
DPTTRS(l) ) DPTTRS(l)
NAME
DPTTRS  solve a tridiagonal system of the form A * X = B using the L*D*L' factorization
of A computed by DPTTRF
SYNOPSIS
SUBROUTINE DPTTRS( N, NRHS, D, E, B, LDB, INFO )
INTEGER INFO, LDB, N, NRHS
DOUBLE PRECISION B( LDB, * ), D( * ), E( * )
PURPOSE
DPTTRS solves a tridiagonal system of the form A * X = B using the L*D*L' factorization of
A computed by DPTTRF. D is a diagonal matrix specified in the vector D, L is a unit bidi
agonal 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) DOUBLE PRECISION array, dimension (N)
The n diagonal elements of the diagonal matrix D from the L*D*L' factorization of
A.
E (input) DOUBLE PRECISION array, dimension (N1)
The (n1) 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 bidi
agonal factor U from the factorization A = U'*D*U.
B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the right hand side vectors B for the system of linear equations. On
exit, the solution vectors, X.
LDB (input) INTEGER
The leading dimension of the array B. LDB >= max(1,N).
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = k, the kth argument had an illegal value
LAPACK version 3.0 15 June 2000 DPTTRS(l) 
