demonstrate integration with PyMumps

[gdmcbain]

A first step in demonstrating integrations #474.

This redoes the MeshTet Poisson Dirichlet problem of ex09 (currently in mind because of the regression involving solver_iter_pcg, build_pc_ilu, and MeshTet.init_tensor #469) using a parallel direct solver from PyMumps.

[gdmcbain]

[gdmcbain]

Hang on, there's more to this.

[kinnala]

Btw, that figure looks really fancy. I need to learn Paraview someday.

[gdmcbain]

Oh, O. K., I'll describe the steps; myself I need to learn to script Paraview, then that would be easy. (Hence my enthusiam for vedo #361.) Anyway, via the GUI (this on Ubuntu 20.04.1 LTS, if that makes a difference).

git checkout mumps
python docs/integrations/solver_pymumps.py 
paraview docs/integrations/solver_pymumps.xdmf &

1. ParaView pops up a dialog asking ‘Open Data With…’. Select ‘Xdmf3ReaderS’.
2. Under Properties, click Apply, which should be highlit green.
3. There's an icon which has the tooltip ‘Contour’. It looks like half an onion, but with white, blue, and green concentric coplanar hemispherical annuli. Click it.
4. Under Properties/Isosurfaces/Value Range, select and delete the default value (0.02764…).
5. Next to the white input box Value Range, there's an icon that looks like a horizontal yardstick, tooltip ‘Add a range of values’. Click that and O. K. to accept defaults.
6. Click the green highlit Apply again.
7. Next to the ‘Contour’ icon, click the ‘Clip’ icon.
8. Click the green highlit Apply again.
9. In the ‘Layout import only works in source-tree #1’ view-port, click the image with the left mouse button and drag around to see the cut surface.
10. File/Save screenshot…