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go_benchmark.c
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go_benchmark.c
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// This file is a part of Julia. License is MIT: http://julialang.org/license
/* Benchmark implementing the board logic for the game of go and
* exercising it by playing random games. Derived from
* http://www.lysator.liu.se/~gunnar/gtp/brown-1.0.tar.gz
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define MAX_BOARD 23
#define EMPTY 0
#define WHITE 1
#define BLACK 2
/* Used in the final_status[] array. */
#define DEAD 0
#define ALIVE 1
#define SEKI 2
#define WHITE_TERRITORY 3
#define BLACK_TERRITORY 4
#define UNKNOWN 5
/* Macro to find the opposite color. */
#define OTHER_COLOR(color) (WHITE + BLACK - (color))
static int board_size = 9;
static float komi = 0.0;
/* Board represented by a 1D array. The first board_size*board_size
* elements are used. Vertices are indexed row by row, starting with 0
* in the upper left corner.
*/
static int board[MAX_BOARD * MAX_BOARD];
/* Stones are linked together in a circular list for each string. */
static int next_stone[MAX_BOARD * MAX_BOARD];
/* Storage for final status computations. */
static int final_status[MAX_BOARD * MAX_BOARD];
/* Point which would be an illegal ko recapture. */
static int ko_i, ko_j;
/* Offsets for the four directly adjacent neighbors. Used for looping. */
static int deltai[4] = {-1, 1, 0, 0};
static int deltaj[4] = {0, 0, -1, 1};
/* Macros to convert between 1D and 2D coordinates. The 2D coordinate
* (i, j) points to row i and column j, starting with (0,0) in the
* upper left corner.
*/
#define POS(i, j) ((i) * board_size + (j))
#define I(pos) ((pos) / board_size)
#define J(pos) ((pos) % board_size)
/* xor-shift random number generator. */
static unsigned int rand_state = 2463534242U;
static void
xor_srand(unsigned int seed)
{
rand_state = seed;
}
static unsigned int
xor_randn(unsigned int n)
{
rand_state ^= (rand_state << 13);
rand_state ^= (rand_state >> 17);
rand_state ^= (rand_state << 5);
return rand_state % n;
}
static void
clear_board()
{
memset(board, 0, sizeof(board));
}
static void
init_brown(unsigned int seed)
{
xor_srand(seed);
clear_board();
}
static int
get_board(int i, int j)
{
return board[i * board_size + j];
}
static int
pass_move(int i, int j)
{
return i == -1 && j == -1;
}
static int
on_board(int i, int j)
{
return i >= 0 && i < board_size && j >= 0 && j < board_size;
}
static int
legal_move(int i, int j, int color)
{
int other = OTHER_COLOR(color);
/* Pass is always legal. */
if (pass_move(i, j))
return 1;
/* Already occupied. */
if (get_board(i, j) != EMPTY)
return 0;
/* Illegal ko recapture. It is not illegal to fill the ko so we must
* check the color of at least one neighbor.
*/
if (i == ko_i && j == ko_j
&& ((on_board(i - 1, j) && get_board(i - 1, j) == other)
|| (on_board(i + 1, j) && get_board(i + 1, j) == other)))
return 0;
return 1;
}
/* Does the string at (i, j) have any more liberty than the one at
* (libi, libj)?
*/
static int
has_additional_liberty(int i, int j, int libi, int libj)
{
int pos = POS(i, j);
do {
int ai = I(pos);
int aj = J(pos);
int k;
for (k = 0; k < 4; k++) {
int bi = ai + deltai[k];
int bj = aj + deltaj[k];
if (on_board(bi, bj) && get_board(bi, bj) == EMPTY
&& (bi != libi || bj != libj))
return 1;
}
pos = next_stone[pos];
} while (pos != POS(i, j));
return 0;
}
/* Does (ai, aj) provide a liberty for a stone at (i, j)? */
static int
provides_liberty(int ai, int aj, int i, int j, int color)
{
/* A vertex off the board does not provide a liberty. */
if (!on_board(ai, aj))
return 0;
/* An empty vertex IS a liberty. */
if (get_board(ai, aj) == EMPTY)
return 1;
/* A friendly string provides a liberty to (i, j) if it currently
* has more liberties than the one at (i, j).
*/
if (get_board(ai, aj) == color)
return has_additional_liberty(ai, aj, i, j);
/* An unfriendly string provides a liberty if and only if it is
* captured, i.e. if it currently only has the liberty at (i, j).
*/
return !has_additional_liberty(ai, aj, i, j);
}
/* Is a move at (i, j) suicide for color? */
static int
suicide(int i, int j, int color)
{
int k;
for (k = 0; k < 4; k++)
if (provides_liberty(i + deltai[k], j + deltaj[k], i, j, color))
return 0;
return 1;
}
/* Remove a string from the board array. There is no need to modify
* the next_stone array since this only matters where there are
* stones present and the entire string is removed.
*/
static int
remove_string(int i, int j)
{
int pos = POS(i, j);
int removed = 0;
do {
board[pos] = EMPTY;
removed++;
pos = next_stone[pos];
} while (pos != POS(i, j));
return removed;
}
/* Do two vertices belong to the same string. It is required that both
* pos1 and pos2 point to vertices with stones.
*/
static int
same_string(int pos1, int pos2)
{
int pos = pos1;
do {
if (pos == pos2)
return 1;
pos = next_stone[pos];
} while (pos != pos1);
return 0;
}
/* Play at (i, j) for color. No legality check is done here. We need
* to properly update the board array, the next_stone array, and the
* ko point.
*/
static void
play_move(int i, int j, int color)
{
int pos = POS(i, j);
int captured_stones = 0;
int k;
/* Reset the ko point. */
ko_i = -1;
ko_j = -1;
/* Nothing more happens if the move was a pass. */
if (pass_move(i, j))
return;
/* If the move is a suicide we only need to remove the adjacent
* friendly stones.
*/
if (suicide(i, j, color)) {
for (k = 0; k < 4; k++) {
int ai = i + deltai[k];
int aj = j + deltaj[k];
if (on_board(ai, aj)
&& get_board(ai, aj) == color)
remove_string(ai, aj);
}
return;
}
/* Not suicide. Remove captured opponent strings. */
for (k = 0; k < 4; k++) {
int ai = i + deltai[k];
int aj = j + deltaj[k];
if (on_board(ai, aj)
&& get_board(ai, aj) == OTHER_COLOR(color)
&& !has_additional_liberty(ai, aj, i, j))
captured_stones += remove_string(ai, aj);
}
/* Put down the new stone. Initially build a single stone string by
* setting next_stone[pos] pointing to itself.
*/
board[pos] = color;
next_stone[pos] = pos;
/* If we have friendly neighbor strings we need to link the strings
* together.
*/
for (k = 0; k < 4; k++) {
int ai = i + deltai[k];
int aj = j + deltaj[k];
int pos2 = POS(ai, aj);
/* Make sure that the stones are not already linked together. This
* may happen if the same string neighbors the new stone in more
* than one direction.
*/
if (on_board(ai, aj) && board[pos2] == color && !same_string(pos, pos2)) {
/* The strings are linked together simply by swapping the
* next_stone pointers.
*/
int tmp = next_stone[pos2];
next_stone[pos2] = next_stone[pos];
next_stone[pos] = tmp;
}
}
/* If we have captured exactly one stone and the new string is a
* single stone it may have been a ko capture.
*/
if (captured_stones == 1 && next_stone[pos] == pos) {
int ai, aj;
/* Check whether the new string has exactly one liberty. If so it
* would be an illegal ko capture to play there immediately. We
* know that there must be a liberty immediately adjacent to the
* new stone since we captured one stone.
*/
for (k = 0; k < 4; k++) {
ai = i + deltai[k];
aj = j + deltaj[k];
if (on_board(ai, aj) && get_board(ai, aj) == EMPTY)
break;
}
if (!has_additional_liberty(i, j, ai, aj)) {
ko_i = ai;
ko_j = aj;
}
}
}
/* Generate a move. */
static void
generate_move(int *i, int *j, int color)
{
int moves[MAX_BOARD * MAX_BOARD];
int num_moves = 0;
int move;
int ai, aj;
int k;
memset(moves, 0, sizeof(moves));
for (ai = 0; ai < board_size; ai++)
for (aj = 0; aj < board_size; aj++) {
/* Consider moving at (ai, aj) if it is legal and not suicide. */
if (legal_move(ai, aj, color)
&& !suicide(ai, aj, color)) {
/* Further require the move not to be suicide for the opponent... */
if (!suicide(ai, aj, OTHER_COLOR(color)))
moves[num_moves++] = POS(ai, aj);
else {
/* ...however, if the move captures at least one stone,
* consider it anyway.
*/
for (k = 0; k < 4; k++) {
int bi = ai + deltai[k];
int bj = aj + deltaj[k];
if (on_board(bi, bj) && get_board(bi, bj) == OTHER_COLOR(color)) {
moves[num_moves++] = POS(ai, aj);
break;
}
}
}
}
}
/* Choose one of the considered moves randomly with uniform
* distribution. (Strictly speaking the moves with smaller 1D
* coordinates tend to have a very slightly higher probability to be
* chosen, but for all practical purposes we get a uniform
* distribution.)
*/
if (num_moves > 0) {
move = moves[xor_randn(num_moves)];
*i = I(move);
*j = J(move);
}
else {
/* But pass if no move was considered. */
*i = -1;
*j = -1;
}
}
/* Set a final status value for an entire string. */
static void
set_final_status_string(int pos, int status)
{
int pos2 = pos;
do {
final_status[pos2] = status;
pos2 = next_stone[pos2];
} while (pos2 != pos);
}
/* Compute final status. This function is only valid to call in a
* position where generate_move() would return pass for at least one
* color.
*
* Due to the nature of the move generation algorithm, the final
* status of stones can be determined by a very simple algorithm:
*
* 1. Stones with two or more liberties are alive with territory.
* 2. Stones in atari are dead.
*
* Moreover alive stones are unconditionally alive even if the
* opponent is allowed an arbitrary number of consecutive moves.
* Similarly dead stones cannot be brought alive even by an arbitrary
* number of consecutive moves.
*
* Seki is not an option. The move generation algorithm would never
* leave a seki on the board.
*
* Comment: This algorithm doesn't work properly if the game ends with
* an unfilled ko. If three passes are required for game end,
* that will not happen.
*/
static void
compute_final_status(void)
{
int i, j;
int pos;
int k;
for (pos = 0; pos < board_size * board_size; pos++)
final_status[pos] = UNKNOWN;
for (i = 0; i < board_size; i++)
for (j = 0; j < board_size; j++)
if (get_board(i, j) == EMPTY)
for (k = 0; k < 4; k++) {
int ai = i + deltai[k];
int aj = j + deltaj[k];
if (!on_board(ai, aj))
continue;
/* When the game is finished, we know for sure that (ai, aj)
* contains a stone. The move generation algorithm would
* never leave two adjacent empty vertices. Check the number
* of liberties to decide its status, unless it's known
* already.
*
* If we should be called in a non-final position, just make
* sure we don't call set_final_status_string() on an empty
* vertex.
*/
pos = POS(ai, aj);
if (final_status[pos] == UNKNOWN) {
if (get_board(ai, aj) != EMPTY) {
if (has_additional_liberty(ai, aj, i, j))
set_final_status_string(pos, ALIVE);
else
set_final_status_string(pos, DEAD);
}
}
/* Set the final status of the (i, j) vertex to either black
* or white territory.
*/
if (final_status[POS(i, j)] == UNKNOWN) {
if ((final_status[pos] == ALIVE) ^ (get_board(ai, aj) == WHITE))
final_status[POS(i, j)] = BLACK_TERRITORY;
else
final_status[POS(i, j)] = WHITE_TERRITORY;
}
}
}
static int
get_final_status(int i, int j)
{
return final_status[POS(i, j)];
}
static float
compute_score()
{
int i, j;
float score = komi;
compute_final_status();
for (i = 0; i < board_size; i++) {
for (j = 0; j < board_size; j++) {
int status = get_final_status(i, j);
if (status == BLACK_TERRITORY) {
score--;
}
else if (status == WHITE_TERRITORY) {
score++;
}
else if ((status == ALIVE) ^ (get_board(i, j) == WHITE)) {
score--;
}
else {
score++;
}
}
}
return score;
}
static void
benchmark(int num_games_per_point)
{
int i, j;
unsigned int random_seed = 1U;
board_size = 9;
komi = 0.5;
init_brown(random_seed);
for (i = 0; i < board_size; i++) {
for (j = 0; j < board_size; j++) {
int white_wins = 0;
int black_wins = 0;
int k;
for (k = 0; k < num_games_per_point; k++) {
int passes = 0;
int num_moves = 1;
int color = WHITE;
clear_board();
play_move(i, j, BLACK);
while (passes < 3 && num_moves < 600) {
int m, n;
generate_move(&m, &n, color);
play_move(m, n, color);
if (pass_move(m, n)) {
passes++;
}
else {
passes = 0;
}
num_moves++;
color = OTHER_COLOR(color);
}
if (passes == 3) {
if (compute_score() > 0) {
white_wins++;
}
else {
black_wins++;
}
}
}
/*
printf("%d %d %f\n", i, j,
(float) black_wins / (float) (black_wins + white_wins));
*/
}
}
}
int
main(int argc, char **argv)
{
int num_games_per_point = 10;
if (argc > 1)
num_games_per_point = atoi(argv[1]);
benchmark(num_games_per_point);
return EXIT_SUCCESS;
}