生成允许在给定范围内重复的随机数
Generating random numbers which allows some repetition within a given range
我正在编写一个 MPI 程序,我允许每个进程在经过的时间内生成它的自己的随机数我会希望某些进程具有与某些其他进程生成的相同随机数。 例如,一个简单的 printf 语句:
Process 1 has generated the number 19
Process 2 has generated the number 8
Process 3 has generated the number 19
.
.
因此,进程1和3生成了相同的随机数。此外,为了确保我可以获得相同的随机数生成,我将限制为仅整数值,而不是双精度值或浮点数。
我写过:
#include <stdio.h>
#include "mpi.h"
#include <stdlib.h>
#include <time.h>
#define numprocess 20
int main(int argc, char *argv[])
{
int rank,size;
int rand_value;
int lower,upper;
MPI_Status status;
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);
upper = 20;
lower = 0;
rand_value = rand()%(upper-lower);
printf("Process %d generated a random number of %d\n",rank,rand_value);
MPI_Finalize();
return 0;
}
但我得到的输出是:
Process 0 generated a random number of 7
Process 2 generated a random number of 7
Process 8 generated a random number of 7
Process 1 generated a random number of 7
Process 3 generated a random number of 7
Process 4 generated a random number of 7
Process 5 generated a random number of 7
Process 6 generated a random number of 7
Process 7 generated a random number of 7
Process 9 generated a random number of 7
Process 11 generated a random number of 7
Process 10 generated a random number of 7
Process 16 generated a random number of 7
Process 17 generated a random number of 7
Process 19 generated a random number of 7
Process 13 generated a random number of 7
Process 12 generated a random number of 7
Process 18 generated a random number of 7
Process 15 generated a random number of 7
Process 14 generated a random number of 7
你可以这样做:
srand(time(NULL)+rank * 10000);
使用 time
将确保您在每个 运行 上获得不同的输出,而使用 rank
可以确保(很有可能但不是 100%)每个线程都有一个不同的种子。常数 10000 是一个任意常数,只是为了降低两个线程意外获得相同种子的可能性。
但这是一个更好的方法:
const int current_time = time(NULL);
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);
srand(current_time+rank);
或使用MPI_Bcast
int current_time;
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);
if(rank == 0)
current_time = time(NULL);
MPI_Bcast(¤t_time, 1, MPI_INT, 0, MPI_COMM_WORLD);
srand(current_time+rank);
我正在编写一个 MPI 程序,我允许每个进程在经过的时间内生成它的自己的随机数我会希望某些进程具有与某些其他进程生成的相同随机数。 例如,一个简单的 printf 语句:
Process 1 has generated the number 19
Process 2 has generated the number 8
Process 3 has generated the number 19
.
.
因此,进程1和3生成了相同的随机数。此外,为了确保我可以获得相同的随机数生成,我将限制为仅整数值,而不是双精度值或浮点数。
我写过:
#include <stdio.h>
#include "mpi.h"
#include <stdlib.h>
#include <time.h>
#define numprocess 20
int main(int argc, char *argv[])
{
int rank,size;
int rand_value;
int lower,upper;
MPI_Status status;
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);
upper = 20;
lower = 0;
rand_value = rand()%(upper-lower);
printf("Process %d generated a random number of %d\n",rank,rand_value);
MPI_Finalize();
return 0;
}
但我得到的输出是:
Process 0 generated a random number of 7
Process 2 generated a random number of 7
Process 8 generated a random number of 7
Process 1 generated a random number of 7
Process 3 generated a random number of 7
Process 4 generated a random number of 7
Process 5 generated a random number of 7
Process 6 generated a random number of 7
Process 7 generated a random number of 7
Process 9 generated a random number of 7
Process 11 generated a random number of 7
Process 10 generated a random number of 7
Process 16 generated a random number of 7
Process 17 generated a random number of 7
Process 19 generated a random number of 7
Process 13 generated a random number of 7
Process 12 generated a random number of 7
Process 18 generated a random number of 7
Process 15 generated a random number of 7
Process 14 generated a random number of 7
你可以这样做:
srand(time(NULL)+rank * 10000);
使用 time
将确保您在每个 运行 上获得不同的输出,而使用 rank
可以确保(很有可能但不是 100%)每个线程都有一个不同的种子。常数 10000 是一个任意常数,只是为了降低两个线程意外获得相同种子的可能性。
但这是一个更好的方法:
const int current_time = time(NULL);
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);
srand(current_time+rank);
或使用MPI_Bcast
int current_time;
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);
if(rank == 0)
current_time = time(NULL);
MPI_Bcast(¤t_time, 1, MPI_INT, 0, MPI_COMM_WORLD);
srand(current_time+rank);