src/value.cpp

   1 /*
   2   Glaurung, a UCI chess playing engine.
   3   Copyright (C) 2004-2008 Tord Romstad
   4
   5   Glaurung is free software: you can redistribute it and/or modify
   6   it under the terms of the GNU General Public License as published by
   7   the Free Software Foundation, either version 3 of the License, or
   8   (at your option) any later version.
   9
  10   Glaurung is distributed in the hope that it will be useful,
  11   but WITHOUT ANY WARRANTY; without even the implied warranty of
  12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13   GNU General Public License for more details.
  14
  15   You should have received a copy of the GNU General Public License
  16   along with this program.  If not, see <http://www.gnu.org/licenses/>.
  17 */
  18
  19
  20 ////
  21 //// Includes
  22 ////
  23
  24 #include <sstream>
  25 #include <string>
  26
  27 #include "value.h"
  28
  29
  30 ////
  31 //// Functions
  32 ////
  33
  34 /// value_to_tt() adjusts a mate score from "plies to mate from the root" to
  35 /// "plies to mate from the current ply".  Non-mate scores are unchanged.
  36 /// The function is called before storing a value to the transposition table.
  37
  38 Value value_to_tt(Value v, int ply) {
  39   if(v >= value_mate_in(100))
  40     return v + ply;
  41   else if(v <= value_mated_in(100))
  42     return v - ply;
  43   else
  44     return v;
  45 }
  46
  47
  48 /// value_from_tt() is the inverse of value_to_tt():  It adjusts a mate score
  49 /// from the transposition table to a mate score corrected for the current
  50 /// ply depth.
  51
  52 Value value_from_tt(Value v, int ply) {
  53   if(v >= value_mate_in(100))
  54     return v - ply;
  55   else if(v <= value_mated_in(100))
  56     return v + ply;
  57   else
  58     return v;
  59 }
  60
  61
  62 /// value_to_centipawns() converts a value from Glaurung's somewhat unusual
  63 /// scale of pawn = 256 to the more conventional pawn = 100.
  64
  65 int value_to_centipawns(Value v) {
  66   return (int(v) * 100) / int(PawnValueMidgame);
  67 }
  68
  69
  70 /// value_from_centipawns() converts a centipawn value to Glaurung's internal
  71 /// evaluation scale.  It's used when reading the values of UCI options
  72 /// containing material values (e.g. futility pruning margins).
  73
  74 Value value_from_centipawns(int cp) {
  75   return Value((cp * 256) / 100);
  76 }
  77
  78
  79 /// value_to_string() converts a value to a string suitable for use with the
  80 /// UCI protocol.
  81
  82 const std::string value_to_string(Value v) {
  83   std::stringstream s;
  84
  85   if(abs(v) < VALUE_MATE - 200)
  86     s << "cp " << value_to_centipawns(v);
  87   else {
  88     s << "mate ";
  89     if(v > 0)
  90       s << (VALUE_MATE - v + 1) / 2;
  91     else
  92       s << -(VALUE_MATE + v) / 2;
  93   }
  94   return s.str();
  95 }