The value of this paramter is a non-zero, positive integer in the range of 1 to 16.
If a computer has more than one processor, many programs are designed to use only one processor at a time. This type of program is referred to as being "single threaded". TANDEM is designed to use multiple processors simultaneously to increase the speed of the calculation: this type of program is referred to as "multithreaded".
TANDEM is written to be quite efficient at utilizing any processor as much as possible. Therefore, using multiple threads is only helpful if there are spare processors available: using more than one thread per processor may actually decrease performance. Also, each thread requires the same amount of memory, so running an unnecessarily large number of threads can produce problems resulting using more memory than a processor has available to it.
X! TANDEM API description project