Type stability around of wrapped plan fft

General Usage
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1

I have a simple struct wrapping a planned fft and I’m not really sure how to make it type stable

I might need to write the type of the fft, but I’m not really sure how to do it (I cannot really interpret the type of a planed fft)

using FFTW

struct wrapper
    pfft
    pifft
end

function simple_fft(x, pfft::wrapper)
    return pfft.pfft * x
end

W = wrapper(plan_fft(zeros(10)), inv(plan_fft(zeros(10))))

@code_warntype simple_fft(zeros(10), W)
2

Sorry only on mobile, so can’t test stuff.

I think the issue here is that your struct has untyped fields which implicitely means Any. You should either put explicit types there (which you can find via typeof(plan_fft(...))) und generic type paramters like

struct wrapper{P,IP}
    pfft::P
    pifft::IP
end
1 Like
3

By the way, depending on what you want to do you might not need to create a wrapper.
In the docs of AbstractFFTs it says:

You can compute the inverse-transform plan by inv(P) and apply the inverse plan with P \ Â (the inverse plan is cached and reused for subsequent calls to inv or \), and apply the inverse plan to a pre-allocated output array A with ldiv!(A, P, Â).

If you want the wrapper for dispatch reasons thats fine of course.