# Using @fastmath

**URL:** <https://discourse.julialang.org/t/using-fastmath/122203>\
**Category:** Performance\
**Created:** [November 3, 2024, 6:42pm UTC](https://discourse.julialang.org/t/using-fastmath/122203 "2024-11-03T18:42:42Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![hssn15](https://avatars.discourse-cdn.com/v4/letter/h/8797f3/32.png) [@hssn15](https://discourse.julialang.org/u/hssn15)\
**Post date:** [November 3, 2024, 6:42pm UTC](https://discourse.julialang.org/t/using-fastmath/122203/1 "2024-11-03T18:42:43Z")

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Hi, I have started to use @fastmath to have fast computations for polynomials. It was great when I pass Float64. But when i pass dual number (e.g. ForwardDiff.Dual(1., 1.)), i noticed that there is no any speed up.

Do you have any suggestions?

Thank You.

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**Author:** ![jling](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/jling/32/212909_2.png) [@jling](https://discourse.julialang.org/u/jling)\
**Post date:** [November 3, 2024, 7:09pm UTC](https://discourse.julialang.org/t/using-fastmath/122203/2 "2024-11-03T19:09:24Z")

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can you give us an example. But in general, `@fastmath` can only transform the expression it sees directly and also it doesnt know anything about the dual numbers