From 21ad356c0900c9eba9b7b1f7453f934eab80f303 Mon Sep 17 00:00:00 2001 From: Michael Chaly Date: Sun, 26 Sep 2021 06:39:27 +0200 Subject: [PATCH] Extend quiet tt moves at PvNodes Idea is to extend some quiet ttMoves if a lot of things indicate that the transposition table move is going to be a good move: 1) move being a killer - so being the best move in nearby node; 2) reply continuation history is really good. This is basically saying that move is good "in general" in this position, that it is a good reply to the opponent move and that it was the best in this position somewhere in search - so extending it makes a lot of sense. In general in past year we had a lot of extensions of different types, maybe there is something more in it :) passed STC LLR: 2.96 (-2.94,2.94) <-0.50,2.50> Total: 42944 W: 10932 L: 10695 D: 21317 Ptnml(0-2): 141, 4869, 11210, 5116, 136 https://tests.stockfishchess.org/tests/view/614cca8e7bdc23e77ceb89f0 passed LTC LLR: 2.93 (-2.94,2.94) <0.50,3.50> Total: 156848 W: 39473 L: 38893 D: 78482 Ptnml(0-2): 125, 16327, 44913, 16961, 98 https://tests.stockfishchess.org/tests/view/614cf93d7bdc23e77ceb8a13 closes https://github.com/official-stockfish/Stockfish/pull/3719 Bench: 5714575 --- src/search.cpp | 18 ++++++++++++------ 1 file changed, 12 insertions(+), 6 deletions(-) diff --git a/src/search.cpp b/src/search.cpp index 8db295f1..48694cb2 100644 --- a/src/search.cpp +++ b/src/search.cpp @@ -1147,7 +1147,14 @@ moves_loop: // When in check, search starts here // Check extensions else if ( givesCheck && depth > 6 - && abs(ss->staticEval) > Value(100)) + && abs(ss->staticEval) > 100) + extension = 1; + + // Quiet ttMove extensions + else if ( PvNode + && move == ttMove + && move == ss->killers[0] + && (*contHist[0])[movedPiece][to_sq(move)] >= 10000) extension = 1; // Add extension to new depth @@ -1223,11 +1230,10 @@ moves_loop: // When in check, search starts here // Decrease/increase reduction for moves with a good/bad history (~30 Elo) r -= ss->statScore / 14721; - // In general we want to cap the LMR depth search at newDepth. But if - // reductions are really negative and movecount is low, we allow this move - // to be searched deeper than the first move in specific cases (note that - // this may lead to hidden double extensions if newDepth got it own extension - // before). + // In general we want to cap the LMR depth search at newDepth. But if reductions + // are really negative and movecount is low, we allow this move to be searched + // deeper than the first move (this may lead to hidden double extensions if + // newDepth got its own extension before). int deeper = r >= -1 ? 0 : noLMRExtension ? 0 : moveCount <= 5 ? 1 -- 2.39.2