[WebGPU] updates webgpu softmax to use online algorithm#29694
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Pull request overview
This PR updates the WebGPU Softmax shader implementation to use an online safe-softmax accumulation scheme (running max + running sum), reducing the separate “max pass” previously used in the naive safe-softmax approach.
Changes:
- Switch Softmax’s per-row reduction to an online accumulation of
(max, sum)per thread, then merge these states across the workgroup. - Introduce
x_element_tusage for scalar max/sum tracking and workgroup shared storage, while keepingx_value_tfor packed/vector element operations.
qjia7
approved these changes
Jul 14, 2026
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| // Find the row's max value | ||
| << thread_max_decl | ||
| // Online accumulation: track scalar running max and scalar running sum. |
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nit: Please add a reference to the original paper: https://arxiv.org/abs/1805.02867.
hariharans29
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hariharans29
approved these changes
Jul 14, 2026
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Feature request from #29393