MPISum.c File Reference

Functions to compute the sum across MPI ranks. More...

#include <mpi.h>

Go to the source code of this file.

Functions
int	MPISum_integer (int *global, int *var, int size, void *comm)
int	MPISum_double (double *global, double *var, int size, void *comm)

Detailed Description

Functions to compute the sum across MPI ranks.

Author

Debojyoti Ghosh

Definition in file MPISum.c.

Function Documentation

MPISum_integer()

int MPISum_integer	(	int *	global,
		int *	var,
		int	size,
		void *	comm
	)

Compute the global sum over all MPI ranks in a given communicator for int datatype.

• If var is an array of size greater than 1, global will be an array of the same size with each element as the sum of that element in var on all the MPI ranks in the given communicator.

Parameters

global	array to contain the global sums
var	the local array
size	size of the local array
comm	MPI communicator

Definition at line 16 of file MPISum.c.

{
#ifdef serial
  int i;
  for (i = 0; i < size; i++)  global[i] = var[i];
#else
  MPI_Allreduce((var==global?MPI_IN_PLACE:var),global,size,MPI_INT,MPI_SUM,*((MPI_Comm*)comm));
#endif
  return(0);
}

MPISum_double()

int MPISum_double	(	double *	global,
		double *	var,
		int	size,
		void *	comm
	)

Compute the global sum over all MPI ranks in a given communicator for double datatype.

• If var is an array of size greater than 1, global will be an array of the same size with each element as the sum of that element in var on all the MPI ranks in the given communicator.

Parameters

global	array to contain the global sums
var	the local array
size	size of the local array
comm	MPI communicator

Definition at line 39 of file MPISum.c.

{
#ifdef serial
  int i;
  for (i = 0; i < size; i++)  global[i] = var[i];
#else
  MPI_Allreduce((var==global?MPI_IN_PLACE:var),global,size,MPI_DOUBLE,MPI_SUM,*((MPI_Comm*)comm));
#endif
  return(0);
}