dptsv(3)

NAME

DPTSV - compute the solution to a real system of linear

equations A*X = B, where A is an N-by-N symmetric positive defi

nite tridiagonal matrix, and X and B are N-by-NRHS 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-by-N symmetric positive defi

nite tridiagonal matrix, and X and B are N-by-NRHS 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 tridiago

nal 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

(N-1)

On entry, the (n-1) subdiagonal elements of the

tridiagonal matrix A. On exit, the (n-1) 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 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).

INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille

gal 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(3)