[Trilinos-Users] Belos::LinearProblem::setProblem() is taking too much time

[John Moore]

I am interested in solving large linear systems within Newton iterations.
My matrix structure remains constant, while only the values change.

I find that most of the time is actually spent in the functions
Belos::LinearProblem::setProblem. Is this to be expected? The case that I
am currently running is detailed below:

TpetraCrsMatrix
# processors:        32 mpi processes
Number of rows:   802225
Number of entries:  71819925
Preconditioner:       Custom
Number of iters:     400
Solve time:            42 Seconds
setProblem time:     35 seconds

The performance only gets work as the problem gets larger.  For a slightly
larger (and denser) problem, the setProblem() time is about 4 times that of
the solve time. For small problems, most of the time is spent in the solve,
as expected. Is there a way to get around calling setProblem() every time I
need to solve the linear system, or could I be doing something wrong?

Thank you,
John
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