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Update IO formats and add new IO namelist controls (CICE-Consortium#928)
This provides new features for CICE IO both thru netCDF and PIO. New namelist are added to control history and restart format, hdf5 compression and chunking, the PIO rearranger, and PIO IO task control. Separate controls are provided for history and restart files. The namelist changes are for _history_format, restart_format history_rearranger, restart_rearranger history_iotasks, history_root, history_stride, restart_iotasks, restart_root, and restart_stride history_chunksize, history_deflate, restart_chunksize, restart_deflate._ In particular, - Update restart_format and history_format options to 'cdf1', 'cdf2', 'cdf5', 'hdf5', 'pnetcdf1', 'pnetcdf2', 'pnetcdf5', 'default'. The old options, 'default', 'pio_netcdf', and 'pio_pnetcdf' are still supported and backwards compatible with lcdf64, but are deprecated and no longer documented. The old options and old namelist lcdf64 are covered by the new options. Support of the old options should be removed in the future. Note that some problems were discovered when opening files with hdf5 format but reading non-hdf5 files with a spack built PIO/netCDF. As a result, the format specified for the restart read is always 'cdf1' which provides flexibility and robustness across software installs, although it may result in serial reads of hdf5 files when a parallel read could be done. - Deprecate lcdf64 namelist. This namelist is no longer needed and is covered by the new restart_format and history_format options. The namelist still exists and is backwards compatible with the old 'default', 'pio_netcdf', and 'pio_pnetcdf' format options, but is no longer documented. This should be removed in the future. - Add new namelist to control PIO pe/task setup (iotasks, root, stride) for history and restart. These settings control the PIO IO tasks. The root, stride, and iotasks are consistent with the MPI communicator. root=0 is the first MPI task. These control PIO IO performance and are usually a function of things like the IO and node hardware. See PIO for more information. CICE computes PIO iotask, root, and stride defaults for cases where -99 is passed in for some or all of these namelist. Those defaults are somewhat constrained by a bug in PIO, NCAR/ParallelIO#1986. The current implementation avoids the bug by limiting the iotasks for some MPI task counts. This is noted in ice_pio.F90. - Add new namelist to control PIO rearranger (rearranger) for history and restart. Supports 'box', 'subset', and 'default'. These control how PIO rearrangment is carried out. default is equivalent to box and the box generally performs better. See PIO for more information. - Add new namelist to support hdf5 compression and chunking (deflate, chunksize) for history and restart. The deflate controls file compression and is an integer between 0 and 9 where 0 means no compression and 9 is maximum compression. Generally, the higher the number, the slower the IO and the smaller the file, but the optimal setting depends on the contents of the file. Chunksize provides a performance control for the hdf5 parallel writes. It is a 2d array and is associated with the size of the piece of the array written by hdf5. hdf5 can be read and written in parallel, but that depends on how netCDF and PIO are built. Note that prior version of PIO, including PIO1, do not support the hdf5 compression and chunking thru the PIO interface. - Add new namelist settings (set_nml files) and update the io_suite to cover the new IO options. Remove old namelist settings associated with the deprecated format options and the lcdf64 namelist. These deprecated feature are no longer tested. - Update documentation to add new namelist and IO features. - Update the nuopc/cmeps driver code to support the new features. - Update the default ice_in to add the new namelist. - Update the derecho netcdf module to a version that supports hdf5. - Clean up some code formatting (indentation) --------- Co-authored-by: Anton Steketee <anton.steketee@anu.edu.au>
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