Performance Degradation in the Presence of Subnormal Floating-Point Values
Orion Sky Lawlor, Hari Govind, Isaac Dooley, Michael Breitenfeld, Laxmikant V. Kalé · 2005
Operating system interference in parallel programs can cause tremendous performance degradation. This paper discusses the interference caused by the quiet generation of subnormal floating point values. We analyze the perfor-mance 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 degredation due to this interference. In ad-dition we provide an simple example program that demon-strates underflow on a single processor. Finally we suggest a novel option for fixing these undesired slowdowns. 1.