[Users] Automatic termination trigger mid-run

[Erik Schnetter]

Ooh, you are using the "Trigger" thorn. I thought you were using "TerminationTrigger". So that's an option -- use that thorn instead.

Otherwise, if you find your requested feature convenient, then please go ahead and implement it! It would be a nice addition to Cactus.

-erik

> On Jun 4, 2026, at 10:19, Jordan Nicoules <jnicoules at ua.pt> wrote:
> 
> Hi Erik,
> 
> Thank you for your reply! I know of CCTK_TerminateNext, I actually use it in one of my thorns (so I could hack it to achieve what I want). In fact, a call to this function is what I would add to Trigger.
> 
> My point is more: with the existing thorns, is there a way to terminate a simulation while it's running (and before its expected end based on final time/iteration), with a parfile directive, without:
> - manually editing the termination file
> - reaching walltime
> - having NaNs
> - and such edge cases.
> 
> Something that would be like:
> ```
> Trigger::Trigger_Checked_Variable    [0] = "ADMBase::lapse"
> Trigger::Trigger_Reduction           [0] = "minimum"
> Trigger::Trigger_Relation            [0] = "<"
> Trigger::Trigger_Checked_Value       [0] = 0.2
> Trigger::Trigger_Reaction            [0] = "terminate"    # <-- This doesn't exist as far as I understand
> ```
> 
> Thanks,
> 
> Jordan
> 
> From: Users <users-bounces at einsteintoolkit.org <mailto:users-bounces at einsteintoolkit.org>> on behalf of Erik Schnetter via Users <users at einsteintoolkit.org <mailto:users at einsteintoolkit.org>>
> Sent: Thursday, June 4, 2026 14:57
> To: users at einsteintoolkit.org <mailto:users at einsteintoolkit.org>
> Subject: Re: [Users] Automatic termination trigger mid-run
>  
> 
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> You can call the function `CCTK_TerminateNext`, which will stop the simulation gracefully after the current iteration finishes. This is built-in, you do not need a special thorn for this.
> 
> This is how TerminationTrigger is implemented: It calls this function when a certain file is created.
> 
> -erik
> 
>> On Jun 4, 2026, at 09:31, Jordan Nicoules via Users <users at einsteintoolkit.org> wrote:
>> 
>> Dear all,
>> 
>> I was wondering if there was a built-in way to trigger the termination of a simulation when something specific happens, along the lines of what Trigger does to steer quantities. From what I understand, Trigger does not offer that possibility, and TerminationTrigger checks either a file or a time limit. What I'm considering would be more along the lines of "an apparent horizon is found so trigger termination", in order to steer some parameters at recovery.
>> 
>> If there's no such explicit way, I'm happy to try to implement that in Trigger. I actually have ideas of other small improvements to Trigger that I could try contributing as well (namely, increase the maximum number of triggers and allow one trigger to have multiple consequences at once).
>> 
>> Unfortunately I won't be able to join the weekly call today to discuss this directly.
>> 
>> Best,
>> 
>> Jordan
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