[CIG-SHORT] Nonlinear solve diverged_function_count

[Bobak Karimi]

Hi Charles,

The tight factors for rtol were purposeful to force the controlling tolerance to be the atol. This was what I had gleaned from session iv, step03 in the 2015 pylith tutorial. My PetSc values are below:

# PETSc
# ----------------------------------------------------------------------
# Set the solver options.

[pylithapp.petsc]

# Preconditioner settings.
pc_type = asm
sub_pc_factor_shift_type = nonzero

# Convergence parameters.
ksp_rtol = 1.0e-20
ksp_atol = 1.0e-11
ksp_max_it = 1000000
ksp_gmres_restart = 100

# Linear solver monitoring options.
ksp_monitor = true
ksp_view = true
ksp_converged_reason = true

# Nonlinear solver monitoring options.
snes_rtol = 1.0e-20
snes_atol = 1.0e-9
snes_max_it = 1000000
snes_monitor = true
snes_view = true
snes_converged_reason = true
snes_error_if_not_converged = true

# PETSc summary -- useful for performance information.
log_summary = true

# Uncomment to launch gdb when starting PyLith.
# start_in_debugger = true


# End of file

From: CIG-SHORT [mailto:cig-short-bounces at geodynamics.org] On Behalf Of Charles Williams
Sent: Sunday, February 28, 2016 2:57 PM
To: cig-short <cig-short at geodynamics.org>
Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count

Dear Bobby,

It’s hard to say without seeing all of your settings, but those seem like pretty tight values for rtol.  Is there a reason you are setting them so small?

Cheers,
Charles


On 27/02/2016, at 6:36 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:

Hello,

I recently got this error on a simulation I was running, and am not sure how to apply a fix for it:

Nonlinear solve did not converge due to DIVERGED_FUNCTION_COUNT iterations 2743

My KSP and NSES rtol = 1.0e-20
KSP_atol = 1.0e-11
SNES_atol = 1.0e-9

The zero-tolerance on my faults is 1.0e-10.

Any help would be much appreciated,

Thanks!
Bobby

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