See http://www.mcs.anl.gov/petsc/petsc-as/documentation/faq.html#differentiterations
Hong On Tue, May 10, 2011 at 2:11 PM, <Nan.Jia at dartmouth.edu> wrote: > Hello all the PETSc users and developers, > I just started learning and exploring PETSc recently. I have a problem for > the example: .../src/ksp/ksp/examples/ex2f.f > I run several times with different numbers of processors. Here are the > results. > > nan_jia at > mir:/thayerfs/research/anatoly/NAN/Petsc/petsc-3.1-p8/src/ksp/ksp/examples/tutorials$ > mpiexec -np 1 ./ex2f -m 100 -n 100 > Norm of error 0.8936E-02 iterations ? ?65 > nan_jia at > mir:/thayerfs/research/anatoly/NAN/Petsc/petsc-3.1-p8/src/ksp/ksp/examples/tutorials$ > mpiexec -np 2 ./ex2f -m 100 -n 100 > Norm of error 0.3148E-01 iterations ? ?89 > nan_jia at > mir:/thayerfs/research/anatoly/NAN/Petsc/petsc-3.1-p8/src/ksp/ksp/examples/tutorials$ > mpiexec -np 3 ./ex2f -m 100 -n 100 > Norm of error 0.3193E-01 iterations ? ?92 > > > What is weird to me is that with more processors, the norm does not decrease > but increases, do does the number of iterations. > > I also try to compare .../src/ksp/ksp/examples/ex2f.f with > .../src/ksp/ksp/examples/ex1f.f ?to see the difference between the > sequential and parallel code in order to understand how PETSc parallelizes > the code. > > This is my first use the PETSc mailing list. Thanks everyone. > > Best, > Nan >
