Charm++ parallel programming system

[Tom Quinn <trq AT astro.washington.edu>]

I should point out: yes, the PUP::able framework does work!  ChaNGa uses 
it for a couple different class hierarchies.  Thanks Orion!

Tom Quinn       Astronomy, University of Washington
Internet:       
trq AT astro.washington.edu
Phone:          206-685-9009

On Thu, 5 Mar 2015, Orion Lawlor wrote:

> Hi, Bob!  For your use case, pup'ing a vector of pointers to derived classes, 
> the big
> problem is this:       pointer = new T;
>
> When T is a base class, when unpacking you'll end up making an instance of 
> the base
> class instead of making a derived class, resulting in a pup mismatch or 
> silently
> replacing derived with base class behavior.
>
> There's actually an old, undocumented, and fairly hairy solution to this 
> called
> PUP::able, that registers classes using a "PUP_ID" so the other side knows 
> which
> constructor to call:
>      http://charm.cs.uiuc.edu/doxygen/charm/pup_8h-source.shtml#l00625
>
> I only know about it because I wrote it over ten years ago, and I'm not even 
> sure if it
> still works, much less how!
>
> On Thu, Mar 5, 2015 at 1:10 PM, Robert Steinke 
> <rsteinke AT uwyo.edu>
>  wrote:
>       Something came up in my code that I think might be generally useful.  I 
> want
>       to pup a std::vector of pointers.  The objects that the pointers point 
> to
>       have pup routines.  The code in pup_stl.h, in the process of pupping the
>       vector, tries to pup each element in the vector.  But the elements in 
> the
>       vector aren't the puppable objects.  They are pointers to those 
> objects.  I
>       came up with this solution:
>
>       // This is a general function to pup a puppable object via a pointer to 
> it.
>       template <typename T> inline void operator|(PUP::er &p, T* &pointer)
>       {
>         bool notNull = (NULL != pointer);
>
>         p | notNull;
>
>         if (notNull)
>           {
>             if (p.isUnpacking())
>               {
>                 pointer = new T;
>               }
>
>             p | *pointer;
>           }
>         else
>           {
>             pointer = NULL;
>           }
>       }
>
>       It seems like this could be generally useful for any situation where you
>       want to pup a pointer to a puppable object.  Would you consider this as 
> an
>       addition to the Charm++ codebase?
>
>
>
>       BTW, the reason my code has a std::vector of pointers is that I want a
>       vector of objects of various subclasses of a single base class. To do 
> this I
>       have a vector of pointers to the base class pointing to dynamically
>       allocated objects of the various subclasses.
>
>       Bob Steinke
>
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>
>
> --
> Dr. Orion Sky Lawlor   
> lawlor AT alaska.edu
> http://www.cs.uaf.edu/~olawlor/