WRF Build with Parallel NetCDF Support

WRF Build with Parallel-NetCDF Support on RAIJIN

Forword

WRF comes with an I/O layer implemented with parallel NetCDF ( pNetCDF) --- an extension of the netCDF library that supports data access to NetCDF files in parallel. Here we will give you the instruction how to build WRF with support pNetCDF and how to run WRF with utilising this feature.

Where is pNetCDF installed on Raijin

The Parallel-NetCDF is installed under /projects/WRF/parallel-netcdf/1.3.1, where 1.3.1 is the version number of pNetCDF. The installation location may be moved to a common place on raijin when more applications and tools will use pNetCDF.

WRF build with pNetCDF support

Firstly, setting the environment PNETCDF before running ./configure, do:

setenv PNETCDF /projects/WRF/parallel-netcdf/1.3.1 (TCSH)

OR

export PNETCDF=/projects/WRF/parallel-netcdf/1.3.1 (BASH)

Secondly, following the instructions as documented in WRF Build on Raijin and WRF Installation

Configure namelist to use pNetCDF

In the namelist.input, the following settings support pNetCDF by setting value to 11:

io_form_boundary

io_form_history

io_form_auxinput2

io_form_auxhist2

Note that you need set nocolons = .true. in the section &time_control of namelist.input

I/O performance with pNetCDF

We have conducted a series of WRF high-resolution runs over 512 CPUs on raijin and the results show that I/O performance gain is considerable ( see an example outputs below ) against NO-pNetCDF support.

With pNetCDF support:

Timing for Writing wrfout_d03_2010-02-06_01_00_00 for domain 3: 77.62950 elapsed seconds. Timing for Writing wrfout_d03_2010-02-06_02_00_00 for domain 3: 75.74540 elapsed seconds. Timing for Writing wrfout_d03_2010-02-06_03_00_00 for domain 3: 80.26440 elapsed seconds.

Without pNetCDF support: Timing for Writing wrfout_d03_2010-02-06_01:00:00 for domain 3: 315.81271 elapsed seconds. Timing for Writing wrfout_d03_2010-02-06_02:00:00 for domain 3: 299.80011 elapsed seconds. Timing for Writing wrfout_d03_2010-02-06_03:00:00 for domain 3: 307.18109 elapsed seconds.

If you have any problems with above, please feel free to email us on [| climate_help@nf.nci.org.au]