Subject: Proposal for mapping to processor subsets

From: Piyush Mehrotra <[email-masked]>
Date: Fri, 21 Jul 1995 09:32:03 -0400

Mapping to Processor Subsets:

Proposal by:  Barbara Chapman, Piyush Mehrotra, Guy Robinson and Hans Zima

Replace HPF syntax rule H311 by the following:

	dist target	is processor-name [( subscript-triplet )]
			or * processor-name [( subscript-triplet )]
			or *

	Constraint: The subscript triplet must specify a subset
	of the named processor array.

This allows a processor subset to be specified wherever
a processor could be named, e.g., in distribute
statements. Note that this does not allow processor
subsets to be named.

Example:

!HPF$ PROCESSORS P(10)
	REAL A(100)
!HPF$ DISTRIBUTE A(BLOCK) ONTO P(2:5)

This distributes A onto processors P(2) to P(5).

This facility has been implemented in the Vienna Fortran Compilation
System.

Extension:
SUBGROUP statement for allowing subgroups to be named, i.e., 
restricted equivalencing of processors arrays

	SUBGROUP <processor-name> OF <target-proc-array> (subscript-triple)

This allows <processor-name> to be a named subgroup of
<target-proc-array>.