MPI bindings for the Crystal language - MPI bindings for Crystal (WIP)

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The Message Passing Interface (MPI) is a specification for a message-passing style concurrency library. Implementations of MPI are often used to structure parallel computation on High Performance Computing systems. The MPI specification describes bindings for the C programming language (and through it C++) as well as for the Fortran programming language.

This library is an attempt to provide Crystal bindings as well. It is unashamedly inspired by rsmpi, which provides MPI bindings for Rust.


This project is a work in progress. The bindings follows the MPI 3.1 specification.


Add this to your application's shard.yml:

    github: RomainFranceschini/
    version: 0.1.0


An implementation of the C language interface that conforms to MPI-3.1. currently support the following implementations:

Since the MPI standard leaves some details of the C API unspecified (e.g. whether to implement certain constants and even functions using preprocessor macros or native C constructs, the details of most types, ...) uses a thin static library written in C (see src/ext/crmpi.c) that tries to capture the underspecified identifiers and re-exports them with a fixed C API to generate functional low-level bindings.

Use make with the optional make variables release=1 or debug=1 to build the static library. Note that make release=1 is automatically executed by shards as a postinstall script.


require "mpi"

MPI.init do |universe|
  comm =
  puts "Hello, world from process #{comm.rank} of #{comm.size}!"


See files in examples folder.

Use make examples with the optional make variables release=true or debug=true to build all examples.

Then, use mpiexec or mpirun to run examples:

$ mpiexec -n 4 ./build/simple
Hello, world from process 0 of 4!
Hello, world from process 1 of 4!
Hello, world from process 2 of 4!
Hello, world from process 3 of 4!



This software is governed by the CeCILL-C license under French law and abiding by the rules of distribution of free software. You can use, modify and/ or redistribute the software under the terms of the CeCILL-C license as circulated by CEA, CNRS and INRIA at the following URL "".

The fact that you are presently reading this means that you have had knowledge of the CeCILL-C license and that you accept its terms.

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