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

[Barry Smith]

  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?