CUDA: fix numerical issue in tile FA kernel #16540
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IMbackK
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I definitely did observe issues with the numerical range when I debugged this, there seems to be an additional bug that specifically occurs |
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* origin/master: (32 commits) metal : FA support F32 K and V and head size = 32 (ggml-org#16531) graph : support cacheless embeddings with FA and iSWA (ggml-org#16528) opencl: fix build targeting CL 2 (ggml-org#16554) CUDA: fix numerical issues in tile FA kernel (ggml-org#16540) ggml : fix build broken with -march=armv9-a on MacOS (ggml-org#16520) CANN: fix CPU memory leak in CANN backend (ggml-org#16549) fix: add remark plugin to render raw HTML as literal text (ggml-org#16505) metal: add support for opt_step_sgd (ggml-org#16539) ggml : fix scalar path for computing norm (ggml-org#16558) CANN: Update several operators to support FP16 data format (ggml-org#16251) metal : add opt_step_adamw and op_sum (ggml-org#16529) webui: remove client-side context pre-check and rely on backend for limits (ggml-org#16506) [SYCL] fix UT fault cases: count-equal, argsort, pad OPs (ggml-org#16521) ci : add Vulkan on Ubuntu with default packages build (ggml-org#16532) common : handle unicode during partial json parsing (ggml-org#16526) common : update presets (ggml-org#16504) ggml : Fix FP16 ELU positive branch (ggml-org#16519) hparams : add check for layer index in is_recurrent (ggml-org#16511) ggml: Correct SVE implementation in ggml_vec_dot_f16_unroll (ggml-org#16518) CUDA: faster tile FA, add oob checks, more HSs (ggml-org#16492) ...
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This reverts commit 7049736.
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Fixes issue described in #16528 (comment) .
The problem as far as I can tell are numerical issues for the rescaling of the VKQ accumulators with the inverse of the KQ sum at the end of the kernel. The input values in
test-backend-opsand the models I tested did not provoke this issue so I did not detect it in #16492 . The fix is to simply use FP32 arithmetic, the impact on performance is negligible since it's only done once per CUDA block.