MPI essentials

Detailed Description

Simplify the initialization/finalization of an MPI environment and the usage of an MPI_Comm object by wrapping it in a C++ class.

A typical Hello world! program using mpi::environment and mpi::communicator is as easy as:

#include <mpi/communicator.hpp>
#include <iostream>
 
int main(int argc, char** argv) {
  // initialize MPI environment
  mpi::environment env(argc, argv);
  mpi::communicator world;
 
  // get rank and greet world
  int rank = world.rank();
  std::cout << "Hello from processor " << rank << "\n";
}

Output (depends on the number of processes and the order is arbitrary):

Hello from processor 2
Hello from processor 3
Hello from processor 0
Hello from processor 1

Classes
class	mpi::communicator
	C++ wrapper around MPI_Comm providing various convenience functions. More...
struct	mpi::environment
	RAII class to initialize and finalize MPI. More...

Functions
bool	mpi::is_initialized () noexcept
	Check if MPI has been initialized.

Variables
static const bool	mpi::has_env
	Boolean variable that is true, if one of the environment variables OMPI_COMM_WORLD_RANK, PMI_RANK, CRAY_MPICH_VERSION or FORCE_MPI_INIT is set, false otherwise.

Function Documentation

is_initialized()

bool mpi::is_initialized ( )

inlinenodiscardnoexcept

#include <mpi/environment.hpp>

Check if MPI has been initialized.

It throws an exception in case a call to the MPI C library fails.

Returns

True if MPI_Init has been called, false otherwise.

Definition at line 42 of file environment.hpp.

Variable Documentation

has_env

const bool mpi::has_env

static

#include <mpi/environment.hpp>

Initial value:

= []() {
    if (std::getenv("OMPI_COMM_WORLD_RANK") != nullptr or std::getenv("PMI_RANK") != nullptr or std::getenv("CRAY_MPICH_VERSION") != nullptr
        or std::getenv("FORCE_MPI_INIT") != nullptr)
      return true;
    else
      return false;
  }()

Boolean variable that is true, if one of the environment variables OMPI_COMM_WORLD_RANK, PMI_RANK, CRAY_MPICH_VERSION or FORCE_MPI_INIT is set, false otherwise.

The environment variables are set, when a program is executed with mpirun or mpiexec.

Definition at line 54 of file environment.hpp.