From: Marco Costalba <mcostalba@gmail.com>
Date: Tue, 1 Dec 2009 10:48:28 +0000 (+0100)
Subject: Try to prune also when approximateEval < beta
X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=3f3365221b571f1e712f1dd66574a866e858256d

Try to prune also when approximateEval < beta

Now we always try to filter out moves, we will have
more wasted evaluation calls, but also more pruned
nodes.

After 786 games

Mod vs Orig +196 =413 -177 +8 ELO

Verified also against Rybka it increases score to 50-51%

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

diff --git a/src/search.cpp b/src/search.cpp
index 4b93a210..5bbc0abd 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -1517,19 +1517,16 @@ namespace {
               continue;
 
           // Value based pruning
-          if (approximateEval < beta)
-          {
-              if (futilityValue == VALUE_NONE)
-                  futilityValue = evaluate(pos, ei, threadID) + FutilityValueMargin;
+          if (futilityValue == VALUE_NONE)
+              futilityValue = evaluate(pos, ei, threadID) + FutilityValueMargin;
 
-              futilityValueScaled = futilityValue - moveCount * IncrementalFutilityMargin;
+          futilityValueScaled = futilityValue - moveCount * IncrementalFutilityMargin;
 
-              if (futilityValueScaled < beta)
-              {
-                  if (futilityValueScaled > bestValue)
-                      bestValue = futilityValueScaled;
-                  continue;
-              }
+          if (futilityValueScaled < beta)
+          {
+              if (futilityValueScaled > bestValue)
+                  bestValue = futilityValueScaled;
+              continue;
           }
       }