The SEVERITY Procedure

Multithreaded Computation

PROC SEVERITY attempts to use all the computational resources of the machine where SAS is running in order to complete the estimation tasks as fast as possible. This section describes the options that control the use of multithreading by PROC SEVERITY.

Threading refers to the organization of computational work into multiple tasks (processing units that can be scheduled by the operating system). A task is associated with a thread. Multithreading refers to the concurrent execution of threads. When multithreading is possible, substantial performance gains can be realized compared to sequential (single-threaded) execution.

The number of threads spawned by the SEVERITY procedure is determined by the number of CPUs on a machine. You can control the number of threads by specifying either the CPUCOUNT= or the NOTHREADS SAS system option.

  • You can specify the CPU count with the CPUCOUNT= SAS system option. For example, if you specify the following statement, then PROC SEVERITY schedules threads as if it executed on a system with four CPUs, regardless of the actual CPU count:

    options cpucount=4;

    On most systems, the default value of the CPUCOUNT= system option is set to the number of actual CPU cores available for processing.

  • If you do not want PROC SEVERITY to use multithreading, then you can turn off the THREADS SAS system option by specifying the following statement:

    options nothreads;

    On most systems, the THREADS option is turned on by default.

You can examine the current settings of these system options in the SAS log by submitting the following PROC OPTIONS step:

proc options option=(threads cpucount);