else
Threads.stop = true;
}
- else if ( Threads.increaseDepth
- && !mainThread->ponder
+ else if ( !mainThread->ponder
&& Time.elapsed() > totalTime * 0.53)
- Threads.increaseDepth = false;
+ Threads.increaseDepth = false;
else
- Threads.increaseDepth = true;
+ Threads.increaseDepth = true;
}
mainThread->iterValue[iterIdx] = bestValue;
&& ttValue != VALUE_NONE // Possible in case of TT access race
&& (tte->bound() & (ttValue >= beta ? BOUND_LOWER : BOUND_UPPER)))
{
- // If ttMove is quiet, update move sorting heuristics on TT hit (~1 Elo)
+ // If ttMove is quiet, update move sorting heuristics on TT hit (~2 Elo)
if (ttMove)
{
if (ttValue >= beta)
{
- // Bonus for a quiet ttMove that fails high (~3 Elo)
+ // Bonus for a quiet ttMove that fails high (~2 Elo)
if (!ttCapture)
update_quiet_stats(pos, ss, ttMove, stat_bonus(depth));
- // Extra penalty for early quiet moves of the previous ply (~0 Elo)
+ // Extra penalty for early quiet moves of the previous ply (~0 Elo on STC, ~2 Elo on LTC)
if ((ss-1)->moveCount <= 2 && !priorCapture)
update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, -stat_bonus(depth + 1));
}
else // Fall back to (semi)classical complexity for TT hits, the NNUE complexity is lost
complexity = abs(ss->staticEval - pos.psq_eg_stm());
- // ttValue can be used as a better position evaluation (~4 Elo)
+ // ttValue can be used as a better position evaluation (~7 Elo)
if ( ttValue != VALUE_NONE
&& (tte->bound() & (ttValue > eval ? BOUND_LOWER : BOUND_UPPER)))
eval = ttValue;
thisThread->complexityAverage.update(complexity);
- // Use static evaluation difference to improve quiet move ordering (~3 Elo)
+ // Use static evaluation difference to improve quiet move ordering (~4 Elo)
if (is_ok((ss-1)->currentMove) && !(ss-1)->inCheck && !priorCapture)
{
int bonus = std::clamp(-19 * int((ss-1)->staticEval + ss->staticEval), -1914, 1914);
: 168;
improving = improvement > 0;
- // Step 7. Razoring.
+ // Step 7. Razoring (~1 Elo).
// If eval is really low check with qsearch if it can exceed alpha, if it can't,
// return a fail low.
if (eval < alpha - 369 - 254 * depth * depth)
return value;
}
- // Step 8. Futility pruning: child node (~25 Elo).
+ // Step 8. Futility pruning: child node (~40 Elo).
// The depth condition is important for mate finding.
if ( !ss->ttPv
&& depth < 8
&& eval < 28031) // larger than VALUE_KNOWN_WIN, but smaller than TB wins
return eval;
- // Step 9. Null move search with verification search (~22 Elo)
+ // Step 9. Null move search with verification search (~35 Elo)
if ( !PvNode
&& (ss-1)->currentMove != MOVE_NULL
&& (ss-1)->statScore < 17139
probCutBeta = beta + 191 - 54 * improving;
- // Step 10. ProbCut (~4 Elo)
+ // Step 10. ProbCut (~10 Elo)
// If we have a good enough capture and a reduced search returns a value
// much above beta, we can (almost) safely prune the previous move.
if ( !PvNode
}
// Step 11. If the position is not in TT, decrease depth by 3.
- // Use qsearch if depth is equal or below zero (~4 Elo)
+ // Use qsearch if depth is equal or below zero (~9 Elo)
if ( PvNode
&& !ttMove)
depth -= 3;
moves_loop: // When in check, search starts here
- // Step 12. A small Probcut idea, when we are in check (~0 Elo)
+ // Step 12. A small Probcut idea, when we are in check (~4 Elo)
probCutBeta = beta + 417;
if ( ss->inCheck
&& !PvNode
Value delta = beta - alpha;
- // Step 14. Pruning at shallow depth (~98 Elo). Depth conditions are important for mate finding.
+ // Step 14. Pruning at shallow depth (~120 Elo). Depth conditions are important for mate finding.
if ( !rootNode
&& pos.non_pawn_material(us)
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY)
{
- // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold (~7 Elo)
+ // Skip quiet moves if movecount exceeds our FutilityMoveCount threshold (~8 Elo)
moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search
if ( capture
|| givesCheck)
{
- // Futility pruning for captures (~0 Elo)
+ // Futility pruning for captures (~2 Elo)
if ( !givesCheck
&& !PvNode
&& lmrDepth < 7
+ captureHistory[movedPiece][to_sq(move)][type_of(pos.piece_on(to_sq(move)))] / 6 < alpha)
continue;
- // SEE based pruning (~9 Elo)
+ // SEE based pruning (~11 Elo)
if (!pos.see_ge(move, Value(-222) * depth))
continue;
}
history += 2 * thisThread->mainHistory[us][from_to(move)];
- // Futility pruning: parent node (~9 Elo)
+ // Futility pruning: parent node (~13 Elo)
if ( !ss->inCheck
&& lmrDepth < 13
&& ss->staticEval + 106 + 145 * lmrDepth + history / 52 <= alpha)
continue;
- // Prune moves with negative SEE (~3 Elo)
+ // Prune moves with negative SEE (~4 Elo)
if (!pos.see_ge(move, Value(-24 * lmrDepth * lmrDepth - 15 * lmrDepth)))
continue;
}
}
- // Step 15. Extensions (~66 Elo)
+ // Step 15. Extensions (~100 Elo)
// We take care to not overdo to avoid search getting stuck.
if (ss->ply < thisThread->rootDepth * 2)
{
- // Singular extension search (~58 Elo). If all moves but one fail low on a
+ // Singular extension search (~94 Elo). If all moves but one fail low on a
// search of (alpha-s, beta-s), and just one fails high on (alpha, beta),
// then that move is singular and should be extended. To verify this we do
// a reduced search on all the other moves but the ttMove and if the
// Avoid search explosion by limiting the number of double extensions
if ( !PvNode
&& value < singularBeta - 25
- && ss->doubleExtensions <= 9)
+ && ss->doubleExtensions <= 10)
{
extension = 2;
depth += depth < 12;
&& abs(ss->staticEval) > 82)
extension = 1;
- // Quiet ttMove extensions (~0 Elo)
+ // Quiet ttMove extensions (~1 Elo)
else if ( PvNode
&& move == ttMove
&& move == ss->killers[0]
// Step 16. Make the move
pos.do_move(move, st, givesCheck);
- // Step 17. Late moves reduction / extension (LMR, ~98 Elo)
- // We use various heuristics for the sons of a node after the first son has
- // been searched. In general we would like to reduce them, but there are many
- // cases where we extend a son if it has good chances to be "interesting".
- if ( depth >= 2
- && moveCount > 1 + (PvNode && ss->ply <= 1)
- && ( !ss->ttPv
- || !capture
- || (cutNode && (ss-1)->moveCount > 1)))
- {
- Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);
+ Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);
- // Decrease reduction if position is or has been on the PV
- // and node is not likely to fail low. (~3 Elo)
- if ( ss->ttPv
- && !likelyFailLow)
- r -= 2;
+ // Decrease reduction if position is or has been on the PV
+ // and node is not likely to fail low. (~3 Elo)
+ if ( ss->ttPv
+ && !likelyFailLow)
+ r -= 2;
- // Decrease reduction if opponent's move count is high (~1 Elo)
- if ((ss-1)->moveCount > 7)
- r--;
+ // Decrease reduction if opponent's move count is high (~1 Elo)
+ if ((ss-1)->moveCount > 7)
+ r--;
- // Increase reduction for cut nodes (~3 Elo)
- if (cutNode)
- r += 2;
+ // Increase reduction for cut nodes (~3 Elo)
+ if (cutNode)
+ r += 2;
- // Increase reduction if ttMove is a capture (~3 Elo)
- if (ttCapture)
- r++;
+ // Increase reduction if ttMove is a capture (~3 Elo)
+ if (ttCapture)
+ r++;
- // Decrease reduction for PvNodes based on depth
- if (PvNode)
- r -= 1 + 11 / (3 + depth);
+ // Decrease reduction for PvNodes based on depth
+ if (PvNode)
+ r -= 1 + 11 / (3 + depth);
- // Decrease reduction if ttMove has been singularly extended (~1 Elo)
- if (singularQuietLMR)
- r--;
+ // Decrease reduction if ttMove has been singularly extended (~1 Elo)
+ if (singularQuietLMR)
+ r--;
- // Decrease reduction if we move a threatened piece (~1 Elo)
- if ( depth > 9
- && (mp.threatenedPieces & from_sq(move)))
- r--;
+ // Decrease reduction if we move a threatened piece (~1 Elo)
+ if ( depth > 9
+ && (mp.threatenedPieces & from_sq(move)))
+ r--;
- // Increase reduction if next ply has a lot of fail high
- if ((ss+1)->cutoffCnt > 3)
- r++;
+ // Increase reduction if next ply has a lot of fail high
+ if ((ss+1)->cutoffCnt > 3)
+ r++;
- ss->statScore = 2 * thisThread->mainHistory[us][from_to(move)]
- + (*contHist[0])[movedPiece][to_sq(move)]
- + (*contHist[1])[movedPiece][to_sq(move)]
- + (*contHist[3])[movedPiece][to_sq(move)]
- - 4433;
+ ss->statScore = 2 * thisThread->mainHistory[us][from_to(move)]
+ + (*contHist[0])[movedPiece][to_sq(move)]
+ + (*contHist[1])[movedPiece][to_sq(move)]
+ + (*contHist[3])[movedPiece][to_sq(move)]
+ - 4433;
- // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
- r -= ss->statScore / (13000 + 4152 * (depth > 7 && depth < 19));
+ // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
+ r -= ss->statScore / (13000 + 4152 * (depth > 7 && depth < 19));
+ // Step 17. Late moves reduction / extension (LMR, ~117 Elo)
+ // We use various heuristics for the sons of a node after the first son has
+ // been searched. In general we would like to reduce them, but there are many
+ // cases where we extend a son if it has good chances to be "interesting".
+ if ( depth >= 2
+ && moveCount > 1 + (PvNode && ss->ply <= 1)
+ && ( !ss->ttPv
+ || !capture
+ || (cutNode && (ss-1)->moveCount > 1)))
+ {
// In general we want to cap the LMR depth search at newDepth, but when
// reduction is negative, we allow this move a limited search extension
// beyond the first move depth. This may lead to hidden double extensions.
// Adjust full depth search based on LMR results - if result
// was good enough search deeper, if it was bad enough search shallower
const bool doDeeperSearch = value > (alpha + 64 + 11 * (newDepth - d));
- const bool doEvenDeeperSearch = value > alpha + 582;
+ const bool doEvenDeeperSearch = value > alpha + 582 && ss->doubleExtensions <= 5;
const bool doShallowerSearch = value < bestValue + newDepth;
+ ss->doubleExtensions = ss->doubleExtensions + doEvenDeeperSearch;
+
newDepth += doDeeperSearch - doShallowerSearch + doEvenDeeperSearch;
if (newDepth > d)
}
}
- // Step 18. Full depth search when LMR is skipped
+ // Step 18. Full depth search when LMR is skipped. If expected reduction is high, reduce its depth by 1.
else if (!PvNode || moveCount > 1)
{
- value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth, !cutNode);
+ value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, newDepth - (r > 4), !cutNode);
}
// For PV nodes only, do a full PV search on the first move or after a fail
quietsSearched, quietCount, capturesSearched, captureCount, depth);
// Bonus for prior countermove that caused the fail low
- else if ( (depth >= 5 || PvNode)
+ else if ( (depth >= 5 || PvNode || bestValue < alpha - 62 * depth)
&& !priorCapture)
{
//Assign extra bonus if current node is PvNode or cutNode
//or fail low was really bad
bool extraBonus = PvNode
- || cutNode
- || bestValue < alpha - 62 * depth;
+ || cutNode;
+
+ bool doubleExtraBonus = extraBonus && bestValue < alpha - 85 * depth;
- update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus));
+ update_continuation_histories(ss-1, pos.piece_on(prevSq), prevSq, stat_bonus(depth) * (1 + extraBonus + doubleExtraBonus));
}
if (PvNode)
if ((ss->staticEval = bestValue = tte->eval()) == VALUE_NONE)
ss->staticEval = bestValue = evaluate(pos);
- // ttValue can be used as a better position evaluation (~7 Elo)
+ // ttValue can be used as a better position evaluation (~13 Elo)
if ( ttValue != VALUE_NONE
&& (tte->bound() & (ttValue > bestValue ? BOUND_LOWER : BOUND_UPPER)))
bestValue = ttValue;
moveCount++;
- // Futility pruning and moveCount pruning (~5 Elo)
+ // Futility pruning and moveCount pruning (~10 Elo)
if ( bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& !givesCheck
&& to_sq(move) != prevSq
[pos.moved_piece(move)]
[to_sq(move)];
- // Continuation history based pruning (~2 Elo)
+ // Continuation history based pruning (~3 Elo)
if ( !capture
&& bestValue > VALUE_TB_LOSS_IN_MAX_PLY
&& (*contHist[0])[pos.moved_piece(move)][to_sq(move)] < 0
projects / stockfish / blobdiff