[Users] Multiple time levels

[Erik Schnetter]

You can set the prologation type of "mask" such that it is never
prolongated, then you don't need a second time level.

I'll need more details to investigate. Do you receive warnings at
startup about prolongation?

-erik

On Tue, Jan 5, 2016 at 4:34 PM, Steven R. Brandt <sbrandt at cct.lsu.edu> wrote:
> On 01/05/2016 03:23 PM, Erik Schnetter wrote:
>>
>> If you have n time levels, then it is natural to set
>> prolongation_order_time = n-1.
>
> Originally, the error message occurred for a variable named mask, which had
> a single time level. I guessed that since the error message showed a single,
> wrong value, that having two time levels to choose from might make it work.
> So I gave mask two time levels and started copying in CCTK_PRESTEP. The
> error then showed up in eta, which always had 2 timelevels (because it's
> evolved with RK3).
>>
>>
>> When does the error occur? Does it happen during initial data setup,
>> or during evolution? Applying boundary conditions for the initial
>
> Iteration 0 prints, so evolution.
>>
>> 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.
>
> Not sure I follow what you're saying here. I calculate all data for time =
> 0.
>
> Cheers,
> Steve
>
>> -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/