cannot allocate memory

Having problems running the WRF Preprocessing Sysmte (WPS)?

cannot allocate memory

Postby stormlab » Fri Apr 11, 2014 3:14 pm

Hello,

The program real.exe 3.5.1 show error:

"Cannot allocated memory"

Obviously the RAM is not enough. I tried with ulimit -s unlimited and ulimit -s 10000000000, added and swap file. May be the problem is in the 32-bit Linux memory limit, but as I know the swap should work, even slower, on much larger domains like 500x500,1000x1000, obviously the real.exe cannot use it. Do you know if it's possible to run large domain on swap, I can wait a week to calc it.

Angel
stormlab
 
Posts: 11
Joined: Wed Nov 21, 2012 3:18 pm

Re: cannot allocate memory

Postby Phillip » Wed Apr 16, 2014 12:26 pm

I remember doing a simulation where the memory was too small without any error. It was just so much slower, that I immediately terminated it. Not sure if your problem is directly related to that or if there is a workaround for 32 bit systems.

Just to give you an example: My RAM is capable of transferring up to 20 GB/s, my SSD manages up to 250 MB/s, my normal HD transfers between 30 and 50 MB/s. So if you need 6 GB of memory and only have 4 GB, the model will have to read and write more than 2 GB for every time step. It will be much more in reality.

I could be wrong but in my opinion one week is not even close to what you will have to wait, depending on the length of the simulation and the time step. When it happened to me, my calculation speed dropped from around 4 seconds down to over 100 seconds per time step.

Is that really your error message or is it more detailed?
Phillip
 
Posts: 46
Joined: Thu Jul 19, 2012 3:29 am

Re: cannot allocate memory

Postby stormlab » Wed Apr 16, 2014 2:26 pm

Hello Phillip,

The 32-bit is relatively easy to upgrade. The swap was added as a file, not as a partition. My wrf.exe don't uses the swap. I don't know why. Even very slow, it's okay. Just to experiment.

Angel
stormlab
 
Posts: 11
Joined: Wed Nov 21, 2012 3:18 pm


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