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Fix floor_divide for integers - #4515
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ml-explore/mlx#4515 makes integer floor_divide floor toward -inf in the next MLX release, which would fail the assertion that it truncates. The right_shift helper stays correct on every version; the docstring now says so. MLX argsort stability is documented since 0.32.2. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01WpxsXyNmLskVHUCzfNu59g
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The signed-integer CPU Divide computed x / y before it checked y != 0. C++ does not define integer division by 0, so the compiler could remove the check. It also always computed q - 1, which overflows for min // 1. Now the functor divides by 1 where y == 0 or where min is divided by -1, returns 0 for x // 0 and min for min // -1 (the values arm64 gave before), and subtracts 1 only in the lanes that need it. Add tests with 40 elements, so the 16-lane int8 and int16 SIMD path runs, and CPU tests for x // 0 and min // -1. State the upstream ml-explore#4515 risk, the CUDA functor and the mlx-swift generated copies in fork.yaml. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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In MLX v0.32.3, integer floor_divide (ml-explore/mlx#4515) built its logical_and on the calling thread's own default stream. When the result was evaluated on any other thread, the process stopped with "There is no Stream(gpu, N) in current thread". mlx-swift-lm's MoE gather sort calls floorDivide on integer indices and evaluates on its generation thread, so every MoE generation in PicoCore crashed. The mlx submodule now points at PicoMLX/mlx pico/0.32.3: v0.32.3 plus the one-line fix that passes the stream through. CMake fetches the same commit. v0.32.4 replaces this code with a FloorDivide primitive (ml-explore/mlx#4642). StreamTests.testIntegerFloorDivideEvaluatesOnAnotherThread builds an integer floorDivide on one thread and reads it on another. Without the fix it stops the process with that error. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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Fixes [BUG] Inconsistent behaviour of the floot_divide integer arrays truncates towards 0 #4450 , making quotient for integer division floor towards -inf
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