From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 18 May 2009 07:51:46 +0000 (+0200)
Subject: Reduce history 4 times instead of 2 when reach the maximum
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=25286e9932f7e28e1d0cddffb0b1e7df3232de7c;hp=4f7ec4128fd39ed49e7cc4b22a7143d9c2d22750

Reduce history 4 times instead of 2 when reach the maximum

This gives more weight to newer entries.

After 999 games at 1'+ 0" we have:

Mod vs Orig +233/-208/=558 51.25% +9 ELO

Confirmed by another session of 437 games:

Mod vs Orig +109/-92/=236 51.95% +14 ELO

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

diff --git a/src/history.cpp b/src/history.cpp
index 6fe222fe..edd5cdb7 100644
--- a/src/history.cpp
+++ b/src/history.cpp
@@ -64,7 +64,7 @@ void History::success(Piece p, Square to, Depth d) {
   if (history[p][to] >= HistoryMax)
       for (int i = 0; i < 16; i++)
           for (int j = 0; j < 64; j++)
-              history[i][j] /= 2;
+              history[i][j] /= 4;
 }