Custom MPI Wrapper for Fortran

Welcome to the Custom MPI Wrapper project! This repository contains a Fortran-based implementation of MPI wrappers that bind directly to native MPI library routines using ISO_C_BINDING. The goal is to eliminate intermediate C wrappers and call MPI functions directly from Fortran.

This project currently supports MPI routines such as MPI_Init, MPI_Bcast, MPI_Reduce, MPI_Comm_split_type, MPI_Recv, MPI_Ssend, MPI_Waitall, and more. In addition, the repository provides several tests to verify the correctness of these custom wrappers.

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Prerequisites

• Fortran Compiler:
  You can use LFortran, gfortran, or any standard Fortran compiler.

• MPI Library:
  This project supports OpenMPI and MPICH. Install the desired MPI library along with its development headers.

• Pixi (Optional):
  pixi provides an environment <compiler>-<mpi> for each compiler (gfortran, lfortran, and on Linux also flang and ifx) and MPI (openmpi, mpich), the same ones the CI uses. The compiler is passed to the task:

  pixi run -e lfortran-mpich test 'lfortran --cpp'
  pixi run -e gfortran-openmpi test 'gfortran -cpp -O3 -march=native'
  pixi run -e gfortran-openmpi test-without-wrappers
  pixi run -e flang-mpich test 'flang -cpp'
  pixi run -e gfortran-mpich pot3d 'gfortran -cpp'
  pixi run -e lfortran-openmpi pot3d-lfortran 'lfortran --cpp'

  With Open MPI, pixi also passes -DOPEN_MPI=yes to the compiler. POT3D with flang or ifx needs a larger stack, ulimit -s unlimited.

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Running Tests

The repository contains a collection of standalone tests located in the tests/ directory. These tests validate the functionality of the custom MPI wrappers.

Running All Standalone Tests

To execute all standalone tests, navigate to the tests/ directory and run:

cd tests/
FC='lfortran --cpp' ./run_tests.sh

or, to run them with GFortran compiler, do:

cd tests/
FC='gfortran -cpp' ./run_tests.sh

Running a Specific Standalone Test

If you want to run a single test (for example, test_filename.f90), execute:

cd tests/
FC='lfortran --cpp' ./run_tests.sh test_filename.f90

or, to run it with GFortran compiler, do:

cd tests/
FC='gfortran -cpp' ./run_tests.sh test_filename.f90

Running the pot3d Test

To build and run the pot3d test, navigate to the tests/pot3d/ directory.

• For LFortran run:

cd tests/pot3d/
FC='lfortran --cpp' ./build_and_run_lfortran.sh

• For GFortran run:

cd tests/pot3d/
FC='gfortran -cpp' ./build_and_run_gfortran.sh

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Customizing Compiler Flags

You can pass custom flags to your Fortran compiler using the FC environment variable. For example, to compile with optimization flags using gfortran, run:

FC='gfortran -cpp -O3' ./run_tests.sh

This enables you to tailor the compilation process to your needs.