Definition
MPI_DOUBLE is an MPI_Datatype that represents a double-length floating point number type in MPI, it corresponds to a double in C.
Datatypes
C
MPI_DOUBLE is an MPI_Datatype that represents a double-length floating point number type in MPI, it corresponds to a double in C.
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
/**
* @brief Illustrate how to communicate a double between 2 MPI processes.
* @details This application is meant to be run with 2 MPI processes: 1 sender
* and 1 receiver. The former sends a double to the latter, which prints it.
**/
int main(int argc, char* argv[])
{
MPI_Init(&argc, &argv);
// Check that 2 MPI processes are used.
int size;
MPI_Comm_size(MPI_COMM_WORLD, &size);
if(size != 2)
{
printf("This application is meant to be run with 2 MPI processes.\n");
MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
}
// Get my rank and do the corresponding job.
enum role_ranks { SENDER, RECEIVER };
int my_rank;
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
switch(my_rank)
{
case SENDER:
{
// Send the double
double doubleToSend = 123.456;
printf("[MPI process %d] I send double: %.3f.\n", my_rank, doubleToSend);
MPI_Ssend(&doubleToSend, 1, MPI_DOUBLE, RECEIVER, 0, MPI_COMM_WORLD);
break;
}
case RECEIVER:
{
// Receive the double
double doubleReceived;
MPI_Recv(&doubleReceived, 1, MPI_DOUBLE, SENDER, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
printf("[MPI process %d] I received double: %.3f.\n", my_rank, doubleReceived);
break;
}
}
MPI_Finalize();
return EXIT_SUCCESS;
}
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
/**
* @brief Illustrate how to communicate an array of doubles between 2 MPI
* processes.
* @details This application is meant to be run with 2 MPI processes: 1 sender
* and 1 receiver. The former sends an array of doubles to the latter, which
* prints it.
**/
int main(int argc, char* argv[])
{
MPI_Init(&argc, &argv);
// Check that 2 MPI processes are used.
int size;
MPI_Comm_size(MPI_COMM_WORLD, &size);
if(size != 2)
{
printf("This application is meant to be run with 2 MPI processes.\n");
MPI_Abort(MPI_COMM_WORLD, EXIT_FAILURE);
}
// Get my rank and do the corresponding job.
enum role_ranks { SENDER, RECEIVER };
int my_rank;
MPI_Comm_rank(MPI_COMM_WORLD, &my_rank);
switch(my_rank)
{
case SENDER:
{
// Send the doubles
double doublesToSend[2] = { 12.34, 56.78 };
printf("[MPI process %d] I send doubles: %.2f and %.2f.\n", my_rank, doublesToSend[0], doublesToSend[1]);
MPI_Ssend(doublesToSend, 2, MPI_DOUBLE, RECEIVER, 0, MPI_COMM_WORLD);
break;
}
case RECEIVER:
{
// Receive the doubles
double doublesReceived[2];
MPI_Recv(doublesReceived, 2, MPI_DOUBLE, SENDER, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
printf("[MPI process %d] I received doubles: %.2f and %.2f.\n", my_rank, doublesReceived[0], doublesReceived[1]);
break;
}
}
MPI_Finalize();
return EXIT_SUCCESS;
}