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Remove early return in Probcut code

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We simplify away early return in ProbCut, as it seems not to bring any strength anymore.

STC:
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 42632 W: 3705 L: 3617 D: 35310
Ptnml(0-2): 123, 2947, 15110, 2991, 145
https://tests.stockfishchess.org/tests/view/609c49da7746e3dc74ffae02

LTC:
LLR: 2.96 (-2.94,2.94) <-2.50,0.50>
Total: 35384 W: 1314 L: 1251 D: 32819
Ptnml(0-2): 11, 1130, 15355, 1177, 19
https://tests.stockfishchess.org/tests/view/609c71467746e3dc74ffae47

---

While at it, we also update the Elo estimate of ProbCut
(see https://tests.stockfishchess.org/tests/view/609bfb597746e3dc74ffabe3).

closes https://github.com/official-stockfish/Stockfish/pull/3462

bench: 3764662
This commit is contained in:
bmc4 2021-05-13 11:12:56 -03:00 • committed by Stéphane Nicolet
parent bd756ee45c
commit 24b8b3098b
1 changed files with 1 additions and 10 deletions
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11
src/search.cpp
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@ -847,7 +847,7 @@ namespace {
probCutBeta = beta + 209 - 44 * improving;
// Step 9. ProbCut (~10 Elo)
// Step 9. ProbCut (~4 Elo)
// If we have a good enough capture and a reduced search returns a value
// much above beta, we can (almost) safely prune the previous move.
if ( !PvNode
@ -862,15 +862,6 @@ namespace {
&& ttValue != VALUE_NONE
&& ttValue < probCutBeta))
{
// if ttMove is a capture and value from transposition table is good enough produce probCut
// cutoff without digging into actual probCut search
if ( ss->ttHit
&& tte->depth() >= depth - 3
&& ttValue != VALUE_NONE
&& ttValue >= probCutBeta
&& ttMove
&& pos.capture_or_promotion(ttMove))
return probCutBeta;
assert(probCutBeta < VALUE_INFINITE);