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.