[Users] Multiple time levels

[Erik Schnetter]

If you have n time levels, then it is natural to set
prolongation_order_time = n-1.

When does the error occur? Does it happen during initial data setup,
or during evolution? Applying boundary conditions for the initial
conditions also requires prolongation. Depending on your initial data
scheme, you may even be applying boundary conditions to past time
levels for the initial conditions.

-erik


On Tue, Jan 5, 2016 at 4:11 PM, Steven R. Brandt <sbrandt at cct.lsu.edu> wrote:
> OK, so copying data in CCTK_PRESTEP seems to work.
>
> My next question is, I think, trickier... My par file looks something like
> this
>
> Carpet::time_refinement_factors = "[1,1]"
> Time::timestep_method = "given"
> Time::timestep = 0.05
> Carpet::prolongation_order_time = 0
> ...
>
> Unfortunately, when I try to run the code I get this:
>
> WARNING level 0 from host 18-5e-f-12-9b-2a.wlan.lsu.edu process 0
>   while executing schedule bin (none), routine (no thorn)::(no routine)
>   in thorn CarpetLib, file
> /home/sbrandt/cactus/CactusFW/arrangements/Carpet/CarpetLib/src/gdata.cc:375:
>   -> Internal error: extrapolation in time. variable=FUNWAVE::eta  time=0
> times=[0.050000000000000003]
> cactus_sim:
> /home/sbrandt/cactus/CactusFW/arrangements/Carpet/Carpet/src/helpers.cc:269:
> int Carpet::Abort(const cGH*, int): Assertion `0' failed.
>
> It's trying to get data from the same time level, but it seems to only have
> the wrong one.
>
> My theory is that prolongation_order_time = 1 is going to give me what I
> want, because it's going to prolong to one of the endpoints (the code runs,
> at least). Does this mean that prolongation_order_time = 0 is broken?
>
> Cheers,
> Steve
>
>
> On 01/05/2016 01:06 PM, Erik Schnetter wrote:
>>
>> Steve
>>
>> If a grid variable has multiple time levels, then it will be cycled at
>> the beginning of every time step. You need to copy the past to the
>> current time level after time level cycling to preserve the previous
>> behaviour.
>>
>> -erik
>>
>>
>> On Tue, Jan 5, 2016 at 1:46 PM, Steven R. Brandt <sbrandt at cct.lsu.edu>
>> wrote:
>>>
>>> In the code I'm working on, I have a set of variables living at a single
>>> timestep. For various reasons, I want to shift to having them at two
>>> timelevels, but simply making the change in interface and schedule
>>> results in failure to run old test suites. Is there a recipe I should be
>>> following to make this work?
>>>
>>> Cheers,
>>> Steve
>>> _______________________________________________
>>> Users mailing list
>>> Users at einsteintoolkit.org
>>> http://lists.einsteintoolkit.org/mailman/listinfo/users
>>
>>
>>
>



-- 
Erik Schnetter <schnetter at cct.lsu.edu>
http://www.perimeterinstitute.ca/personal/eschnetter/