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Clean up search

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* Correct IIR scaling comments
* Replace `(PvNode || cutNode)` with `!allNode`
* Consistent formatting for scaler tags
* Add comments to some recently-introduced LMR terms
* Add comments on PCM bonus tweaks

Passed Non-regression STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 389472 W: 102457 L: 102622 D: 184393
Ptnml(0-2): 1676, 41887, 107798, 41676, 1699
https://tests.stockfishchess.org/tests/view/67a0ea670774dfd78deb23cd

closes https://github.com/official-stockfish/Stockfish/pull/5854

Bench: 1585741
This commit is contained in:
Shawn Xu
2025-02-27 12:43:58 -08:00
committed by Disservin
parent 27428a61c2
commit 4e49f8dff9
1 changed files with 22 additions and 23 deletions
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45
src/search.cpp
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@@ -658,8 +658,7 @@ Value Search::Worker::search(
Value bestValue, value, eval, maxValue, probCutBeta;
bool givesCheck, improving, priorCapture, opponentWorsening;
bool capture, ttCapture;
int priorReduction = (ss - 1)->reduction;
(ss - 1)->reduction = 0;
int priorReduction;
Piece movedPiece;
ValueList<Move, 32> capturesSearched;
@@ -704,11 +703,13 @@ Value Search::Worker::search(
assert(0 <= ss->ply && ss->ply < MAX_PLY);
bestMove = Move::none();
Square prevSq = ((ss - 1)->currentMove).is_ok() ? ((ss - 1)->currentMove).to_sq() : SQ_NONE;
bestMove = Move::none();
priorReduction = (ss - 1)->reduction;
(ss - 1)->reduction = 0;
ss->statScore = 0;
ss->isPvNode = PvNode;
(ss + 2)->cutoffCnt = 0;
Square prevSq = ((ss - 1)->currentMove).is_ok() ? ((ss - 1)->currentMove).to_sq() : SQ_NONE;
ss->statScore = 0;
ss->isPvNode = PvNode;
// Step 4. Transposition table lookup
excludedMove = ss->excludedMove;
@@ -927,8 +928,8 @@ Value Search::Worker::search(
// Step 10. Internal iterative reductions
// For PV nodes without a ttMove as well as for deep enough cutNodes, we decrease depth.
// (* Scaler) Especially if they make IIR more aggressive.
if (((PvNode || cutNode) && depth >= 7 - 3 * PvNode) && !ttData.move)
// (*Scaler) Especially if they make IIR less aggressive.
if (depth >= 7 - 3 * PvNode && !allNode && !ttData.move)
depth--;
// Step 11. ProbCut
@@ -1153,7 +1154,7 @@ moves_loop: // When in check, search starts here
// and if the result is lower than ttValue minus a margin, then we will
// extend the ttMove. Recursive singular search is avoided.
// (* Scaler) Generally, higher singularBeta (i.e closer to ttValue)
// (*Scaler) Generally, higher singularBeta (i.e closer to ttValue)
// and lower extension margins scale well.
if (!rootNode && move == ttData.move && !excludedMove
@@ -1233,8 +1234,8 @@ moves_loop: // When in check, search starts here
// These reduction adjustments have no proven non-linear scaling
r += 306 - moveCount * 34;
r += 306; // Base reduction offset to compensate for other tweaks
r -= moveCount * 34;
r -= std::abs(correctionValue) / 29696;
if (PvNode && std::abs(bestValue) <= 2000)
@@ -1280,18 +1281,14 @@ moves_loop: // When in check, search starts here
// beyond the first move depth.
// To prevent problems when the max value is less than the min value,
// std::clamp has been replaced by a more robust implementation.
Depth d = std::max(1, std::min(newDepth - r / 1024,
newDepth + !allNode + (PvNode && !bestMove)))
+ (!cutNode && (ss - 1)->isPvNode && moveCount < 8);
ss->reduction = newDepth - d;
value = -search<NonPV>(pos, ss + 1, -(alpha + 1), -alpha, d, true);
ss->reduction = 0;
// Do a full-depth search when reduced LMR search fails high
if (value > alpha && d < newDepth)
{
@@ -1487,12 +1484,14 @@ moves_loop: // When in check, search starts here
// Bonus for prior quiet countermove that caused the fail low
else if (!priorCapture && prevSq != SQ_NONE)
{
int bonusScale =
(std::min(78 * depth - 312, 194) + 34 * !allNode + 164 * ((ss - 1)->moveCount > 8)
+ 141 * (!ss->inCheck && bestValue <= ss->staticEval - 100)
+ 121 * (!(ss - 1)->inCheck && bestValue <= -(ss - 1)->staticEval - 75)
+ 86 * ((ss - 1)->isTTMove) + 86 * (ss->cutoffCnt <= 3)
+ std::min(-(ss - 1)->statScore / 112, 303));
int bonusScale = std::min(-(ss - 1)->statScore / 112, 303);
bonusScale += std::min(78 * depth - 312, 194);
bonusScale += 34 * !allNode;
bonusScale += 164 * ((ss - 1)->moveCount > 8);
bonusScale += 86 * (ss - 1)->isTTMove;
bonusScale += 86 * (ss->cutoffCnt <= 3);
bonusScale += 141 * (!ss->inCheck && bestValue <= ss->staticEval - 100);
bonusScale += 121 * (!(ss - 1)->inCheck && bestValue <= -(ss - 1)->staticEval - 75);
bonusScale = std::max(bonusScale, 0);
@@ -1903,14 +1902,14 @@ void update_all_stats(const Position& pos,
ValueList<Move, 32>& quietsSearched,
ValueList<Move, 32>& capturesSearched,
Depth depth,
Move TTMove,
Move ttMove,
int moveCount) {
CapturePieceToHistory& captureHistory = workerThread.captureHistory;
Piece moved_piece = pos.moved_piece(bestMove);
PieceType captured;
int bonus = std::min(141 * depth - 89, 1613) + 311 * (bestMove == TTMove);
int bonus = std::min(141 * depth - 89, 1613) + 311 * (bestMove == ttMove);
int malus = std::min(695 * depth - 215, 2808) - 31 * (moveCount - 1);
if (!pos.capture_stage(bestMove))