PETSc is getting slower in C++?

Matthew Knepley knepley at
Tue Sep 1 18:31:01 CDT 2009

We can't say anything without at least seeing

  a) The output of -log_summary

  b) The output -ksp_monitor and -ksp_view for a few solves


On Tue, Sep 1, 2009 at 6:25 PM, xiaoyin ji <sapphire.jxy at> wrote:

> Hi,
> I'm embedding a PETSc solver inside a molecular dynamics program. I
> used MATMPIAIJ matrix format and set ksp solver with KSPBICG and
> preconditioer as PCBJACOBI. Now the problem is ksp solver is getting
> slower and slower for each MD step, at the very beginning it takes
> about 1sec, and after 5000 steps the solving part takes up to
> 10sec.(increasing gradually) However, I've also have an identical
> program in Fortran version, which did exactly the same thing and did
> not have such problem for over 1000000 steps, th Fortran version
> always solve within 1sec. The MPI_Wtime() shows that ksp solver is
> exactly the slowing down part. Thanks for any hints.
> Best,
> Xiaoyin Ji
> Department of Material Science and Engineering
> North Carolina State University

What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
-- Norbert Wiener
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