[C] OpenMPI初试

编译：mpicc filename.c -o filename
运行：mpirun -np 4 filename
1.Hello World

#include 
#include
int main (int argc, char **argv) {
	int rank, num, i;
	MPI_Init (&argc, &argv);
	MPI_Comm_rank (MPI_COMM_WORLD, &rank);
	MPI_Comm_size (MPI_COMM_WORLD, &num);
	printf ("Hello from process %i of %i\n", rank, num);
	MPI_Finalize ();
	return 0;
}

2.PingPong 主机向其他人发送Ping，收到Pong

#include
#include
#include 
int main(int argc,char **argv){
	MPI_Init(&argc, &argv);
	int rank,num,i,source;
	MPI_Comm_rank(MPI_COMM_WORLD, &rank);
	MPI_Comm_size(MPI_COMM_WORLD, &num);
	if(rank == 0){
		char sendMess[] = "Ping";
		int len = strlen(sendMess) + 1;
		for(i = 1; i < num;i++){
			MPI_Send(sendMess,len,MPI_CHAR,i,99,MPI_COMM_WORLD);
		}
		
		MPI_Status status;
		char recvMess[100];
		for (source = 1; source < num; source++) {
            MPI_Recv(recvMess, 100, MPI_CHAR, source, 99,MPI_COMM_WORLD, &status);
            printf("%i received %s from %i\n",rank, recvMess,source);
        }
	}else{
		char mess[100];
		MPI_Status status;
		MPI_Recv(mess,100,MPI_CHAR,0,99,MPI_COMM_WORLD,&status);
		printf("%i received %s\n",rank, mess);
		
		char sendMess[] = "Pong";
		int len = strlen(sendMess) + 1;
		
		MPI_Send(sendMess,len,MPI_CHAR,0,99,MPI_COMM_WORLD);
	}
	MPI_Finalize();
}

3.矩阵乘法

#include 
#include "mpi.h"
#include 
#include 
#include 
#include 

int **genMatrix(int size)
{
    int num = 0,m;
    int **matrix;
    matrix = (int **)malloc(sizeof(int *) * size);
    for(m = 0; m < size; m++)
        matrix[m] = (int *)malloc(sizeof(int) * size);
    int i,j;
    srand(time(NULL) + rand());
    for(i = 0; i < size; i++){
        for(j = 0; j < size; j++){
            matrix[i][j]= rand() % 20;
        }
    }
    return matrix;
}

void showMatrx(int **a,int size)
{
    int i,j;
    for(i = 0; i < size; i++){
        for(j = 0; j < size; j++){
            printf("%d ",a[i][j]);
        }
        printf("\n");
    }
    printf("\n");
}
int * Multiplication(int **a,int b[],int size){
    int *result;
    result = (int *)malloc(sizeof(int) * size);
    int i,m,n,sum = 0;
    for(m = 0; m < size; m++){
        for(n = 0; n < size; n++){
            sum += a[n][m] * b[n];
        }
        result[m] = sum;
        sum = 0;
    }
    return result;
}
int main(int argc,char **argv){
    int size,rank,dest;
    MPI_Comm comm = MPI_COMM_WORLD;
    MPI_Status status;
    MPI_Init(&argc,&argv);
    MPI_Comm_size(comm,&size);
    MPI_Comm_rank(comm,&rank);


    int **matrix1;
    int **matrix2;
    int send_buff[size*size];
    matrix1 = genMatrix(size);
    matrix2 = genMatrix(size);
    if(rank == 0){
        printf("matrix1 is :\n");
        showMatrx((int **)matrix1,size);

        printf("matrix2 is :\n");
        showMatrx((int **)matrix2,size);

        int j,k,tmp = 0;
        for(j = 0; j < size; j++)
            for(k = 0; k < size; k++){
                send_buff[tmp] = matrix1[j][k];
                tmp++;
            }
    }


    int rbuf[size];
    int final_buff[size];

    int *result;

    result = (int *)malloc(sizeof(int) * size);

    MPI_Scatter(send_buff,size,MPI_INT,rbuf,size,MPI_INT,0,comm);
    result = Multiplication((int **)matrix2,rbuf,size);
    MPI_Barrier(comm);


    int *recv_buff;
    if(rank == 0)
        recv_buff = (int*)malloc(sizeof(int)*size*size); 
    MPI_Barrier(comm);
    MPI_Gather(result,size,MPI_INT,recv_buff,size,MPI_INT,0,comm);
    if(rank == 0){
        printf("\nresult is :\n");
        int m,n,tmp = 0;
        for(m = 0; m < size; m++){
            for(n = 0;n < size;n++){
                printf("%d ",recv_buff[tmp]);
                tmp++;
            }
            printf("\n");

        }
        printf("\n");
    }



    MPI_Finalize();
    return 0;
}