[CIG-SHORT] Nonlinear solve diverged_function_count
Bobak Karimi
bkarimi at clarion.edu
Wed Mar 2 12:31:11 PST 2016
Hi Charles,
We are using a model similar to that in step12.cfg (static friction with quasi-static dirichlet boundary conditions).
I'll give the single through-going fault a try.
Bobby
Sent via the Samsung Galaxy Note5, an AT&T 4G LTE smartphone
-------- Original message --------
From: Charles Williams <willic3 at gmail.com>
Date: 03/02/2016 3:21 PM (GMT-05:00)
To: cig-short <cig-short at geodynamics.org>
Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count
Hi Bobby,
I’m not sure how to increase the value for ksp_sub. I would have to dig around in the code or documentation. Can you remind me again what sort of frictional model you are using, and what sort of friction values? Also, what are you using for a normal stress?
As a further test to isolate the problem, maybe you can turn off everything except for one throughgoing fault, and see if that converges.
Cheers,
Charles
On 3/03/2016, at 2:11 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:
Hi Charles,
To make it run faster, and actually make it past the first timestep, we have increased our tolerances significantly: ksp_atol (1.0e-7) < zero_tolerance (1.0e-6) < snes_atol (1.0e-5). Turning off the faults gave us results where the deformation field from the quasi-static boundaries looked as expected, so I don’t believe the problem is with our mesh. I’ve notice that when we increase the mesh discretization that the simulations run longer (as in they make it to further time steps) before ending with the DIVERGED_FUNCTION_COUNT error. We are working on implementing the exact solver.
In the meantime, the ksp for the faults seems to be what is causing the error we are receiving. The ksp_sub has a divergence set at 10,000. Is there a way to increase this?
Thanks,
Bobby
From: CIG-SHORT [mailto:cig-short-bounces at geodynamics.org] On Behalf Of Charles Williams
Sent: Monday, February 29, 2016 8:26 PM
To: cig-short <cig-short at geodynamics.org<mailto:cig-short at geodynamics.org>>
Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count
Hi Bobby,
Two things I might try are:
1. Turn off the faults and see what convergence looks like with just your external boundary conditions. This will make sure there is not some issue with your mesh or normalization.
2. If the linear convergence looks good in that case, try using the exact solver for the fault and see if that works.
Cheers,
Charles
On 1/03/2016, at 10:05 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:
1. Is this a 2D or 3D problem, and how large is it?
a. It is a 2D problem and has around 13,000 cells (dimension wise it’s about 400 km long and 300 km wide)
2. Is it a single fault or multiple faults?
a. Multiple faults. One through-going, and several intersecting faults.
3. What does the convergence for the linear solver look like (slow convergence, large number of iterations, etc.)?
a. Convergence is pretty slow, iterations around 2,800.
4. Have you tried using an exact solver for the fault (look in pylith/share/settings)?
a. We haven’t tried an exact solver.
5. Is your mesh of high quality?
a. The mesh quality is high quality.
From: CIG-SHORT [mailto:cig-short-bounces at geodynamics.org] On Behalf Of Charles Williams
Sent: Monday, February 29, 2016 3:00 PM
To: cig-short <cig-short at geodynamics.org<mailto:cig-short at geodynamics.org>>
Subject: Re: [CIG-SHORT] Nonlinear solve diverged_function_count
I guess it might help to know more about your problem and what the current convergences are like. I see that you have really large values for your maximum iterations. Have those been necessary? Here are some questions for you:
1. Is this a 2D or 3D problem, and how large is it?
2. Is it a single fault or multiple faults?
3. What does the convergence for the linear solver look like (slow convergence, large number of iterations, etc.)?
4. Have you tried using an exact solver for the fault (look in pylith/share/settings)?
5. Is your mesh of high quality?
That’s all I can think of right now, but let me know if you make any progress on this.
Cheers,
Charles
On 1/03/2016, at 3:14 AM, Bobak Karimi <bkarimi at clarion.edu<mailto:bkarimi at clarion.edu>> wrote:
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<mailto: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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Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt 5040
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ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz<mailto:C.Williams at gns.cri.nz>
_______________________________________________
CIG-SHORT mailing list
CIG-SHORT at geodynamics.org<mailto:CIG-SHORT at geodynamics.org>
http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt 5040
New Zealand
ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz<mailto:C.Williams at gns.cri.nz>
_______________________________________________
CIG-SHORT mailing list
CIG-SHORT at geodynamics.org<mailto:CIG-SHORT at geodynamics.org>
http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt 5040
New Zealand
ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz<mailto:C.Williams at gns.cri.nz>
_______________________________________________
CIG-SHORT mailing list
CIG-SHORT at geodynamics.org<mailto:CIG-SHORT at geodynamics.org>
http://lists.geodynamics.org/cgi-bin/mailman/listinfo/cig-short
Charles A. Williams
Scientist
GNS Science
1 Fairway Drive, Avalon
PO Box 30368
Lower Hutt 5040
New Zealand
ph (office): 0064-4570-4566
fax (office): 0064-4570-4600
C.Williams at gns.cri.nz<mailto:C.Williams at gns.cri.nz>
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