From 07e0741dfbca07097f38e46f3f7752b48675a515 Mon Sep 17 00:00:00 2001
From: VoyagerOne <excelgeek@gmail.com>
Date: Sun, 15 Nov 2015 20:38:01 -0800
Subject: [PATCH] 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
---
 src/search.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

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;
-- 
2.39.2