[petsc-users] testing scalability for ksp/ex22.c (now ex45.c)

Francis Poulin fpoulin at uwaterloo.ca
Fri Feb 24 14:43:35 CST 2012


I wanted to thank everyone for the help and say that I managed to get it running on the cluster and I have done some efficiency calculations. To run the code I used,

mpirun -np # ./ex45 -da_grid_x 5 -da_grid_y 5 -da_grid_z 5 -da_refine 6 -ksp_monitor -pc_type mg -mg_levels_ksp_type richardson -mg_levels_pc_type sor -log_summary

as suggested and found the following

p(#cpu)	Tp (parallel) 		T1 (serial) 	Efficiency [ = Tp/(p*T1) ]
1		904				904			1.00
2		553				904			0.82
4		274				904			0.83
8		138				904			0.82
16		70				904			0.81
32		36				904			0.78

It seems to scale beautifully starting at 2 but there is a big drop from 1 to 2.  I suspect there's a very good reason for this, I just don't know what.

Thanks again for all of your help,

On 2012-02-24, at 12:59 PM, Jed Brown wrote:

> On Fri, Feb 24, 2012 at 11:49, Francis Poulin <fpoulin at uwaterloo.ca> wrote:
> I don't seem to have the hydra in my bin folder but I do have petscmpiexec that I've been using.
> That's just the name of my mpiexec. Use whichever one is used with your build of PETSc.
>> Use these, it will run the same method and sizes as the options I gave for ex22 before.
>> mpiexec.hydra -n 2 ./ex45 -da_grid_x 5 -da_grid_y 5 -da_grid_z 5 -da_refine 5 -ksp_monitor -pc_type mg -mg_levels_ksp_type richardson -mg_levels_pc_type sor -log_summary
> Also, I want to install PetSc on an SGI machine that I have access to.  I have been told that using MPT would give better performance compared to mpich2.  When I configure petsc on this server I don't suppose
> -with-mpi-dir=/opt/sgi/mpt
>  the above would work because of the different name.  Do you have a suggestion as to what I could try?  
> It's just the way you launch parallel jobs.

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