[petsc-users] No speedup of tutorial in parallel

[Ivo Roghair]

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