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
--
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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