v0.8.0 causing segfault 11 on macOS #207

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1. davidmezzetti

   assigned

   gouyt13

   on Nov 1, 2026
2. davidmezzetti

   added

   bugSomething isn't workingSomething isn't working

   on Nov 1, 2026
3. gouyt13

   closed this as completedin 005d8c4on Nov 1, 2026
4. gouyt13 commented on Nov 1, 2026

   

   gouyt13

   on Nov 1, 2026

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   Thanks for the report, and sorry for the breakage.

   Cause: in 0.8.0, IvfIndex.add() defaults to num_threads=0 (all available CPUs); 0.7 defaulted to 1. txtai's append calls add(embeddings), so with 0.8.0 it starts an OpenMP worker team. On macOS, Faiss, PyTorch and rabitqlib each bundle their own libomp. When Faiss and PyTorch are loaded in the same process, starting workers in rabitqlib's runtime crashes with OMP: Error #179: Function pthread_mutex_init failed, followed by a segfault.

   0.8.0 also ignores OMP_NUM_THREADS, so txtai's existing macOS setting (OMP_NUM_THREADS=1) didn't apply. The crash does not reproduce on Linux.

   Fix (#208): 0.8.1 is now on PyPI. It caps num_threads=0 by OMP_NUM_THREADS (omp_get_max_threads()), as Faiss does. With txtai's existing macOS setting, add runs single-threaded again and needs no change on your side. We checked this on a macos-15 arm64 runner with txtai at e5d8d43, running unittest discover -k testann:

   • The 0.8.0 wheel segfaults in testRabitQ.
   • A wheel built from the fix passes all 72 tests.

   You can drop the rabitqlib==0.7.2 pin from your CI. To stay safe on macOS regardless of that environment variable, you can also pass the thread count explicitly, which every 0.7.x and 0.8.x version accepts:

   self.backend.add(embeddings, num_threads=1)

   👍React with 👍1Reacted by David Mezzetti
5. davidmezzetti commented on Nov 1, 2026

   

   davidmezzetti

   on Nov 1, 2026

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   Thank you for the quick fix!
6. TamimEhsan

   added a commit that references this issue on Nov 2, 2026

   fix: cap automatic thread counts by OMP_NUM_THREADS

   ...

   This issue will close once commit 005d8c4 is merged into the 'main' branch.

   005d8c4