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avoid last recursive call

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'make test' output:
### testing SNR for  1024 point FFTs
#### DOUBLE
snr_t2f = 295.35
snr_f2t = 308.32
#### FLOAT
snr_t2f = 146.71
snr_f2t = 143.02
#### SHORT
snr_t2f = 54.718
snr_f2t = 24.494

#### timing 10000 x 1024 point FFTs
#### DOUBLE
Elapsed:0:23.05 user:18.95 sys:0.24
#### FLOAT
Elapsed:0:06.45 user:5.17 sys:0.10
#### SHORT
Elapsed:0:05.59 user:4.72 sys:0.06
This commit is contained in:
Mark Borgerding 2003-10-11 14:43:13 +00:00
parent 7ec9402d5b
commit 043da3b65d
1 changed files with 11 additions and 25 deletions
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36
kiss_fft.c
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@ -39,14 +39,11 @@ typedef struct {
kiss_fft_cpx * scratch;
}kiss_fft_state;
#ifdef FIXED_POINT
#define C_ADD(x,a,b) \
do{ (x).r = (a).r+(b).r;\
(x).i = (a).i+(b).i;}while(0)
# define C_ADD(x,a,b) \
do{ (x).r = ( ( (a).r+(b).r ) );\
(x).i = ( ( (a).i+(b).i ) ); }while(0)
# define C_SUB(x,a,b) \
do{ (x).r = ( ( (a).r-(b).r ) );\
(x).i = ( ( (a).i-(b).i ) ); }while(0)
#ifdef FIXED_POINT
/* We don't have to worry about overflow from multiplying by twiddle factors since they
* all have unity magnitude. Still need to shift away fractional bits after adding 1/2 for
* rounding.
@ -58,12 +55,6 @@ typedef struct {
#else // not FIXED_POINT
#define C_ADD(x,a,b) \
do{ (x).r = (a).r+(b).r;\
(x).i = (a).i+(b).i;}while(0)
#define C_SUB(x,a,b) \
do{ (x).r = (a).r-(b).r;\
(x).i = (a).i-(b).i;}while(0)
#define C_MUL(m,a,b) \
do{ (m).r = (a).r*(b).r - (a).i*(b).i;\
(m).i = (a).r*(b).i + (a).i*(b).r; }while(0)
@ -83,12 +74,6 @@ kiss_fft_cpx cexp(double phase)
return x;
}
static kiss_fft_cpx csub(kiss_fft_cpx a,kiss_fft_cpx b)
{
kiss_fft_cpx c;
C_SUB(c,a,b);
return c;
}
static kiss_fft_cpx cadd(kiss_fft_cpx a,kiss_fft_cpx b)
{
kiss_fft_cpx c;
@ -120,15 +105,20 @@ void fft_work(
int m,p=0,q,q1,u,k;
kiss_fft_cpx t;
/*
if (n==1) {
*Fout = *f;
return;
}
*/
p=*factors++;
m=*factors++;//m = n/p;
for (q=0;q<p;++q) {
fft_work( Fout + m*q, f+q*fstride, fstride*p, m,Norig,inverse, scratch ,twiddles,factors);
if (m==1)
*(Fout + m*q) = *(f+q*fstride);
else
fft_work( Fout + m*q, f+q*fstride, fstride*p, m,Norig,inverse, scratch ,twiddles,factors);
}
for ( u=0; u<m; ++u ) {
@ -177,7 +167,6 @@ void * kiss_fft_alloc(int nfft,int inverse_fft)
st->twiddles = (kiss_fft_cpx*)malloc( sizeof(kiss_fft_cpx)*nfft );
st->tmpbuf = (kiss_fft_cpx*)malloc( sizeof(kiss_fft_cpx)*nfft );
st->scratch = (kiss_fft_cpx*)malloc( sizeof(kiss_fft_cpx)*nfft );
st->factors = (int*)malloc( sizeof(int)*nfft );
for (i=0;i<nfft;++i) {
@ -212,9 +201,6 @@ void kiss_fft(const void * cfg,kiss_fft_cpx *f)
const kiss_fft_state * st = cfg;
n = st->nfft;
for (i=0;i<n;++i)
st->tmpbuf[i] = f[i];
memcpy(st->tmpbuf,f,sizeof(kiss_fft_cpx)*n);
fft_work( f, st->tmpbuf, 1, n,n, st->inverse, st->scratch ,st->twiddles,st->factors);
}