Novel HPC techniques to batch execution of many variable size BLAS computations on GPUs

This paper presents a software framework for solving large numbers of relatively small matrix problems using GPUs. Our approach combines novel and existing HPC techniques to methodically apply performance analysis, kernel design, low-level optimizations, and autotuning to exceed in performance proprietary vendor libraries. As a case study, we discuss the fundamental matrix operations defined by the Basic Linear Algebra Subprograms (BLAS) standard. This case study is significantly important for wide range of applications, including astrophysics, tensor contractions, sparse direct solvers, and others. We provide a generic design that is capable of dealing with problems of different sizes, and handling the irregularity arising from size variations. The developed solution adopts a batched computation scheme, where the same operation is concurrently applied to all matrices within a single computational kernel. The paper discusses the data layout, kernel design, and optimization techniques. We also propose a design scheme that is centralized around matrix-matrix multiplication (GEMM) kernel, so that any improvement on this particular kernel propagates automatically to other routines. Our performance results show significant speedups using a Pascal generation GPU (Tesla P100) against state-of-the-art solutions using cuBLAS, as well as against two 10-core Haswell CPUs running the MKL library. This work is part of the MAGMA library.