const size_t HalfDensitySize = std::extent<decltype(HalfDensity)>::value;
+ Value bonus(Depth depth) { int d = depth / ONE_PLY ; return Value(d * d + 2 * d - 2); }
+ Value penalty(Depth depth) { int d = depth / ONE_PLY ; return -Value(d * d + 4 * d + 1); }
+
EasyMoveManager EasyMove;
Value DrawValue[COLOR_NB];
template <NodeType NT>
- Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode);
+ Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode, bool skipEarlyPruning);
template <NodeType NT, bool InCheck>
- Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth);
+ Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth = DEPTH_ZERO);
Value value_to_tt(Value v, int ply);
Value value_from_tt(Value v, int ply);
&& rootMoves[0].pv[0] != MOVE_NONE)
{
for (Thread* th : Threads)
- if ( th->completedDepth > bestThread->completedDepth
- && th->rootMoves[0].score > bestThread->rootMoves[0].score)
+ {
+ Depth depthDiff = th->completedDepth - bestThread->completedDepth;
+ Value scoreDiff = th->rootMoves[0].score - bestThread->rootMoves[0].score;
+
+ if (scoreDiff > 0 && depthDiff >= 0)
bestThread = th;
+ }
}
previousScore = bestThread->rootMoves[0].score;
// high/low anymore.
while (true)
{
- bestValue = ::search<PV>(rootPos, ss, alpha, beta, rootDepth, false);
+ bestValue = ::search<PV>(rootPos, ss, alpha, beta, rootDepth, false, false);
// Bring the best move to the front. It is critical that sorting
// is done with a stable algorithm because all the values but the
// search<>() is the main search function for both PV and non-PV nodes
template <NodeType NT>
- Value search(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth, bool cutNode) {
+ 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;
if (!rootNode)
{
// Step 2. Check for aborted search and immediate draw
- if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw() || ss->ply >= MAX_PLY)
+ if (Signals.stop.load(std::memory_order_relaxed) || pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
return ss->ply >= MAX_PLY && !inCheck ? evaluate(pos)
: DrawValue[pos.side_to_move()];
ss->currentMove = (ss+1)->excludedMove = bestMove = MOVE_NONE;
ss->counterMoves = nullptr;
- (ss+1)->skipEarlyPruning = false;
(ss+2)->killers[0] = (ss+2)->killers[1] = MOVE_NONE;
+ Square prevSq = to_sq((ss-1)->currentMove);
// Step 4. Transposition table lookup. We don't want the score of a partial
// search to overwrite a previous full search TT value, so we use a different
// If ttMove is quiet, update killers, history, counter move on TT hit
if (ttValue >= beta && ttMove)
{
- int d = depth / ONE_PLY;
-
if (!pos.capture_or_promotion(ttMove))
- {
- Value bonus = Value(d * d + 2 * d - 2);
- update_stats(pos, ss, ttMove, nullptr, 0, bonus);
- }
+ update_stats(pos, ss, ttMove, nullptr, 0, bonus(depth));
// Extra penalty for a quiet TT move in previous ply when it gets refuted
if ((ss-1)->moveCount == 1 && !pos.captured_piece())
- {
- Value penalty = Value(d * d + 4 * d + 1);
- Square prevSq = to_sq((ss-1)->currentMove);
- update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
- }
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth));
}
return ttValue;
}
// Step 4a. Tablebase probe
if (!rootNode && TB::Cardinality)
{
- int piecesCnt = pos.count<ALL_PIECES>(WHITE) + pos.count<ALL_PIECES>(BLACK);
+ int piecesC
ount = pos.count<ALL_PIECES>(WHITE) + pos.count<ALL_PIECES>(BLACK);
- if ( piecesCnt <= TB::Cardinality
- && (piecesCnt < TB::Cardinality || depth >= TB::ProbeDepth)
+ if ( piecesCount <= TB::Cardinality
+ && (piecesCount < TB::Cardinality || depth >= TB::ProbeDepth)
&& pos.rule50_count() == 0
&& !pos.can_castle(ANY_CASTLING))
{
ss->staticEval, TT.generation());
}
- if (ss->skipEarlyPruning)
+ if (skipEarlyPruning)
goto moves_loop;
// Step 6. Razoring (skipped when in check)
&& eval + razor_margin[depth / ONE_PLY] <= alpha)
{
if (depth <= ONE_PLY)
- return qsearch<NonPV, false>(pos, ss, alpha, beta, DEPTH_ZERO);
+ return qsearch<NonPV, false>(pos, ss, alpha, alpha+1);
Value ralpha = alpha - razor_margin[depth / ONE_PLY];
- Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1, DEPTH_ZERO);
+ Value v = qsearch<NonPV, false>(pos, ss, ralpha, ralpha+1);
if (v <= ralpha)
return v;
}
Depth R = ((823 + 67 * depth / ONE_PLY) / 256 + std::min((eval - beta) / PawnValueMg, 3)) * ONE_PLY;
pos.do_null_move(st);
- (ss+1)->skipEarlyPruning = true;
- nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode);
- (ss+1)->skipEarlyPruning = false;
+ nullValue = depth-R < ONE_PLY ? -qsearch<NonPV, false>(pos, ss+1, -beta, -beta+1)
+ : - search<NonPV>(pos, ss+1, -beta, -beta+1, depth-R, !cutNode, true);
pos.undo_null_move();
if (nullValue >= beta)
return nullValue;
// Do verification search at high depths
- ss->skipEarlyPruning = true;
- Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta, DEPTH_ZERO)
- : search<NonPV>(pos, ss, beta-1, beta, depth-R, false);
- ss->skipEarlyPruning = false;
+ Value v = depth-R < ONE_PLY ? qsearch<NonPV, false>(pos, ss, beta-1, beta)
+ : search<NonPV>(pos, ss, beta-1, beta, depth-R, false, true);
if (v >= beta)
return nullValue;
ss->currentMove = move;
ss->counterMoves = &thisThread->counterMoveHistory[pos.moved_piece(move)][to_sq(move)];
pos.do_move(move, st);
- value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode);
+ value = -search<NonPV>(pos, ss+1, -rbeta, -rbeta+1, rdepth, !cutNode, false);
pos.undo_move(move);
if (value >= rbeta)
return value;
&& (PvNode || ss->staticEval + 256 >= beta))
{
Depth d = (3 * depth / (4 * ONE_PLY) - 2) * ONE_PLY;
- ss->skipEarlyPruning = true;
- search<NT>(pos, ss, alpha, beta, d, cutNode);
- ss->skipEarlyPruning = false;
+ search<NT>(pos, ss, alpha, beta, d, cutNode, true);
tte = TT.probe(posKey, ttHit);
ttMove = ttHit ? tte->move() : MOVE_NONE;
Value rBeta = std::max(ttValue - 2 * depth / ONE_PLY, -VALUE_MATE);
Depth d = (depth / (2 * ONE_PLY)) * ONE_PLY;
ss->excludedMove = move;
- ss->skipEarlyPruning = true;
- value = search<NonPV>(pos, ss, rBeta - 1, rBeta, d, cutNode);
- ss->skipEarlyPruning = false;
+ value = search<NonPV>(pos, ss, rBeta - 1, rBeta, d, cutNode, true);
ss->excludedMove = MOVE_NONE;
if (value < rBeta)
&& !pos.see_ge(move, Value(-35 * lmrDepth * lmrDepth)))
continue;
}
- else if (depth < 7 * ONE_PLY && !extension)
- {
- Value v = -Value(399 + 35 * depth / ONE_PLY * depth / ONE_PLY);
-
- if (PvNode)
- v += beta - alpha - 1;
-
- if (!pos.see_ge(move, v))
+ else if ( depth < 7 * ONE_PLY
+ && !extension
+ && !pos.see_ge(move, -PawnValueEg * (depth / ONE_PLY)))
continue;
- }
}
// Speculative prefetch as early as possible
// castling moves, because they are coded as "king captures rook" and
// hence break make_move().
else if ( type_of(move) == NORMAL
- && type_of(pos.piece_on(to_sq(move))) != PAWN
&& !pos.see_ge(make_move(to_sq(move), from_sq(move)), VALUE_ZERO))
r -= 2 * ONE_PLY;
Depth d = std::max(newDepth - r, ONE_PLY);
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true, false);
doFullDepthSearch = (value > alpha && d != newDepth);
}
// Step 16. Full depth search when LMR is skipped or fails high
if (doFullDepthSearch)
value = newDepth < ONE_PLY ?
- givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha, DEPTH_ZERO)
- : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
+ givesCheck ? -qsearch<NonPV, true>(pos, ss+1, -(alpha+1), -alpha)
+ : -qsearch<NonPV, false>(pos, ss+1, -(alpha+1), -alpha)
+ : - search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode, false);
// For PV nodes only, do a full PV search on the first move or after a fail
// high (in the latter case search only if value < beta), otherwise let the
(ss+1)->pv[0] = MOVE_NONE;
value = newDepth < ONE_PLY ?
- givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : -qsearch<PV, false>(pos, ss+1, -beta, -alpha, DEPTH_ZERO)
- : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false);
+ givesCheck ? -qsearch<PV, true>(pos, ss+1, -beta, -alpha)
+ : -qsearch<PV, false>(pos, ss+1, -beta, -alpha)
+ : - search<PV>(pos, ss+1, -beta, -alpha, newDepth, false, false);
}
// Step 17. Undo move
if (value > alpha)
{
- // If there is an easy move for this position, clear it if unstable
- if ( PvNode
- && thisThread == Threads.main()
- && EasyMove.get(pos.key())
- && (move != EasyMove.get(pos.key()) || moveCount > 1))
- EasyMove.clear();
-
bestMove = move;
if (PvNode && !rootNode) // Update pv even in fail-high case
: inCheck ? mated_in(ss->ply) : DrawValue[pos.side_to_move()];
else if (bestMove)
{
- int d = depth / ONE_PLY;
// Quiet best move: update killers, history and countermoves
if (!pos.capture_or_promotion(bestMove))
- {
- Value bonus = Value(d * d + 2 * d - 2);
- update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus);
- }
+ update_stats(pos, ss, bestMove, quietsSearched, quietCount, bonus(depth));
// Extra penalty for a quiet TT move in previous ply when it gets refuted
if ((ss-1)->moveCount == 1 && !pos.captured_piece())
- {
- Value penalty = Value(d * d + 4 * d + 1);
- Square prevSq = to_sq((ss-1)->currentMove);
- update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, -penalty);
- }
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, penalty(depth));
}
// Bonus for prior countermove that caused the fail low
else if ( depth >= 3 * ONE_PLY
&& !pos.captured_piece()
&& is_ok((ss-1)->currentMove))
- {
- int d = depth / ONE_PLY;
- Value bonus = Value(d * d + 2 * d - 2);
- Square prevSq = to_sq((ss-1)->currentMove);
- update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus);
- }
+ update_cm_stats(ss-1, pos.piece_on(prevSq), prevSq, bonus(depth));
tte->save(posKey, value_to_tt(bestValue, ss->ply),
bestValue >= beta ? BOUND_LOWER :
// qsearch() is the quiescence search function, which is called by the main
- // search function when the remaining depth is zero (or, to be more precise,
- // less than ONE_PLY).
+ // search function with depth zero, or recursively with depth less than ONE_PLY.
template <NodeType NT, bool InCheck>
Value qsearch(Position& pos, Stack* ss, Value alpha, Value beta, Depth depth) {
ss->ply = (ss-1)->ply + 1;
// Check for an instant draw or if the maximum ply has been reached
- if (pos.is_draw() || ss->ply >= MAX_PLY)
+ if (pos.is_draw(ss->ply) || ss->ply >= MAX_PLY)
return ss->ply >= MAX_PLY && !InCheck ? evaluate(pos)
: DrawValue[pos.side_to_move()];
projects / stockfish / blobdiff