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<H2><A NAME="SECTION04413000000000000000">Scoped Operations</A></H2>
<A NAME="2315"> </A> <A NAME="secscope"> </A>
<P>
An operation that involves more than
just a sender and a receiver is called
a <EM>scoped</EM> operation<A NAME="2318"> </A>.
All processes that participate in a scoped
operation are said to be within the operation's scope.
<P>
On a system using a linear array of processes,
the only natural scope is all processes. Using
a two-dimensional rectangular process grid, we
have three natural scopes<A NAME="2319"> </A>,
as shown in table <A HREF="node72.html#tabscopes">4.1</A>. Refer to [<A HREF="node189.html#lawn93">24</A>]
for further details.
<P>
<P><A NAME="7956"> </A><IMG WIDTH=453 HEIGHT=90 ALIGN=BOTTOM ALT="table2322" SRC="img253.gif"><BR>
<STRONG>Table 4.1:</STRONG> Scopes provided by a two-dimensional process grid<A NAME="tabscopes"> </A><BR>
<P>
<P>
These groupings of processes are of
particular interest to the linear algebra
programmer, since distributed data
decompositions of a two-dimensional
array (a linear algebra matrix) tend
to follow this process mapping.
For instance, all of a distributed
matrix row can be found on a <EM>process row</EM>.
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<BR> <HR>
<P><ADDRESS>
<I>Susan Blackford <BR>
Tue May 13 09:21:01 EDT 1997</I>
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