Different file formats for MPI and non-MPI versions

[ageorgou]

The parallel version of the code writes results in the MPI format, whereas the sequential version uses the native Fortran format (which may vary between compilers?). This makes it difficult to share intermediate results between different runs, requiring the use of TROVE-MPI2FTN.

Ideally, both versions will use the same file format. One way may be to have parallel processes write to the same file (in native format), enforcing the right order, as is done in PDSYEV. Another could be to use HDF5, which appears to supports parallel I/O, and would be a more standard format generally.