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Extend quiet tt moves at PvNodes

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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
This commit is contained in:
Michael Chaly 2021-09-26 06:39:27 +02:00 • committed by Stéphane Nicolet
parent 919da65d70
commit 21ad356c09
1 changed files with 12 additions and 6 deletions
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18
src/search.cpp
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@ -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