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Simplify away rangeReduction

Browse source 
Remove rangeReduction, introduced in [#3717](https://github.com/official-stockfish/Stockfish/pull/3717),
as it seemingly doesn't bring enough ELO anymore. It might be interesting to add
new forms of reduction or tune the reduction formula in the future.

STC:
LLR: 2.95 (-2.94,2.94) <-2.25,0.25>
Total: 45008 W: 12114 L: 11972 D: 20922
Ptnml(0-2): 174, 5031, 11952, 5173, 174
https://tests.stockfishchess.org/tests/view/61d08b7b069ca917749c9f6f

LTC:
LLR: 2.94 (-2.94,2.94) <-2.25,0.25>
Total: 30792 W: 8235 L: 8086 D: 14471
Ptnml(0-2): 24, 3162, 8882, 3297, 31
https://tests.stockfishchess.org/tests/view/61d0a6ad069ca917749ca420

closes https://github.com/official-stockfish/Stockfish/pull/3878

Bench: 4048312
This commit is contained in:
lonfom169 2022-01-01 14:09:08 -03:00 • committed by Stéphane Nicolet
parent 061f98a9e3
commit 0b41887527
1 changed files with 4 additions and 10 deletions
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14
src/search.cpp
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@ -69,9 +69,9 @@ namespace {
// Reductions lookup table, initialized at startup // Reductions lookup table, initialized at startup
int Reductions[MAX_MOVES]; // [depth or moveNumber] int Reductions[MAX_MOVES]; // [depth or moveNumber]
Depth reduction(bool i, Depth d, int mn, bool rangeReduction, Value delta, Value rootDelta) { Depth reduction(bool i, Depth d, int mn, Value delta, Value rootDelta) {
int r = Reductions[d] * Reductions[mn]; int r = Reductions[d] * Reductions[mn];
return (r + 1358 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 904) + rangeReduction; return (r + 1358 - int(delta) * 1024 / int(rootDelta)) / 1024 + (!i && r > 904);
} }
constexpr int futility_move_count(bool improving, Depth depth) { constexpr int futility_move_count(bool improving, Depth depth) {
@ -938,8 +938,6 @@ namespace {
moves_loop: // When in check, search starts here moves_loop: // When in check, search starts here
int rangeReduction = 0;
// Step 11. A small Probcut idea, when we are in check (~0 Elo) // Step 11. A small Probcut idea, when we are in check (~0 Elo)
probCutBeta = beta + 409; probCutBeta = beta + 409;
if ( ss->inCheck if ( ss->inCheck
@ -1026,7 +1024,7 @@ moves_loop: // When in check, search starts here
moveCountPruning = moveCount >= futility_move_count(improving, depth); moveCountPruning = moveCount >= futility_move_count(improving, depth);
// Reduced depth of the next LMR search // Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, rangeReduction > 2, delta, thisThread->rootDelta), 0); int lmrDepth = std::max(newDepth - reduction(improving, depth, moveCount, delta, thisThread->rootDelta), 0);
if ( captureOrPromotion if ( captureOrPromotion
|| givesCheck) || givesCheck)
@ -1159,7 +1157,7 @@ moves_loop: // When in check, search starts here
|| !captureOrPromotion || !captureOrPromotion
|| (cutNode && (ss-1)->moveCount > 1))) || (cutNode && (ss-1)->moveCount > 1)))
{ {
Depth r = reduction(improving, depth, moveCount, rangeReduction > 2, delta, thisThread->rootDelta); Depth r = reduction(improving, depth, moveCount, delta, thisThread->rootDelta);
// Decrease reduction at some PvNodes (~2 Elo) // Decrease reduction at some PvNodes (~2 Elo)
if ( PvNode if ( PvNode
@ -1206,10 +1204,6 @@ moves_loop: // When in check, search starts here
value = -search<NonPV>(pos, ss+1, -(alpha+1), -alpha, d, true); 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 // If the son is reduced and fails high it will be re-searched at full depth
doFullDepthSearch = value > alpha && d < newDepth; doFullDepthSearch = value > alpha && d < newDepth;
doDeeperSearch = value > (alpha + 62 + 20 * (newDepth - d)); doDeeperSearch = value > (alpha + 62 + 20 * (newDepth - d));