;
- if (!SpNode && !captureOrPromotion && playedMoveCount < 64)
- movesSearched[playedMoveCount++] = move;
+ if (!SpNode && !captureOrPromotion && quietCount < 64)
+ quietsSearched[quietCount++] = move;
// Step 14. Make the move
pos.do_move(move, st, ci, givesCheck);
// If we have pruned all the moves without searching return a fail-low score
if (bestValue == -VALUE_INFINITE)
- {
- assert(!playedMoveCount);
-
bestValue = alpha;
- }
- if (bestValue >= beta) // Failed high
+ TT.store(posKey, value_to_tt(bestValue, ss->ply),
+ bestValue >= beta ? BOUND_LOWER :
+ PvNode && bestMove ? BOUND_EXACT : BOUND_UPPER,
+ depth, bestMove, ss->staticEval, ss->evalMargin);
+
+ // Quiet best move: update killers, history and countermoves
+ if ( bestValue >= beta
+ && !pos.is_capture_or_promotion(bestMove)
+ && !inCheck)
{
- TT.store(posKey, value_to_tt(bestValue, ss->ply), BOUND_LOWER, depth,
- bestMove, ss->staticEval, ss->evalMargin);
-
- if (!pos.is_capture_or_promotion(bestMove) && !inCheck)
+ if (ss->killers[0] != bestMove)
{
- if (bestMove != ss->killers[0])
- {
- ss->killers[1] = ss->killers[0];
- ss->killers[0] = bestMove;
- }
-
- // Increase history value of the cut-off move
- Value bonus = Value(int(depth) * int(depth));
- History.update(pos.piece_moved(bestMove), to_sq(bestMove), bonus);
- if (is_ok((ss-1)->currentMove))
- Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, bestMove);
+ ss->killers[1] = ss->killers[0];
+ ss->killers[0] = bestMove;
+ }
- // Decrease history of all the other played non-capture moves
- for (int i = 0; i < playedMoveCount - 1; i++)
- {
- Move m = movesSearched[i];
- History.update(pos.piece_moved(m), to_sq(m), -bonus);
- }
+ // Increase history value of the cut-off move and decrease all the other
+ // played non-capture moves.
+ Value bonus = Value(int(depth) * int(depth));
+ History.update(pos.piece_moved(bestMove), to_sq(bestMove), bonus);
+ for (int i = 0; i < quietCount - 1; i++)
+ {
+ Move m = quietsSearched[i];
+ History.update(pos.piece_moved(m), to_sq(m), -bonus);
}
+
+ if (is_ok((ss-1)->currentMove))
+ Countermoves.update(pos.piece_on(prevMoveSq), prevMoveSq, bestMove);
}
- else // Failed low or PV search
- TT.store(posKey, value_to_tt(bestValue, ss->ply),
- PvNode && bestMove != MOVE_NONE ? BOUND_EXACT : BOUND_UPPER,
- depth, bestMove, ss->staticEval, ss->evalMargin);
assert(bestValue > -VALUE_INFINITE && bestValue < VALUE_INFINITE);
ttDepth = InCheck || depth >= DEPTH_QS_CHECKS ? DEPTH_QS_CHECKS
: DEPTH_QS_NO_CHECKS;
- // Transposition table lookup. At PV nodes, we don't use the TT for
- // pruning, but only for move ordering.
+ // Transposition table lookup
posKey = pos.key();
tte = TT.probe(posKey);
ttMove = tte ? tte->move() : MOVE_NONE;
if ( tte
&& tte->depth() >= ttDepth
&& ttValue != VALUE_NONE // Only in case of TT access race
- && ( PvNode ? tte->type() == BOUND_EXACT
- : ttValue >= beta ? (tte->type() & BOUND_LOWER)
- : (tte->type() & BOUND_UPPER)))
+ && ( PvNode ? tte->bound() == BOUND_EXACT
+ : ttValue >= beta ? (tte->bound() & BOUND_LOWER)
+ : (tte->bound() & BOUND_UPPER)))
{
ss->currentMove = ttMove; // Can be MOVE_NONE
return ttValue;
void RootMove::extract_pv_from_tt(Position& pos) {
StateInfo state[MAX_PLY_PLUS_2], *st = state;
- TTEntry* tte;
+ const TTEntry* tte;
int ply = 0;
Move m = pv[0];
void RootMove::insert_pv_in_tt(Position& pos) {
StateInfo state[MAX_PLY_PLUS_2], *st = state;
- TTEntry* tte;
+ const TTEntry* tte;
int ply = 0;
do {
projects / stockfish / blobdiff