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DftiComputeBackward

Computes the backward FFT.

Syntax

status
=
DftiComputeBackward
(
desc_handle
,
x_inout
)
;
status
=
DftiComputeBackward
(
desc_handle
,
y_in
,
x_out
)
;
status
=
DftiComputeBackward
(
desc_handle
,
xre_in
out,
xim_inout
)
;
status
=
DftiComputeBackward
(
desc_handle
,
yre_in
,
yim_in
,
xre_out
,
xim_out
)
;
Input Parameters
Name
Type
Description
desc_handle
DFTI_DESCRIPTOR_HANDLE
FFT descriptor.
x_inout, y_in
Array of type
float
or
double
depending on the precision of the transform, specified in the
DFTI_PRECISION
configuration setting.
Data to be transformed in case of a real backward domain, determined by the
DFTI_FORWARD_DOMAIN
configuration setting.
xre_inout, xim_inout, yre_in, yim_in
Array of type
float
or
double
depending on the precision of the transform.
Real and imaginary parts of the data to be transformed in the case of a complex backward domain, determined by the
DFTI_FORWARD_DOMAIN
configuration setting.
The suffix in parameter names corresponds to the value of the configuration parameter
DFTI_PLACEMENT
as follows:
  • _inout
    to
    DFTI_INPLACE
  • _in
    to
    DFTI_NOT_INPLACE
Output Parameters
Name
Type
Description
x_out
Array of type
float
or
double
depending on the precision of the transform.
The transformed data in case of a real forward domain, specified in the
DFTI_FORWARD_DOMAIN
configuration setting.
xre_inout, xim_inout, xre_out, xim_out
Array of type
float
or
double
depending on the precision of the transform.
Real and imaginary parts of the transformed data in the case of a complex forward domain, specified in the
DFTI_FORWARD_DOMAIN
configuration setting.
status
MKL_LONG
Function completion status.
The suffix in parameter names corresponds to the value of the configuration parameter
DFTI_PLACEMENT
as follows:
  • _inout
    to
    DFTI_INPLACE
  • _out
    to
    DFTI_NOT_INPLACE
Include Files
  • mkl.h
Description
The function accepts the descriptor handle parameter and one or more data parameters. Given a successfully configured and committed descriptor,
the DftiComputeBackward
function computes the
inverse
FFT, that is, the transform with the
plus
sign in the exponent,
δ
= +1
.
The
DFTI_COMPLEX_STORAGE, DFTI_REAL_STORAGE
, and
DFTI_CONJUGATE_EVEN_STORAGE
configuration parameters define the layout of the input and output data and must be properly set in a call to the DftiSetValue function.
The FFT descriptor must be properly configured prior to the function call. Function calls needed to configure an FFT descriptor for a particular call to an FFT computation function are summarized in Configuring and Computing an FFT in C C++ .
The number and types of the data parameters that the function requires may vary depending on the configuration of the descriptor. This variation is accommodated by
variable parameters
.
The function returns zero when it completes successfully.
See Status Checking Functions for more information on the returned status.
Prototype
      MKL_LONG DftiComputeBackward( DFTI_DESCRIPTOR_HANDLE, void *, ... );  

Product and Performance Information

1

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804