# Questions tagged [fast-fourier-transform]

Use this tag for questions related to the fast Fourier transform, an algorithm that samples a signal over a period of time (or space) and divides it into its frequency components.

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### Optimization for getting amplitude of FFT results for real signals

I need to compute amplitude of FFT result for real signals, which means that I don't need the precise result of FFT or phase information of the result. So I think I don't need to implement the ...
619 views

### Why, traditionally, does FFT use complex numbers as a wrapper for magnitude and phase?

I've read questions like this one, this one, and this one which ask why we use complex numbers instead of real numbers, and that's one half of the question, but the other half, which I've never seen ...
508 views

### NTT for fast multiplication of polynomials over a finite field, and the connection to polynomial evaluation

Trying to code NTT and INTT in order to have faster polynomial multiplication. That has been extremely mind boggling for me. The polynomials are over a finite field $GF(q)$. I've already coded some ...
76 views

### Analysis of a linear increase in standard divination. What might cause a linear increase in floating point error?

Background: We are doing mathematical transformations on large matrices of inline fraunhofer holography data (the nature of this isn't really important, but if you are curious, essentially it is a ...
194 views

### Chossing a prime for fft of size $2^n$

I have a $p$ degree polynomial where $p$ is prime, I want to find the value of this polynomial at all points from $1$ to $p-1$,to make the fft on this polynomial easier I padded it with zeroes up to ...
130 views

### FFT butterfly diagram

I got confused in the FFT butterfly diagram. Can someone please help me understand it? If I have the vector $x = (-3, -2, -1, 0, 1, 2, 3, 4)$, and I want to apply FFT to it using the Butterfly ...
489 views

### Fourier series Coefficients and wolframalpha

1) Please can my answers be checked, including my final Fourier series. 2) Is it possible to use Wolframalpha to check my answers? If so, how will I go about doing this? Deduce the Fourier series ...