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Simplify away singularQuietLMR

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While at it, we also update the Elo estimate of reduction at non-PV nodes
(source: https://tests.stockfishchess.org/tests/view/61acf97156fcf33bce7d6303 )

STC:
LLR: 2.94 (-2.94,2.94) <-2.25,0.25>
Total: 243632 W: 62874 L: 63022 D: 117736
Ptnml(0-2): 810, 28024, 64249, 27970, 763
https://tests.stockfishchess.org/tests/view/61b8b1b7dffbe89a35814c0d

LTC:
LLR: 2.93 (-2.94,2.94) <-2.25,0.25>
Total: 91392 W: 23520 L: 23453 D: 44419
Ptnml(0-2): 51, 9568, 26387, 9643, 47
https://tests.stockfishchess.org/tests/view/61b97316dffbe89a35817da7

closes https://github.com/official-stockfish/Stockfish/pull/3854

bench: 4217785
This commit is contained in:
bmc4 2021-12-14 12:00:45 -03:00 • committed by Stéphane Nicolet
parent 3bea736a2a
commit 0889210262
1 changed files with 3 additions and 9 deletions
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12
src/search.cpp
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@ -590,8 +590,7 @@ namespace {
Depth extension, newDepth;
Value bestValue, value, ttValue, eval, maxValue, probCutBeta;
bool givesCheck, improving, didLMR, priorCapture;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning,
ttCapture, singularQuietLMR;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, ttCapture;
Piece movedPiece;
int moveCount, captureCount, quietCount, bestMoveCount, improvement;
@ -982,7 +981,7 @@ moves_loop: // When in check, search starts here
ss->ply);
value = bestValue;
singularQuietLMR = moveCountPruning = false;
moveCountPruning = false;
// Indicate PvNodes that will probably fail low if the node was searched
// at a depth equal or greater than the current depth, and the result of this search was a fail low.
@ -1106,7 +1105,6 @@ moves_loop: // When in check, search starts here
if (value < singularBeta)
{
extension = 1;
singularQuietLMR = !ttCapture;
// Avoid search explosion by limiting the number of double extensions
if ( !PvNode
@ -1190,7 +1188,7 @@ moves_loop: // When in check, search starts here
&& !likelyFailLow)
r -= 2;
// Increase reduction at non-PV nodes
// Increase reduction at non-PV nodes (~3 Elo)
if (!PvNode)
r++;
@ -1198,10 +1196,6 @@ moves_loop: // When in check, search starts here
if ((ss-1)->moveCount > 13)
r--;
// Decrease reduction if ttMove has been singularly extended (~1 Elo)
if (singularQuietLMR)
r--;
// Increase reduction for cut nodes (~3 Elo)
if (cutNode && move != ss->killers[0])
r += 2;