I am using v3.1 of PETSc.

I changed the grid sizes slightly and I'm including 4 log_summary files.

The times are shown below.  I have not modified the example at all except in specifying the matrix size.  Could it be that I need much larger?  When I tried much larger matrices I think I might have got an error because I was using too much memory.

n  time

2 22s

4 29.8s

8 33.7s

16 28.3s

Sorry for my first email but I hope this has more information.

Cheers, Francis