Parallel-NetCDF (or PNetCDF) is a high-performance parallel I/O library for accessing Unidata's NetCDF. It is built upon MPI-IO, the I/O extension to MPI communications. Using the high-level NetCDF data structures, the Parallel-NetCDF libraries can make use of optimizations to efficiently distribute the file read and write applications between multiple processors.

In addition to the conventional NetCDF read and write APIs, PNetCDF provides a new set of non-blocking APIs. Non-blocking APIs allow users to post multiple read and write requests first and let PNetCDF aggregate them into a large request, hence to achieve better performance. Through full use of existing optimizations available in MPI-IO implementation, PNetCDF has been demonstrated to be able to deliver high-performance parallel I/O.

Parallel I/O in the Unidata NetCDF library has been supported since release 4.0, for HDF5 data files. Since version 4.1.1 the Unidata NetCDF C library supports parallel I/O to classic and 64-bit offset files using the Parallel-NetCDF library, but with the NetCDF API.

• To apply a parallel I/O library for applications to access NetCDF formats on parallel computers. 
• To achieve high I/O performance.

• Interpret the PNetCDF files structure:
  • Header
  • Non-record variables (all dimensions specified)
  • Record variables (ones with an unlimited dimension)
• Store and retrieve data in PNetCDF.
• Show basic API use and error checking.