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Cleanup of likelyFailLow logic

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This patch broadens and simplifies definition of PvNode that is likely to fail low.
New definition can be described as following "If node was already researched
at depth >= current depth and failed low there" which is more logical than the
previous version and takes less space + allows to not recompute it every time during move loop.

Passed simplification STC
https://tests.stockfishchess.org/tests/view/609148bf95e7f1852abd2e82
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 20128 W: 1865 L: 1751 D: 16512
Ptnml(0-2): 63, 1334, 7165, 1430, 72

Passed simplification LTC
https://tests.stockfishchess.org/tests/view/6091691295e7f1852abd2e8b
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 95128 W: 3498 L: 3481 D: 88149
Ptnml(0-2): 41, 2956, 41549, 2981, 37

closes https://github.com/official-stockfish/Stockfish/pull/3455

Bench: 3933037
This commit is contained in:
Vizvezdenec 2021-05-05 19:03:20 +03:00 • committed by Joost VandeVondele
parent ca250e969c
commit d777ea79ff
1 changed files with 7 additions and 8 deletions
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15
src/search.cpp
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@ -1006,6 +1006,13 @@ moves_loop: // When in check, search starts from here
value = bestValue; value = bestValue;
singularQuietLMR = moveCountPruning = false; singularQuietLMR = 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.
bool likelyFailLow = PvNode
&& ttMove
&& (tte->bound() & BOUND_UPPER)
&& tte->depth() >= depth;
// Mark this node as being searched // Mark this node as being searched
ThreadHolding th(thisThread, posKey, ss->ply); ThreadHolding th(thisThread, posKey, ss->ply);
@ -1044,14 +1051,6 @@ moves_loop: // When in check, search starts from here
movedPiece = pos.moved_piece(move); movedPiece = pos.moved_piece(move);
givesCheck = pos.gives_check(move); givesCheck = pos.gives_check(move);
// Indicate PvNodes that will probably fail low if node was searched with non-PV search
// at depth equal or greater to current depth and result of this search was far below alpha
bool likelyFailLow = PvNode
&& ttMove
&& (tte->bound() & BOUND_UPPER)
&& ttValue < alpha + 200 + 100 * depth
&& tte->depth() >= depth;
// Calculate new depth for this move // Calculate new depth for this move
newDepth = depth - 1; newDepth = depth - 1;