By default, the maximum number of threads are used.  To reduce this number, use THREADS=n, where n is the number of threads to be used.

If n is greater than the maximum, it will be re-set to the maximum.  If n is less than 1 it will be re-set to 1.

The maximum number of threads is normally equal to the number of cores, even if each core supports two threads.

In the special case of THREADS=1, parallelization is switched off.

See also NOGPU.