[Users] SubstepOutput

[Ian Hinder]

On 16 Mar 2012, at 14:04, Erik Schnetter wrote:

> On Fri, Mar 16, 2012 at 7:03 AM, Ian Hinder <ian.hinder at aei.mpg.de> wrote:
>> Hi all,
>> 
>> I have a small thorn which might be useful for debugging.  It enables output of grid variables on each MoL substep, so you can see what is happening on each one.  The variables are output into files with the substep number appended, so you get, for example,
>> 
>>        phi.x.asc
>>        phi_0.x.asc
>>        phi_1.x.asc
>>        phi_2.x.asc
>> 
>> for a 3-step method (e.g. RK3).  The first step is 0 (in contrast to how MoL counts internally, which is backwards).
>> 
>> This happens
>> 
>>        in MoL_Step after MoL_RHSBoundaries before MoL_NaNCheck
> 
> This means that the output corresponds to the internal state just
> before the respective step, right? If so, that should be worth
> mentioning -- Cactus output for iteration N corresponds to the state
> after iteration N, not before.

Yes.  It's the output before the time integrator "addition" step, but after the right-hand-sides are calculated.  So the first right hand side is in 0, the second in 1, etc.  For the evolved variables, phi_0 should contain the phi of the previous time-step.

-- 
Ian Hinder
http://numrel.aei.mpg.de/people/hinder