--- a +++ b/src/fftn.h @@ -0,0 +1,117 @@ +/*--------------------------------*-C-*---------------------------------* + * File: + * fftn.h + * + * Singleton's multivariate complex Fourier transform, computed in + * place using mixed-radix Fast Fourier Transform algorithm. + * + * Called here `fftn' since it does a radix-n FFT on n-dimensional data + * + * Copyright(c)1995,97 Mark Olesen <olesen@me.QueensU.CA> + * Queen's Univ at Kingston (Canada) + * + * Permission to use, copy, modify, and distribute this software for + * any purpose without fee is hereby granted, provided that this + * entire notice is included in all copies of any software which is + * or includes a copy or modification of this software and in all + * copies of the supporting documentation for such software. + * + * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR + * IMPLIED WARRANTY. IN PARTICULAR, NEITHER THE AUTHOR NOR QUEEN'S + * UNIVERSITY AT KINGSTON MAKES ANY REPRESENTATION OR WARRANTY OF ANY + * KIND CONCERNING THE MERCHANTABILITY OF THIS SOFTWARE OR ITS + * FITNESS FOR ANY PARTICULAR PURPOSE. + * + * All of which is to say that you can do what you like with this + * source code provided you don't try to sell it as your own and you + * include an unaltered copy of this message (including the + * copyright). + * + * It is also implicitly understood that bug fixes and improvements + * should make their way back to the general Internet community so + * that everyone benefits. + * + * Brief overview of parameters: + * ---------------------------------------------------------------------* + * Re[]: real value array + * Im[]: imaginary value array + * nTotal: total number of complex values + * nPass: number of elements involved in this pass of transform + * nSpan: nspan/nPass = number of bytes to increment pointer + * in Re[] and Im[] + * isign: exponent: +1 = forward -1 = reverse + * scaling: normalizing constant by which the final result is DIVIDED + * scaling == -1, normalize by total dimension of the transform + * scaling < -1, normalize by the square-root of the total dimension + * + * + * Slightly more detailed information: + * ----------------------------------------------------------------------* + * void fft_free (void); + * + * free-up allocated temporary storage after finished all the Fourier + * transforms. + * + * ----------------------------------------------------------------------* + * + * int fftn (int ndim, const int dims[], REAL Re[], REAL Im[], + * int iSign, double scaling); + * + * NDIM = the total number dimensions + * DIMS = a vector of array sizes + * if NDIM is zero then DIMS must be zero-terminated + * + * RE and IM hold the real and imaginary components of the data, and + * return the resulting real and imaginary Fourier coefficients. + * Multidimensional data *must* be allocated contiguously. There is + * no limit on the number of dimensions. + * + * ISIGN = the sign of the complex exponential + * (ie, forward or inverse FFT) + * the magnitude of ISIGN (normally 1) is used to determine + * the correct indexing increment (see below). + * + * SCALING = normalizing constant by which the final result is DIVIDED + * if SCALING == -1, normalize by total dimension of the transform + * if SCALING < -1, normalize by the square-root of the total dimension + * + * example: + * tri-variate transform with Re[n3][n2][n1], Im[n3][n2][n1] + * + * int dims[3] = {n1,n2,n3} + * fftn (3, dims, Re, Im, 1, scaling); + * + * or, using a null terminated dimension list + * int dims[4] = {n1,n2,n3,0} + * fftn (0, dims, Re, Im, 1, scaling); + * ----------------------------------------------------------------------*/ +#ifndef _FFTN_H +#define _FFTN_H +#ifdef __cplusplus +extern "C" { +#endif + extern void fft_free (void); + + /* double precision routine */ + extern int fftn (int /* ndim */, + const int /* dims */[], + double /* Re */[], + double /* Im */[], + int /* isign */, + double /* scaling */); + + /* float precision routine */ + extern int fftnf (int /* ndim */, + const int /* dims */[], + float /* Re */[], + float /* Im */[], + int /* isign */, + double /* scaling */); + +#ifdef __cplusplus +} +#endif +#endif /* _FFTN_H */ +/*----------------------- end-of-file (C header) -----------------------*/ + +