You can set the number of threads using the environment variable OMP_NUM_THREADS. To change the number of OpenMP threads, in the command shell in which the program is going to run, enter:
set OMP_NUM_THREADS=<number of threads to use>.
Some shells require the variable and its value to be exported:
export OMP_NUM_THREADS=<number of threads to use>.
You can alternatively assign value to the environment variable using Microsoft Windows*OS Control Panel.