On 03/22/2018 03:22 PM, Ben Shields wrote:
I did some digging into the Trilinos reinit_matrix, and I've found that
all of my lost time is coming from the operation
graph->FillComplete(input_col_map, input_row_map)
This step is accounting for as much as 20 seconds per call for a
1x200,000 matrix on 4 processors. I also found that this bottleneck is
non-existent running in serial. There is a check earlier in
reinit_matrix which calls graph.reset differently for 1 processor vs.
multiple processors. The comments suggest that there's an explicit
reason for treating the mpi case this way, but that treatment seems to
be causing the problem for my case.
I think Martin Kronbichler might have to tell you why this is.
But if you're adventurous, take a look how the FillComplete function in
Trilinos looks like and whether you could possibly find the same kinds
of savings there that I found in deal.II. I suspect that it is this
function:
https://github.com/trilinos/Trilinos/blob/master/packages/epetra/src/Epetra_CrsGraph.cpp#L974
Best
W.
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Wolfgang Bangerth email: bange...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/
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