# Is that possible to specify dimensions in gemm?

**URL:** <https://discourse.julialang.org/t/is-that-possible-to-specify-dimensions-in-gemm/100433>\
**Category:** Numerics\
**Created:** [June 16, 2023, 5:37am UTC](https://discourse.julialang.org/t/is-that-possible-to-specify-dimensions-in-gemm/100433 "2023-06-16T05:37:47Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Nellatur](https://avatars.discourse-cdn.com/v4/letter/n/76d3ee/32.png) [@Nellatur](https://discourse.julialang.org/u/Nellatur)\
**Post date:** [June 16, 2023, 5:37am UTC](https://discourse.julialang.org/t/is-that-possible-to-specify-dimensions-in-gemm/100433/1 "2023-06-16T05:37:47Z")

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In [Linear Algebra · The Julia Language](https://docs.julialang.org/en/v1/stdlib/LinearAlgebra/#BLAS-functions)  
`gemm` has fewer entries than [LAPACK: dgemm](https://netlib.org/lapack/explore-html/d1/d54/group __double__ blas__level3_gaeda3cbd99c8fb834a60a6412878226e1.html), e.g., dimensions of matrices `A` and `B`. Specifying dimensions sometimes can let higher dimensional arrays look like matrices  
[arrays - How to speed up reshape in higher rank tensor contraction by BLAS in Fortran? - Stack Overflow](https://stackoverflow.com/questions/66253618/how-to-speed-up-reshape-in-higher-rank-tensor-contraction-by-blas-in-fortran)

Is that possible in julia? or has to be used as rank-2 matrix explicitly in Julia?

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**Author:** ![Paulo\_Jabardo](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/paulo_jabardo/32/3196_2.png) [@Paulo\_Jabardo](https://discourse.julialang.org/u/Paulo_Jabardo)\
**Post date:** [June 16, 2023, 5:32pm UTC](https://discourse.julialang.org/t/is-that-possible-to-specify-dimensions-in-gemm/100433/2 "2023-06-16T17:32:26Z")

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I don’t know if I am understanding correctly but you could use a view to get a subarray from the original n dimensional array.

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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:** [June 16, 2023, 5:48pm UTC](https://discourse.julialang.org/t/is-that-possible-to-specify-dimensions-in-gemm/100433/3 "2023-06-16T17:48:34Z")

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They probably want a reshape, not a view. TensorOperarions.jl may also be worth a look.

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<div class="post-metadata">

**Author:** ![Nellatur](https://avatars.discourse-cdn.com/v4/letter/n/76d3ee/32.png) [@Nellatur](https://discourse.julialang.org/u/Nellatur)\
**Post date:** [June 16, 2023, 7:39pm UTC](https://discourse.julialang.org/t/is-that-possible-to-specify-dimensions-in-gemm/100433/4 "2023-06-16T19:39:01Z")

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The specifying dimension in `dgemm` for higher rank array will avoid reshape.