[英]Variably modified array at file scope and subscripted value is neither array nor pointer
I have the following code for calculating n-queen puzzle using pthreads. 我有以下代码用于使用pthreads计算n-queen拼图。 But when I try to compile that code I get the following error message:
但是当我尝试编译该代码时,我收到以下错误消息:
wikithread.c:7:5: error: variably modified 'hist' at file scope
wikithread.c:7:5:错误:在文件范围内修改了'hist'
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <pthread.h>
int NTHREADS, SIZE;
int hist[SIZE];
int count = 0;
int solve(int col, int tid)
{
int start = tid * SIZE/NTHREADS;
int end = (tid+1) * (SIZE/NTHREADS) - 1;
int i, j;
if (col == SIZE)
{
count++;
}
#define attack(i, j) (hist[j] == i || abs(hist[j] - i) == col - j)
for (i = start; i <= end; i++) {
for (j = 0; j < col && !attack(i, j); j++);
if (j < col) continue;
hist[col] = i;
solve(col + 1, tid);
}
return count;
}
void *worker(void *arg)
{
int tid = (int)arg;
solve(0, tid);
}
int main(int argc, char* argv[])
{
pthread_t* threads;
int rc, i;
// checking whether user has provided the needed arguments
if(argc != 3)
{
printf("Usage: %s <number_of_queens> <number_of_threads>\n", argv[0]);
exit(1);
}
// passing the provided arguments to the SIZE and NTHREADS
// variable, initializing matrices, and allocating space
// for the threads
SIZE = atoi(argv[1]);
NTHREADS = atoi(argv[2]);
threads = (pthread_t*)malloc(NTHREADS * sizeof(pthread_t));
// declaring the needed variables for calculating the running time
struct timespec begin, end;
double time_spent;
// starting the run time
clock_gettime(CLOCK_MONOTONIC, &begin);
for(i = 0; i < NTHREADS; i++) {
rc = pthread_create(&threads[i], NULL, worker, (void *)i);
assert(rc == 0); // checking whether thread creating was successfull
}
for(i = 0; i < NTHREADS; i++) {
rc = pthread_join(threads[i], NULL);
assert(rc == 0); // checking whether thread join was successfull
}
// ending the run time
clock_gettime(CLOCK_MONOTONIC, &end);
// calculating time spent during the calculation and printing it
time_spent = end.tv_sec - begin.tv_sec;
time_spent += (end.tv_nsec - begin.tv_nsec) / 1000000000.0;
printf("Elapsed time: %.2lf seconds.\n", time_spent);
printf("\nNumber of solutions: %d\n", count);
return 0;
}
If I change the upper part, and dynamically allocate memory for the array, I get the following error: 如果我更改上部,并为数组动态分配内存,我会收到以下错误:
int NTHREADS, SIZE;
int *hist;
hist = (int*)malloc(SIZE * sizeof(int));
Then I get the following errors: 然后我收到以下错误:
wikithread.c:8:1: warning: data definition has no type or storage class [enabled by default] wikithread.c:8:1: error: conflicting types for 'hist' wikithread.c:7:6: note: previous declaration of 'hist' was here wikithread.c:8:1: error: initializer element is not constant wikithread.c: In function 'solve': wikithread.c:23:27: error: subscripted value is neither array nor pointer nor vector wikithread.c:23:27: error: subscripted value is neither array nor pointer nor vector wikithread.c:26:7: error: subscripted value is neither array nor pointer nor vector
wikithread.c:8:1:警告:数据定义没有类型或存储类[默认启用] wikithread.c:8:1:错误:'hist'的冲突类型wikithread.c:7:6:注意:上一个'hist'的声明在这里wikithread.c:8:1:错误:初始化元素不是常量wikithread.c:在函数'solve'中:wikithread.c:23:27:错误:下标值既不是数组也不是指针也不是vector wikithread.c:23:27:错误:下标值既不是数组也不是指针也不是向量wikithread.c:26:7:错误:下标值既不是数组也不是指针也不是向量
Anyone, can help me solve the problem? 任何人,可以帮我解决问题吗?
You use SIZE
to initialize an array without having defined it-- 你使用
SIZE
初始化一个数组而没有定义它 -
int NTHREADS, SIZE;
int hist[SIZE];
Undoubtedly this is causing problems. 毫无疑问,这会造成问题。
As for your second error, you have this at file scope: 至于你的第二个错误,你有这个在文件范围:
hist = (int*)malloc(SIZE * sizeof(int));
but statements are not allowed outside a function body, just declarations. 但是声明不允许在函数体外部,只是声明。
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