Explore the HDF5 codes (hdf5-writerank.c or hdf5-writerank.F90) and try to compile them.
On Lumi, you will need to load the module cray-hdf5-parallel/1.12.2.7 before you
can compile the code:
module load cray-hdf5-parallel/1.12.2.7
Now you shoud be able to compile with
cc hdf5-writerank.c -lhdf5
or
ftn hdf5-writerank.F90 -lhdf5_fortran
On Mahti, you will need to load the module hdf5/1.10.7-mpi before you
can compile the code:
module load hdf5/1.10.7-mpi
Now you shoud be able to compile with
mpicc hdf5-writerank.c -lhdf5
or
mpif90 hdf5-writerank.F90 -I/appl/spack/v017/install-tree/gcc-11.2.0/hdf5-1.10.7-qc3apk/include -lhdf5_fortran
After compiling, try running the program with some number of MPI ranks. After this, try using the h5dump and h5ls commands to check the values in the HDF5 file that is produced by running the example. Do you understand what the program does and what are the values in the file (as shown by h5dump)?