Performance Degradataion in the Presence of Subnormal Floating-Point Values
Workshop on Operating System Interference in High Performance Applications at PACT (OSIHPA) 2005
Publication Type: Talk
Operating system interference in parallel programs can cause tremendous performance degradation. This talk discusses the interference caused by the quiet generation of subnormal floating point values. We analyze the performance impact of subnormal values in a parallel simulation of a stress wave propagating through a three dimensional bar. The floating-point exception handling mechanisms of various parallel architectures and operating systems lead to widely differing performance for the same program. We show that a parallel program will exhibit greatly amplified performance degradation due to this interference. In addition we provide a simple example program that demonstrates underflow on a single processor. Finally we suggest a novel option for fixing these undesired slowdowns.