[英]How to convert MPI blocking code into non blocking
我想執行矩陣乘法。 我必須編寫兩個代碼,一個是 MPI 阻塞,另一個是 MPI 非阻塞。 我已經完成了 MPI 阻塞。 我需要一些幫助來將下面的代碼轉換為 MPI 非阻塞。
這是帶有阻塞的矩陣乘法代碼,我想將其轉換為 MPI 非阻塞。 如果有人有空請回復..
#include <stdlib.h>
#include <stdio.h>
#include "mpi.h"
#include <time.h>
#include <sys/time.h>
// Number of rows and columnns in a matrix
#define N 4
MPI_Status status;
// Matrix holders are created
double matrix_a[N][N],matrix_b[N][N],matrix_c[N][N];
int main(int argc, char **argv)
{
int processCount, processId, slaveTaskCount, source, dest, rows, offset;
struct timeval start, stop;
// MPI environment is initialized
MPI_Init(&argc, &argv);
// Each process gets unique ID (rank)
MPI_Comm_rank(MPI_COMM_WORLD, &processId);
// Number of processes in communicator will be assigned to variable -> processCount
MPI_Comm_size(MPI_COMM_WORLD, &processCount);
// Number of slave tasks will be assigned to variable -> slaveTaskCount
slaveTaskCount = processCount - 1;
// Root (Master) process
if (processId == 0) {
// Matrix A and Matrix B both will be filled with random numbers
srand ( time(NULL) );
for (int i = 0; i<N; i++) {
for (int j = 0; j<N; j++) {
matrix_a[i][j]= rand()%10;
matrix_b[i][j]= rand()%10;
}
}
printf("\n\t\tMatrix - Matrix Multiplication using MPI\n");
// Print Matrix A
printf("\nMatrix A\n\n");
for (int i = 0; i<N; i++) {
for (int j = 0; j<N; j++) {
printf("%.0f\t", matrix_a[i][j]);
}
printf("\n");
}
// Print Matrix B
printf("\nMatrix B\n\n");
for (int i = 0; i<N; i++) {
for (int j = 0; j<N; j++) {
printf("%.0f\t", matrix_b[i][j]);
}
printf("\n");
}
rows = N/slaveTaskCount;
offset = 0;
for (dest=1; dest <= slaveTaskCount; dest++)
{
// Acknowledging the offset of the Matrix A
MPI_Send(&offset, 1, MPI_INT, dest, 1, MPI_COMM_WORLD);
// Acknowledging the number of rows
MPI_Send(&rows, 1, MPI_INT, dest, 1, MPI_COMM_WORLD);
// Send rows of the Matrix A which will be assigned to slave process to compute
MPI_Send(&matrix_a[offset][0], rows*N, MPI_DOUBLE,dest,1, MPI_COMM_WORLD);
// Matrix B is sent
MPI_Send(&matrix_b, N*N, MPI_DOUBLE, dest, 1, MPI_COMM_WORLD);
// Offset is modified according to number of rows sent to each process
offset = offset + rows;
}
for (int i = 1; i <= slaveTaskCount; i++)
{
source = i;
// Receive the offset of particular slave process
MPI_Recv(&offset, 1, MPI_INT, source, 2, MPI_COMM_WORLD, &status);
// Receive the number of rows that each slave process processed
MPI_Recv(&rows, 1, MPI_INT, source, 2, MPI_COMM_WORLD, &status);
// Calculated rows of the each process will be stored int Matrix C according to their offset and
// the processed number of rows
MPI_Recv(&matrix_c[offset][0], rows*N, MPI_DOUBLE, source, 2, MPI_COMM_WORLD, &status);
}
// Print the result matrix
printf("\nResult Matrix C = Matrix A * Matrix B:\n\n");
for (int i = 0; i<N; i++) {
for (int j = 0; j<N; j++)
printf("%.0f\t", matrix_c[i][j]);
printf ("\n");
}
printf ("\n");
}
// Slave Processes
if (processId > 0) {
// Source process ID is defined
source = 0;
MPI_Recv(&offset, 1, MPI_INT, source, 1, MPI_COMM_WORLD, &status);
// The slave process receives number of rows sent by root process
MPI_Recv(&rows, 1, MPI_INT, source, 1, MPI_COMM_WORLD, &status);
// The slave process receives the sub portion of the Matrix A which assigned by Root
MPI_Recv(&matrix_a, rows*N, MPI_DOUBLE, source, 1, MPI_COMM_WORLD, &status);
// The slave process receives the Matrix B
MPI_Recv(&matrix_b, N*N, MPI_DOUBLE, source, 1, MPI_COMM_WORLD, &status);
// Matrix multiplication
for (int k = 0; k<N; k++) {
for (int i = 0; i<rows; i++) {
// Set initial value of the row summataion
matrix_c[i][k] = 0.0;
// Matrix A's element(i, j) will be multiplied with Matrix B's element(j, k)
for (int j = 0; j<N; j++)
matrix_c[i][k] = matrix_c[i][k] + matrix_a[i][j] * matrix_b[j][k];
}
}
// value in matrix C
MPI_Send(&offset, 1, MPI_INT, 0, 2, MPI_COMM_WORLD);
// Number of rows the process calculated will be sent to root process
MPI_Send(&rows, 1, MPI_INT, 0, 2, MPI_COMM_WORLD);
// Resulting matrix with calculated rows will be sent to root process
MPI_Send(&matrix_c, rows*N, MPI_DOUBLE, 0, 2, MPI_COMM_WORLD);
}
MPI_Finalize();
}
以這種方式看待非阻塞:不是拼寫“現在我發送這個,現在你收到那個”,而是在計算階段決定:“這里將傳達的所有消息是什么”。 然后你對所有的發送做一個Irecv
,對所有相應的接收做一個Isend
。 然后等待所有結果請求。
一個問題是這些Isend/Irecv
操作中的每一個都需要自己的緩沖區,因此您可能需要分配更多內存。
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