DESCRIPTION: In-place fast Fourier transform for complex arrays in $n_d$ dimensions. The forward transform is scaled by one over the size of the array. Uses a modified version of the FFTPACK5 library.
INPUT/OUTPUT PARAMETERS: nd : number of dimensions (in,integer) n : mesh size (in,integer(nd)) sgn : FFT direction, -1: forward, 1: backward (in,integer) c : array to transform (inout,complex(n(1)n(2)...*n(nd)))
Copyright (C) 2005 J. K. Dewhurst Distributed under the terms of the GNU General Public License. See the file COPYING for license details.
Notes by ASIER
sgn=+1 Means Fourier Transform, i.e. Sum_{r=1,N} Exp[+I*k*r] u_r
sgn=-1 Means Inverse Fourier Transform, i.e. Sum_{k=1,N} Exp[-I*k*r] u_k/N
| Type | Intent | Optional | Attributes | Name | ||
|---|---|---|---|---|---|---|
| integer, | intent(in) | :: | nd | |||
| integer, | intent(in) | :: | n(nd) | |||
| integer, | intent(in) | :: | sgn | |||
| complex(kind=prec), | intent(inout) | :: | c(*) |