[CIG-SHORT] Intermediate Results

Sun Mar 10 12:56:12 PDT 2013

Hi Bobby,

Are all of the solutions converging (both linear and nonlinear)?  I would have to look more at the different solution settings to see which of the two you've shown is more reasonable.

Cheers,
Charles

On 9/03/2013, at 6:11 AM, BOK10 at pitt.edu wrote:

> Thanks! I tried a mixture of those suggestions, and i was able to get it
> to reduce its runtime by half.
> 
> I do have a question regarding the most suitable ksp/snes tolerances though:
> 
> I ran two simulations. The first had the following:
> 
> for the fault zero_tolerance = 1e-12
> ksp_rtol/snes_rtol = 1e-20
> ksp_atol = 1e-13
> snes_atol = 1e-11
> 
> The second had this:
> 
> for the fault zero_tolerance = 1e-14
> ksp_rtol/snes_rtol = 1e-20
> ksp_atol = 1e-15
> snes_atol = 1e-13
> 
> What I'm trying to do is look at the time it takes for certain portions of
> my fault to rupture >1m. Running both simulations, I got wildly different
> results, and I'm not sure which to rely on at this point. Is there any
> insight you might be able to give me regarding the best tolerances to
> settle on?
> 
> Bobby
> 
> 
>> Hmm.  It sounds to me as though you need to play with your parameters a
>> bit.  I'm assuming you're using a frictional fault, which can definitely
>> take a while to converge; however, you can do a few things to speed things
>> up:
>> 
>> 1.  Follow all of the suggestions Brad had from his previous e-mail.
>> 2.  Make sure you have the highest quality mesh you can get.  Just one
>> poorly formed element, especially on the fault, can really slow things
>> down.
>> 3.  Possibly try reducing your time step size.  It's possible that your
>> load increment per timestep is too high for reasonable convergence.
>> 
>> When you have a chance, I would see if you can build PyLith from source on
>> your cluster.  In addition to allowing parallel runs, this will let you
>> take advantage of any machine-specific tools (e.g., optimized math
>> libraries, etc.).
>> 
>> Let us know whether any of this helps.
>> 
>> Cheers,
>> Charles
>> 
>> 
>> On 7/03/2013, at 12:15 PM, BOK10 at pitt.edu wrote:
>> 
>>> Hi Charles,
>>> 
>>> I'm not running in parallel (I couldn't get the model to process in
>>> parallel on the cluster). Each time step takes ~80 minutes with loose
>>> tolerances, and about 2 hours for tighter tolerances.
>>> 
>>> The mesh itself is about 6,000 cells (2D). The faults have a 2 km
>>> discretization, and the boundaries have a 5 km discretization. Im using
>>> elasticplanestrain.
>>> 
>>> Bobby
>>> 
>>>> What sort of machine are you running on, and are you running in
>>>> parallel?
>>>> I'm not sure what your problem size is, but 80 time steps shouldn't
>>>> take
>>>> that long to run, unless it's a very nonlinear problem.  How large is
>>>> your
>>>> mesh, and what sort of rheology are you using?
>>>> 
>>>> Cheers,
>>>> Charles
>>>> 
>>>> 
>>>> On 7/03/2013, at 11:36 AM, BOK10 at pitt.edu wrote:
>>>> 
>>>>> Hi Charles,
>>>>> 
>>>>> It takes pretty long for a simulation to finish processing, and I was
>>>>> hoping to split the simulation up into parts so I can come back to it
>>>>> later. It's not a necessity, but more a convenience issue.
>>>>> 
>>>>> I think I'll just continue on with running it overnight.
>>>>> 
>>>>> Thanks,
>>>>> Bobby
>>>>> 
>>>>> 
>>>>> 
>>>>>> Hi Bobby,
>>>>>> 
>>>>>> I'm not quite sure what you have in mind.  If you're running any sort
>>>>>> of
>>>>>> viscoelastic problem, you would need to save the entire state at the
>>>>>> end
>>>>>> of each run.  I don't see what benefit there would be from doing
>>>>>> this,
>>>>>> since you would still need to finish each run to get all the state
>>>>>> variables at the end of each chunk, and then feed them into the next
>>>>>> simulation as initial state variables.
>>>>>> 
>>>>>> If your problem is completely elastic, I suppose you could run them
>>>>>> in
>>>>>> the
>>>>>> way you're suggesting, and then use linear superposition to obtain
>>>>>> the
>>>>>> final result.  What is your reason for wanting to break up the
>>>>>> simulation?
>>>>>> 
>>>>>> Cheers,
>>>>>> Charles
>>>>>> 
>>>>>> 
>>>>>> On 7/03/2013, at 11:22 AM, BOK10 at pitt.edu wrote:
>>>>>> 
>>>>>>> Is it possible to split a simulation into parts? I'm running my
>>>>>>> model
>>>>>>> for
>>>>>>> 400 years at 5 year time intervals, but is it possible to split it
>>>>>>> to
>>>>>>> 100
>>>>>>> year chunks and run them serially?
>>>>>>> 
>>>>>>> Bobby
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> 
>>>>>>> _______________________________________________
>>>>>>> CIG-SHORT mailing list
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>>>>>> 
>>>>>> Charles A. Williams
>>>>>> Scientist
>>>>>> GNS Science
>>>>>> 1 Fairway Drive, Avalon
>>>>>> PO Box 30368
>>>>>> Lower Hutt  5040
>>>>>> New Zealand
>>>>>> ph (office): 0064-4570-4566
>>>>>> fax (office): 0064-4570-4600
>>>>>> C.Williams at gns.cri.nz
>>>>>> 
>>>>>> 
>>>>>> Notice: This email and any attachments are confidential.
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>>>>>> 
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>>>>> 
>>>>> 
>>>>> _______________________________________________
>>>>> CIG-SHORT mailing list
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>>>> 
>>>> Charles A. Williams
>>>> Scientist
>>>> GNS Science
>>>> 1 Fairway Drive, Avalon
>>>> PO Box 30368
>>>> Lower Hutt  5040
>>>> New Zealand
>>>> ph (office): 0064-4570-4566
>>>> fax (office): 0064-4570-4600
>>>> C.Williams at gns.cri.nz
>>>> 
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>>> 
>>> 
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>> 
>> Charles A. Williams
>> Scientist
>> GNS Science
>> 1 Fairway Drive, Avalon
>> PO Box 30368
>> Lower Hutt  5040
>> New Zealand
>> ph (office): 0064-4570-4566
>> fax (office): 0064-4570-4600
>> C.Williams at gns.cri.nz
>> 
>> _______________________________________________
>> CIG-SHORT mailing list
>> CIG-SHORT at geodynamics.org
>> http://geodynamics.org/cgi-bin/mailman/listinfo/cig-short
> 
> 

Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt  5040
New Zealand
ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz

Notice: This email and any attachments are confidential.
If received in error please destroy and immediately notify us.
Do not copy or disclose the contents.

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