[petsc-users] slepc eating all my ram

[Simon Burton]

On Fri, 15 Jul 2016 19:53:31 +0200
"Jose E. Roman" <jroman at dsic.upv.es> wrote:

> 
> The default spectral transformation (STSHIFT) will allocate just one vector. At which exact point are you seeing that it allocates a bunch of vectors?

Yes I think you are right.
I can get beyond STSetUp with the right settings.
Now the solver runs out of memory inside EPSGetStartVector.

> 
> Is this the unmodified ex3.c? Or did you change anything like EPSSetOperators(eps,A,B) ?

good question. I didn't change much, let me try again the original.

> Do you get the same behaviour with the original ex3 with the same problem size?

Yes

> 
> Do you have the same problem with a smaller problem? (half size, say)

Halving n gives a quarter of the dimension, which is 8gb vector sizes.
It works fine and uses a total of 48gb ram. Oh, I see at one point during
initialization it hits a maximum of 56gb.

So I guess it needs to keep 6 vectors in total.
With the original problem size this becomes 192gb which is
just a few gb too much to crunch. I guess I can still try it,
but it doesn't feel good hitting the harddrive that much.

Thanks for the suggestions.

Simon.