X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fmaterial.cpp;h=a1eff233302982c1a6728da40c603075864dc5a2;hp=068d88e702092a67259ae312165bb33683cb101e;hb=0118623495e2ef8a29cbe6ac76609521417490d2;hpb=3ed86ed3f95f712587bea62f4a7fc474812db458

diff --git a/src/material.cpp b/src/material.cpp
index 068d88e7..a1eff233 100644
--- a/src/material.cpp
+++ b/src/material.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) 2008-2013 Marco Costalba, Joona Kiiski, Tord Romstad
+  Copyright (C) 2008-2014 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
@@ -60,8 +60,8 @@ namespace {
     { 106,  101,   3,   151,  171,    0 }  // Queen
   };
 
-  // Endgame evaluation and scaling functions accessed direcly and not through
-  // the function maps because correspond to more then one material hash key.
+  // Endgame evaluation and scaling functions are accessed directly and not through
+  // the function maps because they correspond to more then one material hash key.
   Endgame<KmmKm> EvaluateKmmKm[] = { Endgame<KmmKm>(WHITE), Endgame<KmmKm>(BLACK) };
   Endgame<KXK>   EvaluateKXK[]   = { Endgame<KXK>(WHITE),   Endgame<KXK>(BLACK) };
 
@@ -93,7 +93,7 @@ namespace {
           && pos.count<PAWN>(Them) >= 1;
   }
 
-  /// imbalance() calculates imbalance comparing piece count of each
+  /// imbalance() calculates the imbalance by comparing the piece count of each
   /// piece type for both colors.
 
   template<Color Us>
@@ -147,9 +147,9 @@ Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
   e->factor[WHITE] = e->factor[BLACK] = (uint8_t)SCALE_FACTOR_NORMAL;
   e->gamePhase = game_phase(pos);
 
-  // Let's look if we have a specialized evaluation function for this
-  // particular material configuration. First we look for a fixed
-  // configuration one, then a generic one if previous search failed.
+  // Let's look if we have a specialized evaluation function for this particular
+  // material configuration. Firstly we look for a fixed configuration one, then
+  // for a generic one if the previous search failed.
   if (endgames.probe(key, e->evaluationFunction))
       return e;
 
@@ -194,7 +194,7 @@ Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
   }
 
   // Generic scaling functions that refer to more then one material
-  // distribution. Should be probed after the specialized ones.
+  // distribution. They should be probed after the specialized ones.
   // Note that these ones don't return after setting the function.
   if (is_KBPsKs<WHITE>(pos))
       e->scalingFunction[WHITE] = &ScaleKBPsK[WHITE];
@@ -246,6 +246,16 @@ Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
       (npm_w == npm_b || npm_b < RookValueMg ? 0 : NoPawnsSF[std::min(pos.count<BISHOP>(BLACK), 2)]);
   }
 
+  if (pos.count<PAWN>(WHITE) == 1 && npm_w - npm_b <= BishopValueMg)
+  {
+      e->factor[WHITE] = (uint8_t) SCALE_FACTOR_ONEPAWN;
+  }
+
+  if (pos.count<PAWN>(BLACK) == 1 && npm_b - npm_w <= BishopValueMg)
+  {
+      e->factor[BLACK] = (uint8_t) SCALE_FACTOR_ONEPAWN;
+  }
+
   // Compute the space weight
   if (npm_w + npm_b >= 2 * QueenValueMg + 4 * RookValueMg + 2 * KnightValueMg)
   {
@@ -256,7 +266,7 @@ Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
   }
 
   // Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
-  // for the bishop pair "extended piece", this allow us to be more flexible
+  // for the bishop pair "extended piece", which allows us to be more flexible
   // in defining bishop pair bonuses.
   const int pieceCount[COLOR_NB][PIECE_TYPE_NB] = {
   { pos.count<BISHOP>(WHITE) > 1, pos.count<PAWN>(WHITE), pos.count<KNIGHT>(WHITE),