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man pages->IRIX man pages -> complib/cfftm1d (3)
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### Contents

```
cfftm1d,zfftm1d(3F)					   cfftm1d,zfftm1d(3F)

```

### NAME[Toc][Back]

```     cfftm1d, zfftm1d -	Multiple 1D, complex-to-complex, Fast Fourier
Transforms.
```

### SYNOPSYS[Toc][Back]

```     Fortran :
subroutine	cfftm1d( sign, n, p, array, inc, lda, coef )
integer	     sign, n, p, inc, lda
complex	    array(lda,p), coef(n+15)

subroutine	zfftm1d( sign, n, p, array, inc, lda, coef )
integer	     sign, n, p, inc, lda
double complex    array(lda,p), coef(n+15)

C :
#include <fft.h>
int cfftm1d ( int sign, int n, int	p, complex *array,
int inc,	int lda, complex *coef);
int zfftm1d ( int sign, int n, int	p, zomplex *array,
int inc,	int lda, zomplex *coef);

```

### DESCRIPTION[Toc][Back]

```     cfftm1d and zfftm1d compute the complex Fourier transform of P complex
sequences of N samples each. The k-th index F(k) of the Transform of an N
sample sequence f(i) is equal to:
F(k) = Sum ( W^(i*k) * f(i) ), for i =0, ...,	(N-1)
W = exp(	(Sign*2*sqrt(-1)*PI) / N )

The Fourier transforms are	computed in-place so the input sequence	is
overwritten by the	Fourier	transform output.

```

### PARAMETERS[Toc][Back]

```     SIGN - Integer specifying which sign to be	used for the expression	of W
(see above) - must	be either +1 or	-1.
Unchanged on exit.

N - Integer, the number of	samples	in each	sequence.
Unchanged on exit.

P - Integer, the number of	sequences.  Unchanged on exit.

ARRAY - Array containing the samples of the sequence to be	transformed.
On	input, the element "i" of the sequence "j" is stored as	A(i*inc,j) in
Fortran , and A[i*inc+j*lda] in C.
On	exit, the array	is overwritten by its transform.

Page 1

cfftm1d,zfftm1d(3F)					   cfftm1d,zfftm1d(3F)

INC - Integer, increment between two consecutive elements of a sequence.
Unchanged on exit.

LDA - Integer, leading dimension: increment between the first samples of
two consecutive sequences.	Unchanged on exit.

COEFF - Array of at least ( N + 15	) elements.  On	entry it contains the
Sines/Cosines and factorization of	N. COEFF needs to be initialized with
a call to cfftm1di	or zfftm1di.  Unchanged	on exit.

Example	of Calling Sequence
Compute 1D	FFTs computed for 64 sequences of 1024 complex values each.
The elements of each sequence are stored with increment (stride) 1, and
the offset	between	the first element of two succesive sequences (leading
dimension)	is 2049.
Fortran
complex array(0:2049-1,0:64-1), coeff(1024+15)
call cfftm1di( 1024, coeff)
call cfftm1d(	-1, 1024, 64, array, 1,	2049, coeff)

C
#include <fft.h>
complex array[64*2049], *coeff;
coeff	= cfftm1di( 1024, NULL);
cfftm1d( -1, 1024, 64, array,	1, 2049, coeff);

```

```     fft, cfftm1di, zfftm1di