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<H2><A NAME="SECTION04241000000000000000">Initialize the Process Grid</A></H2>
<A NAME="797"> </A>
<P>
A call to the ScaLAPACK TOOLS routine SL_INIT initializes
the process grid. This routine initializes a <IMG WIDTH=57 HEIGHT=25 ALIGN=MIDDLE ALT="tex2html_wrap_inline12182" SRC="img25.gif">
(denoted <IMG WIDTH=165 HEIGHT=22 ALIGN=MIDDLE ALT="tex2html_wrap_inline12614" SRC="img51.gif"> in the source code)
process grid by using a row-major ordering of the processes, and obtains
a default system <EM>context</EM><A NAME="801"> </A>.
For more information on contexts, refer to section <A HREF="node71.html#secblacscontext">4.1.2</A>
or [<A HREF="node189.html#lawn94">54</A>].
<P>
The user can then query the process
grid to identify each process's coordinates
(<I>MYROW</I>,<I>MYCOL</I>)<A NAME="804"> </A><A NAME="805"> </A>)<A NAME="806"> </A><A NAME="807"> </A> via a call
to BLACS_GRIDINFO<A NAME="808"> </A>.
<P>
A typical code fragment (as obtained from the example program in
section <A HREF="node28.html#example1">2.3</A>) to accomplish this task would be the following:
<PRE> CALL SL_INIT( ICTXT, NPROW, NPCOL )
CALL BLACS_GRIDINFO( ICTXT, NPROW, NPCOL, MYROW, MYCOL )</PRE>
<P>
where details of the calling sequence for SL_INIT are provided below.
Detailed descriptions of calling sequences
for each BLACS routine can be found in [<A HREF="node189.html#lawn94">54</A>] and
Appendix <A HREF="node185.html#chapqrefblacs">D.3</A>. <EM>Note
that underlined arguments in the calling sequence denote output arguments</EM>.
<P>
<UL>
<LI> SL_INIT( <U>, NPROW, NPCOL )<BR>
<A NAME="815"> </A>
<DL COMPACT><DT>ICTXT
<DD> (global output) INTEGER <BR>
ICTXT specifies the BLACS context identifying the created process grid.
<DT>NPROW
<DD> (global input) INTEGER <BR>
NPROW specifies the number of process rows in the process grid to
be created.
<DT>NPCOL
<DD> (global input) INTEGER <BR>
NPCOL specifies the number of process columns in the process grid
to be created.
<P>
</DL></UL></U>
<P>
For a description of these variables names, please refer to the
example program notation in section <A HREF="node28.html#example1">2.3</A> and [<A HREF="node189.html#lawn94">54</A>].
<P>
<BR> <HR>
<P><ADDRESS>
<I>Susan Blackford <BR>
Tue May 13 09:21:01 EDT 1997</I>
</ADDRESS>
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