Re: faceVariable missing copy method

On Jul 11, 2008, at 8:11 PM, Tony S Yu wrote:

> I think `faceVariable` may be missing a `copy` method. I've included  
> a patch below, which is basically a copy of `cellVariable`'s `copy`  
> method (minus it's `hasOld` attribute and changing the rename from +  
> '_old' to + '_copy').

We've never needed it, which is why it never got written, but I don't  
see that it's harmful in anyway.

> Also, the patch includes a fix for matplotlib2DViewer.py, which has  
> changed since I originally submitted the patch.

Thanks for that.

Both of these are committed as r2670.

> In case you're curious about a use case: I wanted to set *almost*  
> all of the exterior faces to a no flux boundary condition. So I  
> naturally I tried
>
> >>> no_flux_faces = mesh.getExteriorFaces()
> >>> no_flux_faces.setValue(array[False], where=faces_with_other_BC)
>
> But it turns out the above commands change the faces that the mesh  
> recognizes as exterior

I would have implemented this as

 >>> no_flux_faces = mesh.getExteriorFaces() & ~faces_with_other_BC

> (`getExteriorFaces` doesn't automatically copy; for performance  
> reasons, maybe?).

Yes. I have it on my to-do list to re-implement a great many things  
like `getExteriorFaces()` with read-only descriptors.

> But, `faceVariable`'s `copy` method defaults to `Variable`'s `copy`  
> method. As a result, the copied variable doesn't have a `mesh`  
> attribute.

That's certainly no good.