Application Performance on the High Performance Switch

In 2004 the HPCx system underwent a major upgrade, including the replacement of the 1.3 GHz POWER4 processors by 1.7 GHz POWER4+ and the “Colony ” SP Switch2 being superceded by IBM’s High Performance Switch (HPS). The aim of the upgrade was to effect a factor of two performance increase in the overall capability of the system. We present the results of a benchmarking programme to compare the performance of the Phase1 and Phase2 systems across a range of capability applications of key importance to UK science. Codes are considered from a diverse section of application domains; materials science, molecular simulation and molecular electronic structure, computational engineering and environmental science. Whereas all codes performed better on the Phase2 system, the extent of the improvement is highly application dependent. Those which already showed excellent scaling on the Phase1 system, CPMD, CRYSTAL, NAMD, PCHAN and POLCOMS, in some cases following significant optimisation effort by the HPCx Terascaling Team, showed a speed-up which was close to the increase in processor cloc