[Carpet] [CactusMaint] Cactus/2057: add new flesh functions to register/unregister notify callbacks for parameter set operations

[Thomas Radke]

Erik Schnetter wrote:
> On Sep 20, 2006, at 09:50:11, tradke at aei.mpg.de wrote:
> 
>>> Description:
>>
>> This patch implements what was proposed in a discussion on the  Cactus 
>> developers mailing list (see http://www.cactuscode.org/old/ 
>> pipermail/developers/2006-September/005090.html)
> 
> 
> I had the impression that there would be no regular expression that  
> selects thorns or parameters.  Maybe my memory misleads me, because  
> that was the way I tried to argue.
> 
> There is no other part of Cactus where thorns or parameters are  
> selected via regular expressions.  It would be difficult to find  
> regular expressions that select exactly the thorns or parameters that  
> one is interested in.  In most cases (e.g., I/O routines), people  will 
> be interested either in a very specific set of parameters, or in  all 
> parameters from a given thorn.
> 
> I'm afraid that regular expressions make notifications more  expensive, 
> since each parameter that is steered has to be checked  against all 
> regular expressions for all listeners.
> 
> I would either use a plain mask, as in "interested in only this  thorn", 
> or "only this parameter from this thorn", or let the listener  handle 
> make its own decision.  If the listener wants to use a regular  
> expression, then the function call overhead is negligible in comparison.

The two regex parameters in the registration of a notify callback are 
optional. If they are given as NULL pointer or an empty string, no 
regcomp() is done in CCTK_ParameterSet() (this reminds me that I didn't 
document it). I thought that this might be useful feature, with no cost 
if it isn't used.

We can also leave it entirely up to the listener.

-- 
Cheers, Thomas.