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Skip quiet moves based on moveCount pruning threshold and history stats

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If we can moveCountPrune and next quiet move has negative stats,
then go directly to the next move stage (Bad_Captures).

Reduction formula is tweaked to compensate for the decrease in move count that is used in LMR.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 6847 W: 1276 L: 1123 D: 4448

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 48687 W: 6503 L: 6226 D: 35958

Bench: 5919519

Closes #1036
This commit is contained in:
VoyagerOne
2017-03-18 15:41:55 -07:00
committed by Joona Kiiski
parent c80d52c845
commit 352bd6f5aa
3 changed files with 12 additions and 7 deletions
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11
src/search.cpp
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@@ -163,7 +163,7 @@ void Search::init() {
for (int d = 1; d < 64; ++d)
for (int mc = 1; mc < 64; ++mc)
{
double r = log(d) * log(mc) / 2;
double r = log(d) * log(mc) / 1.95;
Reductions[NonPV][imp][d][mc] = int(std::round(r));
Reductions[PV][imp][d][mc] = std::max(Reductions[NonPV][imp][d][mc] - 1, 0);
@@ -542,7 +542,7 @@ namespace {
Depth extension, newDepth;
Value bestValue, value, ttValue, eval;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets;
Piece moved_piece;
int moveCount, quietCount;
@@ -829,10 +829,11 @@ moves_loop: // When in check search starts from here
&& !excludedMove // Recursive singular search is not allowed
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
skipQuiets = false;
// Step 11. Loop through moves
// Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
while ((move = mp.next_move()) != MOVE_NONE)
while ((move = mp.next_move(skipQuiets)) != MOVE_NONE)
{
assert(is_ok(move));
@@ -906,8 +907,10 @@ moves_loop: // When in check search starts from here
&& (!pos.advanced_pawn_push(move) || pos.non_pawn_material() >= 5000))
{
// Move count based pruning
if (moveCountPruning)
if (moveCountPruning) {
skipQuiets = true;
continue;
}
// Reduced depth of the next LMR search
int lmrDepth = std::max(newDepth - reduction<PvNode>(improving, depth, moveCount), DEPTH_ZERO) / ONE_PLY;