Hi Jeff --
> If the user wants to keep A around the proper way, is there a language
> mechanism to pass by value?
I'm not sure what you mean by "proper" here, but yes, there are ways to
have array A copied into the asynchronous task. For example:
begin with(in A) foo(A); // copy A into the task that runs foo()
Another way to get A to outlive its scope would be to wrap it in a class:
class C {
var A: [1..10] real;
}
{
var myC = new C();
begin foo(myC.A);
// don't delete 'myC'
} // myC leaves scope, but the object it refers to persists due
// to reference-/Java-style semantics for classes
of course, a user who does this will want/need to implement some sort of
reference counting scheme themselves to make sure they eventually reclaim
the class.
> Does Chapel have a static attribute that would give A global scope?
We don't at present, though we could consider it. I think the main reason
we didn't adopt this feature from the outset was fear that it didn't
necessarily make sense in a parallel setting (i.e., it seems likely to
lead to races when such variables are themselves declared in procedures
that may be called by several tasks simultaneously -- like foo() above).
Supporting it in procedures that are not executed in parallel settings
seems like a no-brainer, though today we don't semantically distinguish
between procedures in this way (but there are other reasons why it might
be nice to beyond this).
Of course, A could also be manually moved to global scope (or to its own
module to provide some namespace control).
> Even if the answers are no to both, I like this proposed change
> because I would expect <begin> to act like pthread_create.
Glad it doesn't seem surprising/off-putting from that perspective, and no
need to apologize for "participating"! (a nicer term than lurking)
-Brad
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