写一个用MPI广播求素数
时间: 2023-06-02 07:04:24 浏览: 62
感谢您的提问。以下是用MPI广播求素数的代码示例,供您参考:
```C
#include <stdio.h>
#include <math.h>
#include <mpi.h>
int main(int argc, char *argv[])
{
int rank, size, n, i, j, count;
int local_start, local_end, global_start, global_end;
int root = 0;
int prime_count = 0;
int *prime_list, *prime_recv;
double elapsed_time = 0.0;
MPI_Status status;
MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
n = atoi(argv[1]);
global_start = 2, global_end = n;
local_start = global_start + rank * (global_end - global_start) / size;
local_end = global_start + (rank + 1) * (global_end - global_start) / size;
if (rank == 0)
elapsed_time = -MPI_Wtime();
if (local_start % 2 == 0)
local_start = local_start + 1;
count = (local_end - local_start) / 2 + 1;
prime_list = (int*)malloc(count * sizeof(int));
for (i = 0; i < count; i++)
prime_list[i] = 1;
for (i = 3; i <= sqrt(n); i += 2)
{
if (i*i > local_start)
j = i*i - local_start;
else if (local_start % i == 0)
j = 0;
else
j = i - (local_start % i);
for (; j < count; j += i)
prime_list[j] = 0;
}
if (rank == 0)
{
count = (global_end - global_start) / 2 + 1;
prime_recv = (int*)malloc(count * sizeof(int));
}
MPI_Reduce(prime_list, prime_recv, count, MPI_INT, MPI_LOR, root, MPI_COMM_WORLD);
if (rank == 0)
{
elapsed_time += MPI_Wtime();
for (i = 0; i < count; i++)
if (prime_recv[i])
prime_count++;
printf("Found %d primes in [%d, %d] in %lf seconds.\n", prime_count, global_start, global_end, elapsed_time);
}
MPI_Finalize();
return 0;
}
```
这段代码可以在多个处理器上并行计算素数,并使用MPI广播将结果回传到根进程。具体实现方式是将待求范围分成多个子区间,每个处理器计算自己的子区间内的素数,并将结果作为布尔数组传递给根进程,然后根进程将各处理器的结果合并,得到整个范围内的素数个数。