how to deal with the cpu's cores and parallel program

i have a 64 cores workstation. a parallel program need 8 cores when running. when I use to Matlab run this program twice（16 cores needed) . The cores which the tow programs are using are the same? that is to say ,the second program's 8 cores are the same 8 cores with the first one?

by the way ,any way to control? or not thank you for your answer.

[Walter Roberson]

How do you run the program twice?