[CIG-SHORT] Adaptive time stepping in PyLith

[Tabrez Ali]

I just want to confirm:

1. If adaptive time stepping factors in the relaxation time.
2. It can be used safely when we have velocity BC's in place

Also,

- I just ran an example having velocity BC's (total_time=1.0*year)  
with a fixed time step of 0.1*year and it runs fine.

- With adaptive time stepping (max_dt=1.0*year; adapt_skip=10) it  
also runs fine and seems to take a time step of 0.088*year.

- But if I use max_dt=5.0*year (adapt_skip=10) then things go wrong  
as the solution fails to converge. Even though it appears as if the  
time step it takes is 0.088*year (from looking at the "Finishing  
advancing solution from ..." info).

Now I have checked everything twice and am confused as to how is this  
even possible. Why in one case (max_dt=1.0*year) the solution  
converges and in the second case (max_dt=5.0*year) it doesnt even  
when the time step PyLith seems to take appears to be the same  
(0.088*year) in both cases.

Tabrez