[Developers] should we document that CCTK_MyProc(NULL) works?

Tom Goodale goodale at cct.lsu.edu
Fri Jan 12 10:36:36 CST 2007

The only problem is that in principle drivers could be using a different 
processor mapping - e.g. when using MPI the driver could use a different 
communicator - which would give a different result with NULL than with a 
cGH, so I would prefer to not document that NULL is acceptable.  It is 
only used in the flesh in extreme cases, which are mainly before a driver 
has been initialised.



On Fri, 12 Jan 2007, David Rideout wrote:

> If it is guaranteed to work then there is no need for the argument.
> Perhaps you might write that most drivers behave this way, but there
> is no guarantee?  And that the calling routine might check that it
> returns a valid (non-negative) value?
> Cheers,
> David
> On 1/12/07, Jonathan Thornburg <jthorn at aei.mpg.de> wrote:
>> Hi,
>> With all current drivers (or at least all known to the people I've
>> talked to), it's legal to call CCTK_MyProc() with a NULL GH pointer,
>> and doing so works (CCTK_MyProc() returns the correct result).
>> IMHO this is very useful behavior.  For example, it lets code which
>> doesn't have a GH still generate unique filenames for logging debug
>> data.  The problem is, right now this behavior is not documented in
>> the Cactus Reference Manual.
>> Does anyone object to my documenting the current behavior in the
>> Cactus Reference Manual?  Should we go farther and also promise
>> (document) that this is guaranteed to work for any driver?
>> ciao,
>> --
>> -- Jonathan Thornburg <jthorn at aei.mpg.de>
>>    Max-Planck-Institut fuer Gravitationsphysik (Albert-Einstein-Institut),
>>    Golm, Germany, "Old Europe"     http://www.aei.mpg.de/~jthorn/home.html
>>    "Washing one's hands of the conflict between the powerful and the
>>     powerless means to side with the powerful, not to be neutral."
>>                                       -- quote by Freire / poster by Oxfam
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