README.md

MPICPP

MPICPP is a simple C++ interface for the MPI C library standard. It brings a few tried-and-true C++ principles to bear over the plain C API:

1. True RAII: no user ever has to call an explicit destructor or finalize function. The mpicpp::environment class initializes and finalizes MPI. The mpicpp::comm class takes ownership of the communicator, destroys it in its destructor and duplicates it in the copy constructor. The mpicpp::request class waits on the request in its destructor.
2. Exception-based error handling. All return codes from MPI C API functions are put through mpicpp::handle_error which will throw an exception of type mpicpp::exception in the case of anything but MPI_SUCCESS.
3. Template-based MPI datatype deduction for fundamental types in C++. Since MPI_Datatype is in general a runtime-constructed object as opposed to a fully compile-time description, we don't attempt to implement MPI_Datatype construction for arbitrary user types. Instead we simply map fundamental C++ types to their built-in MPI_Datatype.
4. Blocking is a special case of non-blocking via RAII. We only wrap the non-blocking communication APIs, and return an mpicpp::request from these calls. Since the mpicpp::request object calls MPI_Wait in its destructor, then calling the non-blocking MPICPP method and simply ignoring its return value is equivalent to calling the blocking MPI C API.

Here is an example of usage:

#include <iostream>
#include "mpicpp.hpp"

int main(int argc, char** argv) {
  auto mpi_env = mpicpp::environment(argc, argv);
  auto comm = mpicpp::comm::world();
  double value = 1.0;
  // MPI_Datatype is deduced because double is a fundamental type
  // ignoring the return value makes this blocking
  comm.iallreduce(&value, 1, mpicpp::op::sum());
  std::cout << "sum of ones is " << value << '\n';
  // MPI_Finalize is called from environment destructor
}

At Sandia, MPICPP is SCR# 2757