Intel® Math Kernel Library 2018 Developer Reference - C
The computation step for some FFT algorithms requires a scratch space for permutation or other purposes. To manage the use of the auxiliary storage, Intel MKL enables you to set the configuration parameter DFTI_WORKSPACE with the following values:
DFTI_ALLOW |
(default) Permits the use of the auxiliary storage. |
DFTI_AVOID |
Instructs Intel MKL to avoid using the auxiliary storage if possible. |