MPI + HDF5 Parallel Hello World

This project demonstrates parallel writing to an HDF5 file using MPI and the HDF5 C++ API, and includes a verification step to validate the written data.

Overview

• main.cpp: Uses MPI to run multiple processes, each writing its rank to a shared HDF5 dataset (rank_data) in parallel using collective I/O.
• verify.cpp: Reads the resulting HDF5 file and verifies that each rank wrote the correct value.
• CMakeLists.txt: CMake configuration to build both programs and run tests.

Requirements

• CMake ≥ 3.20
• MPI (e.g., OpenMPI or MPICH)
• HDF5 with C++ support

Building

mkdir build
cd build
cmake ..
make

This builds the following executables:

hello_mpi_hdf5: Writes an HDF5 file in parallel using MPI

verify_hdf5: Verifies the contents of the HDF5 file

Running

You can run the parallel writer manually with a specified number of MPI processes:

mpirun -np 4 ./hello_mpi_hdf5

This will generate a file named parallel_hello.h5, with each process writing its rank to the dataset.

Then run the verifier:

./verify_hdf5

It will read the file and confirm that the data is correct.

Optional: Custom File Name

You may provide a custom filename as the first argument:

mpirun -np 4 ./hello_mpi_hdf5 my_output_file.h5

Testing

You can run the built-in CMake tests using:

ctest --output-on-failure --verbose

This performs:

• A 4-process MPI run that writes the file.
• A verification step to ensure the output is correct.

Installation

To install the executables:

make install

They will be placed in your system's binary directory (e.g., /usr/local/bin or ${CMAKE_INSTALL_PREFIX}/bin).

License

This project is licensed under the GNU General Public License v3.0 (GPL-3.0).

See the LICENSE file for full license text.