Developer Reference

Contents

Configuration Settings

Each of the configuration parameters is identified by a named constant in the
MKL_DFTI
module.
These
named constants have the enumeration type
DFTI_CONFIG_PARAM
.
All the
Intel® MKL
FFT configuration parameters are readable. Some of them are read-only, while others can be set using the
DftiCreateDescriptor
or
DftiSetValue
function.
Values of the configuration parameters fall into the following groups:
  • Values that have native data types. For example, the number of simultaneous transforms requested has an integer value, while the scale factor for a forward transform is a single-precision number.
  • Values that are discrete in nature and are provided in the
    MKL_DFTI
    module as named constants. For example, the domain of the forward transform requires values to be named constants.
    The
    named constants for configuration values have the enumeration type
    DFTI_CONFIG_VALUE
    .
The Table
"Configuration Parameters"
summarizes the information on configuration parameters, along with their types and values. For more details of each configuration parameter, see the subsection describing this parameter.
Configuration Parameters
Configuration Parameter
Type/Value
Comments
Most common configuration parameters, no default, must be set explicitly by
DftiCreateDescriptor
Named constant
DFTI_SINGLE
or
DFTI_DOUBLE
Precision of the computation.
Named constant
DFTI_COMPLEX
or
DFTI_REAL
Type of the transform.
Integer scalar
Dimension of the transform.
Integer scalar/array
Lengths of each dimension.
Common configuration parameters, settable by
DftiSetValue
Named constant
DFTI_INPLACE
or
DFTI_NOT_INPLACE
Defines whether the result overwrites the input data. Default value:
DFTI_INPLACE
.
Floating-point scalar
Scale factor for the forward transform.
Default value: 1.0.
Precision of the value should be the same as defined by
DFTI_PRECISION
.
Floating-point scalar
Scale factor for the backward transform.
Default value: 1.0.
Precision of the value should be the same as defined by
DFTI_PRECISION
.
Integer scalar
This configuration parameter is no longer used and kept for compatibility with previous versions of
Intel® MKL
.
Integer scalar
Limits the number of threads for the DftiComputeForward and DftiComputeBackward .
Default value: 0.
DFTI_DESCRIPTOR_NAME
Character string
Assigns a name to a descriptor. Assumed length of the string is
DFTI_MAX_NAME_LENGTH
.
Default value: empty string.
Data layout configuration parameters for single and multiple transforms. Settable by
DftiSetValue
Integer array
Defines the input data layout.
Integer array
Defines the output data layout.
Integer scalar
Number of transforms.
Default value: 1.
Integer scalar
Defines the distance between input data sets for multiple transforms.
Default value: 0.
Integer scalar
Defines the distance between output data sets for multiple transforms.
Default value: 0.
Named constant
DFTI_COMPLEX_COMPLEX
or
DFTI_REAL_REAL
Defines whether the real and imaginary parts of data for a complex transform are interleaved in one array or split in two arrays.
Default value:
DFTI_COMPLEX_COMPLEX
.
Named constant
DFTI_REAL_REAL
Defines how real data for a real transform is stored. Only the
DFTI_REAL_REAL
value is supported.
Named constant
DFTI_COMPLEX_COMPLEX
or
DFTI_COMPLEX_REAL
Defines whether the complex data in the backward domain of a real transform is stored as complex elements or as real elements.
For the default value, see the detailed description.
Named constant
DFTI_CCE_FORMAT, DFTI_CCS_FORMAT, DFTI_PACK_FORMAT
, or
DFTI_PERM_FORMAT
Defines the layout of real elements in the backward domain of a one-dimensional or two-dimensional real transform.
Advanced configuration parameters, settable by
DftiSetValue
Named constant
DFTI_ALLOW
or
DFTI_AVOID
Defines whether the library should prefer algorithms using additional memory.
Default value:
DFTI_ALLOW
.
Named constant
DFTI_ORDERED
or
DFTI_BACKWARD_SCRAMBLED
Defines whether the result of a complex transform is ordered or permuted.
Default value:
DFTI_ORDERED
.
Read-Only configuration parameters
Named constant
DFTI_UNCOMMITTED
or
DFTI_COMMITTED
Readiness of the descriptor for computation.
DFTI_VERSION
String
Version of
Intel® MKL
. Assumed length of the string is
DFTI_VERSION_LENGTH
.

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