[petsc-users] randomness from MATSOLVERPACKAGE

[Hui Zhang]

> How is the matrix assembled?
> 
In a deterministic way.
> How different?
> 
Not very much. The last residual can vary in its trailing digits, e.g. from 6.5819e-7 to 6.5820e-7
> You should usually not expect deterministic associativity.
> 
Ok, I see.  Thanks!

> If your results are sensitive, you may be able to make it deterministic (with extra work and choice of package), but you should probably reformulate the problem
> 
> On May 30, 2012 9:21 AM, "Hui Zhang" <mike.hui.zhang at hotmail.com> wrote:
> 
> > I suspect there are some randomness from external matsolverpackage. I use a parallel matrix
> > as preconditioner, and the preconditioner is exactly LU factored, then I saw the KSP (gmres)
> > residuals are different from different runs.
> 
> Besides, for sequential matrix, there is no such phenomenon, only for parallel matrix.
> 
> >
> > Is it true of randomness from matsolverpackage?  Thanks a lot!
> 

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