cal the matrix by mpi
use send and receive to do it
// comm_sz is 4*n+1 n is int and n>=0
#include "mpi.h"
#include <iostream>
using namespace std;
void matMulti(int *A,int *B,int *C,int row,int n);
void matGene(int *A,int size,int actual_size);
void printRecv(int *Matrix,int my_rank,int length,int n);
int main(int argc,char* argv[])
{
int n=atoi(argv[1]);
int my_rank=0,comm_sz=0;
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&my_rank);
MPI_Comm_size(MPI_COMM_WORLD,&comm_sz);
MPI_Status status;
int each_row=n/(comm_sz-1),beginRow,endRow;
double beginTime=MPI_Wtime();
if (my_rank==0)
{
int* A =new int [n*n];
int* B =new int [n*n];
int* C =new int [n*n];
cout<<"create A matrix:"<<endl;
matGene(A,n,n);
cout<<"create B matrix:"<<endl;
matGene(B,n,n);
for (int i=0;i<comm_sz-1;i++)
{
beginRow=each_row*i,endRow=each_row*(i+1);
MPI_Send(&A[beginRow*n+0],each_row*n,MPI_INT,i+1,1,MPI_COMM_WORLD);
MPI_Send(&B[0*n+0],n*n,MPI_INT,i+1,2,MPI_COMM_WORLD);
}
// Recv: C[beginRow: endRow,: ]
for (int i=0;i<comm_sz-1;i++)
{
beginRow=each_row*i,endRow=each_row*(i+1);
MPI_Recv(&C[beginRow*n+0],each_row*n,MPI_INT,i+1,3,MPI_COMM_WORLD,&status);
cout << "I am alive in receiving data from process "<<i+1<<endl;
}
printRecv(C,my_rank,n*n,n);
cout<<"cost of main process time is "<<MPI_Wtime()-beginTime<<endl;
}
if (my_rank!=0)
{
// other processes: calculate A*B
// beginRow = each_row*(my_rank-1), endRow = each_row * my_rank;
int* A=new int[each_row * n]; //A[beginRow:endRow,:]
int* B=new int [n*n];
int* C= new int[each_row*n]; //C[beginRow:endRow, :]
MPI_Recv(&A[0*n+0],each_row*n,MPI_INT,0,1,MPI_COMM_WORLD,&status); // from A[0][0] to B[0][0] begin to connect
// printRecv(A,my_rank,each_row*n);
MPI_Recv(&B[0*n+0],n*n,MPI_INT,0,2,MPI_COMM_WORLD,&status);
// printRecv(B,my_rank,n*n);
matMulti(A,B,C,each_row,n);
printRecv(C,my_rank,each_row*n,n);
MPI_Send(&C[0*n+0],each_row*n,MPI_INT,0,3,MPI_COMM_WORLD); // beginning place is C[my_rank-1][00], size is each_row*n
cout<<"cost of time is "<<MPI_Wtime()-beginTime<<" by process rank "<<my_rank<<endl;
}
MPI_Finalize();
return 0;
}
void matMulti(int *A,int *B,int *C,int row,int n)
{
for (int i=0;i<row;i++)
{
for (int j=0;j<n;j++)
{
C[i*n+j]=0;
for (int k=0;k<n;k++)
C[i*n+j]=A[i*n+k]*B[k*n+j];
}
}
}
void matGene(int *A,int size,int actual_size)
{
//actual size: the matrix we use may have a larger dimension than n*n
for (int i=0;i<actual_size;i++)
{
for (int j=0;j<actual_size;j++)
{
if (i<size && j<size)
A[i*actual_size+j]=rand()%10;
else
A[i*actual_size+j]=0;
cout<<A[i*actual_size+j]<<" ";
}
cout<<endl;
}
}
void printRecv(int *Matrix,int my_rank,int length,int n)
{
cout<<"process "<<my_rank<<" receive Matrix"<<endl;
for (int i=0;i<length;i++)
{
cout<<Matrix[i]<<" ";
if ((i+1)%n==0)
cout<<endl;
}
cout<<endl;
}
expain
- init the matrix A and matrix B in process 0
- cut the matrix A averagely and send other process in process 0(process 0 don't take part in cal)
- other process multi the data and send the result C matrix
use Bcast and Scatter and Gather to do it
#include "mpi.h"
#include <iostream>
using namespace std;
void matMulti(int *A,int *B,int *C,int row,int n);
void matGene(int *A,int size,int actual_size);
void printRecv(int *Matrix,int my_rank,int length,int n);
int main(int argc,char* argv[])
{
int n=atoi(argv[1]);
int my_rank=0,comm_sz=0;
MPI_Init(&argc,&argv);
MPI_Comm_rank(MPI_COMM_WORLD,&my_rank);
MPI_Comm_size(MPI_COMM_WORLD,&comm_sz);
MPI_Status status;
int each_row=n/comm_sz,beginRow,endRow;
double beginTime=MPI_Wtime();
int* A =new int [n*n];
int* B =new int [n*n];
int* C =new int [n*n];
int* partA=new int [each_row*n];
int* partC=new int [each_row*n];
if (my_rank==0)
{
cout<<"create A matrix:"<<endl;
matGene(A,n,n);
cout<<"create B matrix:"<<endl;
matGene(B,n,n);
cout<<"Bcast and Scatter are finished!"<<endl;
}
MPI_Scatter(&A[0*n+0],each_row*n,MPI_INT,&partA[0*n+0],each_row*n,MPI_INT,0,MPI_COMM_WORLD);
MPI_Bcast(&B[0*n+0],n*n,MPI_INT,0,MPI_COMM_WORLD);
cout<<"partA: "<<endl;
printRecv(partA,my_rank,n*each_row,n);
matMulti(partA,B,partC,each_row,n);
cout<<"partC: "<<endl;
printRecv(partC,my_rank,n*each_row,n);
// MPI_Barrier(MPI_COMM_WORLD);
MPI_Gather(&partC[0*n+0],each_row*n,MPI_INT,&C[0*n+0],each_row*n,MPI_INT,0,MPI_COMM_WORLD);
if (my_rank==0)
{
cout<<"cost of time is "<<MPI_Wtime()-beginTime<<" by process rank "<<my_rank<<endl;
printRecv(C,my_rank,n*n,n);
}
MPI_Finalize();
return 0;
}
void matMulti(int *A,int *B,int *C,int row,int n)
{
for (int i=0;i<row;i++)
{
for (int j=0;j<n;j++)
{
C[i*n+j]=0;
for (int k=0;k<n;k++)
C[i*n+j]=A[i*n+k]*B[k*n+j];
}
}
}
void matGene(int *A,int size,int actual_size)
{
//actual size: the matrix we use may have a larger dimension than n*n
for (int i=0;i<actual_size;i++)
{
for (int j=0;j<actual_size;j++)
{
if (i<size && j<size)
A[i*actual_size+j]=rand()%10;
else
A[i*actual_size+j]=0;
cout<<A[i*actual_size+j]<<" ";
}
cout<<endl;
}
}
void printRecv(int *Matrix,int my_rank,int length,int n)
{
cout<<"process "<<my_rank<<" receive Matrix"<<endl;
for (int i=0;i<length;i++)
{
cout<<Matrix[i]<<" ";
if ((i+1)%n==0)
cout<<endl;
}
cout<<endl;
}
tips
- if put the Bcast and Scatter in only process 0, other processes' data may have problems, so Bcast and Scatter function should to be in main().
