Remove sorting optimization for many zeroes

With negative history we don't have anymore a
lot of zeroes to score, so just split moves in
positives and non-positives sets.

Speed up is almost zero, we cannot test speed directly
because node count changed due to reorder, but I have
verified sorting is correct. With a profiler I have
seen we gain a little in sort_moves() and lose a little
in insertion_sort(), so the net effect is almost zero,
but code is simpler.

No real change, just move reordering.

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

diff --git a/src/move.h b/src/move.h
index 9702d9fbebcfbd0ab6a9088b3889f4807eb754c2..71def812d85743708d1a6ed22622aba696c2f6d0 100644 (file)
--- a/src/move.h
+++ b/src/move.h
@@ -86,8 +86,8 @@ inline void insertion_sort(T* firstMove, T* lastMove)
         }
 }
 
-// Our dedicated sort in range [firstMove, lastMove), it is well
-// tuned for non-captures where we have a lot of zero scored moves.
+// Our dedicated sort in range [firstMove, lastMove), first splits
+// positive scores from ramining then order seaprately the two sets.
 template<typename T>
 inline void sort_moves(T* firstMove, T* lastMove)
 {
@@ -114,28 +114,8 @@ inline void sort_moves(T* firstMove, T* lastMove)
 
     } while (p != d);
 
-    // Sort positives
+    // Sort positives and non-positives separately
     insertion_sort<T>(firstMove, p);
-
-    d = lastMove;
-    p--;
-
-    // Split zero vs negatives
-    do {
-        while ((++p)->score == 0);
-
-        if (p != d)
-        {
-            while (--d != p && d->score < 0);
-
-            tmp = *p;
-            *p = *d;
-            *d = tmp;
-        }
-
-    } while (p != d);
-
-    // Sort negatives
     insertion_sort<T>(p, lastMove);
 }