Computational complexity of Inverse FFT

Question

I am trying to calculate the computational complexity of ifft, I know it’s NlogN for a N*1 dimension, signal. But I have a product of two signals then I want to get ifft, and then calculate the computational complexity. So simply, if X(w) and Q(w) are Fourier transform of two time signal , then what is computational complexity of their product.
Note: X(w) and Q(w) has same (N*1) size.
ifft(X(w)*Q(w))=???

Should be on programmers stackexchange – Daniel Mann Nov 16 '13 at 18:41 — Daniel Mann, Nov 16 '13 at 18:41

score 3 · Accepted Answer · answered Nov 16 '13 at 18:47

3

It is still O(N log N). The ifft doesn't care how you get the data, and the element-wise multiplication is O(N).

answered Nov 16 '13 at 18:47

Evan

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thanks mate. I was thinking same, but I had doubt lol. anywat im not into programming so much. @evan – SAH Nov 16 '13 at 18:49

Computational complexity of Inverse FFT

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