# Unexpectedly slow performance of "eigs" with a Hermitian view

**URL:** <https://discourse.julialang.org/t/unexpectedly-slow-performance-of-eigs-with-a-hermitian-view/13701>\
**Category:** Performance\
**Created:** [August 19, 2018, 6:36am UTC](https://discourse.julialang.org/t/unexpectedly-slow-performance-of-eigs-with-a-hermitian-view/13701 "2018-08-19T06:36:17Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![mohamed82008](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/mohamed82008/32/18171_2.png) [@mohamed82008](https://discourse.julialang.org/u/mohamed82008)\
**Post date:** [August 19, 2018, 7:01am UTC](https://discourse.julialang.org/t/unexpectedly-slow-performance-of-eigs-with-a-hermitian-view/13701/2 "2018-08-19T07:01:00Z")

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I think what you are seeing is [Slow sparse matrix-vector product with symmetric matrices](https://discourse.julialang.org/t/slow-sparse-matrix-vector-product-with-symmetric-matrices/3968)

```julia
julia> @btime mul!($c, $A, $b);
  120.341 μs (0 allocations: 0 bytes)

julia> _A = Hermitian(A);

julia> @btime mul!($c, $_A, $b);
  37.587 ms (4008 allocations: 187.88 KiB)

```

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