MatmulNBits prepacking scales fix#27412
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hariharans29 merged 11 commits intomainfrom Feb 24, 2026
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…es processing the B input
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Pull request overview
This PR fixes a critical bug in the MatMulNBits operator's PrePack method for the MLFloat16 specialization. The bug occurs when prepacking the B input tensor (weights) and scales need to be converted from MLFloat16 to float32. The code was incorrectly using the B tensor's size instead of the scales tensor's size for buffer allocation and conversion, which could lead to buffer overruns or underruns depending on the relative sizes of B and scales tensors.
Changes:
- Fixed incorrect size calculation when prepacking scales for MLFloat16 MatMulNBits operator
- Changed from using B tensor size to scales tensor size for scales conversion buffer allocation
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guschmue
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tianleiwu
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guschmue
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tianleiwu
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hariharans29
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Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
guschmue
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tianleiwu
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### Description Fix incorrect scales element count while pre-packing scales while we processing the B input in the Prepack() method of MatmulNBits operator ### Motivation and Context Fix potential crash due to incorrect element count --------- Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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This cherry-picks the following commits for the release: | Commit ID | PR Number | Commit Title | |-----------|-----------|-------------| | decd177 | #27090 | Fix GatherND division by zero when batch dimensions mismatch | | 55f8234 | #27360 | Fix QMoE CPU Operator | | df9146f | #27403 | [MLAS] Adding DynamicQGemm function pointers and ukernel interface | | 0f93853 | #27318 | [js/web] Use embedded WASM module in Blob URL workers when wasmBinary is provided | | b2a6e69 | #27364 | QMoE CPU Performance Update (Up to 4x on 4-bit) | | f501e1d | #27413 | Fix refcount bug in map input conversion that caused shutdown segfault | | b32b205 | #27421 | Fix error where bytes is not assigned for dynamic qgemm pack b size | | 426b006 | #27397 | Fix DllImportResolver | | 0982844 | #27412 | MatmulNBits prepacking scales fix | | 9afb0d2 | #27430 | Fix validation for external data paths for models loaded from bytes | | 71d2cd0 | #27401 | Enable Python 3.14 CI and Upgrade Dependencies | | 79e0676 | #27419 | fix: out of bounds access for resize operation | | 82eb99c | #27459 | Fix SkipLayerNorm fusion incorrectly applied when gamma/beta are not 1D | | 355278a | #27444 | Fix GatherCopyData Integer Truncation Leading to Heap Out-of-Bounds Read/Write | | cf96123 | #27411 | [web] fix usage of wasmBinary together with a blob URL for .mjs | | 1131a86 | #27399 | [web] remove the unhelpful "Unknown CPU vendor" warning. | | ffbbc4f | #27316 | Build Windows ARM64X binaries as part of packaging pipeline | --------- Signed-off-by: Jonathan Clohessy <Jonathan.Clohessy@arm.com> Co-authored-by: patryk-kaiser-ARM <patryk.kaiser@arm.com> Co-authored-by: don <70039285+0-don@users.noreply.github.com> Co-authored-by: Jonathan Clohessy <jonathan.clohessy@arm.com> Co-authored-by: Hariharan Seshadri <shariharan91@gmail.com> Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com> Co-authored-by: Adrian Lizarraga <adlizarraga@microsoft.com> Co-authored-by: Lukas Folle <126877803+lukas-folle-snkeos@users.noreply.github.com> Co-authored-by: Chi Lo <54722500+chilo-ms@users.noreply.github.com> Co-authored-by: Yulong Wang <7679871+fs-eire@users.noreply.github.com> Co-authored-by: Chaya <cha182350@gmail.com> Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com> Co-authored-by: Copilot <198982749+Copilot@users.noreply.github.com> Co-authored-by: Erik <erscor@microsoft.com> Co-authored-by: Edward Chen <18449977+edgchen1@users.noreply.github.com>
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Description
Fix incorrect scales element count while pre-packing scales while we processing the B input in the Prepack() method of MatmulNBits operator
Motivation and Context
Fix potential crash due to incorrect element count