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34 Cray T3E User’s Guide

PBLAS, ScaLAPACK, BLACS, and FFT. The most straightforward way to

obtain more information on these libraries is through the man command

as follows:

man intro_lapack

There is a manual page for almost all subroutines in Libsci, the most

notable exception being the routines under the PBLAS library. Unfortu-

nately, there are also manual pages for some non-existent routines such

as those solving sparse linear systems.

For more information, you can look up the following WWW addresses:

Package WWW address

BLAS http://www.netlib.org/blas/index.html

LAPACK http://www.netlib.org/lapack/

ScaLAPACK http://www.netlib.org/scalapack/

PBLAS http://www.netlib.org/scalapack/html/

pblas_qref.html

BLACS http://www.netlib.org/blacs/index.html

The Libsci library is automatically linked when programs are loaded.

4.3.1 BLAS

BLAS (Basic Linear Algebra Subroutines) is the ﬁrst in a series of subrou-

tine packages designed for solving eﬃciently computational problems

in linear algebra. As the name indicates, the tasks that the BLAS rou-

tines perform are of the most fundamental kind: adding and multiplying

vectors and matrices.

BLAS is divided into three levels: level 1 routines handle operations

between two vectors, level 2 routines take care of operations between a

vector and a matrix, and, ﬁnally, the routines at level 3 can manipulate

two or more matrices. For instance, the routine SDOT computes the dot

product (inner product) of two vectors. This routine belongs to the level

1 BLAS, whereas the SGEMV routine multiplies a vector by a matrix and

is thus a level 2 routine.

4.3.2 LAPACK

LAPACK (Linear Algebra PACKage) is a collection of subroutines aimed

for more complicated problems such as solving a system of linear equa-

tions or ﬁnding the eigenvalues of a matrix. LAPACK is built on top of

BLAS.

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Cypress CSC-1200T Guía de usuario Pagina 34