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The on construct and the active process group

In the section 3 the idiom

  if(p.member()) {
    ...
  }
appeared. Our language provides a short way of writing this construct
  on(p) {
    ...
  }
In fact the on construct provides some extra value. Informally we said in section 3 that the active process group is restricted to p inside the body of the p.member() conditional construct. The language incorporates a more formal idea of an active process group (APG). At any point of execution some process group is singled out as the APG. An on(p) construct specifically changes the value of the APG to p. On exit from the construct, the APG is restored to its value on entry.

Elevating the active process group to a part of the language allows some simplifications. For example, it provides a natural default for the on clause in array constructors. More importantly, formally defining the active process group simplifies the statement of various rules about what operations are legal inside distributed control constructs like on.


next up previous
Next: Higher-level ranges and locations Up: HPJava: data parallel extensions Previous: Distributed arrays
Bryan Carpenter 2002-07-11