/*
Stockfish, a UCI chess playing engine derived from Glaurung 2.1
Copyright (C) 2004-2008 Tord Romstad (Glaurung author)
- Copyright (C) 2008 Marco Costalba
+ 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/>.
*/
-
-////
-//// Includes
-////
-
#include <cassert>
-#include "bitbase.h"
#include "bitboard.h"
-#include "move.h"
-#include "square.h"
-
-
-////
-//// Local definitions
-////
+#include "types.h"
namespace {
RESULT_UNKNOWN,
RESULT_INVALID,
RESULT_WIN,
- RESULT_LOSS,
RESULT_DRAW
};
struct KPKPosition {
+ Result classify_knowns(int index);
+ Result classify(int index, Result db[]);
+
+ private:
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;
-
+ Result classify_white(const Result db[]);
+ Result classify_black(const Result db[]);
+ 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;
-
- 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);
-
-}
+ // The possible pawns squares are 24, the first 4 files and ranks from 2 to 7
+ const int IndexMax = 2 * 24 * 64 * 64; // color * wp_sq * wk_sq * bk_sq = 196608
+
+ // Each uint32_t stores results of 32 positions, one per bit
+ uint32_t KPKBitbase[IndexMax / 32];
-////
-//// Functions
-////
+ int compute_index(Square wksq, Square bksq, Square wpsq, Color stm);
+}
-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());
+uint32_t probe_kpk_bitbase(Square wksq, Square wpsq, Square bksq, Color stm) {
- // 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;
- }
+ int index = compute_index(wksq, bksq, wpsq, stm);
- // Release allocated memory:
- delete [] Bitbase;
+ return KPKBitbase[index / 32] & (1 << (index & 31));
}
-namespace {
+void kpk_bitbase_init() {
- 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));
- }
+ Result db[IndexMax];
+ KPKPosition pos;
+ int index, bit, repeat = 1;
+ // Initialize table
+ for (index = 0; index < IndexMax; index++)
+ db[index] = pos.classify_knowns(index);
- 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;
- }
+ // Iterate until all positions are classified (30 cycles needed)
+ while (repeat)
+ for (repeat = index = 0; index < IndexMax; index++)
+ if ( db[index] == RESULT_UNKNOWN
+ && pos.classify(index, db) != RESULT_UNKNOWN)
+ repeat = 1;
+ // Map 32 position results into one KPKBitbase[] entry
+ for (index = 0; index < IndexMax / 32; index++)
+ for (bit = 0; bit < 32; bit++)
+ if (db[32 * index + bit] == RESULT_WIN)
+ KPKBitbase[index] |= (1 << bit);
+}
- 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;
- }
+namespace {
- return false;
- }
+ // A KPK bitbase index is an integer in [0, IndexMax] range
+ //
+ // Information is mapped in this way
+ //
+ // bit 0: side to move (WHITE or BLACK)
+ // bit 1- 6: black king square (from SQ_A1 to SQ_H8)
+ // bit 7-12: white king square (from SQ_A1 to SQ_H8)
+ // bit 13-14: white pawn file (from FILE_A to FILE_D)
+ // bit 15-17: white pawn rank - 1 (from RANK_2 - 1 to RANK_7 - 1)
+ int compute_index(Square wksq, Square bksq, Square wpsq, Color stm) {
- 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));
- }
-
+ assert(square_file(wpsq) <= FILE_D);
- Bitboard KPKPosition::wk_attacks() const {
- return StepAttackBB[WK][whiteKingSquare];
- }
+ int p = square_file(wpsq) + 4 * (square_rank(wpsq) - 1);
+ int r = stm + 2 * bksq + 128 * wksq + 8192 * p;
+ assert(r >= 0 && r < IndexMax);
- Bitboard KPKPosition::bk_attacks() const {
- return StepAttackBB[BK][blackKingSquare];
+ return r;
}
+ void KPKPosition::from_index(int index) {
- Bitboard KPKPosition::pawn_attacks() const {
- return StepAttackBB[WP][pawnSquare];
+ int s = index >> 13;
+ sideToMove = Color(index & 1);
+ blackKingSquare = Square((index >> 1) & 63);
+ whiteKingSquare = Square((index >> 7) & 63);
+ pawnSquare = make_square(File(s & 3), Rank((s >> 2) + 1));
}
+ Result KPKPosition::classify_knowns(int index) {
- 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++;
- }
- }
- }
+ from_index(index);
+
+ // Check if two pieces are on the same square
+ if ( whiteKingSquare == pawnSquare
+ || whiteKingSquare == blackKingSquare
+ || blackKingSquare == pawnSquare)
+ return RESULT_INVALID;
+ // Check if a king can be captured
+ if ( bit_is_set(wk_attacks(), blackKingSquare)
+ || (bit_is_set(pawn_attacks(), blackKingSquare) && sideToMove == WHITE))
+ return RESULT_INVALID;
- bool next_iteration() {
- KPKPosition p;
- int previousUnknownCount = UnknownCount;
-
- for(int i = 0; i < IndexMax; i++)
- if(Bitbase[i] == RESULT_UNKNOWN) {
- p.from_index(i);
+ // The position is an immediate win if it is white to move and the
+ // white pawn can be promoted without getting captured.
+ if ( square_rank(pawnSquare) == RANK_7
+ && sideToMove == WHITE
+ && whiteKingSquare != pawnSquare + DELTA_N
+ && ( square_distance(blackKingSquare, pawnSquare + DELTA_N) > 1
+ || bit_is_set(wk_attacks(), pawnSquare + DELTA_N)))
+ return RESULT_WIN;
+
+ // Check for known draw positions
+ //
+ // Case 1: Stalemate
+ if ( sideToMove == BLACK
+ && (bk_attacks() & ~(wk_attacks() | pawn_attacks())) == EmptyBoardBB)
+ return RESULT_DRAW;
+
+ // Case 2: King can capture pawn
+ if ( sideToMove == BLACK
+ && bit_is_set(bk_attacks(), pawnSquare) && !bit_is_set(wk_attacks(), pawnSquare))
+ return RESULT_DRAW;
- Bitbase[i] = (p.sideToMove == WHITE)? classify_wtm(p) : classify_btm(p);
+ // Case 3: Black king in front of white pawn
+ if ( blackKingSquare == pawnSquare + DELTA_N
+ && square_rank(pawnSquare) < RANK_7)
+ return RESULT_DRAW;
- if(Bitbase[i] == RESULT_WIN || Bitbase[i] == RESULT_LOSS ||
- Bitbase[i] == RESULT_DRAW)
- UnknownCount--;
- }
+ // Case 4: White king in front of pawn and black has opposition
+ if ( whiteKingSquare == pawnSquare + DELTA_N
+ && blackKingSquare == pawnSquare + DELTA_N + DELTA_N + DELTA_N
+ && square_rank(pawnSquare) < RANK_5
+ && sideToMove == WHITE)
+ return RESULT_DRAW;
- return UnknownCount != previousUnknownCount;
+ // Case 5: Stalemate with rook pawn
+ if ( blackKingSquare == SQ_A8
+ && square_file(pawnSquare) == FILE_A)
+ return RESULT_DRAW;
+
+ return RESULT_UNKNOWN;
}
+ Result KPKPosition::classify(int index, Result db[]) {
+
+ from_index(index);
+ db[index] = (sideToMove == WHITE ? classify_white(db) : classify_black(db));
+ return db[index];
+ }
- Result classify_wtm(const KPKPosition &p) {
+ Result KPKPosition::classify_white(const Result db[]) {
- // 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.
+ // If one move leads to a position classified as RESULT_WIN, 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;
-
- // 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;
+ Result r;
- case RESULT_UNKNOWN:
- unknownFound = true;
- break;
+ // King moves
+ b = wk_attacks();
+ while (b)
+ {
+ s = pop_1st_bit(&b);
+ r = db[compute_index(s, blackKingSquare, pawnSquare, BLACK)];
- case RESULT_DRAW: case RESULT_INVALID:
- break;
+ if (r == RESULT_WIN)
+ return RESULT_WIN;
- default:
- assert(false);
- }
+ if (r == RESULT_UNKNOWN)
+ unknownFound = true;
}
// 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);
+ if (square_rank(pawnSquare) < RANK_7)
+ {
+ s = pawnSquare + DELTA_N;
+ r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)];
+
+ if (r == RESULT_WIN)
+ return RESULT_WIN;
+
+ if (r == RESULT_UNKNOWN)
+ unknownFound = true;
+
+ // Double pawn push
+ if (square_rank(s) == RANK_3 && r != RESULT_INVALID)
+ {
+ s += DELTA_N;
+ r = db[compute_index(whiteKingSquare, blackKingSquare, s, BLACK)];
+
+ if (r == RESULT_WIN)
+ return RESULT_WIN;
+
+ if (r == RESULT_UNKNOWN)
+ unknownFound = true;
}
- }
}
-
- return unknownFound? RESULT_UNKNOWN : RESULT_DRAW;
+ return unknownFound ? RESULT_UNKNOWN : RESULT_DRAW;
}
-
- Result classify_btm(const KPKPosition &p) {
+ Result KPKPosition::classify_black(const Result db[]) {
// 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.
+ // of the current position is RESULT_DRAW. If all moves lead to positions
+ // classified as RESULT_WIN, the position is classified as RESULT_WIN.
+ // Otherwise, the current position is classified as RESULT_UNKNOWN.
bool unknownFound = false;
Bitboard b;
Square s;
+ Result r;
// 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;
+ b = bk_attacks();
+ while (b)
+ {
+ s = pop_1st_bit(&b);
+ r = db[compute_index(whiteKingSquare, s, pawnSquare, WHITE)];
- case RESULT_WIN: case RESULT_INVALID:
- break;
+ if (r == RESULT_DRAW)
+ return RESULT_DRAW;
- default:
- assert(false);
- }
+ if (r == RESULT_UNKNOWN)
+ unknownFound = true;
}
-
- 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;
+ return unknownFound ? RESULT_UNKNOWN : RESULT_WIN;
}
-
- int compress_result(Result r) {
- return (r == RESULT_WIN || r == RESULT_LOSS)? 1 : 0;
- }
-
-}
+}
projects / stockfish / blobdiff