From: Marco Costalba <mcostalba@gmail.com>
Date: Mon, 28 Apr 2014 15:15:16 +0000 (+0200)
Subject: Rearrange interpolation formula
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=db229504e2c68a92177985bfbf7a870349257301;hp=918c29f83ab8a013d3946916887e1d1d7b9cfb9a

Rearrange interpolation formula

Put the division at the end to reduce
rounding errors. This alters the bench
due to different rounding errors, but
should not alter ELO in any way.

bench: 7615217
---

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index ccc3d915..ede94ec0 100644
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -779,9 +779,9 @@ namespace {
              sf = ScaleFactor(50 * sf / SCALE_FACTOR_NORMAL);
     }
 
-    // Interpolate between a middlegame and an endgame score, scaling by 'sf'
+    // Interpolate between a middlegame and a (scaled by 'sf') endgame score
     Value v =  mg_value(score) * int(ei.mi->game_phase())
-             + eg_value(score) * int(sf) / SCALE_FACTOR_NORMAL * int(PHASE_MIDGAME - ei.mi->game_phase());
+             + eg_value(score) * int(PHASE_MIDGAME - ei.mi->game_phase()) * sf / SCALE_FACTOR_NORMAL;
 
     v /= PHASE_MIDGAME;