FYI, I have pushed this fix into master. And to help searchers here is the syntax change:
-pc_gamg_square_graph false --> -pc_gamg_square_graph 0 -pc_gamg_square_graph true --> -pc_gamg_square_graph 1 -pc_gamg_square_graph true --> -pc_gamg_square_graph 100 // pre January 2015 behavior: square infinity levels Mark On Sat, May 2, 2015 at 8:28 AM, Mark Adams <[email protected]> wrote: > BTW, I have pushed a fix in mark/gamg-square. The parameter is now an > integer. You will want at least 2. Inf should give you the old, pre > January, semantics. > Mark > > On Thu, Apr 30, 2015 at 3:10 PM, Mark Adams <[email protected]> wrote: > >> >> >>> Yes, thanks, this is the change. If I switch back to using the square >>> of the adjacency graph on all levels then I recover the previous >>> behaviour. Mark, any comments? >>> >>> >> The intent here is that you need to get faster coarsening on most >> problems, especially not high order discretizations. After the first coarse >> grid the number of non-zeros increases and this seems to be enough to >> coarsen a good rate for the problems that I test: lowish order FE elements >> (8 and maybe 27 node hexes). >> >> You have about 10 non-zeros per row. This is very low and squaring is >> not even really enough. BTW, if you can add fake zeros to make a large >> stencil and use a negative threshold value, GAMG will use that fake graph >> for coarsening, that is, it will not drop the zeros from the coarsening >> graph. >> >> BTW, I hated making this change for this reason but made a mistake in >> implementing this. I was always intending to do turn the squaring off >> after the first level, but realized earlier this year that I was not >> turning it off. >> >> Anyway, I would suggest that we turn the square graph argument into an >> integer for the number of levels that you want. Zero would be like false, >> one would be like true, and then you can add what you want. >> >> If there are no objections I will do this. It will break everyone that >> uses this parameter but it is a better interface. >> >> Mark >> >> >> >>> Cheers, >>> >>> Lawrence >>> >>> -----BEGIN PGP SIGNATURE----- >>> Version: GnuPG v1 >>> >>> iQEcBAEBAgAGBQJVP1ipAAoJECOc1kQ8PEYve1QH/3SChuuIZhDOoOOfxYnezCuC >>> beXRvqrjem6SWMBIft67kvmAr9htGsiGg/vE+NRP9EwNu20kD+fYocJ+mBBcxFit >>> 2FdUperqA8F9gys2wJ+TijEQx58ieBNJJyPmQRa1DOmKHmD/WWcCIBV5q+yML9kt >>> B3z59ujUH1kJrmmpYmUk6aMUDAG0qU2KlVHX+p6zL1kV7ooGdYcKbiAbYdYrKO1l >>> 6vNw65+51Oiyi2X/oAsnxeJeAvMN2ljaSYLZJ1RZgAndSLi6bcZPQZvtzwXfOLs9 >>> C0qSPfXbd5O2DoenYnKzCS7t/kLnl0J3QimYex4tOSQxNQ7MtMG4CMNDmAIepUs= >>> =OY/s >>> -----END PGP SIGNATURE----- >>> >> >> >
