X10

Var assignment within parallel loop broken with WORK_STEALING

Details

  • Testcase included:
    yes
  • Number of attachments :
    1

Description

The following code compiles happily with x10/x10c++, and should print "1.0".

var x:Double = 0;
finish {
    for (i in 1..100) async {
        if (i == 17) {
            x = 1.0;
        }
    }
}
Console.OUT.println("x = " + x);

When compiled with the default (help-first) runtime, it prints "1.0" as expected. However when compiled with -WORK_STEALING=true, it prints "0.0".
Interesting this only happens in the context of a loop; for example the following works correctly:

var x:Double = 0;
finish {
    async x = 1.0;
}
Console.OUT.println("x = " + x);
  1. File
    AsyncVar.x10
    29/Aug/11 9:11 PM
    0.8 kB
    Josh Milthorpe

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Olivier Tardieu added a comment -

We transform loop this into a divide-and-conquer parallel loop. The transformation incorrectly captures x by value.

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Olivier Tardieu added a comment - We transform loop this into a divide-and-conquer parallel loop. The transformation incorrectly captures x by value.
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David Grove added a comment -

bulk defer of "feature-like" issues to next major release (2.3 to 2.4).

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David Grove added a comment - bulk defer of "feature-like" issues to next major release (2.3 to 2.4).

People

  • Assignee:
    Olivier Tardieu
    Reporter:
    Josh Milthorpe
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    Updated: