Datatypes
C
MPI_LONG_DOUBLE
Definition
MPI_LONG_DOUBLE is an MPI_Datatype that represents a long double-length floating point number type in MPI, it corresponds to a long double in C.
Example
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
/**
* @brief Illustrate how to communicate a long 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 long 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 long double
long double longDoubleToSend = 123.456;
printf("[MPI process %d] I send long double: %.3Lf.\n", my_rank, longDoubleToSend);
MPI_Ssend(&longDoubleToSend, 1, MPI_LONG_DOUBLE, RECEIVER, 0, MPI_COMM_WORLD);
break;
}
case RECEIVER:
{
// Receive the long double
long double longDoubleReceived;
MPI_Recv(&longDoubleReceived, 1, MPI_LONG_DOUBLE, SENDER, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
printf("[MPI process %d] I received long double: %.3Lf.\n", my_rank, longDoubleReceived);
break;
}
}
MPI_Finalize();
return EXIT_SUCCESS;
}
#include <stdio.h>
#include <stdlib.h>
#include <mpi.h>
/**
* @brief Illustrate how to communicate an array of long 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 long 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
long double longDoublesToSend[2] = { 12.34, 56.78 };
printf("[MPI process %d] I send long doubles: %.2Lf and %.2Lf.\n", my_rank, longDoublesToSend[0], longDoublesToSend[1]);
MPI_Ssend(longDoublesToSend, 2, MPI_LONG_DOUBLE, RECEIVER, 0, MPI_COMM_WORLD);
break;
}
case RECEIVER:
{
// Receive the doubles
long double longDoublesReceived[2];
MPI_Recv(longDoublesReceived, 2, MPI_LONG_DOUBLE, SENDER, 0, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
printf("[MPI process %d] I received long doubles: %.2Lf and %.2Lf.\n", my_rank, longDoublesReceived[0], longDoublesReceived[1]);
break;
}
}
MPI_Finalize();
return EXIT_SUCCESS;
}