From: lucasart <lucas.braesch@gmail.com>
Date: Fri, 7 Nov 2014 21:40:24 +0000 (+0000)
Subject: Prune ttMove like any other
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=7ebb872409d23b7c745d71ce5c21bea786d81aa0;ds=sidebyside

Prune ttMove like any other

This should reduce search inconsistencies, and doesn't seem to have a measurable ELO Impact:

STC with Hash=16
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 49264 W: 10076 L: 10007 D: 29181

LTC with Hash=64
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 82149 W: 14044 L: 14023 D: 54082

Plus an extra test, to make sure it doesn't regress with strong hash pressure:

STC with Hash=4
LLR: 2.95 (-2.94,2.94) [-4.00,0.00]
Total: 21498 W: 4327 L: 4246 D: 12925

Bench: 7302735

Resolves #100
---

diff --git a/src/search.cpp b/src/search.cpp
index fedad432..44eb4ccc 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -747,7 +747,6 @@ moves_loop: // When in check and at SpNode search starts from here
           && !captureOrPromotion
           && !inCheck
           && !dangerous
-       /* &&  move != ttMove Already implicit in the next condition */
           &&  bestValue > VALUE_MATED_IN_MAX_PLY)
       {
           // Move count based pruning
@@ -813,9 +812,8 @@ moves_loop: // When in check and at SpNode search starts from here
       // Step 15. Reduced depth search (LMR). If the move fails high it will be
       // re-searched at full depth.
       if (    depth >= 3 * ONE_PLY
-          && !pvMove
+          &&  moveCount > 1
           && !captureOrPromotion
-          &&  move != ttMove
           &&  move != ss->killers[0]
           &&  move != ss->killers[1])
       {
@@ -1111,7 +1109,6 @@ moves_loop: // When in check and at SpNode search starts from here
       if (   !PvNode
           && !InCheck
           && !givesCheck
-          &&  move != ttMove
           &&  futilityBase > -VALUE_KNOWN_WIN
           && !pos.advanced_pawn_push(move))
       {
@@ -1141,7 +1138,6 @@ moves_loop: // When in check and at SpNode search starts from here
       // Don't search moves with negative SEE values
       if (   !PvNode
           && (!InCheck || evasionPrunable)
-          &&  move != ttMove
           &&  type_of(move) != PROMOTION
           &&  pos.see_sign(move) < VALUE_ZERO)
           continue;