Notes: 2026-08-25 CoreCollective Windows on Arm Technical

25 Aug 2026

      Hi all,

Sorry about the abrupt end to the call.  I thought I had clicked the
"reclaim host" button when I joined the call, but apparently it did not
work & Grant was still assigned as alternate host, so Zoom took the call
down when he left. 😅

The notes from this week's call are below.  Please let us know if you spot
any errors or important omissions.

Thanks & regards,
Nathalie
-- 
CoreCollective Community Manager
Android & WoA working groups
Next OOO: Sep 9-11

*Attended:*
Anthony R.
Carlos S.
Dave W.
Evgeny K.
Gleb K.
Grant L.
John S.
Julianus
Kiran C.
Leandro L.
Marcus P.
Mayank A.
Mike H.
Nathalie CKC
Omair J.
Paul B.
Rajath H.
Rick D.
Saket J.
Thomas D.
Tyler M.

*Links shared in chat:*

   - From Kiran: https://packages.msys2.org/base/mingw-w64-flang
   - From Mayank:
      - https://github.com/openai/tiktoken/pull/501
      - https://github.com/pytorch/pytorch/pull/194563
      - https://github.com/Multicorewareinc/tensorflow
      - https://github.com/tensorflow/tensorflow/pull/124329
   - From Gleb:
      - https://github.com/confluentinc/confluent-kafka-python/pull/2190

*AI Notes - please notify us of inaccuracies:*
Meeting Overview

   -

   Discussed compiler support for Fortran and GNU toolchain integration on
   Windows on Arm, focusing on Flang, GFortran, and MSYS2 compatibility.
   -

   Reviewed Python package enablement progress on Windows on Arm, including
   PyArrow ABI3 migration, PyTorch performance optimizations, TensorFlow
   external releases, and CI runner availability in Azure DevOps.
   -

   Received technical updates on GCC upstreaming efforts, SEH (Structured
   Exception Handling) patches, native Bash execution for Git for Windows, and
   LLVM release and PGO build performance.

Decisions/Key Takeaways

   -

   MulticoreWare created a fork and published a beta release of TensorFlow
   for Windows Arm64 in their external repository while upstream review
   continues.
   -

   SEH support for Binutils has been successfully upstreamed, with the
   final GCC SEH patch currently undergoing upstream review.
   -

   [Deferred] Decision on whether to prioritize Flang GNU-compatibility
   changes versus GFortran development for Windows on Arm deferred pending
   further community input and testing results.

Action Items

   -

   *Gleb K.*
   -

      Provide context to Anthony on PyArrow ABI3 migration PRs discussion
      -

   *Anthony R.*
   -

   -

      Review PyArrow ABI3 migration PRs and context provided by Gleb K.
      -

   *Evgeny K.*
   -

      Prepare a summary of cross-compilation test results for Fortran on
      Linux for the next meeting.
      -

   *Marcus P.*
   -

      Follow up on Azure DevOps Arm runner availability and free-tier
      support plans for open-source projects.
      -

      Follow up with Michael regarding the status of PyTorch releases on
      PyPI.
      -

      Follow up offline with Omair on processing power for LLVM builds
      -

   *Mayank A.*
   -

      Check team's status on confluent-kafka-python signature process issue
      and report back.
      -

      Discuss setting up weekly builds and tests for TensorFlow with Gaurav.
      -

      Make the PR for Open3D (instead of having Ke do it) and reach out to
      WoA list once the PR is created.
      -

   *Nathalie C.*
   -

      Set up CoreCollective Hub accounts for Rajath H. and Annamalai C. by
      later this week.
      -

   *Rajath H.*
   -

      Follow up offline with Gleb K. regarding the required NVIDIA Python
      and CUDA package list.
      -

      Assist in finding an OpenAI contact for the tiktoken PR.

For Future

   -

   Evgeny K. scheduled to present a summary of Fortran cross-compilation
   test results at the next meeting.
   -

   Cryptography release with Windows on Arm support scheduled for September.

Notes

*Fortran and Flang Toolchain for Windows on Arm*

   -

   Fortran on Windows on Arm currently lacks a GNU-style compatible
   compiler, restricting the execution of the GFortran test suite, R tools,
   and GNU-dependent libraries.
   -

   Current Flang implementations are compatible with MSVC ABI, leading to
   integration issues when building libraries like OpenBLAS and LAPACK that
   rely on GNU-style infrastructure.
   -

   Two potential solutions under evaluation include updating Flang
   driver/linker directives for GNU library compatibility or developing
   GFortran for Windows on Arm.
   -

   MSYS2 currently contains downstream packages for Flang on Arm64; Kiran
   recommended reviewing these downstream patches for upstreaming
   opportunities.
   -

   Upstream GCC work has made progress with SEH integrated into Binutils,
   enabling native toolchain builds once the final GCC patch is accepted.

*Python Package Enablement and CI Infrastructure*

   -

   PyArrow maintainers require an ABI3 migration to reduce wheel build
   output and CI storage load before accepting the Windows on Arm support PR.
   -

   Anaconda's roadmap indicates that conda and Miniconda support for
   Windows on Arm is not expected to be completed before October.
   -

   MulticoreWare submitted performance optimization PRs for PyTorch on
   Windows Arm64 and published a beta release of TensorFlow based on their
   fork.
   -

   Tiktoken PR #501 for Windows Arm64 support has been submitted to OpenAI,
   with outreach ongoing to connect with OpenAI maintainers.  NVidia will join
   in helping to find an OpenAI Tiktoken contact.
   -

   Azure plans to expand Arm runner support, but matching the free tier is
   not currently on their roadmap & that will be a blocker for open-source
   projects
   -

   Cryptography release for Windows on Arm is targeted for September
   -

   Confluent-kafka-python PR #2190 signature process is under review
   following initial technical issues.

*GCC, LLVM, and System Utilities*

   -

   Native Bash execution under MSYS2 was successfully cross-compiled and
   tested internally by MulticoreWare, demonstrating 3x to 5x performance
   improvements over emulation.
   -

   Pull requests for Git for Windows integration with native Bash are
   currently under review by maintainers & QC to address feedback
   -

   LLVM 23 release is expected imminently from upstream.
   -

   LLVM release build testing using ThinLTO, PGO, and PDB generation on a
   16-core Arm machine required 6 hours and 45 minutes, prompting discussions
   on increasing GitHub runner resources.

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Nathalie Chan King Choy (Windows on Arm)

Grant Likely (Windows on Arm)

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