[CIG-SHORT] pylith time stepping

[Christopher DiCaprio]

It looks like the problem with the data files occurs when
total_time / max_dt  < output.skip

- Chris


On May 12, 2009, at 6:45 AM, Brad Aagaard wrote:

> Chris-
>
> As Charles noted, the time step for the Maxwell model is independent  
> of the deformation rate, so the adaptive time step is uniform. It  
> does depend on the Maxwell time. The time step for an elastic  
> material is infinite (actually 1.0e+30); any time step gives a  
> numerically stable solution. If you use an elastic material with  
> adaptive time stepping, the time step is 1.0e+30, so the number of  
> time steps is being rounded off to 0. The output manager currently  
> uses the number of time steps as a flag to decide whether it is  
> writing "info" or "data". If the number of time steps is 0, it  
> thinks it is writing "info".
>
> The adaptive time stepping correctly writes "data" files when using  
> a Maxwell model. See examples/3d/hex8/savageprescott.cfg.
>
> Brad
>
>
> Charles Williams wrote:
>> At present, the automatic time stepping is controlled purely by the  
>> Maxwell time (for viscoelastic materials).  Since the current  
>> viscoelastic materials are all linear, the time step size is  
>> independent of the deformation rate.  Once we include nonlinear  
>> materials (e.g, power-law rheology), this will no longer be true.
>> We will have to look at the second thing you mention.  I don't  
>> think we had noticed that before.
>> Thanks,
>> Charles
>> On 12/05/2009, at 3:55 PM, Christopher DiCaprio wrote:
>>> Hi,
>>>
>>> It's not clear to me what is supported for the nonuniform,  
>>> automatic  time stepping. The release notes for 1.3.0 say "For the  
>>> current bulk  constitutive models, the automatically determined  
>>> time step is  independent of the deformation rate, so it is  
>>> uniform."
>>>
>>> The release notes for 1.3.1 don't mention time stepping, but the   
>>> manual implies that there is support for non-uniform time steps.
>>>
>>> One other thing: when using nonuniform, automatic time stepping,  
>>> the  *_info.vtk files are overwritten with what should go in the   
>>> *_t0000.vtk files. This doesn't happen when using user-specified  
>>> time  stepping.
>>>
>>> Thanks,
>>> Chris
>>>
>>>
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>> Charles A. Williams
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