On 11/14/16 1:17 PM, Stefano Zampini wrote:
> I do have pasted the output for ts_monitor for the first three steps.
I meant -ts_adapt_monitor, I wanted to see what TS solvers are used: The
first step is probably an Euler method, that's why you have 10 SNES
solves in place of 7 for the later ones.
> The entry you are referring to in Table 11 actually breaks the TS
> assumption that the ODE can be written F(u,udot,t) = G(u,t) (I was
> thinking it was a typo)
It works for certain forms as listed in the table. I'm not aware of any
RK method that handles this case with G(u,t) treated explicitly.
In your case, you would either use the setup corresponding to "stiff
ODE w/ mass matrix" or "nonstiff ODE w/ mass matrix”.
I’m not interested in solving this specific advection problem with
arkimex. I came across this problem when writing a general interface to
TS from a FEM library.
Normally, I do that by solving udot=M^-1 f(u) + M^-1 g(u)
It is difficult to create a decision tree for every way of writing the
splittings. Do you find Table 11 not clear about what splitting to
use? I would welcome any kind of feedback for improving it.
If the entry in Table 11 is correct, please add a comment on the manual
stating that ARKIMEX does not fully support the F(u,udot,t) = G(u,t)
interface.
I see how the first statement in the caption can be confusing; The last
statement in the caption states:
"General cases such as F(t;y;y')=G(t;y) are not amenable to IMEX
Runge-Kutta, but can be solved by using fully implicit methods." A line
in the table may be more clear. I'll go for that.
Emil
