[export] set enable_gqa in export flash->math decomp#158604
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[export] set enable_gqa in export flash->math decomp#158604
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🔗 Helpful Links🧪 See artifacts and rendered test results at hud.pytorch.org/pr/158604
Note: Links to docs will display an error until the docs builds have been completed. ✅ You can merge normally! (2 Unrelated Failures)As of commit ebeb0a9 with merge base 82f8e04 ( FLAKY - The following job failed but was likely due to flakiness present on trunk:
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This pull request was exported from Phabricator. Differential Revision: D78524147 |
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facebook-github-bot
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Summary: For `scaled_dot_product_attention(..., enable_gqa=True)`: - the Math backend passes the flag through, performing the extra [KV broadcast](https://github.com/pytorch/pytorch/blob/6e07d6a0ff386d99d8c2f1d25978b0683988a4cb/aten/src/ATen/native/transformers/attention.cpp#L902) if set to True - the Flash backend has no flag, and relies on correct indexing in the C++ kernel - Export used to default to Math for `enable_gqa=True`, but #157893 landed and enabled Flash. At the same time, there's an export-only [decomp](https://github.com/pytorch/pytorch/blob/6e07d6a0ff386d99d8c2f1d25978b0683988a4cb/torch/_decomp/decompositions.py#L4968) redirecting flash -> math, calling with `enable_gqa` unset, because that info isn't available. This led to https://fb.workplace.com/groups/1028545332188949/posts/1264609398582540 crashing, calling the Math non-GQA variant, with GQA inputs. This assumes GQA for seqlen mismatches in the export decomp, setting `enable_gqa = <q seqlen> != <kv seqlen>`, relying on prior backend checks to raise on invalid input shapes. Test Plan: test_export Rollback Plan: Differential Revision: D78524147
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This pull request was exported from Phabricator. Differential Revision: D78524147 |
angelayi
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Jul 23, 2025
Summary: For `scaled_dot_product_attention(..., enable_gqa=True)`: - the Math backend passes the flag through, performing the extra [KV broadcast](https://github.com/pytorch/pytorch/blob/6e07d6a0ff386d99d8c2f1d25978b0683988a4cb/aten/src/ATen/native/transformers/attention.cpp#L902) if set to True - the Flash backend has no flag, and relies on correct indexing in the C++ kernel - Export used to default to Math for `enable_gqa=True`, but #157893 landed and enabled Flash. At the same time, there's an export-only [decomp](https://github.com/pytorch/pytorch/blob/6e07d6a0ff386d99d8c2f1d25978b0683988a4cb/torch/_decomp/decompositions.py#L4968) redirecting flash -> math, calling with `enable_gqa` unset, because that info isn't available. This led to https://fb.workplace.com/groups/1028545332188949/posts/1264609398582540 crashing, calling the Math non-GQA variant, with GQA inputs. This assumes GQA for seqlen mismatches in the export decomp, setting `enable_gqa = <q seqlen> != <kv seqlen>`, relying on prior backend checks to raise on invalid input shapes. Test Plan: test_export Rollback Plan: Reviewed By: angelayi Differential Revision: D78524147
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This pull request was exported from Phabricator. Differential Revision: D78524147 |
drisspg
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Jul 24, 2025
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@pytorchbot merge (Initiating merge automatically since Phabricator Diff has merged) |
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Merge startedYour change will be merged once all checks pass (ETA 0-4 Hours). Learn more about merging in the wiki. Questions? Feedback? Please reach out to the PyTorch DevX Team |
yangw-dev
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Aug 1, 2025
Differential Revision: D78524147 For `scaled_dot_product_attention(..., enable_gqa=True)`: - the Math backend passes the flag through, performing the extra [KV broadcast](https://github.com/pytorch/pytorch/blob/6e07d6a0ff386d99d8c2f1d25978b0683988a4cb/aten/src/ATen/native/transformers/attention.cpp#L902) if set to True - the Flash backend has no flag, and relies on correct indexing in the C++ kernel - Export used to default to Math for `enable_gqa=True`, but #157893 landed and enabled Flash. At the same time, there's an export-only [decomp](https://github.com/pytorch/pytorch/blob/6e07d6a0ff386d99d8c2f1d25978b0683988a4cb/torch/_decomp/decompositions.py#L4968) redirecting flash -> math, calling with `enable_gqa` unset, because that info isn't available. This led to https://fb.workplace.com/groups/1028545332188949/posts/1264609398582540 crashing, calling the Math non-GQA variant, with GQA inputs. This assumes GQA for seqlen mismatches in the export decomp, setting `enable_gqa = <q seqlen> != <kv seqlen>`, relying on prior backend checks to raise on invalid input shapes. Pull Request resolved: #158604 Approved by: https://github.com/angelayi, https://github.com/drisspg
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Differential Revision: D78524147
For
scaled_dot_product_attention(..., enable_gqa=True):enable_gqa=True, but [CPU] Support GQA for flash attention #157893 landed and enabled Flash. At the same time, there's an export-only decomp redirecting flash -> math, calling withenable_gqaunset, because that info isn't available. This led to https://fb.workplace.com/groups/1028545332188949/posts/1264609398582540 crashing, calling the Math non-GQA variant, with GQA inputs.This assumes GQA for seqlen mismatches in the export decomp, setting
enable_gqa = <q seqlen> != <kv seqlen>, relying on prior backend checks to raise on invalid input shapes.