Revert sigmoid interpolator

After deep test (1000 games) it seems do not improve anything,
actually seems slightly weaker.

So remove it for now.

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

diff --git a/src/evaluate.cpp b/src/evaluate.cpp
index a7e5f2d5b8ccf333c8daf583c664946d2c816a8b..3e396af3032d6e11c2329d15763853f0f4f85b8f 100644 (file)
--- a/src/evaluate.cpp
+++ b/src/evaluate.cpp
@@ -1120,13 +1120,7 @@ namespace {
 
     ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
 
 
     ev = apply_scale_factor(ev, sf[(ev > Value(0) ? WHITE : BLACK)]);
 

-    // Linearized sigmoid interpolator
-    int sph = int(ph);
-    sph -= (64 - sph) / 4;
-    sph = Min(PHASE_MIDGAME, Max(PHASE_ENDGAME, sph));
-
-    Value result = Value(int((mv * sph + ev * (128 - sph)) / 128));
-
+    Value result = Value(int((mv * ph + ev * (128 - ph)) / 128));

     return Value(int(result) & ~(GrainSize - 1));
   }
 
     return Value(int(result) & ~(GrainSize - 1));
   }