dft – Tarik Billa

Why is FFT of (A+B) different from FFT(A) + FFT(B)?

May 23, 2023 by Tarik

I solved it!! The problem was the calculation of the Nonl term: Nonl[i*Ny+j][0] = dh[i*Ny+j][0]*dh[i*Ny+j][0]*dh[i*Ny+j][0]; Nonl[i*Ny+j][1] = 0.0; That needs to be changed to: Nonl[i*Ny+j][0] = dh[i*Ny+j][0]*dh[i*Ny+j][0]*dh[i*Ny+j][0] -3.0*dh[i*Ny+j][0]*dh[i*Ny+j][1]*dh[i*Ny+j][1]; Nonl[i*Ny+j][1] = -dh[i*Ny+j][1]*dh[i*Ny+j][1]*dh[i*Ny+j][1] +3.0*dh[i*Ny+j][0]*dh[i*Ny+j][0]*dh[i*Ny+j][1]; In other words: I need to consider dh as a complex function (even though it should be real). Basically, because of stupid rounding … Read more

only integers, slices (`:`), ellipsis (`…`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices

March 3, 2023 by Tarik

I believe your problem is this: in your while loop, n is divided by 2, but never cast as an integer again, so it becomes a float at some point. It is then added onto y, which is then a float too, and that gives you the warning.