Utilities

Detailed Description

Some other utilities used in the mpi library.

Concepts
concept	mpi::MPICompatibleRange
	A concept that checks if a range type is contiguous and sized and has an MPI compatible value type.

Functions
void	mpi::check_mpi_call (int errcode, const std::string &mpi_routine)
	Check the success of an MPI call.
template<typename R>
auto	mpi::chunk (R &&rg, communicator c={})
	Divide a given range as evenly as possible across the MPI processes in a communicator and get the subrange assigned to the calling process.
long	mpi::chunk_length (long end, int nranges, int i, long min_size=1)
	Get the length of the ith subrange after splitting the integer range [0, end) as evenly as possible across n subranges.

Function Documentation

check_mpi_call()

void mpi::check_mpi_call ( int errcode, const std::string & mpi_routine )

inline

#include <mpi/utils.hpp>

Check the success of an MPI call.

It checks if the given error code returned by an MPI routine is equal to MPI_SUCCESS. If it isn't, it throws an exception.

It is intended to simply wrap any calls to the MPI C library:

int value = 5;
int result = 0;
check_mpi_call(MPI_Allreduce(&value, &result, 1, mpi::mpi_type<int>::get(), MPI_MAX, comm.get()), "MPI_Allreduce");

Parameters

errcode	Error code returned by an MPI routine.
mpi_routine	Name of the MPI routine used in the error message.

Definition at line 51 of file utils.hpp.

chunk()

template<typename R>

auto mpi::chunk ( R && rg, communicator c = {} )

nodiscard

#include <mpi/chunk.hpp>

Divide a given range as evenly as possible across the MPI processes in a communicator and get the subrange assigned to the calling process.

Template Parameters

R	Range type.

Parameters

rg	Range to divide.
c	mpi::communicator.

Returns

An itertools::sliced range assigned to the calling process.

Definition at line 66 of file chunk.hpp.

chunk_length()

long mpi::chunk_length ( long end, int nranges, int i, long min_size = 1 )

inlinenodiscard

#include <mpi/chunk.hpp>

Get the length of the i^th subrange after splitting the integer range [0, end) as evenly as possible across n subranges.

The optional parameter min_size can be used to first divide the range into equal parts of size min_size before distributing them as evenly as possible across the number of specified subranges.

It is expected that min_size > 0 and that min_size is a divisor of end.

Parameters

end	End of the integer range [0, end).
nranges	Number of subranges.
i	Index of the subrange of interest.
min_size	Minimum size of the subranges.

Returns

Length of the i^th subrange.

Definition at line 50 of file chunk.hpp.