Hey guys,

So I've implemented Larisa's smoother inside libmesh (well... I've shoehorned her code into a mesh_smoother based class and hooked everything up so it works... there is still a _lot_ of improvement left to be done) and now I'm trying to use it... I was trying to use it in mid-iteration during an explicit solve (modified example10)... and after doing the smooth I was getting an error of:

ERROR: negative Jacobian!
[0] src/fe/fe_map.C, line 312, compiled Jun  5 2006 at 20:27:59

After thinking about it for a while I decided to run mesh.prepare_for_use().  This seems to work.... but I'm kind of in the dark as to why.  What is it about moving the mesh nodes that needs prepare_for_use?  Further, is this really what I should be doing, or is there another function I should be using instead?

Thanks for the help,
Derek