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Old   May 22, 2003, 07:33
Default Memory
  #1
Christian Cordeiro
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Hello, I am having a lot of problems of CPU memory and the solve time in my simulation. My model have the following characteristic:

3 fluids Inlet with equation 1 000 000 elements This model is using 900M of virtual memory and 150M of Ram memory. Is it ok ? I try interpolate this model with other model with less elements and try use initial values but the problem is pass the first interaction. What are the rules to interpolate and to use initial value ? Some suggestion ? What is the best way to build a final model ?

Thank you
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Old   May 24, 2003, 08:12
Default Re: Memory
  #2
zahid
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Hi Christian Cordeiro I think you should increase RAM of your PC. Use at least 1 GB RAM. I am using Pentium 4, 1.7 GH processor with 1 GB RAM and its performance is satisfactory. I have not properly understood your second question. What do you mean by 'problem is pass the first interaction'? Please explain so that I can help you. Also mention the software you are using. Best regards.
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Old   May 26, 2003, 07:37
Default Re: Memory
  #3
Christian Cordeiro
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Thank you.

Ok, I will increase RAM. I work with the CFX 5.5.1. About the 'problem', when the CFX is solving the simulation, the steps are very slow but I think is because the RAM.

Thank you again.
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Old   May 26, 2003, 10:33
Default Re: Memory
  #4
zxaar
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dear people,

i don't know how much it is relevent to this conversation but still i observed it so i am mentioning it.

when i used to work with CFX4.4, i observed for many times that if i stop the iteration and try to give run again. it used to give me some error. in the start i thought i have done some change in command file that these errors are coming. but soon (since i was confident that whatever changes i made are correct) i made conclusion that these errors are because of memory. cfx doesn't release the memory it used in last run, so to handle it what i did is restarted the machine and viola things are running again without error messages. hope this might help somewhere (this helped me a lot , since i knew when it is giving me bogus errors).
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Old   May 26, 2003, 12:36
Default Re: Memory
  #5
Robin
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zhaar: This not a problem with CFX-5 and should not be happening with CFX-4 if you shut it down properly.

Christian: CFD is memory intensive. If you are running into swap space you are guaranteed to have problems.

Robin
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Old   May 27, 2003, 11:15
Default Re: Memory
  #6
zxaar
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well after using it for 2 years (with cfx4.3 and 4.4) i think i understood it how to shutdown properly.

anyway, the prob seems to be with my machine and operating system (or interaction of cfx with OS which was WinNT), but i can't say much since i haven't seen it running on other machines and OS. and when i say it doesn't release memory, it means for the bigger cases (involving more than 200 000 nodes), what i felt is, once the run is given the memory is booked , and when it is over, the memory is not freed properly (it needs good chunk of memory for runnign such case) so if i want to run as bug case again, it may be short of memory (as it used to happen and will not happen for small cases). so to do that i needed restarts (and they used to run next time, without probs).
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Old   May 28, 2003, 06:13
Default Re: Memory
  #7
cfd guy
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Swap means Hard Disk Space used to create a virtual memory. If you're running cfd calculations on virtual memory it is expected to obtain very slow solving iterations. Remember, physical memory is much more faster than virtual one. So I'd buy some RAM in your case, or I'd try to use a coarser grid.


Good luck! cfd guy
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Old   June 3, 2003, 07:49
Default Re: Memory
  #8
Nyatoto
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Hi cfd guy,

I wonder whether this belongs here... sorry if it doesnt.

What is this bug that holds the memory or canvas window such that the canvas window does not close if the cap lock is on? I have seen it on and off with CFX4.4 Windows NT, however,I have not seen it with CFX5.5.1.

regards nyatoto
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Old   June 6, 2003, 04:49
Default Re: Memory
  #9
cfd guy
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Nyatoto,
Basically was because CFX-4 was compiled in UNIX you needed an Unix emulator to use it, Hummingbird Exceed. Look, it is not a Exceed problem, at least I think so. This Caps Lock bug sure pissed of a lot of CFX-4 customers in the past.

CFX-5 uses QT as GUI, I think. And you can compile it in multiplatforms. That's why you don't have a caps lock bug, but sure you have other ones.

Regards, cfd guy
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Old   June 11, 2003, 08:12
Default Re: Memory
  #10
Nyatoto
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Hi cfdguy,

Thanks for that useful information.

regards Nyatoto
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