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Melih March 17, 2004 08:33

performance problem in P4 2Ghz
Hi everone,

I have a problem about increasing the performance of FLUENT in Windows 2000 Professional.

I was running a job in Windows Celeron 1.7Ghz 512 KB ram (the system was Windows XP). The CPU time per time step was around 30 seconds. When I looked the task manager, I saw that FLUENT was using 100 per cent of CPU and RAM.

Then, I put the same job in a much faster computer(it was P4 2GHZ), but in another system Windows 2000 professional. What I saw was a nonsense, because the CPU time was almost the same(around 25 seconds)!!!!.When I looked the task manager, I found out the problem. In that case FLUENT was using 50 percent CPU and 300 KB RAM. No matter I tried, I could not increase the performance of FLUENT even 1 per cent (for example, I changed the prority of FLUENT above normal in the task manager). So, could you please give me some advise? Should I change the system back to XP, or is there a way to increase the CPU and RAM usage in Windows 2000?

Thanks in advance...Best regards...

ozgur March 17, 2004 08:54

Re: performance problem in P4 2Ghz

Does your CPU has "Hyper Treating" feature? If so, then even you have physically 1 CPU, it behaves like there are 2 virtual CPUs. Try to run Fluent in parallel mode with 2 processors. If it does not work, disable hyper treating from the bios, and run fluent (not in parallel mode this time).


Melih March 17, 2004 09:23

Re: performance problem in P4 2Ghz
Hi Ozgur,

Thanks for your help. I tried your second advise since I don't know how to run FLUENT in parallel mode.

You were right!!!I disabled the Hyper Treating feature in BIOS. Now the CPU usage is full. And the time, required for convergence per time step, decreased to 20 seconds. Although the CPU usage is full, memory usage is still 300 KB. If I am able to increase the memory usage for FLUENT (more then 300K,because I have still 1.7 GB free), can the required time for convergence decrease much more? Because, I think the diference between the Celeron 1.7 Ghz 512 KB and the P4 2.8 Ghz 2GB should be much more. Do you or does anybody know how to increase the RAM usage for a FLUENT job in Windows 2000 professional?


ozgur March 17, 2004 10:34

Re: performance problem in P4 2Ghz

Maybe your simulation problem is not a memory intensive one, so that only 300 mb of the memory is used. If you start Fluent with the following command, then you are in parallel solver:

fluent 2ddp -t 2

2ddp means 2d solver with double precision. If you dont want dp and your case is 3D, then change it to:

fluent 3d -t 2


Gamma23 March 17, 2004 15:05

Re: performance problem in P4 2Ghz
it is quite impossible to increase the RAM usage in order to decrease the CPU time. The RAM usage quantity basically depends on your model setup and your mesh resolution. Of course, floating point mode will also increase the RAM usage. You don't have to add more RAM if your task manager showing that your current RAM usage is less than your physical memory available. However, if vice versa, you'll find that even with p4 3.0GHz, it will act slow.

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