Hello again, 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
On 2012-02-23, at 3:27 PM, Jed Brown wrote:
Always send output with -log_summary for each run that you do. On Thu, Feb 23, 2012 at 14:16, Francis Poulin <[email protected]> wrote: Hello,
I am learning to use PetSc but am just a notice. I have a rather basic question to ask and couldn't not find it on the achieves.
I am wanting to test the scalability of a Multigrid solver to the 3D Poisson equation. I found ksp/ex22.c that seems to solve the problem that I'm interested in. I ran it on a large server using different processors.
The syntax that I use to run using MPI was
./ex22 -da_grid_x 64 -da_grid_y 64 -da_grid_z 32
Which version of PETSc?
I tested it using 2, 4, 8, 16 cpus and found that the time increases. See below. Clearly there is something that I don't understand since the time should be reduced.
n wtime --------------------- 2 3m58s 4 3m54s 8 5m51s 16 7m23s
Any advice would be greatly appreciated.
Best regrads, Francis