SPTTS2(3S)SPTTS2(3S)NAME
SPTTS2 - solve a tridiagonal system of the form A * X = B using the
L*D*L' factorization of A computed by SPTTRF
SYNOPSIS
SUBROUTINE SPTTS2( N, NRHS, D, E, B, LDB )
INTEGER LDB, N, NRHS
REAL B( LDB, * ), D( * ), E( * )
IMPLEMENTATION
These routines are part of the SCSL Scientific Library and can be loaded
using either the -lscs or the -lscs_mp option. The -lscs_mp option
directs the linker to use the multi-processor version of the library.
When linking to SCSL with -lscs or -lscs_mp, the default integer size is
4 bytes (32 bits). Another version of SCSL is available in which integers
are 8 bytes (64 bits). This version allows the user access to larger
memory sizes and helps when porting legacy Cray codes. It can be loaded
by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
only one of the two versions; 4-byte integer and 8-byte integer library
calls cannot be mixed.
PURPOSE
SPTTS2 solves a tridiagonal system of the form A * X = B using the L*D*L'
factorization of A computed by SPTTRF. D is a diagonal matrix specified
in the vector D, L is a unit bidiagonal matrix whose subdiagonal is
specified in the vector E, and X and B are N by NRHS matrices.
ARGUMENTS
N (input) INTEGER
The order of the tridiagonal matrix A. N >= 0.
NRHS (input) INTEGER
The number of right hand sides, i.e., the number of columns of
the matrix B. NRHS >= 0.
D (input) REAL array, dimension (N)
The n diagonal elements of the diagonal matrix D from the L*D*L'
factorization of A.
E (input) REAL array, dimension (N-1)
The (n-1) subdiagonal elements of the unit bidiagonal factor L
from the L*D*L' factorization of A. E can also be regarded as
the superdiagonal of the unit bidiagonal factor U from the
factorization A = U'*D*U.
B (input/output) REAL array, dimension (LDB,NRHS)
On entry, the right hand side vectors B for the system of linear
equations. On exit, the solution vectors, X.
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SPTTS2(3S)SPTTS2(3S)
LDB (input) INTEGER
The leading dimension of the array B. LDB >= max(1,N).
SEE ALSOINTRO_LAPACK(3S), INTRO_SCSL(3S)
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