mirror of
https://github.com/peterosterlund2/droidfish.git
synced 2024-12-04 17:30:56 +01:00
266 lines
9.7 KiB
C++
266 lines
9.7 KiB
C++
/*
|
|
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
|
|
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
|
|
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
|
|
the Free Software Foundation, either version 3 of the License, or
|
|
(at your option) any later version.
|
|
|
|
Stockfish is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#include <algorithm> // For std::min
|
|
#include <cassert>
|
|
#include <cstring>
|
|
|
|
#include "material.h"
|
|
|
|
using namespace std;
|
|
|
|
namespace {
|
|
|
|
// Polynomial material balance parameters
|
|
|
|
// pair pawn knight bishop rook queen
|
|
const int LinearCoefficients[6] = { 1852, -162, -1122, -183, 249, -154 };
|
|
|
|
const int QuadraticCoefficientsSameSide[][PIECE_TYPE_NB] = {
|
|
// OUR PIECES
|
|
// pair pawn knight bishop rook queen
|
|
{ 0 }, // Bishop pair
|
|
{ 39, 2 }, // Pawn
|
|
{ 35, 271, -4 }, // knight OUR PIECES
|
|
{ 0, 105, 4, 0 }, // Bishop
|
|
{ -27, -2, 46, 100, -141 }, // Rook
|
|
{-177, 25, 129, 142, -137, 0 } // Queen
|
|
};
|
|
|
|
const int QuadraticCoefficientsOppositeSide[][PIECE_TYPE_NB] = {
|
|
// THEIR PIECES
|
|
// pair pawn knight bishop rook queen
|
|
{ 0 }, // Bishop pair
|
|
{ 37, 0 }, // Pawn
|
|
{ 10, 62, 0 }, // Knight OUR PIECES
|
|
{ 57, 64, 39, 0 }, // Bishop
|
|
{ 50, 40, 23, -22, 0 }, // Rook
|
|
{ 98, 105, -39, 141, 274, 0 } // Queen
|
|
};
|
|
|
|
// Endgame evaluation and scaling functions are accessed directly and not through
|
|
// the function maps because they correspond to more than one material hash key.
|
|
Endgame<KXK> EvaluateKXK[] = { Endgame<KXK>(WHITE), Endgame<KXK>(BLACK) };
|
|
|
|
Endgame<KBPsK> ScaleKBPsK[] = { Endgame<KBPsK>(WHITE), Endgame<KBPsK>(BLACK) };
|
|
Endgame<KQKRPs> ScaleKQKRPs[] = { Endgame<KQKRPs>(WHITE), Endgame<KQKRPs>(BLACK) };
|
|
Endgame<KPsK> ScaleKPsK[] = { Endgame<KPsK>(WHITE), Endgame<KPsK>(BLACK) };
|
|
Endgame<KPKP> ScaleKPKP[] = { Endgame<KPKP>(WHITE), Endgame<KPKP>(BLACK) };
|
|
|
|
// Helper templates used to detect a given material distribution
|
|
template<Color Us> bool is_KXK(const Position& pos) {
|
|
const Color Them = (Us == WHITE ? BLACK : WHITE);
|
|
return !pos.count<PAWN>(Them)
|
|
&& pos.non_pawn_material(Them) == VALUE_ZERO
|
|
&& pos.non_pawn_material(Us) >= RookValueMg;
|
|
}
|
|
|
|
template<Color Us> bool is_KBPsKs(const Position& pos) {
|
|
return pos.non_pawn_material(Us) == BishopValueMg
|
|
&& pos.count<BISHOP>(Us) == 1
|
|
&& pos.count<PAWN >(Us) >= 1;
|
|
}
|
|
|
|
template<Color Us> bool is_KQKRPs(const Position& pos) {
|
|
const Color Them = (Us == WHITE ? BLACK : WHITE);
|
|
return !pos.count<PAWN>(Us)
|
|
&& pos.non_pawn_material(Us) == QueenValueMg
|
|
&& pos.count<QUEEN>(Us) == 1
|
|
&& pos.count<ROOK>(Them) == 1
|
|
&& pos.count<PAWN>(Them) >= 1;
|
|
}
|
|
|
|
/// imbalance() calculates the imbalance by comparing the piece count of each
|
|
/// piece type for both colors.
|
|
|
|
template<Color Us>
|
|
int imbalance(const int pieceCount[][PIECE_TYPE_NB]) {
|
|
|
|
const Color Them = (Us == WHITE ? BLACK : WHITE);
|
|
|
|
int pt1, pt2, pc, v;
|
|
int value = 0;
|
|
|
|
// Second-degree polynomial material imbalance by Tord Romstad
|
|
for (pt1 = NO_PIECE_TYPE; pt1 <= QUEEN; ++pt1)
|
|
{
|
|
pc = pieceCount[Us][pt1];
|
|
if (!pc)
|
|
continue;
|
|
|
|
v = LinearCoefficients[pt1];
|
|
|
|
for (pt2 = NO_PIECE_TYPE; pt2 <= pt1; ++pt2)
|
|
v += QuadraticCoefficientsSameSide[pt1][pt2] * pieceCount[Us][pt2]
|
|
+ QuadraticCoefficientsOppositeSide[pt1][pt2] * pieceCount[Them][pt2];
|
|
|
|
value += pc * v;
|
|
}
|
|
|
|
return value;
|
|
}
|
|
|
|
} // namespace
|
|
|
|
namespace Material {
|
|
|
|
/// Material::probe() takes a position object as input, looks up a MaterialEntry
|
|
/// object, and returns a pointer to it. If the material configuration is not
|
|
/// already present in the table, it is computed and stored there, so we don't
|
|
/// have to recompute everything when the same material configuration occurs again.
|
|
|
|
Entry* probe(const Position& pos, Table& entries, Endgames& endgames) {
|
|
|
|
Key key = pos.material_key();
|
|
Entry* e = entries[key];
|
|
|
|
// If e->key matches the position's material hash key, it means that we
|
|
// have analysed this material configuration before, and we can simply
|
|
// return the information we found the last time instead of recomputing it.
|
|
if (e->key == key)
|
|
return e;
|
|
|
|
std::memset(e, 0, sizeof(Entry));
|
|
e->key = key;
|
|
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. 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;
|
|
|
|
if (is_KXK<WHITE>(pos))
|
|
{
|
|
e->evaluationFunction = &EvaluateKXK[WHITE];
|
|
return e;
|
|
}
|
|
|
|
if (is_KXK<BLACK>(pos))
|
|
{
|
|
e->evaluationFunction = &EvaluateKXK[BLACK];
|
|
return e;
|
|
}
|
|
|
|
// OK, we didn't find any special evaluation function for the current
|
|
// material configuration. Is there a suitable scaling function?
|
|
//
|
|
// We face problems when there are several conflicting applicable
|
|
// scaling functions and we need to decide which one to use.
|
|
EndgameBase<ScaleFactor>* sf;
|
|
|
|
if (endgames.probe(key, sf))
|
|
{
|
|
e->scalingFunction[sf->color()] = sf;
|
|
return e;
|
|
}
|
|
|
|
// Generic scaling functions that refer to more than one material
|
|
// 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];
|
|
|
|
if (is_KBPsKs<BLACK>(pos))
|
|
e->scalingFunction[BLACK] = &ScaleKBPsK[BLACK];
|
|
|
|
if (is_KQKRPs<WHITE>(pos))
|
|
e->scalingFunction[WHITE] = &ScaleKQKRPs[WHITE];
|
|
|
|
else if (is_KQKRPs<BLACK>(pos))
|
|
e->scalingFunction[BLACK] = &ScaleKQKRPs[BLACK];
|
|
|
|
Value npm_w = pos.non_pawn_material(WHITE);
|
|
Value npm_b = pos.non_pawn_material(BLACK);
|
|
|
|
if (npm_w + npm_b == VALUE_ZERO && pos.pieces(PAWN))
|
|
{
|
|
if (!pos.count<PAWN>(BLACK))
|
|
{
|
|
assert(pos.count<PAWN>(WHITE) >= 2);
|
|
e->scalingFunction[WHITE] = &ScaleKPsK[WHITE];
|
|
}
|
|
else if (!pos.count<PAWN>(WHITE))
|
|
{
|
|
assert(pos.count<PAWN>(BLACK) >= 2);
|
|
e->scalingFunction[BLACK] = &ScaleKPsK[BLACK];
|
|
}
|
|
else if (pos.count<PAWN>(WHITE) == 1 && pos.count<PAWN>(BLACK) == 1)
|
|
{
|
|
// This is a special case because we set scaling functions
|
|
// for both colors instead of only one.
|
|
e->scalingFunction[WHITE] = &ScaleKPKP[WHITE];
|
|
e->scalingFunction[BLACK] = &ScaleKPKP[BLACK];
|
|
}
|
|
}
|
|
|
|
// No pawns makes it difficult to win, even with a material advantage. This
|
|
// catches some trivial draws like KK, KBK and KNK and gives a very drawish
|
|
// scale factor for cases such as KRKBP and KmmKm (except for KBBKN).
|
|
if (!pos.count<PAWN>(WHITE) && npm_w - npm_b <= BishopValueMg)
|
|
e->factor[WHITE] = uint8_t(npm_w < RookValueMg ? SCALE_FACTOR_DRAW : npm_b <= BishopValueMg ? 4 : 12);
|
|
|
|
if (!pos.count<PAWN>(BLACK) && npm_b - npm_w <= BishopValueMg)
|
|
e->factor[BLACK] = uint8_t(npm_b < RookValueMg ? SCALE_FACTOR_DRAW : npm_w <= BishopValueMg ? 4 : 12);
|
|
|
|
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)
|
|
{
|
|
int minorPieceCount = pos.count<KNIGHT>(WHITE) + pos.count<BISHOP>(WHITE)
|
|
+ pos.count<KNIGHT>(BLACK) + pos.count<BISHOP>(BLACK);
|
|
|
|
e->spaceWeight = make_score(minorPieceCount * minorPieceCount, 0);
|
|
}
|
|
|
|
// Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder
|
|
// 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),
|
|
pos.count<BISHOP>(WHITE) , pos.count<ROOK>(WHITE), pos.count<QUEEN >(WHITE) },
|
|
{ pos.count<BISHOP>(BLACK) > 1, pos.count<PAWN>(BLACK), pos.count<KNIGHT>(BLACK),
|
|
pos.count<BISHOP>(BLACK) , pos.count<ROOK>(BLACK), pos.count<QUEEN >(BLACK) } };
|
|
|
|
e->value = (int16_t)((imbalance<WHITE>(pieceCount) - imbalance<BLACK>(pieceCount)) / 16);
|
|
return e;
|
|
}
|
|
|
|
|
|
/// Material::game_phase() calculates the phase given the current
|
|
/// position. Because the phase is strictly a function of the material, it
|
|
/// is stored in MaterialEntry.
|
|
|
|
Phase game_phase(const Position& pos) {
|
|
|
|
Value npm = pos.non_pawn_material(WHITE) + pos.non_pawn_material(BLACK);
|
|
|
|
return npm >= MidgameLimit ? PHASE_MIDGAME
|
|
: npm <= EndgameLimit ? PHASE_ENDGAME
|
|
: Phase(((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit));
|
|
}
|
|
|
|
} // namespace Material
|