void *worker(void *arg) {
struct board_t w_board;
enum player_t player;
int depth, col, type;
double result;
while (1) {
MPI_Recv(&type, 1, MPI_INT, MPI_ANY_SOURCE,
REQUEST, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
if (type == WORKER_QUIT) {
break;
} else if (type == WORKER_START) {
MPI_Recv((char *)&w_board, sizeof(board), MPI_CHAR, MPI_ANY_SOURCE,
REQUEST, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
MPI_Recv((char *)&player, sizeof(player), MPI_CHAR, MPI_ANY_SOURCE,
REQUEST, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
MPI_Recv(&col, 1, MPI_INT, MPI_ANY_SOURCE,
REQUEST, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
MPI_Recv(&depth, 1, MPI_INT, MPI_ANY_SOURCE,
REQUEST, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
BoardMove(&w_board, col, player);
result = EvaluateBoard(&w_board, player, col, depth);
MPI_Send(&result, 1, MPI_DOUBLE, 0, col, MPI_COMM_WORLD);
}
}
return NULL;
}
float alphaBetaMax(BNTBoard board, float alpha, float beta, float depthleft, BNTPlayer player)
{
if (depthleft == 0 || IsGameEnd(board))
return EvaluateBoard(board, player);
for (int x = 0; x < BOARD_SIZE; ++x)
{
for (int y = 0; y < BOARD_SIZE; ++y)
{
if (board[x][y] == BNTPlayerNone)
{
board[x][y] = NextPlayer(board);
float score = alphaBetaMin(board, alpha, beta, depthleft - 1, player);
board[x][y] = BNTPlayerNone;
if (score >= beta) {
return beta;
}
if (score > alpha) {
alpha = score;
}
}
}
}
return alpha;
}
double EvaluateBoard(struct board_t *current, enum player_t last, int last_col, int depth) {
double result, total;
enum player_t now;
int all_win = 1, all_lose = 1;
int moves, col;
if (BoardIsGameOver(current, last_col)) {
if (last == COMPUTER) {
return 1;
} else {
return -1;
}
}
if (depth == 0) {
return 0;
}
if (last == COMPUTER) {
now = HUMAN;
} else {
now = COMPUTER;
}
total = 0;
moves = 0;
for (col = 0; col < BOARD_COLS; ++col) {
if (BoardIsValidMove(current, col)) {
moves ++;
BoardMove(current, col, now);
result = EvaluateBoard(current, now, col, depth - 1);
BoardUndoMove(current, col);
if (result > -1) all_lose = 0;
if (result < 1) all_win = 0;
if (result == 1 && now == COMPUTER) return 1;
if (result == -1 && now == HUMAN) return -1;
total += result;
}
}
if (all_win) return 1;
if (all_lose) return -1;
return total / moves;
}
int EvaluateMove(Board& board, int alpha, int beta, int depth, bool maximizing)
{
if (board.kingDead)
{
return maximizing ? -999111 : 999111;
}
if (depth == 0)
{
return EvaluateBoard(board);
}
vector<Move> possibleMoves;
possibleMoves.reserve(100);
GenerateAll(board, possibleMoves);
int returnVal;
if (maximizing)
{
for (Move move : possibleMoves)
{
board.MakeMove(move);
alpha = max(alpha, EvaluateMove(board, alpha, beta, depth - 1, false));
if (beta <= alpha)
{
board.UndoMove();
break;
}
board.UndoMove();
}
returnVal = alpha;
}
else
{
for (Move move : possibleMoves)
{
board.MakeMove(move);
beta = min(beta, EvaluateMove(board, alpha, beta, depth - 1, true));
if (beta <= alpha)
{
board.UndoMove();
break;
}
board.UndoMove();
}
returnVal = beta;
}
return returnVal;
}
float alphabeta(BNTBoard board, int depth, float alpha, float beta, BNTPlayer player)
{
if (depth == 0 || IsGameEnd(board))
return EvaluateBoard(board, player) * (player == BNTPlayerX ? 1 : -1);
if (player == BNTPlayerX)
{
for (int x = 0; x < BOARD_SIZE; ++x)
{
for (int y = 0; y < BOARD_SIZE; ++y)
{
if (board[x][y] == BNTPlayerNone)
{
board[x][y] = player;
alpha = DEPTH_PENALTY * MAX(alpha, alphabeta(board, depth-1, alpha, beta, OppositePlayer(player)));
board[x][y] = BNTPlayerNone;
if (beta <= alpha)
{
break;/* Beta cut-off */
}
}
}
}
return alpha;
}
else
{
for (int x = 0; x < BOARD_SIZE; ++x)
{
for (int y = 0; y < BOARD_SIZE; ++y)
{
if (board[x][y] == BNTPlayerNone)
{
board[x][y] = player;
beta = DEPTH_PENALTY * MIN(beta, alphabeta(board, depth-1, alpha, beta, OppositePlayer(player)));
board[x][y] = BNTPlayerNone;
if (beta <= alpha)
{
break;/* Alpha cut-off */
}
}
}
}
return beta;
}
}
float alphaBetaMin(BNTBoard board, float alpha, float beta, float depthleft, BNTPlayer player)
{
if (depthleft == 0 || IsGameEnd(board))
return -1 * EvaluateBoard(board, player);
for (int x = 0; x < BOARD_SIZE; ++x)
{
for (int y = 0; y < BOARD_SIZE; ++y)
{
if (board[x][y] == BNTPlayerNone)
{
board[x][y] = NextPlayer(board);
float score = alphaBetaMax(board, alpha, beta, depthleft - 1, player);
board[x][y] = BNTPlayerNone;
if(score <= alpha)
return alpha; // fail hard alpha-cutoff
if(score < beta)
beta = score; // beta acts like min in MiniMax
}
}
}
return beta;
}