Here we list a few major changes from the previous release. For the full list of detailed changes, please refer to the release note.

New APIs

• Fortran 90 APIs. All F90 APIs have prefix name "nf90mpi_" and support function overloading.
• varn APIs - ​ncmpi_get_varn_<type> and ​ncmpi_put_varn_<type> for reading/writing a list of sub-requests to a single variable.
• mput/mget APIs - ncmpi_mput_var<kind>_<type> for making multiple put/get requests to multiple variables.
• ​ncmpi_inq_put_size - reports the write amount in bytes committed by far
• ​ncmpi_inq_get_size - reports the read amount in bytes committed by far

New run-time environment variable

• ​PNETCDF_SAFE_MODE environment variable can be used to enable/disable the internal checking for data/argument consistency across all processes. Set it to 1 to enable the checking. Default is 0, i.e. disabled.
• ​PNETCDF_HINTS environment variable can be used to pass the I/O hints to PnetCDF library.

New example programs

• new example programs are added in all C, F77, and F90 versions
• Refer README for descriptions of the example programs

New programs for I/O benchmarks

• benchmarks/C/aggregation.c -- evaluate PnetCDF's performance on I/O aggregation across multiple requests with different data access patterns.
• benchmarks/C/write_block_read_column.c -- writes variables and reads back using different data partitioning patterns
• benchmarks/FLASH-IO -- I/O kernel of FLASH, a reacting hydrodynamics code developed at University of Chicago

New optimization: I/O request aggregation

• nonblocking requests are aggregated as much as possible, even for interleaved requests.

Improved build process

• configure process can now detect available MPI compilers and compile flags