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Increase reduction if tt-move is a capture 

The idea is that chances are the tt-move is best and will be difficult to raise alpha when playing a quiet move.

STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 7582 W: 1415 L: 1259 D: 4908

LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 59553 W: 7885 L: 7573 D: 44095

Bench: 5725676

Closes #1147
pull/1147/merge
VoyagerOne 2017-06-21 14:05:14 -07:00 committed by Joona Kiiski
parent 612d93234b
commit 77342126d8
1 changed files with 10 additions and 1 deletions
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11
src/search.cpp
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@ -554,7 +554,7 @@ namespace {
Depth extension, newDepth;
Value bestValue, value, ttValue, eval;
bool ttHit, inCheck, givesCheck, singularExtensionNode, improving;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets;
bool captureOrPromotion, doFullDepthSearch, moveCountPruning, skipQuiets, ttCapture;
Piece moved_piece;
int moveCount, quietCount;
@ -842,6 +842,7 @@ moves_loop: // When in check search starts from here
&& (tte->bound() & BOUND_LOWER)
&& tte->depth() >= depth - 3 * ONE_PLY;
skipQuiets = false;
ttCapture = false;
// Step 11. Loop through moves
// Loop through all pseudo-legal moves until no moves remain or a beta cutoff occurs
@ -959,6 +960,9 @@ moves_loop: // When in check search starts from here
ss->moveCount = --moveCount;
continue;
}
if (move == ttMove && captureOrPromotion)
ttCapture = true;
// Update the current move (this must be done after singular extension search)
ss->currentMove = move;
@ -979,6 +983,11 @@ moves_loop: // When in check search starts from here
r -= r ? ONE_PLY : DEPTH_ZERO;
else
{
// Increase reduction if ttMove is a capture
if (ttCapture)
r += ONE_PLY;
// Increase reduction for cut nodes
if (cutNode)
r += 2 * ONE_PLY;