# Is matrix multiplication multi-threaded for Double64?

**URL:** <https://discourse.julialang.org/t/is-matrix-multiplication-multi-threaded-for-double64/111081>\
**Category:** Performance\
**Tags:** doublefloats\
**Created:** [March 3, 2024, 3:58am UTC](https://discourse.julialang.org/t/is-matrix-multiplication-multi-threaded-for-double64/111081 "2024-03-03T03:58:33Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![photor](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/photor/32/14343_2.png) [@photor](https://discourse.julialang.org/u/photor)\
**Post date:** [March 3, 2024, 3:58am UTC](https://discourse.julialang.org/t/is-matrix-multiplication-multi-threaded-for-double64/111081/1 "2024-03-03T03:58:33Z")

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I tested multiplication of two Double64 matrices and saw no effects on performance by using BLAS.set\_num\_threads(n).

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**Author:** ![Elrod](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/elrod/32/22461_2.png) [@Elrod](https://discourse.julialang.org/u/Elrod)\
**Post date:** [March 3, 2024, 4:23am UTC](https://discourse.julialang.org/t/is-matrix-multiplication-multi-threaded-for-double64/111081/2 "2024-03-03T04:23:19Z")

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Do you mean `Float64`? If so, yes. What size matrices?

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<div class="post-metadata">

**Author:** ![photor](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/photor/32/14343_2.png) [@photor](https://discourse.julialang.org/u/photor)\
**Post date:** [March 3, 2024, 4:29am UTC](https://discourse.julialang.org/t/is-matrix-multiplication-multi-threaded-for-double64/111081/3 "2024-03-03T04:29:26Z")

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No, I mean Double64 in DoubleFloats.jl.

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**Author:** ![Oscar\_Smith](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/oscar_smith/32/25343_2.png) [@Oscar\_Smith](https://discourse.julialang.org/u/Oscar_Smith)\
**Post date:** [March 3, 2024, 4:36am UTC](https://discourse.julialang.org/t/is-matrix-multiplication-multi-threaded-for-double64/111081/4 "2024-03-03T04:36:12Z")

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It both isn’t threaded and it also isn’t using BLAS. BLAS only supports Float32 and Float64.

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<div class="post-metadata">

**Author:** ![Elrod](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/elrod/32/22461_2.png) [@Elrod](https://discourse.julialang.org/u/Elrod)\
**Post date:** [March 3, 2024, 5:01am UTC](https://discourse.julialang.org/t/is-matrix-multiplication-multi-threaded-for-double64/111081/5 "2024-03-03T05:01:22Z")

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To be precise, it supports

```julia
julia> LinearAlgebra.BlasFloat
Union{Float32, Float64, ComplexF64, ComplexF32}

```