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Simplify LMR rules for statScore

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We simplify two parts of LMR which seem not to bring strength anymore.

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Individual Tests:
https://tests.stockfishchess.org/tests/view/609d1cc15085663412d0856a
https://tests.stockfishchess.org/tests/view/609cb0cc7746e3dc74ffae8d
https://tests.stockfishchess.org/tests/view/609d1c9f5085663412d08568

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LTC:
LLR: 2.97 (-2.94,2.94) <-2.50,0.50>
Total: 84184 W: 3093 L: 3066 D: 78025
Ptnml(0-2): 47, 2755, 36458, 2788, 44
https://tests.stockfishchess.org/tests/view/609d84615085663412d08e2f

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While at it, we also update the Elo estimate of the previous rule in LMR, see:
https://tests.stockfishchess.org/tests/view/609a933c3a33eb67a844f7ca
https://tests.stockfishchess.org/tests/view/609a959c3a33eb67a844f7d5
https://tests.stockfishchess.org/tests/view/609afff73a33eb67a844f870

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closes https://github.com/official-stockfish/Stockfish/pull/3464

Bench: 4156523
This commit is contained in:
bmc4 2021-05-13 23:47:41 -03:00 • committed by Stéphane Nicolet
parent 24b8b3098b
commit c82f6f56a6
1 changed files with 6 additions and 17 deletions
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23
src/search.cpp
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@ -1131,12 +1131,12 @@ moves_loop: // When in check, search starts from here
{ {
Depth r = reduction(improving, depth, moveCount); Depth r = reduction(improving, depth, moveCount);
// Decrease reduction if the ttHit running average is large // Decrease reduction if the ttHit running average is large (~0 Elo)
if (thisThread->ttHitAverage > 537 * TtHitAverageResolution * TtHitAverageWindow / 1024) if (thisThread->ttHitAverage > 537 * TtHitAverageResolution * TtHitAverageWindow / 1024)
r--; r--;
// Decrease reduction if position is or has been on the PV // Decrease reduction if position is or has been on the PV
// and node is not likely to fail low. (~10 Elo) // and node is not likely to fail low. (~3 Elo)
if ( ss->ttPv if ( ss->ttPv
&& !likelyFailLow) && !likelyFailLow)
r -= 2; r -= 2;
@ -1162,9 +1162,10 @@ moves_loop: // When in check, search starts from here
r++; r++;
// Increase reduction at root if failing high // Increase reduction at root if failing high
r += rootNode ? thisThread->failedHighCnt * thisThread->failedHighCnt * moveCount / 512 : 0; if (rootNode)
r += thisThread->failedHighCnt * thisThread->failedHighCnt * moveCount / 512;
// Increase reduction for cut nodes (~10 Elo) // Increase reduction for cut nodes (~3 Elo)
if (cutNode) if (cutNode)
r += 2; r += 2;
@ -1174,20 +1175,8 @@ moves_loop: // When in check, search starts from here
+ (*contHist[3])[movedPiece][to_sq(move)] + (*contHist[3])[movedPiece][to_sq(move)]
- 4741; - 4741;
// Decrease/increase reduction by comparing opponent's stat score (~10 Elo)
if (ss->statScore >= -89 && (ss-1)->statScore < -116)
r--;
else if ((ss-1)->statScore >= -112 && ss->statScore < -100)
r++;
// Decrease/increase reduction for moves with a good/bad history (~30 Elo) // Decrease/increase reduction for moves with a good/bad history (~30 Elo)
// If we are not in check use statScore, but if we are in check we use if (!ss->inCheck)
// the sum of main history and first continuation history with an offset.
if (ss->inCheck)
r -= (thisThread->mainHistory[us][from_to(move)]
+ (*contHist[0])[movedPiece][to_sq(move)] - 3833) / 16384;
else
r -= ss->statScore / 14790; r -= ss->statScore / 14790;
} }