Jacek A. Jankowski. Verification and validation of the parallel UnTRIM, 5th UnTRIM Workshop, Trento, 19-21 May 2008.
A new UnTRIM version has been released (see Casulli 2008), featuring better data locality, improved interpolations in the advection scheme and, the most important, a radically new mass-conservative iterative approach to drying and wetting treatment based on Newton iterations with a proven convergence. In the presentation, detailed issues detected during the verification and validation of the refreshed MPI-parallel “2009” version of UnTRIM are presented, treated and resolved. They concern:
- Artificial waves in flows steered by (approximate) stationary boundary conditions.
- Mesh dependency of the advection (the rudimentary serial algorithm).
- Improving the parallel streamline tracking algorithm (traceback treatment, static memory).
- Corrections in the parallelisation of the explicit horizontal diffusion operator in awkward partition interface settings (solved by weighted assembling of partition contributions).
The scalability investigation of the code is performed for 2D (700k cells) and 3D (8m cells) case for up to 192 MPI tasks (SGI Altix 3600 cluster), accompanied by the detailed performance analyse of the code with its profiling for Intel Itanium processors (IA-64 architecture). The results show an overall improvement of the new version computational efficiency.
Transparencies are available.