[D] 60% MatMul Performance Bug in cuBLAS on RTX 5090 [D]
Reddit - Machine Learning
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cuBLAS dispatches an inefficient kernel for every batched FP32 workload, from 256×256 to 8192×8192×8. It only uses ~40% of the available compute on RTX GPUs. Tested with RTX 5090, but likely all RTX non-Pro GPUs are affected. I tested with the latest CUDA 13.2.51, cuBLAS 13.3.0, and driver 595.58.03. Previous versions are even worse. I wrote a simple, yet efficient kernel and compared it to cuBLAS across a variety of workloads. Batched perf vs cuBLAS on 5090 (>100% means my kernel is faste...
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Originally published on April 10, 2026.
Curated by AI News.
