FORWARD_DISTANCE and BACKWARD_DISTANCE¶
The FFT interface enables computation of multiple transforms. To compute multiple transforms, you need to specify the data distribution of the multiple sets of data. The distance between the first data elements of consecutive data sets, FORWARD_DISTANCE for forward domain data or BACKWARD_DISTANCE for backward domain data, specifies the distribution. The configuration setting is a value of std::int64_t data type.
The default value for both configuration settings is one. You must set this parameter explicitly if the number of transforms is greater than one (see Number of Transforms ).
The distance is counted in elements of the data type defined by the descriptor configuration (rather than by the type of the variable passed to the computation functions). Specifically, the domain template parameter, and the COMPLEX_STORAGE, REAL_STORAGE and CONJUGATE_EVEN_STORAGE configuration parameters described in Storage Formats define the type of the elements as shown in the complex_storage, real_storage and conjugate_even_storage tables.
For in-place transforms ( PLACEMENT=INPLACE ), the configuration set by FORWARD_DISTANCE and BACKWARD_DISTANCE should be consistent, that is, the locations of the data sets for input and output must coincide.
Parent topic: Configuration Parameters and Enums