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MPI Programs

P2p.c

2. Write a MPI program to send the message from a process whose rank=3 to all other remaining processes.

#include <stdio.h>
#include <mpi.h>
#include <string.h>
#define BUFFER_SIZE 32

int main(int argc,char *argv[])
{
int MyRank,Numprocs, Destination, iproc;
int tag = 0;
int Root = 0, temp = 1;
char Message[BUFFER_SIZE];
MPI_Init(&argc,&argv);
MPI_Status status;

MPI_Comm_rank(MPI_COMM_WORLD,&MyRank);
MPI_Comm_size(MPI_COMM_WORLD,&Numprocs);

/* print host name, and send message from process with rank 0 to all other processes */
if(MyRank == 3)        {
	system("hostname");
	strcpy(Message, "Hello India"); 
	for (temp=1; temp<Numprocs;temp++)
	{
		MPI_Send(Message, BUFFER_SIZE, MPI_CHAR, temp, tag,MPI_COMM_WORLD);
	}
}
else {          
	system("hostname");
   	MPI_Recv(Message, BUFFER_SIZE, MPI_CHAR, Root, tag,MPI_COMM_WORLD, &status);
	printf("\n%s in process with rank %d from Process with rank %d\n", Message,MyRank,Root);
}

MPI_Finalize();

}

P2p sum.c
4/2. Write a MPI program to find sum of 'n' integers on 'p' processors using point-to-point communication libraries call

#include <stdio.h>
#include "mpi.h"

int main(int argc,char *argv[])
{
int iproc;
int MyRank, Numprocs, Root = 0;
int value, sum = 0;
int Source, Source_tag;
int Destination, Destination_tag;
MPI_Status status;

MPI_Init(&argc,&argv);
MPI_Comm_size(MPI_COMM_WORLD,&Numprocs);
MPI_Comm_rank(MPI_COMM_WORLD,&MyRank);

if(MyRank == Root){

   for(iproc = 1 ; iproc < Numprocs ; iproc++){
       Source     = iproc;
   Source_tag = 0;

   MPI_Recv(&value, 1, MPI_INT, Source, Source_tag, 
	     MPI_COMM_WORLD, &status);
   sum = sum + value;
   }
   printf("MyRank = %d, SUM = %d\n", MyRank, sum);
}
else{
Destination     = 0;
Destination_tag = 0;

MPI_Send(&MyRank, 1, MPI_INT, Destination, Destination_tag, 
	  MPI_COMM_WORLD);
}

MPI_Finalize();

}

Broadcast
5. Write an MPI program where the master processor broadcasts a message “HELLO MSRIT” to the remaining processors using broadcast system call.

#include <stdio.h>
#include "mpi.h"

int main (int argc, char *argv[])
{
int rank, i;

  MPI_Init (&argc, &argv);

MPI_Comm_rank (MPI_COMM_WORLD, &rank);

if (rank == 0) i = 27;

MPI_Bcast ((void *)&i, 1, MPI_INT, 0, MPI_COMM_WORLD);

printf ("[%d] i = %d\n", rank, i);

// Wait for every process to reach this code

MPI_Barrier (MPI_COMM_WORLD);

MPI_Finalize();

return 0;

}

Gather.c
3. Write a MPI program where each processor sends an integer number and its rank to the master processor, where the master gathers all the information and prints the data accordingly

#include <stdio.h>
#include <mpi.h>

void main(int argc, char *argv[])
{
int rank,size;
double param[6],mine;
int sndcnt,rcvcnt;
int i;

MPI_Init(&argc, &argv);
MPI_Comm_rank(MPI_COMM_WORLD,&rank);
MPI_Comm_size(MPI_COMM_WORLD,&size);

sndcnt=1;
mine=23.0+rank;
if(rank==3) rcvcnt=1;

MPI_Gather(&mine,sndcnt,MPI_DOUBLE,param,rcvcnt,MPI_DOUBLE,3,MPI_COMM_WORLD);

if(rank==3)
	for(i=0;i<size;++i) 
	  //printf("PE:%d param[%d] is %f \n",rank,i,param[i]]); 
	  printf(" %d %d  \n",rank,i); 

MPI_Finalize();

}

Pie collective.c

1. Write a MPI program to calculate and print the value of PI.

#include <stdio.h>
#include <math.h>
#include "mpi.h"

double func(double x)
{
return (4.0 / (1.0 + x*x));
}

int main(int argc,char *argv[])
{
int NoInterval, interval;
int MyRank, Numprocs, Root = 0;
double mypi, pi, h, sum, x;
double PI25DT = 3.141592653589793238462643;

/*....MPI initialisation....*/
MPI_Init(&argc,&argv);
MPI_Comm_size(MPI_COMM_WORLD,&Numprocs);
MPI_Comm_rank(MPI_COMM_WORLD,&MyRank);

if(MyRank == Root){
printf("\nEnter the number of intervals : ");
scanf("%d",&NoInterval);
}

/....Broadcast the number of subintervals to each processor..../
MPI_Bcast(&NoInterval, 1, MPI_INT, 0, MPI_COMM_WORLD);

if(NoInterval <= 0){
if(MyRank == Root)
printf("Invalid Value for Number of Intervals .....\n");
MPI_Finalize();
exit(-1);
}

h = 1.0 / (double)NoInterval;
sum = 0.0;
for(interval = MyRank + 1; interval <= NoInterval; interval += Numprocs){
x = h * ((double)interval - 0.5);
sum += func(x);
}
mypi = h * sum;

/....Collect the areas calculated in P0..../
MPI_Reduce(&mypi, &pi, 1, MPI_DOUBLE, MPI_SUM, Root, MPI_COMM_WORLD);

if(MyRank == Root){
printf("pi is approximately %.16f, Error is %.16f\n",
pi, fabs(pi - PI25DT));
}

MPI_Finalize();

}