/*
- Glaurung, a UCI chess playing engine.
- Copyright (C) 2004-2008 Tord Romstad
+ 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
- Glaurung is free software: you can redistribute it and/or modify
+ 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.
-
- Glaurung is distributed in the hope that it will be useful,
+
+ 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
-////
+#include "types.h"
namespace {
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;
-
+ 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;
};
-
- Result *Bitbase;
- const int IndexMax = 2*24*64*64;
- int UnknownCount = 0;
+ const int IndexMax = 2 * 24 * 64 * 64;
- void initialize();
- bool next_iteration();
- Result classify_wtm(const KPKPosition &p);
- Result classify_btm(const KPKPosition &p);
+ 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);
- 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:
+ bool repeat;
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;
+ 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;
}
- // Release allocated memory:
- delete [] Bitbase;
+ // 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;
+
+ int s = (index / 8192) % 24;
+
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))
+
+ 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(this->bk_attacks(), whiteKingSquare))
+ else if (bit_is_set(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;
+
+ 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;
+ else
+ {
+ // Case 1: Stalemate
+ if ( whiteKingSquare == SQ_A8
+ && pawnSquare == SQ_A7
+ && (blackKingSquare == SQ_C7 || blackKingSquare == SQ_C8))
+ return true;
+
+ if ( whiteKingSquare == SQ_H8
+ && pawnSquare == SQ_H7
+ && (blackKingSquare == SQ_F7 || blackKingSquare == SQ_F8))
+ 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];
+ // 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
+ && whiteKingSquare != pawnSquare + DELTA_N
+ && ( square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1
+ || bit_is_set(wk_attacks(), pawnSquare + DELTA_N));
}
+ Result classify_wtm(const KPKPosition& pos, const Result bb[]) {
- Bitboard KPKPosition::bk_attacks() const {
- return StepAttackBB[BK][blackKingSquare];
- }
+ // 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;
- Bitboard KPKPosition::pawn_attacks() const {
- return StepAttackBB[WP][pawnSquare];
- }
+ // 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;
- 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++;
- }
+ 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);
- bool next_iteration() {
- KPKPosition p;
- int previousUnknownCount = UnknownCount;
-
- for(int i = 0; i < IndexMax; i++)
- if(Bitbase[i] == RESULT_UNKNOWN) {
- p.from_index(i);
+ switch (bb[idx]) {
- Bitbase[i] = (p.sideToMove == WHITE)? classify_wtm(p) : classify_btm(p);
+ case RESULT_LOSS:
+ return RESULT_WIN;
- if(Bitbase[i] == RESULT_WIN || Bitbase[i] == RESULT_LOSS ||
- Bitbase[i] == RESULT_DRAW)
- UnknownCount--;
- }
+ case RESULT_UNKNOWN:
+ unknownFound = true;
- return UnknownCount != previousUnknownCount;
- }
+ case RESULT_DRAW:
+ case RESULT_INVALID:
+ break;
+ default:
+ assert(false);
+ }
- Result classify_wtm(const KPKPosition &p) {
+ // 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);
- // 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.
+ switch (bb[idx]) {
- 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);
- }
- }
+ case RESULT_LOSS:
+ return RESULT_WIN;
- // 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);
+ case RESULT_UNKNOWN:
+ unknownFound = true;
+
+ case RESULT_DRAW:
+ case RESULT_INVALID:
+ break;
+
+ default:
+ assert(false);
+ }
}
- }
}
-
- return unknownFound? RESULT_UNKNOWN : RESULT_DRAW;
+ return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
}
- Result classify_btm(const KPKPosition &p) {
+ 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
+ // 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_LOSS. Otherwise, the current position is classified as
// RESULT_UNKNOWN.
bool unknownFound = false;
Bitboard b;
Square s;
+ int idx;
// 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);
- }
- }
+ b = pos.bk_attacks();
+ while (b)
+ {
+ s = pop_1st_bit(&b);
+ idx = compute_index(pos.whiteKingSquare, s, pos.pawnSquare, WHITE);
- return unknownFound? RESULT_UNKNOWN : RESULT_LOSS;
- }
+ switch (bb[idx]) {
+ case RESULT_DRAW:
+ return RESULT_DRAW;
- 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;
- }
+ case RESULT_UNKNOWN:
+ unknownFound = true;
+ case RESULT_WIN:
+ case RESULT_INVALID:
+ break;
- int compress_result(Result r) {
- return (r == RESULT_WIN || r == RESULT_LOSS)? 1 : 0;
+ default:
+ assert(false);
+ }
+ }
+ return unknownFound ? RESULT_UNKNOWN : RESULT_LOSS;
}
-
-}
+
+}
projects / stockfish / blobdiff