Hello Barry, I can do it for each of them if that helps but I suspect the method is the same so I'm sending the information for the first 3, n = 2, 4, 8. In the mean time I will figure out how to change the number of levels.. Thanks, Francis On 2012-02-23, at 4:20 PM, Barry Smith wrote:
Still need the -ksp_view output. It is spending most of the time in the LU factorization and solve. I suspect the coarse problem is way to big (like you are using two levels of multigrid) and since it is solved redundantly that takes all the time. Run with say 5 levels.
Barry
On Feb 23, 2012, at 3:03 PM, Francis Poulin wrote:
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
<saw_log_summary_n2.txt> <saw_log_summary_n4.txt> <saw_log_summary_n8.txt> <saw_log_summary_n16.txt>
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