OpenCL Floating Point Software on Heterogeneous Architectures — Portable or Not?

OpenCL is an emerging platform for parallel computing that promises porta-bility of applications across different architectures. This promise is seriously undermined, however, by the frequent use of floating-point arithmetic in scien-tific applications. Floating-point computations can yield vastly different results on different architectures — even IEEE 754-compliant ones —, potentially caus-ing changes in control flow and ultimately incorrect (not just imprecise) output for the entire program. In this paper, we illustrate a few instances of non-trivial diverging floating-point computations and thus present a case for rigorous static analysis and verification methods for parallel floating point software running on IEEE-754 2008 compliant hardware. We discuss plans for such methods, with the goal to facilitate the automated prediction of portability issues in floating-point software. 1