Make Square and Bitboard operators commutative

[stockfish] / src / bitbase.cpp

diff --git a/src/bitbase.cpp b/src/bitbase.cpp
index 1a6e807603a88a6143f403c8314215a0fd4ad527..9301dcfad13ea51797b10d44e3011c9b7fa36f90 100644 (file)
--- a/src/bitbase.cpp
+++ b/src/bitbase.cpp
@@ -2,7 +2,7 @@
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
   Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad
-  Copyright (C) 2015-2017 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
+  Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -18,7 +18,6 @@
   along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
-#include <algorithm>
 #include <cassert>
 #include <numeric>
 #include <vector>
@@ -28,8 +27,9 @@
 
 namespace {
 
-  // There are 24 possible pawn squares: the first 4 files and ranks from 2 to 7
-  const unsigned MAX_INDEX = 2*24*64*64; // stm * psq * wksq * bksq = 196608
+  // 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
   uint32_t KPKBitbase[MAX_INDEX / 32];
@@ -44,7 +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 {
@@ -111,13 +111,13 @@ namespace {
     ksq[WHITE] = Square((idx >>  0) & 0x3F);
     ksq[BLACK] = Square((idx >>  6) & 0x3F);
     us         = Color ((idx >> 12) & 0x01);
-    psq        = make_square(File((idx >> 13) & 0x3), RANK_7 - Rank((idx >> 15) & 0x7));
+    psq        = make_square(File((idx >> 13) & 0x3), Rank(RANK_7 - ((idx >> 15) & 0x7)));
 
     // Check if two pieces are on the same square or if a king can be captured
     if (   distance(ksq[WHITE], ksq[BLACK]) <= 1
         || ksq[WHITE] == psq
         || ksq[BLACK] == psq
-        || (us == WHITE && (StepAttacksBB[PAWN][psq] & ksq[BLACK])))
+        || (us == WHITE && (PawnAttacks[WHITE][psq] & ksq[BLACK])))
         result = INVALID;
 
     // Immediate win if a pawn can be promoted without getting captured
@@ -125,13 +125,13 @@ namespace {
              && rank_of(psq) == RANK_7
              && ksq[us] != psq + NORTH
              && (    distance(ksq[~us], psq + NORTH) > 1
-                 || (StepAttacksBB[KING][ksq[us]] & (psq + NORTH))))
+                 || (PseudoAttacks[KING][ksq[us]] & (psq + NORTH))))
         result = WIN;
 
     // Immediate draw if it is a stalemate or a king captures undefended pawn
     else if (   us == BLACK
-             && (  !(StepAttacksBB[KING][ksq[us]] & ~(StepAttacksBB[KING][ksq[~us]] | StepAttacksBB[PAWN][psq]))
-                 || (StepAttacksBB[KING][ksq[us]] & psq & ~StepAttacksBB[KING][ksq[~us]])))
+             && (  !(PseudoAttacks[KING][ksq[us]] & ~(PseudoAttacks[KING][ksq[~us]] | PawnAttacks[~us][psq]))
+                 || (PseudoAttacks[KING][ksq[us]] & psq & ~PseudoAttacks[KING][ksq[~us]])))
         result = DRAW;
 
     // Position will be classified later
@@ -152,12 +152,12 @@ namespace {
     // as WIN, the position is classified as WIN, otherwise the current position is
     // classified as UNKNOWN.
 
-    const Color  Them = (Us == WHITE ? BLACK : WHITE);
-    const Result Good = (Us == WHITE ? WIN   : DRAW);
-    const Result Bad  = (Us == WHITE ? DRAW  : WIN);
+    constexpr Color  Them = (Us == WHITE ? BLACK : WHITE);
+    constexpr Result Good = (Us == WHITE ? WIN   : DRAW);
+    constexpr Result Bad  = (Us == WHITE ? DRAW  : WIN);
 
     Result r = INVALID;
-    Bitboard b = StepAttacksBB[KING][ksq[Us]];
+    Bitboard b = PseudoAttacks[KING][ksq[Us]];
 
     while (b)
         r |= Us == WHITE ? db[index(Them, ksq[Them]  , pop_lsb(&b), psq)]