X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fbitbase.cpp;h=e4428d2d4aad5e7afb97e715a7b6570710d243a7;hp=ef067c65bceca3bc809c5b977a8dd4610fcc4bc2;hb=3abccdc82df5e3acc32cde07712f1365b8f84022;hpb=5a156df719790ddd882a928ddf721f8ba81587b1

diff --git a/src/bitbase.cpp b/src/bitbase.cpp
index ef067c65..e4428d2d 100644
--- a/src/bitbase.cpp
+++ b/src/bitbase.cpp
@@ -1,7 +1,7 @@
 /*
   Stockfish, a UCI chess playing engine derived from Glaurung 2.1
   Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
-  Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2008-2013 Marco Costalba, Joona Kiiski, 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
@@ -39,9 +39,9 @@ namespace {
   // bit  6-11: black king square (from SQ_A1 to SQ_H8)
   // bit    12: side to move (WHITE or BLACK)
   // bit 13-14: white pawn file (from FILE_A to FILE_D)
-  // bit 15-17: white pawn 6 - rank (from 6 - RANK_7 to 6 - RANK_2)
+  // 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) + ((6 - rank_of(psq)) << 15);
+    return wksq + (bksq << 6) + (us << 12) + (file_of(psq) << 13) + ((RANK_7 - rank_of(psq)) << 15);
   }
 
   enum Result {
@@ -55,8 +55,8 @@ namespace {
 
   struct KPKPosition {
 
-    operator Result() const { return res; }
-    Result classify_leaf(unsigned idx);
+    KPKPosition(unsigned idx);
+    operator Result() const { return result; }
     Result classify(const std::vector<KPKPosition>& db)
     { return us == WHITE ? classify<WHITE>(db) : classify<BLACK>(db); }
 
@@ -65,7 +65,7 @@ namespace {
 
     Color us;
     Square bksq, wksq, psq;
-    Result res;
+    Result result;
   };
 
 } // namespace
@@ -83,17 +83,18 @@ bool Bitbases::probe_kpk(Square wksq, Square wpsq, Square bksq, Color us) {
 void Bitbases::init_kpk() {
 
   unsigned idx, repeat = 1;
-  std::vector<KPKPosition> db(IndexMax);
+  std::vector<KPKPosition> db;
+  db.reserve(IndexMax);
 
   // Initialize db with known win / draw positions
   for (idx = 0; idx < IndexMax; idx++)
-      db[idx].classify_leaf(idx);
+      db.push_back(KPKPosition(idx));
 
-  // Iterate until all positions are classified (15 cycles needed)
+  // Iterate through the positions until no more of the unknown positions can be
+  // changed to either wins or draws (15 cycles needed).
   while (repeat)
       for (repeat = idx = 0; idx < IndexMax; idx++)
-          if (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN)
-              repeat = 1;
+          repeat |= (db[idx] == UNKNOWN && db[idx].classify(db) != UNKNOWN);
 
   // Map 32 results into one KPKBitbase[] entry
   for (idx = 0; idx < IndexMax; idx++)
@@ -104,34 +105,32 @@ void Bitbases::init_kpk() {
 
 namespace {
 
-  Result KPKPosition::classify_leaf(unsigned idx) {
+  KPKPosition::KPKPosition(unsigned idx) {
 
-    wksq = Square((idx >> 0) & 0x3F);
-    bksq = Square((idx >> 6) & 0x3F);
-    us   = Color((idx >> 12) & 0x01);
-    psq  = File((idx >> 13) & 3) | Rank(6 - (idx >> 15));
+    wksq = Square((idx >>  0) & 0x3F);
+    bksq = Square((idx >>  6) & 0x3F);
+    us   = Color ((idx >> 12) & 0x01);
+    psq  = File  ((idx >> 13) & 0x03) | Rank(RANK_7 - (idx >> 15));
+    result  = UNKNOWN;
 
     // Check if two pieces are on the same square or if a king can be captured
-    if (   wksq == psq || wksq == bksq || bksq == psq
-        || (StepAttacksBB[KING][wksq] & bksq)
+    if (   square_distance(wksq, bksq) <= 1 || wksq == psq || bksq == psq
         || (us == WHITE && (StepAttacksBB[PAWN][psq] & bksq)))
-        return res = INVALID;
+        result = INVALID;
 
-    if (us == WHITE)
+    else if (us == WHITE)
     {
         // Immediate win if pawn can be promoted without getting captured
         if (   rank_of(psq) == RANK_7
             && wksq != psq + DELTA_N
             && (   square_distance(bksq, psq + DELTA_N) > 1
                 ||(StepAttacksBB[KING][wksq] & (psq + DELTA_N))))
-            return res = WIN;
+            result = WIN;
     }
     // Immediate draw if is stalemate or king captures undefended pawn
     else if (  !(StepAttacksBB[KING][bksq] & ~(StepAttacksBB[KING][wksq] | StepAttacksBB[PAWN][psq]))
              || (StepAttacksBB[KING][bksq] & psq & ~StepAttacksBB[KING][wksq]))
-        return res = DRAW;
-
-    return res = UNKNOWN;
+        result = DRAW;
   }
 
   template<Color Us>
@@ -147,26 +146,28 @@ namespace {
     // as WIN, the position is classified WIN otherwise the current position is
     // classified UNKNOWN.
 
+    const Color Them = (Us == WHITE ? BLACK : WHITE);
+
     Result r = INVALID;
     Bitboard b = StepAttacksBB[KING][Us == WHITE ? wksq : bksq];
 
     while (b)
-        r |= Us == WHITE ? db[index(~Us, bksq, pop_lsb(&b), psq)]
-                         : db[index(~Us, pop_lsb(&b), wksq, psq)];
+        r |= Us == WHITE ? db[index(Them, bksq, pop_lsb(&b), psq)]
+                         : db[index(Them, pop_lsb(&b), wksq, psq)];
 
     if (Us == WHITE && rank_of(psq) < RANK_7)
     {
         Square s = psq + DELTA_N;
         r |= db[index(BLACK, bksq, wksq, s)]; // Single push
 
-        if (rank_of(s) == RANK_3 && s != wksq && s != bksq)
+        if (rank_of(psq) == RANK_2 && s != wksq && s != bksq)
             r |= db[index(BLACK, bksq, wksq, s + DELTA_N)]; // Double push
     }
 
     if (Us == WHITE)
-        return res = r & WIN  ? WIN  : r & UNKNOWN ? UNKNOWN : DRAW;
+        return result = r & WIN  ? WIN  : r & UNKNOWN ? UNKNOWN : DRAW;
     else
-        return res = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN;
+        return result = r & DRAW ? DRAW : r & UNKNOWN ? UNKNOWN : WIN;
   }
 
 } // namespace