X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fendgame.cpp;h=90898e8341a58987b46cb0433018cb4d587484e8;hp=01f4101ed8866ce63748d72cd8da177b78a229e1;hb=3376c68f4bb83dc9fd874eb9d710dab09609ae54;hpb=67375f4693c97fb1321864bb4d143812cd824f9b

diff --git a/src/endgame.cpp b/src/endgame.cpp
index 01f4101e..90898e83 100644
--- a/src/endgame.cpp
+++ b/src/endgame.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 Marco Costalba
+  Copyright (C) 2008-2009 Marco Costalba
 
   Stockfish is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
@@ -25,6 +25,7 @@
 #include <cassert>
 
 #include "bitbase.h"
+#include "bitcount.h"
 #include "endgame.h"
 
 
@@ -57,6 +58,7 @@ ScalingFunction<KRPKR> ScaleKRPKR(WHITE), ScaleKRKRP(BLACK); // KRP vs KR
 ScalingFunction<KRPPKRP> ScaleKRPPKRP(WHITE), ScaleKRPKRPP(BLACK); // KRPP vs KRP
 ScalingFunction<KPsK> ScaleKPsK(WHITE), ScaleKKPs(BLACK);    // King and pawns vs king
 ScalingFunction<KBPKB> ScaleKBPKB(WHITE), ScaleKBKBP(BLACK); // KBP vs KB
+ScalingFunction<KBPPKB> ScaleKBPPKB(WHITE), ScaleKBKBPP(BLACK); // KBPP vs KB
 ScalingFunction<KBPKN> ScaleKBPKN(WHITE), ScaleKNKBP(BLACK); // KBP vs KN
 ScalingFunction<KNPK> ScaleKNPK(WHITE), ScaleKKNP(BLACK);    // KNP vs K
 ScalingFunction<KPKP> ScaleKPKPw(WHITE), ScaleKPKPb(BLACK);  // KPKP
@@ -376,13 +378,13 @@ Value EvaluationFunction<KBBKN>::apply(const Position& pos) {
   result += Value(square_distance(bksq, nsq) * 32);
 
   // Bonus for restricting the knight's mobility
-  result += Value((8 - count_1s_max_15(pos.piece_attacks<KNIGHT>(nsq))) * 8);
+  result += Value((8 - count_1s_max_15<false>(pos.piece_attacks<KNIGHT>(nsq))) * 8);
 
   return (strongerSide == pos.side_to_move() ? result : -result);
 }
 
 template<>
-Value EvaluationFunction<KmmKm>::apply(const Position &pos) {
+Value EvaluationFunction<KmmKm>::apply(const Position&) {
   return Value(0);
 }
 
@@ -732,6 +734,80 @@ ScaleFactor ScalingFunction<KBPKB>::apply(const Position &pos) {
 }
 
 
+/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic
+/// draws with opposite-colored bishops.
+template<>
+ScaleFactor ScalingFunction<KBPPKB>::apply(const Position& pos) {
+
+  assert(pos.non_pawn_material(strongerSide) == BishopValueMidgame);
+  assert(pos.piece_count(strongerSide, BISHOP) == 1);
+  assert(pos.piece_count(strongerSide, PAWN) == 2);
+  assert(pos.non_pawn_material(weakerSide) == BishopValueMidgame);
+  assert(pos.piece_count(weakerSide, BISHOP) == 1);
+  assert(pos.piece_count(weakerSide, PAWN) == 0);
+
+  Square wbsq = pos.piece_list(strongerSide, BISHOP, 0);
+  Square bbsq = pos.piece_list(weakerSide, BISHOP, 0);
+
+  if (square_color(wbsq) == square_color(bbsq))
+      // Not opposite-colored bishops, no scaling
+      return SCALE_FACTOR_NONE;
+
+  Square ksq = pos.king_square(weakerSide);
+  Square psq1 = pos.piece_list(strongerSide, PAWN, 0);
+  Square psq2 = pos.piece_list(strongerSide, PAWN, 1);
+  Rank r1 = square_rank(psq1);
+  Rank r2 = square_rank(psq2);
+  Square blockSq1, blockSq2;
+
+  if (relative_rank(strongerSide, psq1) > relative_rank(strongerSide, psq2))
+  {
+      blockSq1 = psq1 + pawn_push(strongerSide);
+      blockSq2 = make_square(square_file(psq2), square_rank(psq1));
+  }
+  else
+  {
+      blockSq1 = psq2 + pawn_push(strongerSide);
+      blockSq2 = make_square(square_file(psq1), square_rank(psq2));
+  }
+
+  switch (file_distance(psq1, psq2))
+  {
+  case 0:
+    // Both pawns are on the same file. Easy draw if defender firmly controls
+    // some square in the frontmost pawn's path.
+    if (   square_file(ksq) == square_file(blockSq1)
+        && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1)
+        && square_color(ksq) != square_color(wbsq))
+        return ScaleFactor(0);
+    else
+        return SCALE_FACTOR_NONE;
+
+  case 1:
+    // Pawns on neighboring files. Draw if defender firmly controls the square
+    // in front of the frontmost pawn's path, and the square diagonally behind
+    // this square on the file of the other pawn.
+    if (   ksq == blockSq1
+        && square_color(ksq) != square_color(wbsq)
+        && (   bbsq == blockSq2
+            || (pos.piece_attacks<BISHOP>(blockSq2) & pos.bishops(weakerSide))
+            || rank_distance(r1, r2) >= 2))
+        return ScaleFactor(0);
+    else if (   ksq == blockSq2
+             && square_color(ksq) != square_color(wbsq)
+             && (   bbsq == blockSq1
+                 || (pos.piece_attacks<BISHOP>(blockSq1) & pos.bishops(weakerSide))))
+        return ScaleFactor(0);
+    else
+        return SCALE_FACTOR_NONE;
+
+  default:
+    // The pawns are not on the same file or adjacent files. No scaling.
+    return SCALE_FACTOR_NONE;
+  }
+}
+
+
 /// KBPKNScalingFunction scales KBP vs KN endgames. There is a single rule:
 /// If the defending king is somewhere along the path of the pawn, and the
 /// square of the king is not of the same color as the stronger side's bishop,