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fftext.c, move the Bourke FFT code to fftext.c (as a backup)

This commit is contained in:
dwarning 2013-11-24 18:27:19 +01:00 committed by rlar
parent 2e79c16f55
commit c61e1bc8c6
3 changed files with 97 additions and 97 deletions
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97
src/frontend/com_fft.c
View File

@ -21,11 +21,6 @@ Author: 2008 Holger Vogt
#include "ngspice/fftext.h"
#ifndef GREEN
static void fftext(double*, double*, long int, long int, int);
#endif
void
com_fft(wordlist *wl)
{
@ -434,95 +429,3 @@ done:
free_pnode(names);
}
#ifndef GREEN
static void
fftext(double *x, double *y, long int n, long int nn, int dir)
{
/*
http://local.wasp.uwa.edu.au/~pbourke/other/dft/
download 22.05.08
Used with permission from the author Paul Bourke
*/
/*
This computes an in-place complex-to-complex FFT
x and y are the real and imaginary arrays
n is the number of points, has to be to the power of 2
nn is the number of points w/o zero padded values
dir = 1 gives forward transform
dir = -1 gives reverse transform
*/
long i, i1, j, k, i2, l, l1, l2;
double c1, c2, tx, ty, t1, t2, u1, u2, z;
int m = 0, M = 1;
/* get the exponent to the base of 2 from the number of points */
while (M < n) {
M *= 2;
m++;
}
/* Do the bit reversal */
i2 = n >> 1;
j = 0;
for (i = 0; i < n-1; i++) {
if (i < j) {
tx = x[i];
ty = y[i];
x[i] = x[j];
y[i] = y[j];
x[j] = tx;
y[j] = ty;
}
k = i2;
while (k <= j) {
j -= k;
k >>= 1;
}
j += k;
}
/* Compute the FFT */
c1 = -1.0;
c2 = 0.0;
l2 = 1;
for (l = 0; l < m; l++) {
l1 = l2;
l2 <<= 1;
u1 = 1.0;
u2 = 0.0;
for (j = 0; j < l1; j++) {
for (i = j; i < n; i += l2) {
i1 = i + l1;
t1 = u1 * x[i1] - u2 * y[i1];
t2 = u1 * y[i1] + u2 * x[i1];
x[i1] = x[i] - t1;
y[i1] = y[i] - t2;
x[i] += t1;
y[i] += t2;
}
z = u1 * c1 - u2 * c2;
u2 = u1 * c2 + u2 * c1;
u1 = z;
}
c2 = sqrt((1.0 - c1) / 2.0);
if (dir == 1)
c2 = -c2;
c1 = sqrt((1.0 + c1) / 2.0);
}
/* Scaling for forward transform */
if (dir == 1) {
double scale = 1.0 / nn;
for (i = 0; i < n; i++) {
x[i] *= scale; /* don't consider zero padded values */
y[i] *= scale;
}
}
}
#endif /* GREEN */

5
src/include/ngspice/fftext.h
View File

@ -108,3 +108,8 @@ void rspectprod(double *data1, double *data2, double *outdata, int N);
//#define CACHELINEFILL (CACHELINESIZE-1)
//#define CEILCACHELINE(p) ((((unsigned long)p+CACHELINEFILL)/CACHELINESIZE)*CACHELINESIZE)
//#define CACHEFILLMALLOC(n) malloc((n)+CACHELINEFILL)
#ifndef GREEN
static void fftext(double*, double*, long int, long int, int);
#endif

92
src/maths/fft/fftext.c
View File

@ -248,3 +248,95 @@ void rspectprod(double *data1, double *data2, double *outdata, int N)
outdata[0] = data1[0] * data2[0];
}
}
#ifndef GREEN
static void
fftext(double *x, double *y, long int n, long int nn, int dir)
{
/*
http://local.wasp.uwa.edu.au/~pbourke/other/dft/
download 22.05.08
Used with permission from the author Paul Bourke
*/
/*
This computes an in-place complex-to-complex FFT
x and y are the real and imaginary arrays
n is the number of points, has to be to the power of 2
nn is the number of points w/o zero padded values
dir = 1 gives forward transform
dir = -1 gives reverse transform
*/
long i, i1, j, k, i2, l, l1, l2;
double c1, c2, tx, ty, t1, t2, u1, u2, z;
int m = 0, M = 1;
/* get the exponent to the base of 2 from the number of points */
while (M < n) {
M *= 2;
m++;
}
/* Do the bit reversal */
i2 = n >> 1;
j = 0;
for (i = 0; i < n-1; i++) {
if (i < j) {
tx = x[i];
ty = y[i];
x[i] = x[j];
y[i] = y[j];
x[j] = tx;
y[j] = ty;
}
k = i2;
while (k <= j) {
j -= k;
k >>= 1;
}
j += k;
}
/* Compute the FFT */
c1 = -1.0;
c2 = 0.0;
l2 = 1;
for (l = 0; l < m; l++) {
l1 = l2;
l2 <<= 1;
u1 = 1.0;
u2 = 0.0;
for (j = 0; j < l1; j++) {
for (i = j; i < n; i += l2) {
i1 = i + l1;
t1 = u1 * x[i1] - u2 * y[i1];
t2 = u1 * y[i1] + u2 * x[i1];
x[i1] = x[i] - t1;
y[i1] = y[i] - t2;
x[i] += t1;
y[i] += t2;
}
z = u1 * c1 - u2 * c2;
u2 = u1 * c2 + u2 * c1;
u1 = z;
}
c2 = sqrt((1.0 - c1) / 2.0);
if (dir == 1)
c2 = -c2;
c1 = sqrt((1.0 + c1) / 2.0);
}
/* Scaling for forward transform */
if (dir == 1) {
double scale = 1.0 / nn;
for (i = 0; i < n; i++) {
x[i] *= scale; /* don't consider zero padded values */
y[i] *= scale;
}
}
}
#endif /* GREEN */