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<H2><A NAME="SECTION04433000000000000000">Array Descriptor for In-core Dense Matrices</A></H2>
<A NAME="secdesc1"> </A>
<P>
The array descriptor <B>DESC_</B>,
whose type is defined as
<B>DESC_(DTYPE_)=1</B><A NAME="2526"> </A>,
is an integer array of length 9.
It is used for the ScaLAPACK
routines solving dense linear
systems and eigenvalue problems.
All global vector and matrix
operands are assumed to be
distributed on the process
grid according to the one-
or two-dimensional block
cyclic data distribution
scheme. Refer to
section <A HREF="node75.html#sec2dbcd">4.3.1</A>
for further details on block
cyclic data distribution.
<P>
A general <TT>M_</TT> by <TT>N_</TT>
distributed matrix is defined by
its dimensions, the size of the
elementary <TT>MB_</TT> by <TT>NB_</TT>
block used for its decomposition,
the coordinates of the process
having in its local memory the first
matrix entry <TT>(RSRC_,CSRC_)</TT>,
and the BLACS context (<TT>CTXT_</TT>)
in which this matrix is defined.
Finally, a local leading dimension
<TT>LLD_</TT> is associated with the
local memory address pointing
to the data structure used for
the local storage of this
distributed matrix.
<P>
Let us assume, for example, that
we have an array descriptor <I>DESCA</I>
for a dense global matrix <I>A</I>.
As previously mentioned, the
notations x_ used in the entries
of the array descriptor denote the
attributes of a global array.
For readability of the code,
we have associated symbolic
names for the descriptor entries.
For example, M_ denotes the
number of rows and M_A specifically
denotes the number of rows in
global matrix A.
<P>
<P><A NAME="2536"> </A><IMG WIDTH=625 HEIGHT=456 ALIGN=BOTTOM ALT="table2535" SRC="img303.gif"><BR>
<STRONG>Table 4.7:</STRONG> Content of the array descriptor for in-core dense matrices<BR>
<P>
<P>
For a detailed description of LOC<IMG WIDTH=6 HEIGHT=7 ALIGN=MIDDLE ALT="tex2html_wrap_inline12112" SRC="img15.gif">()
notation, please refer to section <A HREF="node76.html#seclocalstorage">4.3.2</A>.
<P>
<BR> <HR>
<P><ADDRESS>
<I>Susan Blackford <BR>
Tue May 13 09:21:01 EDT 1997</I>
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