In some situations you may need to limit the number of threads that the

DftiComputeForward

and

DftiComputeBackward

functions use. For example, if more than one thread calls

Intel® oneAPI Math Kernel Library

, it might be important that the thread calling these functions does not oversubscribe computing resources (CPU cores). Similarly, a known limit of the maximum number of threads to be used in computations might help the

DftiCommitDescriptor

function to select a more optimal computation method.

Set the parameter

DFTI_THREAD_LIMIT

as follows:

On an attempt to set a negative value, the

DftiSetValue

function returns an error and does not update the descriptor.

The value of the

DFTI_THREAD_LIMIT

configuration parameter returned by the

DftiGetValue

function is defined as follows:

1 if

Intel® oneAPI Math Kernel Library

runs in the sequential mode

Depends of the commit status of the descriptor if

Intel® oneAPI Math Kernel Library

runs in a threaded mode:

Commit Status	Value
Not committed	The value of DFTI_THREAD_LIMIT set in a previous call to the DftiSetValue function or the default value
Committed	The upper limit on the number of threads used by the DftiComputeForward and DftiComputeBackward functions

To better understand the use of the

DFTI_THREAD_LIMIT

configuration parameter, see this example in your

Intel® oneAPI Math Kernel Library

directory: