# [petsc-users] TS failed due to diverged_step_rejected

Tu, Jiannan Jiannan_Tu at uml.edu
Sat Feb 18 16:28:43 CST 2023

```Thanks for the instruction. This is the boundary condition and there is no udot in the equation. I think this is the way to define IFunction at the boundary. Maybe I’m wrong? Or is there some way to introduce udot into the specification of the equation at the boundary from the aspect of the implementation for TS?

Thank you,
Jiannan

From: Zhang, Hong<mailto:hongzhang at anl.gov>
Sent: Saturday, February 18, 2023 12:40 PM
To: Tu, Jiannan<mailto:Jiannan_Tu at uml.edu>
Cc: Barry Smith<mailto:bsmith at petsc.dev>; Hong Zhang<mailto:hong.zhang at aspiritech.org>; Constantinescu, Emil M.<mailto:emconsta at anl.gov>; petsc-users<mailto:petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] TS failed due to diverged_step_rejected

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On Feb 18, 2023, at 8:44 AM, Tu, Jiannan <Jiannan_Tu at uml.edu> wrote:

The RHS function at the bottom boundary is determined by the boundary condition, which is the second order derivative = 0, i.e. G(u) = 2*X[i=1] – X[i=2]. Then in IFunction, F(u, udot) = X[i=0].

This might be the problem. Your F(u, udot) is missing udot according to your description. Take a simple ODE udot = f(u) + g(u) for example. One way to partition this ODE is to define F = udot - f(u) as the IFunction and G = g(u) as the RHSFunction.

Hong (Mr.)

Thank you,
Jiannan

From: Zhang, Hong<mailto:hongzhang at anl.gov>
Sent: Friday, February 17, 2023 11:54 PM
To: Tu, Jiannan<mailto:Jiannan_Tu at uml.edu>
Cc: Barry Smith<mailto:bsmith at petsc.dev>; Hong Zhang<mailto:hong.zhang at aspiritech.org>; Constantinescu, Emil M.<mailto:emconsta at anl.gov>; petsc-users<mailto:petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] TS failed due to diverged_step_rejected

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On Feb 17, 2023, at 6:19 PM, Tu, Jiannan <Jiannan_Tu at uml.edu> wrote:

I need to find out what causes negative temperature first. Following is the message with adaptivity turned off. The G(u) gives right-hand equation for electron temperature at bottom boundary. The F(u, u’) function is F(u, u’) = X = G(u) and the jacobian element is d F(u, u’) / dX =1.

This looks strange. Can you elaborate a bit on your partitioned ODE? For example, how are your F(u,udot) (IFunction) and G(u) (RHSFunction) defined?

A good IMEX example can be found at ts/tutorial/advection-diffusion-reaction/ex5.c (and reaction_diffusion.c).

Hong (Mr.)

The solution from TSStep is checked for positivity of densities and temperatures.

>From the message below, it is seen that G(u) > 0 (I added output of right-hand equation for electron temperature). The solution for electron temperature X should be X * jacobian element = G(u) > 0 since jacobian element = 1. I don’t understand why it becomes negative. Is my understanding of TS formula incorrect?

Thank you,
Jiannan

----------------------------------
G(u) = 1.86534e-07
0 SNES Function norm 2.274473072183e+03
1 SNES Function norm 8.641749325070e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
G(u) = 1.86534e-07
0 SNES Function norm 8.716501970511e-02
1 SNES Function norm 2.213263548813e-04
2 SNES Function norm 2.779985176426e-08
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
G(u) = 1.86534e-07
0 SNES Function norm 3.177195995186e-01
1 SNES Function norm 3.607702491344e-04
2 SNES Function norm 4.345809629121e-08
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
G(u) = 1.86534e-07
TSAdapt none arkimex 0:3 step   0 accepted t=42960      + 2.189e-02 dt=2.189e-02
electron temperature = -3.6757e-15 at (i, j, k) = (0, 1, 0)

From: Barry Smith<mailto:bsmith at petsc.dev>
Sent: Friday, February 17, 2023 3:45 PM
To: Tu, Jiannan<mailto:Jiannan_Tu at uml.edu>; Hong Zhang<mailto:hong.zhang at aspiritech.org>; Emil Constantinescu<mailto:emconsta at anl.gov>
Cc: petsc-users<mailto:petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] TS failed due to diverged_step_rejected

CAUTION: This email was sent from outside the UMass Lowell network.

On Feb 17, 2023, at 3:32 PM, Tu, Jiannan <Jiannan_Tu at uml.edu> wrote:

The ts_type arkimex is used. There is right hand-side function RHSFunction set by TSSetRHSFunction() and also stiff function set by TSSetIFunction().

With adaptivity shut off, TS can finish its first time step after the 3rd “Nonlinear solve converged due to …”. The solution gives negative electron and neutral temperatures at the bottom boundary. I need to fix the negative temperatures and see how the code works.

BTW, what is this ts_adapt? Is it by default on?

It is default for some of the TSTypes (in particular, the better ones). It adapts the timestep to ensure some local error estimate is below a certain tolerance. As Matt notes normally as it tries smaller and smaller time steps the local error estimate would get smaller and smaller; this is not happening here, hence the error.

Have you tried with the argument -ts_arkimex_fully_implicit ?

I am not an expert but my guess is something is "odd" about your functions, either the RHSFunction or the Function or both. Do you have a hierarchy of models for your problem? Could you try runs with fewer terms in your functions, that may be producing the difficulties? If you can determine what triggers the problem with the local error estimators, that might help the experts in ODE solution (not me) determine what could be going wrong.

Barry

Thank you,
Jiannan

From: Matthew Knepley<mailto:knepley at gmail.com>
Sent: Friday, February 17, 2023 3:15 PM
To: Tu, Jiannan<mailto:Jiannan_Tu at uml.edu>
Cc: Barry Smith<mailto:bsmith at petsc.dev>; petsc-users<mailto:petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] TS failed due to diverged_step_rejected

CAUTION: This email was sent from outside the UMass Lowell network.

I am not sure what TS you are using, but the estimate of the local truncation error is 91.4, and does not seem
to change when you make the step smaller, so something is off. You can shut off the adaptivity using

Thanks,

Matt

On Fri, Feb 17, 2023 at 3:01 PM Tu, Jiannan <Jiannan_Tu at uml.edu<mailto:Jiannan_Tu at uml.edu>> wrote:
These are what I got with the options you suggested.

Thank you,
Jiannan

-------------------------------------------------------------------------------
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 1.673091274668e-03
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 8.715428433630e-02
1 SNES Function norm 4.995727626692e-04
2 SNES Function norm 5.498018152230e-08
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
0 SNES Function norm 3.237461568254e-01
1 SNES Function norm 7.988531005091e-04
2 SNES Function norm 1.280948196292e-07
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 2.189e-02 dt=4.374e-03  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 4.881903203545e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 7.562592690785e-02
1 SNES Function norm 1.143078818923e-04
2 SNES Function norm 9.834547907735e-09
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
0 SNES Function norm 2.683968949758e-01
1 SNES Function norm 1.838028436639e-04
2 SNES Function norm 9.470813523140e-09
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-03 dt=4.374e-04  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 1.821562431175e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 1.005443458812e-01
1 SNES Function norm 3.633336946661e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 1.515368382715e-01
1 SNES Function norm 3.389298316830e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-04 dt=4.374e-05  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 4.541003359206e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 1.713800906043e-01
1 SNES Function norm 1.179958172167e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.020265094117e-01
1 SNES Function norm 1.513971290464e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-05 dt=4.374e-06  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 6.090269704320e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.136603895703e-01
1 SNES Function norm 1.877474016012e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 3.127812462507e-01
1 SNES Function norm 2.713146825704e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-06 dt=4.374e-07  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 2.793512213059e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.205196267430e-01
1 SNES Function norm 2.572653773308e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 3.260057361977e-01
1 SNES Function norm 2.705816087598e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-07 dt=4.374e-08  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 2.764855860446e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.212505522844e-01
1 SNES Function norm 2.958996472386e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 3.273222034162e-01
1 SNES Function norm 2.994512887620e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-08 dt=4.374e-09  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 3.317240589134e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.213246532918e-01
1 SNES Function norm 2.799468604767e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.274570888397e-01
1 SNES Function norm 3.066048050994e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-09 dt=4.374e-10  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072189e+03
1 SNES Function norm 2.653507278572e-03
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.213869585841e-01
1 SNES Function norm 2.177156902895e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.275136370365e-01
1 SNES Function norm 1.962849131557e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-10 dt=4.374e-11  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473072218e+03
1 SNES Function norm 5.664907315679e-03
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.223208399368e-01
1 SNES Function norm 5.688863091415e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.287121218919e-01
1 SNES Function norm 4.085338521320e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-11 dt=4.374e-12  wlte= 91.4  wltea=   -1 wlter=   -1
0 SNES Function norm 2.274473071968e+03
1 SNES Function norm 4.694691905235e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.211786508657e-01
1 SNES Function norm 1.503497433939e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.272667798977e-01
1 SNES Function norm 2.176132327279e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
TSAdapt basic arkimex 0:3 step   0 rejected t=42960      + 4.374e-12 dt=4.374e-13  wlte= 91.4  wltea=   -1 wlter=   -1
[0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
[0]PETSC ERROR:
[0]PETSC ERROR: TSStep has failed due to DIVERGED_STEP_REJECTED
[0]PETSC ERROR: See https://petsc.org/release/faq/<https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpetsc.org%2Frelease%2Ffaq%2F&data=05%7C01%7CJiannan_Tu%40uml.edu%7C683af8c0511e4499d31308db11d72edb%7C4c25b8a617f746f983f054734ab81fb1%7C0%7C0%7C638123388160203530%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=WX7OoIK9oSACKQMSj95fkJ8VilF3QvPVRNw30kyZwB0%3D&reserved=0> for trouble shooting.
[0]PETSC ERROR: Petsc Release Version 3.16.6, Mar 30, 2022
[0]PETSC ERROR: ./iditm3d on a  named office by jtu Fri Feb 17 14:54:22 2023

From: Barry Smith<mailto:bsmith at petsc.dev>
Sent: Friday, February 17, 2023 12:58 PM
To: Tu, Jiannan<mailto:Jiannan_Tu at uml.edu>
Cc: petsc-users<mailto:petsc-users at mcs.anl.gov>
Subject: Re: [petsc-users] TS failed due to diverged_step_rejected

CAUTION: This email was sent from outside the UMass Lowell network.

The output is confusing because it prints that the Nonlinear solve has converged but then TSStep has failed due to DIVERGED_STEP_REJECTED which seems contradictory

On Feb 17, 2023, at 12:09 PM, Tu, Jiannan <Jiannan_Tu at uml.edu<mailto:Jiannan_Tu at uml.edu>> wrote:

My code uses TS to solve a set of multi-fluid MHD equations. The jacobian is provided with function F(t, u, u'). Both linear and nonlinear solvers converge but snes repeats itself until gets "TSStep has failed due to diverged_step_rejected."

Is it because I used TSStep rather than TSSolve? I have checked the condition number. The condition number with pc_type asm is about 1 (without precondition it is about 4x10^4). The maximum ratio of off-diagonal jacobian element over diagonal element is about 21.

Could you help me to identify what is going wrong?

Thank you very much!

Jiannan

---------------------------------------------------------------------------------------------------
Run command with options

mpiexec -n \$1 ./iditm3d -ts_type arkimex -snes_tyep ngmres -ksp_type gmres -pc_type asm \
-ts_rtol 1.0e-4 -ts_atol 1.0e-4 -snes_monitor -snes_rtol 1.0e-4 -snes_atol 1.0e-4 \
-snes_converged_reason

The output message is

0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 1.673091274668e-03
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 8.715428433630e-02
1 SNES Function norm 4.995727626692e-04
2 SNES Function norm 5.498018152230e-08
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
0 SNES Function norm 3.237461568254e-01
1 SNES Function norm 7.988531005091e-04
2 SNES Function norm 1.280948196292e-07
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 4.881903203545e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 7.562592690785e-02
1 SNES Function norm 1.143078818923e-04
2 SNES Function norm 9.834547907735e-09
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
0 SNES Function norm 2.683968949758e-01
1 SNES Function norm 1.838028436639e-04
2 SNES Function norm 9.470813523140e-09
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 2
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 1.821562431175e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 1.005443458812e-01
1 SNES Function norm 3.633336946661e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 1.515368382715e-01
1 SNES Function norm 3.389298316830e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 4.541003359206e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 1.713800906043e-01
1 SNES Function norm 1.179958172167e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.020265094117e-01
1 SNES Function norm 1.513971290464e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 6.090269704320e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.136603895703e-01
1 SNES Function norm 1.877474016012e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 3.127812462507e-01
1 SNES Function norm 2.713146825704e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 2.793512213059e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.205196267430e-01
1 SNES Function norm 2.572653773308e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 3.260057361977e-01
1 SNES Function norm 2.705816087598e-06
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 2.764855860446e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.212505522844e-01
1 SNES Function norm 2.958996472386e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 3.273222034162e-01
1 SNES Function norm 2.994512887620e-05
Nonlinear solve converged due to CONVERGED_FNORM_ABS iterations 1
0 SNES Function norm 2.274473072186e+03
1 SNES Function norm 3.317240589134e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.213246532918e-01
1 SNES Function norm 2.799468604767e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.274570888397e-01
1 SNES Function norm 3.066048050994e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 2.274473072189e+03
1 SNES Function norm 2.653507278572e-03
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.213869585841e-01
1 SNES Function norm 2.177156902895e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.275136370365e-01
1 SNES Function norm 1.962849131557e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 2.274473072218e+03
1 SNES Function norm 5.664907315679e-03
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.223208399368e-01
1 SNES Function norm 5.688863091415e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.287121218919e-01
1 SNES Function norm 4.085338521320e-03
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 2.274473071968e+03
1 SNES Function norm 4.694691905235e-04
Nonlinear solve converged due to CONVERGED_FNORM_RELATIVE iterations 1
0 SNES Function norm 2.211786508657e-01
1 SNES Function norm 1.503497433939e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
0 SNES Function norm 3.272667798977e-01
1 SNES Function norm 2.176132327279e-04
Nonlinear solve converged due to CONVERGED_SNORM_RELATIVE iterations 1
[0]PETSC ERROR: --------------------- Error Message --------------------------------------------------------------
[0]PETSC ERROR:
[0]PETSC ERROR: TSStep has failed due to DIVERGED_STEP_REJECTED
[0]PETSC ERROR: See https://petsc.org/release/faq/<https://nam10.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpetsc.org%2Frelease%2Ffaq%2F&data=05%7C01%7CJiannan_Tu%40uml.edu%7C683af8c0511e4499d31308db11d72edb%7C4c25b8a617f746f983f054734ab81fb1%7C0%7C0%7C638123388160203530%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=WX7OoIK9oSACKQMSj95fkJ8VilF3QvPVRNw30kyZwB0%3D&reserved=0> for trouble shooting.
[0]PETSC ERROR: Petsc Release Version 3.16.6, Mar 30, 2022
[0]PETSC ERROR: ./iditm3d on a  named office by jtu Fri Feb 17 11:59:43 2023

--
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