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Two drop-in kernels make PyTorch's logsumexp 6-11x faster on GPU and 3-6x on CPU

AspireAI community · arXiv (NeurIPS 2026)
Log-Sum-Exp is the numerical primitive behind log-domain computation, and the de facto PyTorch implementation dispatches a chain of nine GPU sub-kernels per call, burning redundant high-bandwidth memory traffic and launch overhead. FuseLSE collapses that into a single fused kernel that evaluates exp and log on the GPU's Special Function Unit, while IntLSE swaps in approximated integer arithmetic for CPUs that have no SFU. The authors report roughly 10-11x speedups on small GPU workloads and around 6x on larger ones, with IntLSE gaining another 3-6x over FuseLSE on CPU. The measurements are workload- and hardware-specific, so the headline number will not transfer unchanged to every workload.
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