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sneak_peek.md

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This is essentially a placeholder for the next release note ...

  • New features

    • none

  • New optimization

    • none

  • New Limitations

    • none

  • Configure options

  • Configure updates:

    • none

  • New constants

    • none

  • New APIs

    • none

  • API syntax changes

    • none

  • API semantics updates

    • API ncmpi_inq_header_size() now can be called in the define mode. This API returns the file header size with metadata defined by the time of the call. This information can be helpful to pick proper values for arguments h_minfree, v_align, v_minfree, r_align when calling ncmpi__enddef() to allocate a sufficiently large free space for file header extent and variable data sections to grow without moving data already stored in the file, i.e. when adding new variables, dimensions, or attributes. See PR #201.

  • New error code precedence

    • none

  • Updated error strings

    • none

  • New error code

    • none

  • New PnetCDF hints

    • 'pnc_data_move_chunk_size' -- When adding new data objects into an existing file, the data section may need to be moved to a higher file offset. The movement is performed in chunks. This hint allows users to customized the chunk size. The default is 1048576 bytes, i.e. 1 MiB. See PR #203.
    • 'pnc_striping' -- When creating a new file on the Lustre file system, this hint advises PnetCDF to set the file's striping configuration. The hint value is either "auto" or "inherit". The former sets the new file's striping unit to 1MiB and striping count to the number of compute nodes found in the MPI communicator passed to ncmpi_create(). The latter sets the stripings of new file to inherit the folder's striping settings, if the folder's striping is set. However, if users also set hint striping_factor or striping_unit, then their values will be used instead of parent folder's. This hint's default value is "auto". See PR #222.
    • "pnc_driver" -- To select the I/O driver. String value of "pncio" is the PnetCDF I/O driver and "mpiio" the MPI-IO driver. The default is "pncio".

  • New run-time environment variables

    • none

  • Build recipes

    • none

  • Updated utility programs

    • none

  • Other updates:

    • none

  • Bug fixes

    • Fix data movement when new record variables are added to an existing file that does not change the starting offset of record variable section. See PR #199.

  • New example programs

    • none

  • New programs for I/O benchmarks

    • none

  • New test program

    • test/testcases/tst_grow_data.c -- adding new variables by re-entering the define mode multiple time, but does not cause file header extent to grow. It also tests a case when adding a new record variable that does not change the starting offset of the record variable section in the file.

  • Issues with NetCDF library

    • none

  • Conformity with NetCDF library

    • none

  • Discrepancy from NetCDF library

    • none

  • Issues related to MPI library vendors:

    • none

  • Issues related to Darshan library:

    • none

  • Clarifications about of PnetCDF hints

    • none