BAG: Faster Matrix Multiplication on a Single GPU
Matrix multiplication is a fundamental computation kernel in many parallel and sequential scientific applications. We target FP32 matrix multiplication on GPUs, a setting required by numerous HPC and scientific workloads. Alternative Basis Matrix Multiplication (ABMM) is a practical Strassen-like algorithm that reduces the number of additions while preserving the same asymptotic exponent and admitting a provable O(n) component-wise error bound. However, optimized GPU support for ABMM remains underexplored. This paper presents BAG (Basis Alternative Matrix Multiplication on GPUs), a GPU-oriented implementation of ABMM for the NVIDIA Ampere architecture. A naive GPU implementation of ABMM suffers from excessive workspace and memory traffic, launch-dominated serialization across heterogeneous steps, and high sensitivity to recursion and blocking parameters. We design fused ABMM kernels to shrink workspace and eliminate redundant global-memory traffic, specialize register usage for different primitive patterns to expose intra/inter-kernel parallelism, and introduce a cost-model-based recursion policy together with a Roofline-guided blocking strategy to stabilize performance across problem sizes and shapes. On an NVIDIA A100, experimental results show that 1-level BAG reaches a break-even point against cuBLAS FP32 GEMM at dimension 1280 for square matrices, and recursive BAG achieves a 1.24 × speedup over cuBLAS FP32 GEMM at dimension 4096. Our code is available at https://doi.org/https://github.com/napleon-liu/bag.