1, PHDF5 will use the MPI optimized 
            code to perform parallel read/write accesses to datasets.
            Currently, this optimization fails when accessing extendable
            datasets.  The default is not to use the optimized code.
    1, PHDF5 will write the metadata 
            via process 0 of each opened parallel HDF5 file.  This should 
            improve I/O throughput.  The default is not to use this 
            optimization.
     configure --help