Scalable Computing and Communications: Theory and Practice

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Optimizing and Tuning Scientific Codes

Qing Yi

13.1  INTRODUCTION

Scientific computing categorizes an important class of software applications that utilize the power of high-end computers to solve important problems in applied disciplines such as physics, chemistry, and engineering. These applications are typically characterized by their extensive use of loops that operate on large data sets stored in multidimensional arrays such as matrices and grids. Applications that can predict the structure of their input data and access these data through array subscripts analyzable by compilers are typically referred to as regular computations, and applications that operate on unstructured data (e.g., graphs of arbitrary shapes) via indirect array references or pointers are referred to as irregular computations.

This chapter focuses on enhancing the performance of regular scientific computations through source-level program transformations, examples of which include loop optimizations such as automatic parallelization, blocking, interchange, and fusion/ fission, redundancy elimination optimizations such as strength reduction of array address calculations, and data layout optimizations such as array copying and scalar replacement. In addition, we introduce POET [1], a scripting language designed for parameterizing architecture-sensitive optimizations so that their configurations can be empirically tuned, and use the POET optimization library to demonstrate ...