From: Marco Costalba <mcostalba@gmail.com>
Date: Thu, 29 Apr 2010 17:21:48 +0000 (+0100)
Subject: Refresh TT entry after a cut-off to avoid aging
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=8425b2b4997c90aaad35ced6ab190df098f24212

Refresh TT entry after a cut-off to avoid aging

Re-save the same TT entry if value is usable and allow
us to cut-off, it means that entry is valuable and
we want to keep it fresh updating the 'generation'
parameter up to the current value.

Patch suggested by J. Wesley Cleveland and better
clarified by Miguel A. Ballicora.

After 999 games at 1+0 64MB hash size
Mod vs Orig +167 =677 -155 +4 ELO

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
---

diff --git a/src/search.cpp b/src/search.cpp
index b2b2414a..1f980fbb 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1301,6 +1301,9 @@ namespace {
 
     if (tte && ok_to_use_TT(tte, depth, beta, ply))
     {
+        // Refresh tte entry to avoid aging
+        TT.store(posKey, tte->value(), tte->type(), tte->depth(), ttMove);
+
         ss[ply].currentMove = ttMove; // Can be MOVE_NONE
         return value_from_tt(tte->value(), ply);
     }
@@ -1624,6 +1627,9 @@ namespace {
     {
         assert(tte->type() != VALUE_TYPE_EVAL);
 
+        // Refresh tte entry to avoid aging
+        TT.store(pos.get_key(), tte->value(), tte->type(), tte->depth(), ttMove);
+
         ss[ply].currentMove = ttMove; // Can be MOVE_NONE
         return value_from_tt(tte->value(), ply);
     }