NAME

dsttrs - computes the solution to a double precision system of linear equations A ∗ X = B

SYNOPSIS

SUBROUTINE DSTTRS(N, NRHS, L, D, SUBL, B, LDB, IPIV, INFO )

INTEGER           N, NRHS, LDB, IPIV( ∗ ), INFO

DOUBLE PRECISION  D( ∗ ), L( ∗ ), SUBL( ∗ ), B( ∗ )

#include <sunperf.h>

void dsttrs(int n, int nrhs, double ∗l, double ∗d, double ∗subl, double ∗b, int ldb, int ∗ipiv, int ∗info) ;

PURPOSE

DSTTRS computes the solution to a double precision system of linear equations A ∗ X = B, where A is an N-by-N symmetric tridiagonal matrix and X and B are N-by-NRHS matrices. 
 

ARGUMENTS

N (input) INTEGER
The order of the 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.

L (input) DOUBLE PRECISION array, dimension (N-1)
On entry, the subdiagonal elements of LL and DD.

D (input) DOUBLE PRECISION array, dimension (N)
On entry, the diagonal elements of DD.

SUBL (input) DOUBLE PRECISION array, dimension (N-2)
On entry, the second subdiagonal elements of LL.

B (input/output) DOUBLE PRECISION array, dimension
(LDB, NRHS) On entry, the N-by-NRHS right hand side matrix B. On exit, if INFO = 0, the N-by-NRHS solution matrix X.

LDB (input) INTEGER
The leading dimension of the array B.  LDB >= max(1, N)

IPIV (output) INTEGER array, dimension (N)
Details of the interchanges and block pivot.  If IPIV(K) > 0, 1 by 1 pivot, and if IPIV(K) = K + 1 an interchange done;  If IPIV(K) < 0, 2 by 2 pivot, no interchange required.

INFO (output) INTEGER
= 0:  successful exit
< 0:  if INFO = -k, the k-th argument had an illegal value

SunOS 5.0  —  Last change: 10 Dec 1998