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Old   March 30, 2005, 13:07
Default Dual processor system
Allan Walsh
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We just upgraded to a dual processor workstation to run Fluent on, under Windows. We are working with Fluent to upgrade our license so that we can use the second processor, I guess by running the parallel version of Fluent.

When I run a serial version of Fluent on the dual processor workstation, and look in with Windows Task Manager, I see that Fluent is using both processors, but each processor is limited to about 50% (typically 50% to 53%).

So, first, why is each processor only limited to half? And, second, what advantage is there to running the parallel version if the serial version can already use both processors?

I know hyperthreading will limit Fluent to only 50% of processor use, but hyperthreading has been disabled in BIOS.
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Old   March 30, 2005, 13:16
Default Re: Dual processor system
Evan Rosenbaum
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Running serial on a dual-CPU box swaps the process back and forth between the two processors. If you use PERFMON to monitor the load on each CPU, you see that one is up when the other is down. The serial version will never use more than 50% of each CPU (on average).

The advange of parallel is, therefore, that you can use ~100% of each CPU.
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Old   March 31, 2005, 04:34
Default Re: Dual processor system
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If you are running Windoze it is easy to set the solver process affinity (use the Task Damager, right click on the solver process and set the affinity) so that the single solver process runs on one CPU only. That will give you nearly 100% on one CPU and 0 on the other. I'm not sure that doing this helps at all. Parallel is the obvious way to go.
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Old   March 31, 2005, 14:39
Default Re: Dual processor system
Allan Walsh
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Thanks guys for the comments. After spending some more time looking at it, and getting input from Fluent support, I started getting the impression I was being misled by Windows Task Manager.
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