Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

DftiComputeForward

Computes the forward FFT.

Syntax

status
=
DftiComputeForward
(
desc_handle
,
x_inout
)
;
status
=
DftiComputeForward
(
desc_handle
,
x_in
,
y_out
)
;
status
=
DftiComputeForward
(
desc_handle
,
xre_in
out,
xim_inout
)
;
status
=
DftiComputeForward
(
desc_handle
,
xre_in
,
xim_in
,
yre_out
,
yim_out
)
;
Input Parameters
Name
Type
Description
desc_handle
DFTI_DESCRIPTOR_HANDLE
FFT descriptor.
x_inout, x_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 forward domain, specified in the
DFTI_FORWARD_DOMAIN
 configuration setting.
xre_inout, xim_inout, xre_in, xim_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 forward domain, specified in 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
y_out
Array of type
float
 or
double
 depending on the precision of the transform.
The transformed data in case of a real backward domain, determined by the
DFTI_FORWARD_DOMAIN
 configuration setting.
xre_inout, xim_inout, yre_out, yim_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 backward domain, determined by 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
DftiComputeForward
 function accepts the descriptor handle parameter and one or more data parameters. Given a successfully configured and committed descriptor, this function computes the forward FFT, that is, the transform with the minus 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 DftiComputeForward( DFTI_DESCRIPTOR_HANDLE, void*, ... ); 

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.