You may wish to consult your system's User Guide for guidance on using PnetCDF.
Start by loading modules for pnetcdf and openmpi (if available) or another MPI.

For instance, on SDSC Expanse, these modules should be loaded:  
1) shared   2) cpu/1.0   3) DefaultModules   4) slurm/expanse/20.02.3
   5) intel/19.1.1.217   6) intel-mpi/2019.8.254

Note that PNetCDF is not among the software installed on Expanse. On a system
where PnetCDF is not present, you will need to download, build and install the
package, after which you set up your environment as follows:

export PNETCDF=<path to the pnetcdf installation>
export PATH=${PNETCDF}/bin:$PATH
export LD_LIBRARY_PATH=${PNETCDF}/lib:${LD_LIBRARY_PATH}

To build the examples:

make all

A Slurm batch script is provided. The script shows how to compare output files
generated by pnetcdf. To check if the single-write and coll-write programs
produce the same output, we can use the ncmpidiff utility:

mpirun -n 16 ncmpidiff output.single output.collective