On Thu, 19 Nov 2009, Jed Brown wrote: > That could be tricky but you might be happy with just computing a > low-bandwidth ordering and assembling into that, e.g. > MatSetLocalToGlobalMapping, then insert with MatSetValuesLocal. The > ordering should cluster rows with identical sparsity pattern so you > would benefit from inodes.
Block variable ordering with "--node_major_dofs" is perhaps the least well-documented option in libMesh, which is saying a lot, but we're already using it. >> That's a shame, too. One application I'm working on right now is >> going to end up with roughly a half dozen variables on a big subdomain >> and one or two dozen on a much bigger subdomain. Storing block >> structure alone would have been nice. > > Sounds like a lot of storage. Well, the definition of "big" and "much bigger" is in the eye of the beholder (and is going to depend on how much refinement we turn out to need). We're setting up a 128 core system for local testing; based on some extrapolation and some results with a different code, I'm hoping we'll be able to fit even the full problem on 64 cores without exceeding per-node RAM. > Are the blocks dense? Not entirely, but close enough that we're not trying to shave a few bytes on the exceptions, especially since it might just cost more bytes in the sparsity pattern. > Have you considered preconditioning with a sparser representation? Barely, but we'll have to cross that bridge when we come to it. For the smaller problems we're using this code on now, there's still memory to spare for ILU. For later I'm not sure. We'll have to construct the true Jacobian for the adjoint problem, but might try to set up a preconditioner based on reduced physics or a coarser grid. --- Roy ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Libmesh-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-devel
