[saga-rg] Task model...

[Thilo Kielmann]

Hi Andre and all,

taking the arguments into account that have been exchanged so far (and giving
it another thought), I am voting for 4a2:

reason:

4a1 indeed emulates a C of Fortran style syntax, which is NOT the right
    thing to do (C++ should look like C++)

4a2 groups the three sets of operations in three sub objects (is that right?),
    at least, there are 3 consistent places where the 3 respective
    functionality groups belong (one place for sync, one place for async,...)

4a3 is using templates in the wrong way: a template defines some code skeleton
    into which arbitrary instantiations can be put. (Like the notorious stack
    from which you can make both a stack of int and a stack molecules)
    But here, we anticipate exactly 3 possible instantiations, which goes
    against the intuition of templates.


Thilo

On Thu, Nov 03, 2005 at 10:56:14AM -0600, Andre Merzky wrote:
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> Date: Thu, 3 Nov 2005 10:56:14 -0600
> From: Andre Merzky <andre at merzky.net>
> To: John Shalf <jshalf at lbl.gov>
> Cc: Andre Merzky <andre at merzky.net>,
> 	Simple API for Grid Applications WG <saga-rg at ggf.org>
> Subject: Re: [saga-rg] Task model...
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> 
> 
> Hi John, Thilo, Group, 
> 
> Hartmut and I would like to argue about the C++ bindings.
> We would like to come to an agreement soon, as our
> implementation is dealing with the async part right now.
> 
> As reminder:
> 
> ---------------------------------------------------------------------
> Example 4a: more versions in C++
> 
> 4a1:               d.mkdir         ("test/");
>                    d.mkdir_sync    ("test/"); // same
>   saga::task t_1 = d.mkdir_async   ("test/");
>   saga::task t_2 = d.mkdir_task    ("test/");
> 
> 4a2:               d.mkdir         ("test/");
>                    d.sync .mkdir   ("test/"); // same
>   saga::task t_1 = d.async.mkdir   ("test/");
>   saga::task t_2 = d.task .mkdir   ("test/");
> 
> 4a3:               d.mkdir         ("test/");
>                    d.mkdir <sync>  ("test/"); // same
>   saga::task t_1 = d.mkdir <async> ("test/");
>   saga::task t_2 = d.mkdir <task>  ("test/");
>   ---------------------------------------------------------------------
> 
> 
> Quoting [John Shalf] (Nov 02 2005):
> > 
> >>   Q5) Any comments to 4a1, 4a2 or 4a3? (not part of the Strawman!)
> > 
> > I prefer 4a1 because it is more readable and the implementation would  
> > be quite straightforward. 
> 
> You favour 4a1.  We think that implementation is very straight
> forward for all three versions.  Readability seems not much
> different to me, and might largely be a matter of taste.
> 
> 
> > It is also a familiar paradigm for any MPI  
> > programmers and anyone who has played with various proprietary Async  
> > I/O implementations. (its a very familiar and conventional approach)
> 
> Well, these are C-API's.  Is there a C++ binding for MPI,
> and does it look the same?
> 
> 
> > I kind of like 4a2 as well from the standpoint of a C++ programmer  
> > (even with Andre's syntax corrections).  However, the resulting  
> > bindings will not be very consistent with the approach we would take  
> > for Fortran or C bindings (eg. those would likely look more like  
> > 4a1).
> 
> But, well, that is the idea of the language binding!  I agree
> that C and Fortran would look more like 4a1, of course.  But that
> is no reason that C++ should look like that as well, or Java,
> Perl etc.
> 
> 
> > It is not really much more readable than 4a1.  Therefore, I'm  
> > uncertain if it is worth fragmenting our approach to bindings in  
> > different languages when there is not a clear benefit in terms of  
> > readability or implementation complexity.
> 
> I think that 4a2/4a3 actually allow nicer implementations, as it
> allows to have the different async parts somewhat separate from
> the sync parts.  We think its nicer :-)
> 
> 
> > I do a lot of C++ programming, but I find the 4a3 option a bit  
> > obscure both in terms of readability and any advantages it might  
> > confer in terms of implementation.
> 
> Hehe - I thought the same :-)  Hartmut likes that version very
> much.  To me it appealed after pondering over it for a couple of
> days.  Now I think it is cute, and quite expressive.
> 
> 
> > It would certainly be easier to  
> > create multi-language bindings for a single code base if we stick  
> > with something more conventional like 4a1.
> 
> I think that C and Fortran bindings for this part are straight
> forward anyway, there is no need to reflect that in C++...
> 
> 
> > Each approach is equally readable to me (less so for 4a3).  I'm  
> > certainly open to any additional information on how the 4a2 and 4a3  
> > approaches could simplify implementation.  
> 
> The main point really is that the object itself has only the sync
> method calls, and the async calls can be put into separate
> header/sources easily, and build (by default) on top of the sync
> calls.  Of course, you can do that with all three versions, but
> its not as obvious in 4a1.
> 
> 
> > If the other approaches  
> > can offer some implementation benefits, then maybe I'd give them  
> > extra consideration, but otherwise, I would prefer a more  
> > conventional approach like 4a1.  
> 
> I would  vote for 4a2 or 4a3 (in that order), but 4a1 would be ok
> if the majority likes that most, of course.  Basically its
> a matter of taste I think.  I am happy that the general point
> seems accaptable to all so far: having sync, async, and task
> versions of the calls, w/o explicit task factory.
> 
> > The only implementation I'm outright  
> > against is the 4b example.
> 
> Good! :-)
> 
> Thanks, Andre.
> 
> 
> > -john
> 
> 
> 
> -- 
> +-----------------------------------------------------------------+
> | Andre Merzky                      | phon: +31 - 20 - 598 - 7759 |
> | Vrije Universiteit Amsterdam (VU) | fax : +31 - 20 - 598 - 7653 |
> | Dept. of Computer Science         | mail: merzky at cs.vu.nl       |
> | De Boelelaan 1083a                | www:  http://www.merzky.net |
> | 1081 HV Amsterdam, Netherlands    |                             |
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> 



-- 
Thilo Kielmann                                 http://www.cs.vu.nl/~kielmann/