NAME

dpttrs - solve a system of linear equations A ∗ X = B with a symmetric positive definite tridiagonal matrix A using the factorization A = L∗D∗L∗∗T or A = U∗∗T∗D∗U computed by DPTTRF

SYNOPSIS

SUBROUTINE DPTTRS( N, NRHS, D, E, B, LDB, INFO )

INTEGER INFO, LDB, N, NRHS

DOUBLE PRECISION B( LDB, ∗ ), D( ∗ ), E( ∗ )

#include <sunperf.h>

void dpttrs(int n, int nrhs, double ∗d, double ∗e, double ∗db, int ldb, int ∗info) ;

PURPOSE

DPTTRS solves a system of linear equations A ∗ X = B with a symmetric positive definite tridiagonal matrix A using the factorization A = L∗D∗L∗∗T or A = U∗∗T∗D∗U computed by DPTTRF.  (The two forms are equivalent if A is real.) 
 

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) DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the diagonal matrix D from the factorization computed by DPTTRF.

E (input) DOUBLE PRECISION array, dimension (N-1)
The (n-1) off-diagonal elements of the unit bidiagonal factor U or L from the factorization computed by DPTTRF.

B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the right hand side matrix B. On exit, the solution matrix X.

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

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

SunOS 5.0  —  Last change: 10 Dec 1998