[petsc-users] sources of floating point randomness in JFNK in serial

[Mark Lohry]

This is on a single MPI rank. I haven't checked the coloring, was just
guessing there. But the solutions/residuals are slightly different from run
to run.

Fair to say that for serial JFNK/asm ilu0/gmres we should expect bitwise
identical results?


On Wed, May 3, 2023, 8:50 PM Barry Smith <bsmith at petsc.dev> wrote:

>
>   No, the coloring should be identical every time. Do you see differences
> with 1 MPI rank? (Or much smaller ones?).
>
>
>
> > On May 3, 2023, at 8:42 PM, Mark Lohry <mlohry at gmail.com> wrote:
> >
> > I'm running multiple iterations of newtonls with an MFFD/JFNK nonlinear
> solver where I give it the sparsity. PC asm, KSP gmres, with
> SNESSetLagJacobian -2 (compute once and then frozen jacobian).
> >
> > I'm seeing slight (<1%) but nonzero differences in residuals from run to
> run. I'm wondering where randomness might enter here -- does the jacobian
> coloring use a random seed?
>
>
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