It would be a lot clearer if it were consistent all the way down. I can
imagine that'd be expensive to do naively, and do it optimally would
require static analysis of nested data structure access. The main use case
I've cheated by using the current behavior is to have a record with a
single atomic var that I can increment across all coforall tasks.
On Mon, Jun 13, 2016 at 7:24 AM, Michael Ferguson <[email protected]>
wrote:
> Hi -
>
> > Even though r is defined to be constant, it clearly is being changed
>
> It's my personal view that this just indicates some missing parts
> in our implementation of const-checking. I think it should be an
> error. I don't know whether or not others agree with me.
>
> -michael
>
> On 6/11/16, 1:55 AM, "Nikhil Padmanabhan" <[email protected]>
> wrote:
>
> >
> >Hi Brad, Brian ---
> >
> >
> >Brad -- thanks for that very detailed explanation. I think all of it
> >makes sense -- although it does make it clear that reasoning about eg.
> >the locality of an object from the source code is sometime subtle.
> >
> >
> >However, your discussion of const ref/in for record types brings up
> >another oddity. Consider the following :
> >
> >
> >record R {
> > var x : int = 3;
> > proc setX(y : int) {
> > x = y;
> > }
> >}
> >
> >
> >proc main() {
> > const r : R;
> > writeln(r);
> > r.setX(10);
> > writeln(r);
> >}
> >
> >
> >
> >If I run it, I get :
> >(x = 3)
> >(x = 10)
> >
> >
> >Even though r is defined to be constant, it clearly is being changed ---
> >and I believe that's because Chapel methods today don't have any notion
> >of const-ness. So, eg. marking an record const ref/in going into a forall
> >loop by default will not prevent
> > a user from creating a data race. Furthermore, I suspect this might
> >break the remote forwarding semantics... although I haven't tried to
> >verify this.
> >
> >
> >Thoughts?
> >-- Nikhil
> >
> >
> >
> >
> >
> >
> >
> >
>
>
>
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