+++ /dev/null
-/*
- Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008-2010 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 <cassert>
-
-#include "bitboard.h"
-#include "types.h"
-
-namespace {
-
- enum Result {
- RESULT_UNKNOWN,
- RESULT_INVALID,
- RESULT_WIN,
- RESULT_LOSS,
- RESULT_DRAW
- };
-
- struct KPKPosition {
- void from_index(int index);
- bool is_legal() const;
- bool is_immediate_draw() const;
- bool is_immediate_win() const;
- Bitboard wk_attacks() const { return StepAttacksBB[WK][whiteKingSquare]; }
- Bitboard bk_attacks() const { return StepAttacksBB[BK][blackKingSquare]; }
- Bitboard pawn_attacks() const { return StepAttacksBB[WP][pawnSquare]; }
-
- Square whiteKingSquare, blackKingSquare, pawnSquare;
- Color sideToMove;
- };
-
- const int IndexMax = 2 * 24 * 64 * 64;
-
- Result classify_wtm(const KPKPosition& pos, const Result bb[]);
- Result classify_btm(const KPKPosition& pos, const Result bb[]);
- int compute_index(Square wksq, Square bksq, Square psq, Color stm);
-}
-
-
-void generate_kpk_bitbase(uint8_t bitbase[]) {
-
- bool repeat;
- int i, j, b;
- KPKPosition pos;
- Result bb[IndexMax];
-
- // Initialize table
- for (i = 0; i < IndexMax; i++)
- {
- pos.from_index(i);
- bb[i] = !pos.is_legal() ? RESULT_INVALID
- : pos.is_immediate_draw() ? RESULT_DRAW
- : pos.is_immediate_win() ? RESULT_WIN : RESULT_UNKNOWN;
- }
-
- // Iterate until all positions are classified (30 cycles needed)
- do {
- repeat = false;
-
- for (i = 0; i < IndexMax; i++)
- if (bb[i] == RESULT_UNKNOWN)
- {
- pos.from_index(i);
-
- bb[i] = (pos.sideToMove == WHITE) ? classify_wtm(pos, bb)
- : classify_btm(pos, bb);
- if (bb[i] != RESULT_UNKNOWN)
- repeat = true;
- }
-
- } while (repeat);
-
- // Compress result and map into supplied bitbase parameter
- for (i = 0; i < 24576; i++)
- {
- b = 0;
- for (j = 0; j < 8; j++)
- if (bb[8*i+j] == RESULT_WIN || bb[8*i+j] == RESULT_LOSS)
- b |= (1 << j);
-
- bitbase[i] = (uint8_t)b;
- }
-}
-
-
-namespace {
-
- int compute_index(Square wksq, Square bksq, Square psq, Color stm) {
-
- int p = int(square_file(psq)) + (int(square_rank(psq)) - 1) * 4;
- int r = int(stm) + 2 * int(bksq) + 128 * int(wksq) + 8192 * p;
-
- assert(r >= 0 && r < IndexMax);
-
- return r;
- }
-
- void KPKPosition::from_index(int index) {
-
- int s = (index / 8192) % 24;
-
- sideToMove = Color(index % 2);
- blackKingSquare = Square((index / 2) % 64);
- whiteKingSquare = Square((index / 128) % 64);
- pawnSquare = make_square(File(s % 4), Rank(s / 4 + 1));
- }
-
- bool KPKPosition::is_legal() const {
-
- if ( whiteKingSquare == pawnSquare
- || whiteKingSquare == blackKingSquare
- || pawnSquare == blackKingSquare)
- return false;
-
- if (sideToMove == WHITE)
- {
- if ( bit_is_set(wk_attacks(), blackKingSquare)
- || bit_is_set(pawn_attacks(), blackKingSquare))
- return false;
- }
- else if (bit_is_set(bk_attacks(), whiteKingSquare))
- return false;
-
- return true;
- }
-
- bool KPKPosition::is_immediate_draw() const {
-
- if (sideToMove == BLACK)
- {
- Bitboard wka = wk_attacks();
- Bitboard bka = bk_attacks();
-
- // Case 1: Stalemate
- if ((bka & ~(wka | pawn_attacks())) == EmptyBoardBB)
- return true;
-
- // Case 2: King can capture pawn
- if (bit_is_set(bka, pawnSquare) && !bit_is_set(wka, pawnSquare))
- return true;
- }
- else
- {
- // Case 1: Stalemate
- if ( whiteKingSquare == SQ_A8
- && pawnSquare == SQ_A7
- && (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8))
- return true;
- }
- return false;
- }
-
- bool KPKPosition::is_immediate_win() const {
-
- // The position is an immediate win if it is white to move and the
- // white pawn can be promoted without getting captured.
- return sideToMove == WHITE
- && square_rank(pawnSquare) == RANK_7
- && ( square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1
- || bit_is_set(wk_attacks(), pawnSquare + DELTA_N));
- }
-
- Result classify_wtm(const KPKPosition& pos, const Result bb[]) {
-
- // If one move leads to a position classified as RESULT_LOSS, the result
- // of the current position is RESULT_WIN. If all moves lead to positions
- // classified as RESULT_DRAW, the current position is classified RESULT_DRAW
- // otherwise the current position is classified as RESULT_UNKNOWN.
-
- bool unknownFound = false;
- Bitboard b;
- Square s;
- int idx;
-
- // King moves
- b = pos.wk_attacks();
- while (b)
- {
- s = pop_1st_bit(&b);
- idx = compute_index(s, pos.blackKingSquare, pos.pawnSquare, BLACK);
-
- switch (bb[idx]) {
-
- case RESULT_LOSS:
- return RESULT_WIN;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
-
- case RESULT_DRAW:
- case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
- }
-
- // Pawn moves
- if (square_rank(pos.pawnSquare) < RANK_7)
- {
- s = pos.pawnSquare + DELTA_N;
- idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK);
-
- switch (bb[idx]) {
-
- case RESULT_LOSS:
- return RESULT_WIN;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
-
- case RESULT_DRAW:
- case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
-
- // Double pawn push
- if ( square_rank(s) == RANK_3
- && s != pos.whiteKingSquare
- && s != pos.blackKingSquare)
- {
- s += DELTA_N;
- idx = compute_index(pos.whiteKingSquare, pos.blackKingSquare, s, BLACK);
-
- switch (bb[idx]) {
-
- case RESULT_LOSS:
- return RESULT_WIN;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
-
- case RESULT_DRAW:
- case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
- }
- }
- return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
- }
-
-
- Result classify_btm(const KPKPosition& pos, const Result bb[]) {
-
- // If one move leads to a position classified as RESULT_DRAW, the result
- // of the current position is RESULT_DRAW. If all moves lead to positions
- // classified as RESULT_WIN, the current position is classified as
- // RESULT_LOSS. Otherwise, the current position is classified as
- // RESULT_UNKNOWN.
-
- bool unknownFound = false;
- Bitboard b;
- Square s;
- int idx;
-
- // King moves
- b = pos.bk_attacks();
- while (b)
- {
- s = pop_1st_bit(&b);
- idx = compute_index(pos.whiteKingSquare, s, pos.pawnSquare, WHITE);
-
- switch (bb[idx]) {
-
- case RESULT_DRAW:
- return RESULT_DRAW;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
-
- case RESULT_WIN:
- case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
- }
- return unknownFound ? RESULT_UNKNOWN : RESULT_LOSS;
- }
-
-}
projects / stockfish / blobdiff