Developer Reference

  • 0.10
  • 10/21/2020
  • Public Content
Contents

DFTI_FORWARD_DOMAIN

The general form of a discrete Fourier transform is
for
k
l
= 0, ...
n
l
-1
(
l
= 1, ...,
d
), where
σ
is a scale factor,
δ
= -1 for the forward transform, and
δ
= +1 for the backward transform.
The
Intel® oneAPI Math Kernel Library
implementation of the FFT algorithm, used for fast computation of discrete Fourier transforms, supports forward transforms on input sequences of two domains, as specified by the
DFTI_FORWARD_DOMAIN
configuration parameter: general complex-valued sequences (
DFTI_COMPLEX
domain) and general real-valued sequences (
DFTI_REAL
domain). The forward transform maps the forward domain to the corresponding backward domain, as shown in Table
"Correspondence of Forward and Backward Domain"
.
The conjugate-even domain covers complex-valued sequences with the symmetry property:
where the index arithmetic is performed modulo respective size, that is,
and therefore
Due to this property of conjugate-even sequences, only a part of such sequence is stored in the computer memory, as described in
DFTI_CONJUGATE_EVEN_STORAGE
.
Correspondence of Forward and Backward Domain
Forward Domain
Implied Backward Domain
Complex (
DFTI_COMPLEX
)
Complex (
DFTI_COMPLEX
)
Real (
DFTI_REAL
)
Conjugate-even
DFTI_FORWARD_DOMAIN
does not have a default value. Set it explicitly by calling the
DftiCreateDescriptor
function.
To better understand usage of the
DFTI_FORWARD_DOMAIN
configuration parameter, you can refer to these examples in your
Intel® oneAPI Math Kernel Library
directory:
./examples/dftc/source/basic_sp_complex_dft_1d.c
./examples/dftc/source/basic_sp_real_dft_1d.c

Product and Performance Information

1

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Notice revision #20110804