[petsc-users] No speedup of tutorial in parallel

Barry Smith bsmith at mcs.anl.gov
Tue Apr 6 18:14:32 CDT 2010


Also run both cases with -log_summary and see what parts of the run  
are not speeding up.


On Apr 6, 2010, at 5:52 PM, Ivo Roghair wrote:

> Hi,
> I am trying to build PETSc into my CFD code. I just built the 3.1-p0
> against a version of open-mpi 1.4.1. I thought
> src/ksp/ksp/ex/tut/ex2.c seemed like a comparable case (though much
> smaller and fewer matrix bands) of what I need. I tried running the
> default ex2.c example on a single-core and on my dualcore (laptop),
> without any changes. The code however runs much, much faster on a
> singlecore (mpirun -np 1 ./ex2) than on 2 cores. I also tried a loop
> over all pc_types and over all ksp_types (loop-in-loop), but the
> problem remains. Is this normal, am I doing something wrong or should
> I take a look at a different example?
> Thanks,
> Ivo

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