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<H1><A NAME="SECTION04120000000000000000">Structure and Functionality</A></H1>
<A NAME="structure"> </A><A NAME="374"> </A>
<P>
ScaLAPACK can solve systems of linear equations, linear least squares
problems, eigenvalue problems, and singular value problems.
ScaLAPACK can also handle many
associated computations such as matrix factorizations<A NAME="375"> </A>
or estimating condition numbers.
<P>
Like LAPACK, the ScaLAPACK
routines are based on block-partitioned algorithms<A NAME="376"> </A><A NAME="377"> </A> in order to minimize the
frequency of data movement between different levels of the memory hierarchy<A NAME="378"> </A><A NAME="379"> </A>.
The fundamental building blocks of the ScaLAPACK library are distributed-memory<A NAME="380"> </A> versions of the Level 1,
Level 2, and Level 3 BLAS, called the Parallel
BLAS or PBLAS [<A HREF="node189.html#lawn100">26</A>, <A HREF="node189.html#petitet96a">104</A>], and a set of Basic Linear Algebra Communication
Subprograms (BLACS) [<A HREF="node189.html#lawn94">54</A>]
for communication
tasks that arise frequently in parallel linear algebra computations.
In the ScaLAPACK routines, the majority of interprocessor communication occurs
within the PBLAS, so the source code of
the top software layer of ScaLAPACK looks similar to that of LAPACK.
<P>
ScaLAPACK contains <B>driver routines</B><A NAME="384"> </A> for solving standard types of
problems,
<B>computational routines</B><A NAME="386"> </A> to perform a distinct
computational task, and <B>auxiliary routines</B><A NAME="388"> </A>
to perform a certain
subtask or common low-level computation. Each driver routine
typically calls a sequence of
computational routines. Taken as a whole, the computational routines
can perform a wider range of tasks than are covered by the driver
routines.
Many of the auxiliary routines may be of use to numerical analysts
or software developers, so we have documented the Fortran source for
these routines with the same level of detail used for the ScaLAPACK
computational routines and driver routines.
<P>
Dense and band matrices are provided for,
but not general sparse matrices. Similar functionality
is provided for real and complex matrices.
See Chapter <A HREF="node38.html#chapcontents">3</A> for a complete summary of the
contents.
<P>
Not all the facilities of LAPACK are covered by Release 1.5 of ScaLAPACK.
<P>
<BR> <HR>
<P><ADDRESS>
<I>Susan Blackford <BR>
Tue May 13 09:21:01 EDT 1997</I>
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