[petsc-users] CPU time of PETSc

[Matthew Knepley]

On Fri, Dec 6, 2013 at 1:51 PM, Qin Lu <lu_qin_2000 at yahoo.com> wrote:

> Hello,
>
> I am using serial PETSc linear solver in a serial Fortran program, which
> uses function CPU_TIME() to count cpu time. In Windows-7, the cpu time
> turns out to be 2 to 3 times as much as elapse time. My questions are:
>
> 1. Does PETSc internally use multi-thread even though I configured it with
> --useThreads=0? I ask so since it is known that CPU_TIME()  adds the cpu
> time of all threads togather.
>

No.


> 2. The same program gets consistent cpu time and elapse time in Linux. Do
> you have any idea why?
>

I am guessing your normalization is wrong. Why not just use -log_summary?
We test for these things.

   Matt


> Thanks for any suggestions.
> Qin
>



-- 
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
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