Issues about FFT

[WangYun1995]

Hello,

I want to analyze the spectrum of a 1D spatial function dens(x) by computing the Fourier Transform of it.
And I find that there are many interfaces for FFT, such as rfft_1d_forward, cfft_1d_forward and cfft_1d_backward.
What are the differences between them? What are the outputs?
Could you introduce them to me briefly?
Thank you!

[aamaricci]

As for SciPy, these are all interface to FFTPACK main functions.
We follow closely the SciPy setup here, take a look at: https://docs.scipy.org/doc/scipy/reference/fft.html
Or directly to FFTPACK documentation.

forward real and complex FFT are wrapped into fft
inverse or backward FFT are wrapped in ifft

There are many different cases (1d, 2d, nd, cos, sin, etc..), there are helpers functions like fftshift.
You should know a bit about discrete FFT to really understand what you need.

There are in addition even simple discrete FT, not really fast, but do the work in simple cases.
A

[WangYun1995]

Hi,
Does the Scifor provide an interface to FFTW?

[aamaricci]

In the current implementation it does not. It should be straightforward to adapt the FFTPACK interface to FFTW library.

[WangYun1995]

Ok, thank you for your reply:) Adriano Amaricci <notifications@github.com> 于2020年12月7日周一 下午4:33写道：

…

In the current implementation it does not. It should be straightforward to adapt the FFTPACK interface to FFTW library. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <https://github.com/QcmPlab/SciFortran/issues/6#issuecomment-739762463>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AQIHH56UQ3RQUZ3WU7L2HU3STSHMJANCNFSM4ULRRPDA> .