+++ /dev/null
-/*
- Stockfish, a UCI chess playing engine derived from Glaurung 2.1
- Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008 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
- 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/>.
-*/
-
-
-////
-//// Includes
-////
-
-#include <cassert>
-
-#include "bitbase.h"
-#include "bitboard.h"
-#include "move.h"
-#include "square.h"
-
-
-////
-//// Local definitions
-////
-
-namespace {
-
- enum Result {
- RESULT_UNKNOWN,
- RESULT_INVALID,
- RESULT_WIN,
- RESULT_LOSS,
- RESULT_DRAW
- };
-
- struct KPKPosition {
- void from_index(int index);
- int to_index() const;
- bool is_legal() const;
- bool is_immediate_draw() const;
- bool is_immediate_win() const;
- Bitboard wk_attacks() const;
- Bitboard bk_attacks() const;
- Bitboard pawn_attacks() const;
-
- Square whiteKingSquare, blackKingSquare, pawnSquare;
- Color sideToMove;
- };
-
-
- Result *Bitbase;
- const int IndexMax = 2*24*64*64;
- int UnknownCount = 0;
-
- void initialize();
- bool next_iteration();
- Result classify_wtm(const KPKPosition &p);
- Result classify_btm(const KPKPosition &p);
- int compute_index(Square wksq, Square bksq, Square psq, Color stm);
- int compress_result(Result r);
-
-}
-
-
-////
-//// Functions
-////
-
-void generate_kpk_bitbase(uint8_t bitbase[]) {
- // Allocate array and initialize:
- Bitbase = new Result[IndexMax];
- initialize();
-
- // Iterate until all positions are classified:
- while(next_iteration());
-
- // Compress bitbase into the supplied parameter:
- int i, j, b;
- for(i = 0; i < 24576; i++) {
- for(b = 0, j = 0; j < 8; b |= (compress_result(Bitbase[8*i+j]) << j), j++);
- bitbase[i] = b;
- }
-
- // Release allocated memory:
- delete [] Bitbase;
-}
-
-
-namespace {
-
- void KPKPosition::from_index(int index) {
- int s;
- sideToMove = Color(index % 2);
- blackKingSquare = Square((index / 2) % 64);
- whiteKingSquare = Square((index / 128) % 64);
- s = (index / 8192) % 24;
- pawnSquare = make_square(File(s % 4), Rank(s / 4 + 1));
- }
-
-
- int KPKPosition::to_index() const {
- return compute_index(whiteKingSquare, blackKingSquare, pawnSquare,
- sideToMove);
- }
-
-
- bool KPKPosition::is_legal() const {
- if(whiteKingSquare == pawnSquare || whiteKingSquare == blackKingSquare ||
- pawnSquare == blackKingSquare)
- return false;
- if(sideToMove == WHITE) {
- if(bit_is_set(this->wk_attacks(), blackKingSquare))
- return false;
- if(bit_is_set(this->pawn_attacks(), blackKingSquare))
- return false;
- }
- else {
- if(bit_is_set(this->bk_attacks(), whiteKingSquare))
- return false;
- }
- return true;
- }
-
-
- bool KPKPosition::is_immediate_draw() const {
- if(sideToMove == BLACK) {
- Bitboard wka = this->wk_attacks();
- Bitboard bka = this->bk_attacks();
-
- // Case 1: Stalemate
- if((bka & ~(wka | this->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(this->wk_attacks(), pawnSquare+DELTA_N));
- }
-
-
- Bitboard KPKPosition::wk_attacks() const {
- return StepAttackBB[WK][whiteKingSquare];
- }
-
-
- Bitboard KPKPosition::bk_attacks() const {
- return StepAttackBB[BK][blackKingSquare];
- }
-
-
- Bitboard KPKPosition::pawn_attacks() const {
- return StepAttackBB[WP][pawnSquare];
- }
-
-
- void initialize() {
- KPKPosition p;
- for(int i = 0; i < IndexMax; i++) {
- p.from_index(i);
- if(!p.is_legal())
- Bitbase[i] = RESULT_INVALID;
- else if(p.is_immediate_draw())
- Bitbase[i] = RESULT_DRAW;
- else if(p.is_immediate_win())
- Bitbase[i] = RESULT_WIN;
- else {
- Bitbase[i] = RESULT_UNKNOWN;
- UnknownCount++;
- }
- }
- }
-
-
- bool next_iteration() {
- KPKPosition p;
- int previousUnknownCount = UnknownCount;
-
- for(int i = 0; i < IndexMax; i++)
- if(Bitbase[i] == RESULT_UNKNOWN) {
- p.from_index(i);
-
- Bitbase[i] = (p.sideToMove == WHITE)? classify_wtm(p) : classify_btm(p);
-
- if(Bitbase[i] == RESULT_WIN || Bitbase[i] == RESULT_LOSS ||
- Bitbase[i] == RESULT_DRAW)
- UnknownCount--;
- }
-
- return UnknownCount != previousUnknownCount;
- }
-
-
- Result classify_wtm(const KPKPosition &p) {
-
- // 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 as
- // RESULT_DRAW. Otherwise, the current position is classified as
- // RESULT_UNKNOWN.
-
- bool unknownFound = false;
- Bitboard b;
- Square s;
-
- // King moves
- b = p.wk_attacks();
- while(b) {
- s = pop_1st_bit(&b);
- switch(Bitbase[compute_index(s, p.blackKingSquare, p.pawnSquare,
- BLACK)]) {
- case RESULT_LOSS:
- return RESULT_WIN;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
- break;
-
- case RESULT_DRAW: case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
- }
-
- // Pawn moves
- if(square_rank(p.pawnSquare) < RANK_7) {
- s = p.pawnSquare + DELTA_N;
- switch(Bitbase[compute_index(p.whiteKingSquare, p.blackKingSquare, s,
- BLACK)]) {
- case RESULT_LOSS:
- return RESULT_WIN;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
- break;
-
- case RESULT_DRAW: case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
-
- if(square_rank(s) == RANK_3 &&
- s != p.whiteKingSquare && s != p.blackKingSquare) {
- s += DELTA_N;
- switch(Bitbase[compute_index(p.whiteKingSquare, p.blackKingSquare, s,
- BLACK)]) {
- case RESULT_LOSS:
- return RESULT_WIN;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
- break;
-
- case RESULT_DRAW: case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
- }
- }
-
- return unknownFound? RESULT_UNKNOWN : RESULT_DRAW;
- }
-
-
- Result classify_btm(const KPKPosition &p) {
-
- // 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;
-
- // King moves
- b = p.bk_attacks();
- while(b) {
- s = pop_1st_bit(&b);
- switch(Bitbase[compute_index(p.whiteKingSquare, s, p.pawnSquare,
- WHITE)]) {
- case RESULT_DRAW:
- return RESULT_DRAW;
-
- case RESULT_UNKNOWN:
- unknownFound = true;
- break;
-
- case RESULT_WIN: case RESULT_INVALID:
- break;
-
- default:
- assert(false);
- }
- }
-
- return unknownFound? RESULT_UNKNOWN : RESULT_LOSS;
- }
-
-
- int compute_index(Square wksq, Square bksq, Square psq, Color stm) {
- int p = int(square_file(psq)) + (int(square_rank(psq)) - 1) * 4;
- int result = int(stm) + 2*int(bksq) + 128*int(wksq) + 8192*p;
- assert(result >= 0 && result < IndexMax);
- return result;
- }
-
-
- int compress_result(Result r) {
- return (r == RESULT_WIN || r == RESULT_LOSS)? 1 : 0;
- }
-
-}
projects / stockfish / blobdiff