[petsc-users] testing scalability for ksp/ex22.c

[Francis Poulin]

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 <fpoulin at uwaterloo.ca> 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
> 
> 
> 

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