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Fix missing stream in gather matmul indices cast - #4687
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zcbenz
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ronaldmannak
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Oct 16, 2026
(cherry picked from commit bebd642)
ronaldmannak
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The same class of bug as integer floor_divide: an MLX op built on the calling thread's own default stream instead of the stream it was given. Evaluating the result on any other thread stops the process with "There is no Stream(gpu, N) in current thread". PicoMLX/mlx pico/0.32.3 cherry-picks both upstream fixes from v0.32.4: - ml-explore/mlx#4687: gather_mm and gather_qmm cast non-uint32 indices to uint32 without the stream. MoE layers that route with int32 indices hit it. - ml-explore/mlx#4663: layer_norm's CPU fallback multiplied without the stream, and SDPA's boolean-mask fallback (CUDA only, since Metal takes boolean masks directly) built its where without it. StreamTests gains testGatherMMWithInt32IndicesEvaluatesOnAnotherThread and testLayerNormOnTheCPUEvaluatesOnAnotherThread. Without #4687, the gather test stops the process with that error. Without #4663, the CPU layer_norm evaluation never returns: the test fails after 30 seconds, and then the process stops with the same error. The floor_divide test now shares their helper, which waits at most 30 seconds. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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indices_or_defaultcasts indices without forwarding the caller’s stream, sogather_mm,gather_qmm, andgather_qqmmon a non-default stream insert extra cross-stream fences per call and stall the caller’s stream. This PR passes the caller’s stream to the cast.