[MITgcm-support] mnc output

[Yosef Ashkenazy]

Hi Ed,

Thank you very much for your suggestions. Indeed, it is possible to 
break the long run into pieces and to start each time from a pickup 
file. However, since my simulations are really long (~80kyr), it is not 
so convenient.
The problem is not related to large memory size since my output files 
are much smaller than 2GB.
I built a very simple configuration to test this problem; a simple 4x4 
box with two vertical layers. It turns out that the problem is related 
to the time step rather than to the actual time of the simulation. 
Please have a look at this test case :
http://www.bgu.ac.il/~ashkena/temp/
You will find there a very short matlab code that demonstrates the 
problem and the entire configuration with the results. I hope we can 
solve this strange problem.

Many thanks,

Yossi

Ed Hill wrote:

>On Tue, 2006-01-24 at 09:20 +0200, Yosef Ashkenazy wrote:
>  
>
>>Hi,
>>
>>Currently I'm performing long runs of the MITgcm. I'm using the mnc 
>>package. After relatively long time of simulation (~19200 years) the 
>>model starts to produce three or four times the same output at each 
>>output point (instead of single output). Do anyone faced this problem 
>>before ? Any suggestions ?
>>    
>>
>
>Hi Yossi,
>
>I've never seen what you describe.  Thats odd.
>
>Could you try the following:
>
> - Run the model from a pickup so that the simulation 
>   time per run is shorter
>
> - Are your output files growing close to or perhaps beyond 
>   2GB in size?  Large files can cause problems with netCDF 
>   and other libraries if they aren't compiled with the 
>   proper large-file-support.  There are various settings that 
>   you can use to decrease the number of time steps saved in 
>   each file such as:  mnc_max_fsize
>
>http://mitgcm.org/r2_web_testing/latest/online_documents/node254.html
>
>If none of the above helps, the best way to track down this problem is
>to create a scenario that repeatedly triggers the problem.  So if all
>else fails, please create a setup that triggers this problem and then we
>can (hopefully) have you send it to us and we'll pick it apart.
>
>Ed
>
>  
>