为什么我在C ++中的异步，未来中会出错 [英] Why am I Getting error in async, future in C++
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问题描述
我第一次使用std :: async和std :: future并收到错误消息，请问我可以解决此问题吗?
I am using std::async and std::future for the first time and am getting the error, Can somone help me rectify it.
错误:
** terminate called after throwing an instance of 'std::future_error'
what(): std::future_error: No associated state**
代码:
long long best_move(int depth, int start_score, char state[8][9],
int state_score[8][8], long long alpha, long long beta){
long long curr = 0;
for(int i=0; i<8; ++i){
for(int j=0; j<8; ++j){
curr += state_score[i][j];
}
}
if(depth == 5){
//printf("Return value in the last node = %lld\n", current_score);
return curr;
}
// TURN OF THE PLAYER THAT MAXIMIZES THE SCORE :
int mid[] = {0, 7, 1, 6, 2, 5, 3, 4};
if(depth % 2 == 0){
//printf("Reached the maximizing player\n");
long long ans = -1e8;
for(int i=0; i<8; ++i){
for(int j=0; j<8; ++j){
if(isUpper(state[i][mid[j]]) && state_score[i][mid[j]]>0){
vector<pair<int, int>> possible_moves = get_moves(i, mid[j], state);
if(possible_moves.size() == 0) continue;
int co = -1;
std::future<long long> fut[possible_moves.size()];
for(auto u : possible_moves){
co = co + 1;
int x = u.first, y = u.second;
long long removed_points = state_score[x][y];
char state_copy[8][9];
int state_score_copy[8][8];
for(int k=0; k<8; ++k){
for(int io=0; io<9; ++io){
if(io!=8) state_score_copy[k][io] = state_score[k][io];
state_copy[k][io] = state[k][io];
}
}
long long new_score = curr - state_score[x][y];
if(depth >= 3 && new_score == start_score) continue;
state_copy[x][y] = state_copy[i][mid[j]];
state_copy[i][mid[j]] = '_';
state_score_copy[x][y] = state_score_copy[i][mid[j]];
state_score_copy[i][mid[j]] = 0;
//long long res = best_move(depth+1, state_copy, state_score_copy, alpha, beta);
fut[co] = std::async (std::launch::async, best_move, depth+1, start_score, state_copy, state_score_copy, alpha, beta);
//long long res = best_move(depth+1, start_score, state_copy, state_score_copy, alpha, beta);
//printf("%lld\n", res);
}
co = 0;
for(co = 0; co < possible_moves.size(); ++co){
long long res = fut[co].get();
ans = max(ans, res);
alpha = max(alpha, ans);
if(beta <= alpha) break;
if(depth == 0 && ans == res){
printf("got the answer = %lld\n", ans);
moveX = i;
moveY = mid[j];
toX = possible_moves[i].first;
toY = possible_moves[i].second;
}
}
}
}
}
return ans;
}
else{
long long ans = +1e8;
//printf("Reached the minimizing player\n");
for(int i=0; i<8; ++i){
for(int j=0; j<8; ++j){
if(isLower(state[i][mid[j]]) && state_score[i][mid[j]]<0){
vector<pair<int, int>> possible_moves = get_moves(i, mid[j], state);
if(possible_moves.size() == 0) continue;
int co = -1;
std::future<long long> fut[possible_moves.size()];
for(auto u : possible_moves){
co = co + 1;
int x = u.first, y = u.second;
long long removed_points = state_score[x][y];
char state_copy[8][9];
int state_score_copy[8][8];
for(int k=0; k<8; ++k){
for(int io=0; io<9; ++io){
if(io!=9) state_score_copy[k][io] = state_score[k][io];
state_copy[k][io] = state[k][io];
}
}
long long new_score = curr - state_score[x][y];
if(depth >= 3 && new_score == start_score) continue;
state_copy[x][y] = state_copy[i][mid[j]];
state_copy[i][mid[j]] = '_';
state_score_copy[x][y] = state_score_copy[i][mid[j]];
state_score_copy[i][mid[j]] = 0;
//long long res = best_move(depth+1, state_copy, state_score_copy, alpha, beta);
fut[co] = std::async (std::launch::async, best_move, depth+1, start_score, state_copy, state_score_copy, alpha, beta);
//long long res = best_move(depth+1, start_score, state_copy, state_score_copy, alpha, beta);
//ans = min(ans, res);
//beta = min(res, beta);
//if(beta <= alpha) break;
}
co = 0;
for(co = 0; co < possible_moves.size(); ++co){
long long res = fut[co].get();
ans = min(ans, res);
beta = min(res, beta);
if(beta <= alpha) break;
}
}
}
}
return ans;
}
}
推荐答案
您似乎正在尝试获得统一未来的价值.
It looks like you are trying to get the value of an unitialized future.
这是由于您的内部循环中的这一行代码所致:
This is due to this line of code in your inner loop:
if (depth >= 3 && new_score == start_score) continue; // skips call to async().
此行表示不能保证 fut [] 将保存 possible_moves.size()初始化的期货.
This line means there is no guarantee that fut[] will hold possible_moves.size() initialized futures.
为确保没有未初始化的期货，可以将期货存储在向量中.
To ensure you do not have uninitialized futures, you could store your futures in a vector.
与
//...
std::vector<std::future<long long>> fut;
fut.reserve(possible_moves.size());
//...
fut.push_back(std::async(/* ... */));
//...
for (size_t i = 0; i < fut.size(); ++i)
{
long long res = fut[i].get();
ans = min(ans, res);
beta = min(res, beta);
if (beta <= alpha) break;
}
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