[petsc-users] Getting DMDA local coordinates
Åsmund Ervik
asmund.ervik at ntnu.no
Mon Oct 21 08:05:22 CDT 2013
On 21. okt. 2013 14:42, Jed Brown wrote:
>
> The coordinates live in a different space than the DM. Why is it
> illogical to use the coordinate DM to access coordinate vectors? It is
> used in several examples, though none of them in Fortran.
>
I guess it is logical for e.g. unstructured meshes or finite elements,
but for someone like me who just wants 2/4/9 real numbers, it seems a
bit overkill to have another DM.
>
> "van der Pol" normally refers to a 2-variable ODE system (e.g.,
> src/ts/examples/tutorials/ex16.c). I assume you are talking about a
> PDE, however.
I am actually talking about that 2-variable ODE. We use it as a test
problem in several of our codes, since it is stiff and has some
"structure", but is much simpler than Euler or Navier-Stokes. In my
example I "distribute" it so that we solve the same equation at all grid
points on all processors, using the same code as a PDE solver but with a
different RHS.
I don't know whether the pattern we use is common or not, so I'll submit
a pull request and then you can see if you think this is useful for
others. Another option would be an example solving full-blown
Navier-Stokes (single phase), but that would take some more work, and I
don't know when I'll have time for that.
Åsmund
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