
DGTSV(l) ) DGTSV(l)
NAME
DGTSV  solve the equation A*X = B,
SYNOPSIS
SUBROUTINE DGTSV( N, NRHS, DL, D, DU, B, LDB, INFO )
INTEGER INFO, LDB, N, NRHS
DOUBLE PRECISION B( LDB, * ), D( * ), DL( * ), DU( * )
PURPOSE
DGTSV solves the equation A*X = B, where A is an n by n tridiagonal matrix, by Gaussian
elimination with partial pivoting.
Note that the equation A'*X = B may be solved by interchanging the order of the argu
ments DU and DL.
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.
DL (input/output) DOUBLE PRECISION array, dimension (N1)
On entry, DL must contain the (n1) subdiagonal elements of A.
On exit, DL is overwritten by the (n2) elements of the second superdiagonal of
the upper triangular matrix U from the LU factorization of A, in DL(1), ...,
DL(n2).
D (input/output) DOUBLE PRECISION array, dimension (N)
On entry, D must contain the diagonal elements of A.
On exit, D is overwritten by the n diagonal elements of U.
DU (input/output) DOUBLE PRECISION array, dimension (N1)
On entry, DU must contain the (n1) superdiagonal elements of A.
On exit, DU is overwritten by the (n1) elements of the first superdiagonal of U.
B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the N by NRHS matrix of 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).
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
> 0: if INFO = i, U(i,i) is exactly zero, and the solution has not been computed.
The factorization has not been completed unless i = N.
LAPACK version 3.0 15 June 2000 DGTSV(l) 
