fft

Fast Fourier Transform. More...

Functions
AFAPI array	fftNorm (const array &in, const double norm_factor, const dim_t odim0=0)
	C++ Interface for fast fourier transform on one dimensional signals. More...
AFAPI void	fftInPlace (array &in, const double norm_factor=1.0)
	C++ Interface for fast fourier transform on one dimensional signals. More...
AFAPI array	fft (const array &in, const dim_t odim0=0)
	C++ Interface for fast fourier transform on one dimensional signals. More...
AFAPI array	dft (const array &in, const double norm_factor, const dim4 outDims)
	C++ Interface for fast fourier transform on any(1d, 2d, 3d) dimensional signals. More...
AFAPI array	dft (const array &in, const dim4 outDims)
	C++ Interface for fast fourier transform on any(1d, 2d, 3d) dimensional signals. More...
AFAPI array	dft (const array &in)
	C++ Interface for fast fourier transform on any(1d, 2d, 3d) dimensional signals. More...
AFAPI array	idft (const array &in, const double norm_factor, const dim4 outDims)
	C++ Interface for inverse fast fourier transform on any(1d, 2d, 3d) dimensional signals. More...
AFAPI array	idft (const array &in, const dim4 outDims)
	C++ Interface for inverse fast fourier transform on any(1d, 2d, 3d) dimensional signals. More...
AFAPI array	idft (const array &in)
	C++ Interface for inverse fast fourier transform on any(1d, 2d, 3d) dimensional signals. More...
AFAPI af_err	af_fft (af_array *out, const af_array in, const double norm_factor, const dim_t odim0)
	C Interface for fast fourier transform on one dimensional signals. More...
AFAPI af_err	af_fft_inplace (af_array in, const double norm_factor)
	C Interface for fast fourier transform on one dimensional signals. More...
AFAPI af_err	af_set_fft_plan_cache_size (size_t cache_size)
	C Interface for setting plan cache size. More...

Detailed Description

Fast Fourier Transform.

The Fast Fourier Transform (FFT) is an efficient algorithm to compute the discrete Fourier transform (DFT) of a signal or array. This is most commonly used to convert data in the time (or space) domain to the frequency domain, Then, the inverse FFT (iFFT) is used to return the data to the original domain.

There are numerous algorithms to compute the FFT of an array, and the specifics of the algorithm depend on the target hardware. Most algorithms, however, use a Cooley-Tukey scheme in a divide-and-conquer approach.

Note

There are some convenience functions provided for fft where normalization factor is not required as input paramter. In such cases, the normalization factor is calculated internally based on the input data provided.

Function Documentation

af_fft()

AFAPI af_err af_fft	(	af_array *	out,
		const af_array	in,
		const double	norm_factor,
		const dim_t	odim0
	)

C Interface for fast fourier transform on one dimensional signals.

Parameters

[out]	out	is the transformed array
[in]	in	is the input array
[in]	norm_factor	is the normalization factor with which the input is scaled after the transformation is applied
[in]	odim0	is the length of output signals - used to either truncate or pad the input signals

Returns

AF_SUCCESS if the fft transform is successful, otherwise an appropriate error code is returned.

af_fft_inplace()

AFAPI af_err af_fft_inplace	(	af_array	in,
		const double	norm_factor
	)

C Interface for fast fourier transform on one dimensional signals.

Parameters

[in,out]	in	is the input array on entry and the output of 1D forward fourier transform at exit
[in]	norm_factor	is the normalization factor with which the input is scaled after the transformation is applied

Returns

AF_SUCCESS if the fft transform is successful, otherwise an appropriate error code is returned.

Note

The input in must be a complex array

af_set_fft_plan_cache_size()

AFAPI af_err af_set_fft_plan_cache_size

(

size_t

cache_size

)

C Interface for setting plan cache size.

This function doesn't do anything if called when CPU backend is active. The plans associated with the most recently used array sizes are cached.

Parameters

[in]

cache_size

is the number of plans that shall be cached

dft() [1/3]

AFAPI array dft

(

const array &

in

)

C++ Interface for fast fourier transform on any(1d, 2d, 3d) dimensional signals.

This version of fft function uses a default norm_factor parameter that is calculated internally based on the input signals.

Parameters

[in]

in

is the input array

Returns

the transformed array

dft() [2/3]

AFAPI array dft	(	const array &	in,
		const dim4	outDims
	)

C++ Interface for fast fourier transform on any(1d, 2d, 3d) dimensional signals.

This version of fft function uses a default norm_factor parameter that is calculated internally based on the input signals.

Parameters

[in]	in	is the input array
[in]	outDims	is an object of dim4 that has the output array dimensions - used to either truncate or pad the input signals

Returns

the transformed array

dft() [3/3]

AFAPI array dft	(	const array &	in,
		const double	norm_factor,
		const dim4	outDims
	)

C++ Interface for fast fourier transform on any(1d, 2d, 3d) dimensional signals.

Parameters

[in]	in	is the input array
[in]	norm_factor	is the normalization factor with which the input is scaled after the transformation is applied
[in]	outDims	is an object of dim4 that has the output array dimensions - used to either truncate or pad the input signals

Returns

the transformed array

fft()

AFAPI array fft	(	const array &	in,
		const dim_t	odim0 = 0
	)

C++ Interface for fast fourier transform on one dimensional signals.

This version of fft function uses a default norm_factor parameter that is calculated internally based on the input signals.

Parameters

[in]	in	is the input array
[in]	odim0	is the length of output signals - used to either truncate or pad the input signals

Returns

the transformed array

fftInPlace()

AFAPI void fftInPlace	(	array &	in,
		const double	norm_factor = 1.0
	)

C++ Interface for fast fourier transform on one dimensional signals.

Parameters

[in,out]	in	is the input array on entry and the output of 1D forward fourier transform on exit
[in]	norm_factor	is the normalization factor with which the input is scaled after the transformation is applied

Note

The input in must be complex

fftNorm()

AFAPI array fftNorm	(	const array &	in,
		const double	norm_factor,
		const dim_t	odim0 = 0
	)

C++ Interface for fast fourier transform on one dimensional signals.

Parameters

[in]	in	is the input array
[in]	norm_factor	is the normalization factor with which the input is scaled after the transformation is applied
[in]	odim0	is the length of output signals - used to either truncate or pad the input signals

Returns

the transformed array

idft() [1/3]

AFAPI array idft

(

const array &

in

)

C++ Interface for inverse fast fourier transform on any(1d, 2d, 3d) dimensional signals.

This version of fft function uses a default norm_factor parameter that is calculated internally based on the input signals.

Parameters

[in]

in

is the input array

Returns

the transformed array

idft() [2/3]

AFAPI array idft	(	const array &	in,
		const dim4	outDims
	)

C++ Interface for inverse fast fourier transform on any(1d, 2d, 3d) dimensional signals.

This version of fft function uses a default norm_factor parameter that is calculated internally based on the input signals.

Parameters

[in]	in	is the input array
[in]	outDims	is an object of dim4 that has the output array dimensions - used to either truncate or pad the input signals

Returns

the transformed array

idft() [3/3]

AFAPI array idft	(	const array &	in,
		const double	norm_factor,
		const dim4	outDims
	)

C++ Interface for inverse fast fourier transform on any(1d, 2d, 3d) dimensional signals.

Parameters

[in]	in	is the input array
[in]	norm_factor	is the normalization factor with which the input is scaled after the transformation is applied
[in]	outDims	is an object of dim4 that has the output array dimensions - used to either truncate or pad the input signals

Returns

the transformed array