Thanks, can you elaborate on computing the time derived? TSMonitor only gives
me the information at the current time step. I guess I could store a copy of
the solution in the context so I can use it in the next call to compute the
difference. On the other hand, I could also store the norm of the RHS function
(since this is equal to the time derivative \frac{\partial \phi}{\partial t}).
Miguel
From: Mark Adams <[email protected]>
Date: Friday, April 30, 2021 at 3:56 PM
To: "Salazar De Troya, Miguel" <[email protected]>
Cc: "Zhang, Hong via petsc-users" <[email protected]>
Subject: Re: [petsc-users] Detecting steady-state with TS
You could add a
https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/TS/TSMonitorSet.html<https://urldefense.us/v3/__https:/www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/TS/TSMonitorSet.html__;!!G2kpM7uM-TzIFchu!hG6eR--4AkxoFHnPn3N8DJF2pPoVkaJT0f6vy9E2qTLMZ0TiqDR_kr5wbAbwapvuLtnSGw$>
method, compute the time derived and decide how to declare converged.
Then set converged
(https://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/TS/TSSetConvergedReason.html<https://urldefense.us/v3/__https:/www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/TS/TSSetConvergedReason.html__;!!G2kpM7uM-TzIFchu!hG6eR--4AkxoFHnPn3N8DJF2pPoVkaJT0f6vy9E2qTLMZ0TiqDR_kr5wbAbwaptYI8kTFA$>)
with TS_CONVERGED_USER
That should cause TS to wrap up the solve and exit cleanly.
Mark
On Thu, Apr 29, 2021 at 3:27 PM Salazar De Troya, Miguel via petsc-users
<[email protected]<mailto:[email protected]>> wrote:
I am solving the signed distance equation
\frac{\partial \phi}{\partial t} + sign (\phi_{0})(|\nabla \phi| - 1) = 0
using a Local Discontinuous Galerkin (LDG) method as described in
https://www.sciencedirect.com/science/article/pii/S0021999110005255<https://urldefense.us/v3/__https:/www.sciencedirect.com/science/article/pii/S0021999110005255__;!!G2kpM7uM-TzIFchu!hG6eR--4AkxoFHnPn3N8DJF2pPoVkaJT0f6vy9E2qTLMZ0TiqDR_kr5wbAbwapsr29KQOw$>
I am interested in solving it close to steady state. I was hoping I could
measure how close to steady state the solution is by using the
TSSetEventHandler infrastructure, but the handler does not have information on
the time derivative. I looked at TSPSEUDO, but it forces me to use an implicit
method, which I cannot provide because how the LDG method works (it calculates
the fluxes solving additional equations). This makes me wonder if the LDG
method is the best choice, so I am open to suggestions.
Given my current progress with the LDG approach, I am wondering if there is a
way to solve to steady state using explicit algorithms such as Runge-Kutta.
Thanks
Miguel
Miguel A. Salazar de Troya
Postdoctoral Researcher, Lawrence Livermore National Laboratory
B141
Rm: 1085-5
Ph: 1(925) 422-6411
