我尝试使用 MPI 来解决蒙特卡洛问题，如果我们生成 x 数量的兰特。num 介于 0 和 1 之间，然后将 n 长度的数字发送到每个处理器。我正在使用 scatter 函数，但我的代码运行不正确，它编译但它不要求输入。我不明白 MPI 如何在没有循环的情况下自行循环，有人可以解释一下，我的代码有什么问题吗？
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
#include "mpi.h"
main(int argc, char* argv[]) {
int my_rank; /* rank of process */
int p; /* number of processes */
int source; /* rank of sender */
int dest; /* rank of receiver */
int tag = 0; /* tag for messages */
char message[100]; /* storage for message */
MPI_Status status; /* return status for */
double *total_xr, *p_xr, total_size_xr, p_size_xr; /* receive */
/* Start up MPI */
MPI_Init(&argc, &argv);
/* Find out process rank */
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
/* Find out number of processes */
MPI_Comm_size(MPI_COMM_WORLD, &p);
double temp;
int i, partial_sum, x, total_sum, ratio_p, area;
total_size_xr = 0;
partial_sum = 0;
if(my_rank == 0){
while(total_size_xr <= 0){
printf("How many random numbers should each process get?: ");
scanf("%f", &p_size_xr);
}
total_size_xr = p*p_size_xr;
total_xr = malloc(total_size_xr*sizeof(double));
//xr generator will generate numbers between 1 and 0
srand(time(NULL));
for(i=0; i<total_size_xr; i++)
{
temp = 2.0 * rand()/(RAND_MAX+1.0) -1.0;
//this will make sure if any number computer stays in the boundry of 0 and 1, doesn't go over into the negative
while(temp < 0.0)
{
temp = 2.0 * rand()/(RAND_MAX+1.0) -1.0;
}
//array set to total random numbers generated to be scatter into processors
total_xr[i] = temp;
}
}
else{
//this will be the buffer for the processors to hold their own numbers to add
p_xr = malloc(p_size_xr*sizeof(double));
printf("\n\narray set\n\n");
//scatter xr into processors
MPI_Scatter(total_xr, total_size_xr, MPI_DOUBLE, p_xr, p_size_xr, MPI_DOUBLE, 0, MPI_COMM_WORLD);
//while in processor the partial sum will be caluclated by using xr and the formula sqrt(1-x*x)
for(i=0; i<p_size_xr; i++)
{
x = p_xr[i];
temp = sqrt(1 - (x*x));
partial_sum = partial_sum + temp;
}
//}
//we will send the partial sums to master processor which is processor 0 and add them and place
//the result in total_sum
MPI_Reduce(&partial_sum, &total_sum, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);
//once we have all of the sums we need to multiply the total sum and multiply it with 1/N
//N being the number of processors, the area should contain the value of pi.
ratio_p = 1/p;
area = total_sum*ratio_p;
printf("\n\nThe area under the curve of f(x) = sqrt(1-x*x), between 0 and 1 is, %f\n\n", area);
/* Shut down MPI */
MPI_Finalize();
} /* main */