From: VoyagerOne <excelgeek@gmail.com>
Date: Mon, 16 Nov 2015 04:38:01 +0000 (-0800)
Subject: History Pruning: Don't prune the main killer move.
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=07e0741dfbca07097f38e46f3f7752b48675a515;ds=sidebyside

History Pruning: Don't prune the main killer move.

Also increased pruned depth to 4.

STC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 23380 W: 4581 L: 4350 D: 14449

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 28934 W: 4329 L: 4105 D: 20500

Bench: 8369743

Resolves #498
---

diff --git a/src/search.cpp b/src/search.cpp
index 13fb4b30..4a0302e5 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -921,7 +921,8 @@ moves_loop: // When in check search starts from here
               continue;
 
           // History based pruning
-          if (   depth <= 3 * ONE_PLY
+          if (   depth <= 4 * ONE_PLY
+              && move != ss->killers[0]
               && thisThread->history[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO
               && cmh[pos.moved_piece(move)][to_sq(move)] < VALUE_ZERO)
               continue;