NASA Evaluates Cell for Climate Modeling

[Ascended_Saiyan]

An internal study was done between the Cell and single core processor offerings in the supercomputing realm. Other multicore processors were not tested because they don't have linear speed increases per additional core (basically, symmetrical multicores don't scale in a linear fashion as you add more cores).

When run on a QS20 Cell blade provided by the UMBC Multicore Computational Center, significant single processor performance gains were recorded against Intel architectures presently in use by the NASA Center for Computational Sciences. Running the maximum test case of 1,024 data columns, Cell showed a 6.76x improvement against Woodcrest@2.66GHz. Against Dempsey@3.2GHz the improvement was 8.91x, and against an Itanium 2 running at 1.5GHz, Cell demonstrated a 9.85-fold improvement. The comparisons were kept single-core due to the non-linear performance scaling of the Intel architectures, with the Intel architectures running the baseline Fortran as opposed to the ported C.

All comparisons were for single precision performance, as the study predates the introduction of the PowerXCell 8i. The study was conducted before the introduction of a Cell Fortran compiler and auto-SIMD tools as well, both of which have since seen release by IBM in calendar 2008. It was with that knowledge in mind, however, that a relatively light ~2,000 line portion of code was chosen to serve as a testbed.

Having shown positive results on solar radiation, the team is now exploring further code porting for the computationally similar moisture, chemistry, and turbulence physics models; collectively these types of physics problems account for ~50% of GEOS-5 compute time. In addition, project lead Shujia Zhou has been working on a hybrid solution towards allowing Fortran to be run directly on the Cell processor.

http://www.beyond3d.com/content/news/672