[CIG-SHORT] Uniform time-stepping for long runs on viscoelastic domain

[Michal Dichter]

Dear PyLith experts,


I am having a strange problem with the uniform time-stepping scheme for "long runs" on a viscoelastic domain. I have set up the time-stepping as:

[pylithapp.problem.formulation.time_step]

total_time = 500.0*year
dt = 0.1*year


The dt value is less than the stable timestep. The simulation runs as expected when total_time is relatively small (for example 5 years). However for longer runs, such as the 500-year run above, PyLith runs great for the first 99% of the simulation but then gets stuck at the very end:


 -- Finishing advancing solution from t=1.57725e+10*s to t=1.57756e+10*s.
 >> /home/michal/PyLith/lib/python2.7/site-packages/pylith/problems/Implicit.py:246:poststep
 -- implicit(info)
 -- Writing solution fields.
 >> /home/michal/PyLith/lib/python2.7/site-packages/pylith/problems/TimeDependent.py:176:run
 -- timedependent(info)
 -- Main time loop, current time is t=1.57756e+10*s
 >> /home/michal/PyLith/lib/python2.7/site-packages/pylith/problems/TimeDependent.py:187:run
 -- timedependent(info)
 -- Preparing to advance solution from time t=1.57756e+10*s to t=1.57788e+10*s.
 >> /home/michal/PyLith/lib/python2.7/site-packages/pylith/problems/Implicit.py:181:prestep
 -- implicit(info)
 -- Setting constraints.
 >> /home/michal/PyLith/lib/python2.7/site-packages/pylith/problems/TimeDependent.py:193:run
 -- timedependent(info)
 -- Advancing solution from t=1.57756e+10*s to t=1.57788e+10*s.
 >> /home/michal/PyLith/lib/python2.7/site-packages/pylith/problems/Formulation.py:579:_reformResidual
 -- implicit(info)
 -- Integrating residual term in operator.


The simulation gets hung-up here. No error message or anything. PyLith isn't busy writing output to files during this time. It also seems that PyLith is trying to advance the solution multiple time steps beyond the 500 years that I've requested: 1.57788e+10 ~ 500.34 years. What's going on here?


Best,


Michal


____________
Michal Dichter
Department of Physics and Astronomy
University of New Mexico
(860) 459-0956
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