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IntervalArithmetic should respect the number of threads #782

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IntervalArithmetic should respect the number of threads#782
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@dpsanders
dpsanders
opened on Oct 6, 2026

The IntervalArithmetic.jl initialization explicitly sets its OpenBLASConsistentFPCSR library to use Sys.CPU_THREADS ÷ 2 threads.

However it should respect OPENBLAS_NUM_THREADS=1 and LinearAlgebra.BLAS.set_num_threads(1) if these are set, so that users can clamp the number of threads used by their process to a given maximum number.

Of course this could be configurable somehow, but a user needs to be able to guarantee not to have half their CPU taken over by IntervalArithmetic without their knowledge or permission :)

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  1. OlivierHnt
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    on Oct 7, 2026

  2. OlivierHnt commented on Oct 7, 2026

    @OlivierHnt
    OlivierHnt
    on Oct 7, 2026
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    I am not sure it makes sense for LinearAlgebra.BLAS.set_num_threads(1) to also impact OpenBLASConsistentFPCSR.

    I think we are doing the same as MKL.jl. Here is a quote from their README file:

    To set or get the global number of threads used by MKL, use MKL.{set/get}_num_threads. This does not affect specific domains where the number of threads is set with mkl_domain_set_num_threads. Calling LinearAlgebra.BLAS.{set/get}_num_threads is domain-specific and only refers to the BLAS domain (unlike other backends, where the number of threads used by LAPACK is also modified).

    Btw setting the number of threads is done via IntervalArithmetic.configure(; nthreads=1).

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