Igor Peshansky/Watson/i...@ibmus wrote on 07/28/2010 07:15:02 PM:
> Dave Hudak <dhu...@osc.edu> wrote on 07/28/2010 02:37:22 PM:
>
> > Hi All,
> >
> > I am trying to write a class that will do a prefix sum on an array. I
> > have written the single-place version and a single-place version that
> > uses multiple activities to compute the sums. I am now trying to
> > write the distributed version. Both classes are included (I will
> > eventually write an interface for these classes).
> >
> > I have been able to write the constructors and call them without run-
> > time exceptions occurring. Now, I want to write a function that
> > returns a single string representation of a dist array. I wrote a
> > function that should create a string representation of all dist array
> > elements at a given location (I called it place_str), and then I want
> > to loop over all places:
> >
> > (from DistPrefixSum.x10):
> >
> > public def str():String
> > {
> > var s : String = ""; //var is mutable
> > for (var place_id:int=0; place_id<Place.MAX_PLACES; place_id++)
{
> > s += at (Place.places(place_id)) place_str();
> > if (place_id != (Place.MAX_PLACES - 1)) {
> > s += ", ";
> > } //if
> > } //for i
> > return s;
> > }
> >
> > My error occurs on the at statement:
> >
> > dhu...@oscnet166 35%> x10c++ -O -o Driver Driver.x10 PrefixSum.x10
> > AsyncPrefixSum.x10 DistPrefixSum.x10
> >
>
/Users/dhudak/osc/research/x10/tutorial/examples/GoodPrefixSum/src/DistPrefixSum.
> > x10:49: Local variable "place_id" is accessed from an inner class or a
> > closure, and must be declared final or shared.
> > 1 error.
> >
> > Does anyone have any recommendations? Creating a single string from a
> > dist array of integers is a reduction just like finding the sum or max
> > of the entries, so I figure its well understood...
>
> Dave,
>
> This is a bug in the typechecking of at expressions. You can work
around
> this by changing the body of the for loop to
>
> val z = new Cell[String](null);
> val h = here;
> at (Place.places(place_id)) { val q = place_str(); at (h)
z.set(q);
> }
> s += z();
> if (place_id != (Place.MAX_PLACES - 1)) {
> s += ", ";
> } //if
>
> The above code is less efficient, but it should work.
> I've opened a JIRA issue: http://jira.codehaus.org/browse/XTENLANG-1632
.
> Please watch that issue for updates on the fix.
> Igor
Dave,
The fix turned out to be simple. This is now fixed in SVN HEAD (r15224),
and will be available in the next X10 release (or you can build from SVN
to pick up the fix).
Igor
--
Igor Peshansky (note the spelling change!)
IBM T.J. Watson Research Center
X10: Parallel Productivity and Performance (http://x10-lang.org/)
XJ: No More Pain for XML's Gain (http://www.research.ibm.com/xj/)
"I hear and I forget. I see and I remember. I do and I understand" --
Confucius
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