The RISC BLAS

Abstract

We describe a version of the Level 3 BLAS which is designed to be efficient on RISC processors. This is an extension of previous studies by the authors and colleagues on a similar approach for efficient serial and parallel implementations on virtual-memory and shared-memory multiprocessors. All our codes are written in Fortran and use loop-unrolling, blocking, and copying to improve the performance. A blocking technique is used to express the BLAS in terms of operations involving triangular blocks and calls to the matrix-matrix multiplication kernel (GEMM). No manufacturer-supplied or assembler code is used. This blocked implementation uses the same blocking ideas as in our implementation for vector machines except that the ordering of loops is designed for efficient reuse of date held in cache and not necessarily for parallelization. All the codes are specifically tuned for RISC processors. The software also includes a tuned version of GEMM. A parameter which controls the blocking allows efficient exploitation of the memory hierarchy on the various target computers. We present results on a range of RISC-based workstations and multiprocessors: CRAY T3D, DEC 8400 5/300, HP 715/64, IBM SP2, MEIKO CS2-HA, SGI Power Challenge 10000, and SUN UltraSPARC-1 model 140. This implementation of the Level 3 BLAS is available on anonymous FTP, and we welcome input from users to improve and extend our BLAS implementation.