
DPTSV(l) ) DPTSV(l)
NAME
DPTSV  compute the solution to a real system of linear equations A*X = B, where A is an
NbyN symmetric positive definite tridiagonal matrix, and X and B are NbyNRHS matrices
SYNOPSIS
SUBROUTINE DPTSV( N, NRHS, D, E, B, LDB, INFO )
INTEGER INFO, LDB, N, NRHS
DOUBLE PRECISION B( LDB, * ), D( * ), E( * )
PURPOSE
DPTSV computes the solution to a real system of linear equations A*X = B, where A is an N
byN symmetric positive definite tridiagonal matrix, and X and B are NbyNRHS matrices.
A is factored as A = L*D*L**T, and the factored form of A is then used to solve the system
of equations.
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.
D (input/output) DOUBLE PRECISION array, dimension (N)
On entry, the n diagonal elements of the tridiagonal matrix A. On exit, the n
diagonal elements of the diagonal matrix D from the factorization A = L*D*L**T.
E (input/output) DOUBLE PRECISION array, dimension (N1)
On entry, the (n1) subdiagonal elements of the tridiagonal matrix A. On exit,
the (n1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L**T
factorization of A. (E can also be regarded as the superdiagonal of the unit
bidiagonal factor U from the U**T*D*U factorization of A.)
B (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the NbyNRHS right hand side matrix B. On exit, if INFO = 0, the Nby
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, the leading minor of order i is not positive definite, and the
solution has not been computed. The factorization has not been completed unless i
= N.
LAPACK version 3.0 15 June 2000 DPTSV(l) 
