Use an affine formula to mix stats and eval

[stockfish] / src / search.cpp

diff --git a/src/search.cpp b/src/search.cpp
index d43a875f68168f4c58f64907daba4c88daf4df7d..3d9c718b9df304c77c37885af263adb9f9b95727 100644 (file)
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -722,12 +722,14 @@ namespace {
     }
     else
     {
     }
     else
     {

-        ss->staticEval = eval =
-        (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) - 10 * ((ss-1)->statScore > 0)
-                                         : -(ss-1)->staticEval + 2 * Eval::Tempo;
+        int p = (ss-1)->statScore;
+        int malus = p > 0 ? (p + 5000) / 1024 :
+                    p < 0 ? (p - 5000) / 1024 : 0;

 
 

-        tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE,
-                  ss->staticEval);
+        ss->staticEval = eval = (ss-1)->currentMove != MOVE_NULL ? evaluate(pos) - malus
+                                                                 : -(ss-1)->staticEval + 2 * Eval::Tempo;
+
+        tte->save(posKey, VALUE_NONE, BOUND_NONE, DEPTH_NONE, MOVE_NONE, ss->staticEval);

     }
 
     // Step 7. Razoring (~2 Elo)
     }
 
     // Step 7. Razoring (~2 Elo)