Multicore Settings

COMSOL supports two modes of parallel operation: shared-memory parallel operations and distributed-memory parallel operations, including cluster support. This section covers shared-memory processing, or multithreading, which is important for the performance of COMSOL computations. Some terms that are frequently used when describing multithreading are:

•	Core: The core is a processor core used in shared-memory parallelism by a computational node with multiple processors.

•	Speedup is how many times faster a job runs on N cores compared to 1 core, on a specific compute node. The speedup depends on the simulation type, the hardware used, and hardware drivers used.

In Windows, the default number of processor cores used by COMSOL is the total number of available physical cores. For example, if you have a 2 x dual core machine, 4 cores are used in parallel by a COMSOL process.

Here is how to find out how many processor cores your Windows machine has:

Window 8 And Later

1	Start the Windows Task Manager (press Ctrl-Shift-Esc or right-click the taskbar and choose Start Task Manager).

2	On the Performance page, click CPU. The number of cores can be seen as the number next to Cores.

Windows 7 and Windows Vista

1	In the Windows file browser, right-click Computer or My Computer, select Properties.

2	Click Advanced system settings. Go to the Advanced tab.

3	Click the Environment Variables button and look in the System variables list. Look for NUMBER_OF_PROCESSORS and check its value. This is actually the number of cores. If you have two processors with 2 cores each, this number is 4. Alternatively, start a Windows command window and type

WMIC CPU Get DeviceID,NumberOfCores

If you want COMSOL to leave out one or more processor cores you can set the number of cores used for a computational job in the Preferences dialog box on the Multicore and Cluster Computing page (by first selecting the Number of cores check box and then entering the number of processor cores to use).

You can also change the default behavior of COMSOL by setting the environment variable COMSOL_NUM_THREADS to the desired number of cores. See the COMSOL Multiphysics Reference Manual for more information.