Analyzing the impact of floating-point precision adaptation in iterative programs

Overview & Synopsis

The amount of floating-point computations in numerical programs is ever increasing. In order to improve their performance, the current trend is to carefully adapt the precision of some floating-point operations, to take advantage of new features of modern architectures. Such adaptation process requires tools to evaluate the impact of these transformations on the accuracy of the output. This article presents an analysis tool to help developers in evaluating the impact of adapting the precision in floating-point programs, with a particular focus on iterative programs. This tool is implemented in the LLVM compilation framework, and it includes two main modules: fp2mp that enables to instrument floating-point programs with multiple-precision computations, and a loop splitter that enables to split the iteration space of a loop into several subspaces. We illustrate the interest of this tool on various examples, and particularly how it enables to evaluate automatically the impact of adapting the precision of floating-point operations in loops by considering different precisions over the iteration space.