On Wed, Jun 1, 2011 at 3:43 PM, John Fettig <john.fettig at gmail.com> wrote:
> Hi Matt, > > On Wed, Jun 1, 2011 at 4:06 PM, Matthew Knepley <knepley at gmail.com> wrote: > > It looks like the calls are taking 0.5 microseconds, but there are 89G > > insertions > > against only 13K MatMults that take about 1s apiece. > > This seems like an awful lot of insertions into a matrix that can be > applied > > in 1s. > > Unless I'm reading it wrong, there are 89M insertions. This is from > 10 timesteps with nonlinear iteration on each timestep, with ~1.5M > elements. The matrices are reconstructed at virtually every substep. > I don't quite understand what you mean by "can be applied in 1s", > doesn't it take ~1ms per call? Anyways, I agree that this is a poor > ratio of work to assemble/use of the matrices. > Yes, both units were wrong. > We had thought about constructing the matrix outside of PETSc and then > passing PETSc pointers to the matrix, but maybe matrix-free would be > better for some of the equations where jacobi preconditioning is > sufficient. > I think it would be hard to speedup the insertion. Why are you reassembling? Just for Newton? You could use a lagged version of the matrix as a preconditioner, and run matrix-free for the matvecs. Matt > Thanks, > John > -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20110601/260ea9f9/attachment.htm>
