Use a faster implementation of Static Exchange Evaluation

[stockfish] / src / bitbase.cpp

diff --git a/src/bitbase.cpp b/src/bitbase.cpp
index 8c8c47020bb2678d74ddc45628bd87f152e6ff88..9301dcfad13ea51797b10d44e3011c9b7fa36f90 100644 (file)
--- a/src/bitbase.cpp
+++ b/src/bitbase.cpp
@@ -27,7 +27,8 @@
 
 namespace {
 
-  // There are 24 possible pawn squares: the first 4 files and ranks from 2 to 7
+  // There are 24 possible pawn squares: files A to D and ranks from 2 to 7.
+  // Positions with the pawn on files E to H will be mirrored before probing.
   constexpr unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
 
   // Each uint32_t stores results of 32 positions, one per bit
@@ -43,7 +44,7 @@ namespace {
   // bit 13-14: white pawn file (from FILE_A to FILE_D)
   // bit 15-17: white pawn RANK_7 - rank (from RANK_7 - RANK_7 to RANK_7 - RANK_2)
   unsigned index(Color us, Square bksq, Square wksq, Square psq) {
-    return wksq | (bksq << 6) | (us << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15);
+    return int(wksq) | (bksq << 6) | (us << 12) | (file_of(psq) << 13) | ((RANK_7 - rank_of(psq)) << 15);
   }
 
   enum Result {