[petsc-dev] strangness in Chebyshev estimate of eigenvalues

[Barry Smith]

> On May 17, 2016, at 2:27 PM, Mark Adams <mfadams at lbl.gov> wrote:
> 
> Other than set userandom = PETSC_TRUE, should I do anything else?

Nothing else. Update the changes/dev.html document and state in the manual page that it uses random by default

> 
> I see:
> 
> ierr = VecSetRandom(B,cheb->random);CHKERRQ(ierr);
> 
> Should I use a special one or change this default to the special one?

    The default is the portable one.

> 
> On Tue, May 17, 2016 at 3:19 PM, Matthew Knepley <knepley at gmail.com> wrote:
> On Tue, May 17, 2016 at 2:11 PM, Jed Brown <jed at jedbrown.org> wrote:
> Barry Smith <bsmith at mcs.anl.gov> writes:
> >   Sounds like Jed is saying he is ok with making the default use the
> >   random number generator. Do this in a branch and be aware that you
> >   have to update a bunch of the test output files to match the new
> >   convergence histories introduced by the change.
> 
> Sure, but if it's all the same to you all, let's use a hash.  This guy
> seems to have a convenient permutation of 32-bit integers.  (Overkill
> for us, but that's not a problem.)
> 
> http://stackoverflow.com/a/12996028/33208
> 
> Use i=(i >> 32)^i for 64-bit input.
> 
> Should we just make this another Random implementation which is only for testing?
> 
>   Matt
> 
> -- 
> What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
> -- Norbert Wiener
>