On Sat, 19 Jan 2008, David Knezevic wrote:

> Roy and John: Thanks for the suggestions.
>
>>> Would it be possible to get all the values you'll need from tau_system
>>> before-hand?  Depending on the size of the problem, and assuming you
>>> could also need multiple values per quadrature point, that might not be
>>> feasible.  I'm not sure how you'd store them all either.
>>>
>>> The benefit would be you wouldn't have to worry about the initialization
>>> states of two different systems at the same time...
>
> In my case it would be possible to store the tau solution data in a
> vector. I'm not sure of the best way to index that vector within
> element_time_derivative though. Assuming the same quadrature rule is
> used in both systems, I suppose one could keep a counter (as a member
> variable in NavierSystem) that is incremented at each new quadrature
> point, and use that to index the tau data?

Only if you're very clever or very lucky.  Half the point of breaking
out element_time_derivative, element_constaint, etc. from a global
assembly function is that library code is no longer limited to calling
them once per element in order.  A trapezoidal rule time integration
calls each _time_derivative once at both the beginning and the end of
the timestep, for example; you'd have to somehow realize that you were
hitting each point twice.
---
Roy

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