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Range reductions

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adding reductions for when the delta between the static eval and the child's eval is consistently low.

passed STC
https://tests.stockfishchess.org/html/live_elo.html?614d7b3c7bdc23e77ceb8a5d
LLR: 2.95 (-2.94,2.94) <-0.50,2.50>
Total: 88872 W: 22672 L: 22366 D: 43834
Ptnml(0-2): 343, 10150, 23117, 10510, 316

passed LTC
https://tests.stockfishchess.org/html/live_elo.html?614daf3e7bdc23e77ceb8a82
LLR: 2.93 (-2.94,2.94) <0.50,3.50>
Total: 24368 W: 6153 L: 5928 D: 12287
Ptnml(0-2): 13, 2503, 6937, 2708, 23

closes https://github.com/official-stockfish/Stockfish/pull/3717

Bench: 5443950
This commit is contained in:
OfekShochat 2021-09-23 23:16:17 +03:00 • committed by Joost VandeVondele
parent ff3fa0c664
commit 00e34a758f
2 changed files with 10 additions and 4 deletions
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1
AUTHORS
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@ -143,6 +143,7 @@ Nikolay Kostov (NikolayIT)
Nguyen Pham (nguyenpham)
Norman Schmidt (FireFather)
notruck
Ofek Shochat (OfekShochat, ghostway)
Ondrej Mosnáček (WOnder93)
Oskar Werkelin Ahlin
Pablo Vazquez

13
src/search.cpp
View file

@ -69,9 +69,9 @@ namespace {
// Reductions lookup table, initialized at startup
int Reductions[MAX_MOVES]; // [depth or moveNumber]
Depth reduction(bool i, Depth d, int mn) {
Depth reduction(bool i, Depth d, int mn, bool rangeReduction) {
int r = Reductions[d] * Reductions[mn];
return (r + 534) / 1024 + (!i && r > 904);
return (r + 534) / 1024 + (!i && r > 904) + rangeReduction;
}
constexpr int futility_move_count(bool improving, Depth depth) {
@ -954,6 +954,7 @@ namespace {
moves_loop: // When in check, search starts here
ttCapture = ttMove && pos.capture_or_promotion(ttMove);
int rangeReduction = 0;
// Step 11. A small Probcut idea, when we are in check
probCutBeta = beta + 409;
@ -1041,7 +1042,7 @@ moves_loop: // When in check, search starts here
moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount), 0);
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2), 0);
if ( captureOrPromotion
|| givesCheck)
@ -1176,7 +1177,7 @@ moves_loop: // When in check, search starts here
|| !ss->ttPv)
&& (!PvNode || ss->ply > 1 || thisThread->id() % 4 != 3))
{
Depth r = reduction(improving, depth, moveCount);
Depth r = reduction(improving, depth, moveCount, rangeReduction > 2);
if (PvNode)
r--;
@ -1236,6 +1237,10 @@ moves_loop: // When in check, search starts here
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true);
// Range reductions (~3 Elo)
if (ss->staticEval - value < 30 && depth > 7)
rangeReduction++;
// If the son is reduced and fails high it will be re-searched at full depth
doFullDepthSearch = value > alpha && d < newDepth;
didLMR = true;