Charm++ parallel programming system

[Phil Miller <mille121 AT illinois.edu>]

On Fri, May 28, 2010 at 15:02, Haowei Huang 
<huangh AT in.tum.de>
 wrote:
>    Another question, For example, I define a Patch object and a patchArray
> then Patch
> has properties and methods.
>
>   we could reference the methods in Patch but couldn't reference properties:
>
>     patchArray(x,y,z).property;
>     patchArray(x,y,z).function();
>
>    when I use first statement I encounter a compiling error:
>    class CProxyElement_Patch’ has no member named ‘property
>
>    Do you have any idea about it? Thank you.

You're trying to treat a chare as if it were a common object. A chare
is an object that can be located anywhere in a distributed parallel
system. Thus, barring advanced techniques, you can't directly access
properties of it. If you really need a value out of some chare, you
can write a synchronous entry method with a non-void return type to
get that value. The caller will have to be a threaded entry method or
some other thread object. This is generally not a good structure to
use.

Related to this is that method calls on a chare's proxy (which is what
subscripting the array proxy gets you) generates a message that will
invoke an entry method sometime later, when the message has been
delivered and scheduled. This is the 'asynchronous remote method
invocation' that's central to the Charm++ programming model. Again, if
you really need to directly call a method on a chare object, there are
advanced techniques to do so (inline entry methods, local pointers),
but those are not the natural constructs that beginners should work
with.