dgttrs(3)

NAME

DGTTRS - solve one of the systems of equations A*X = B or

A'*X = B,

SYNOPSIS

SUBROUTINE  DGTTRS(  TRANS, N, NRHS, DL, D, DU, DU2, IPIV,
B, LDB, INFO )
    CHARACTER      TRANS
    INTEGER        INFO, LDB, N, NRHS
    INTEGER        IPIV( * )
    DOUBLE         PRECISION B( LDB, * ), D( * ), DL( * ),
DU( * ), DU2( * )

PURPOSE

DGTTRS solves one of the systems of equations A*X = B or

A'*X = B, with a tridiagonal matrix A using the LU factorization

computed by DGTTRF.

ARGUMENTS

TRANS (input) CHARACTER

Specifies the form of the system of equations. =

'N': A * X = B (No transpose)
= 'T': A'* X = B (Transpose)
= 'C': A'* X = B (Conjugate transpose = Trans

pose)

N (input) INTEGER

The order of the matrix A.

NRHS (input) INTEGER

The number of right hand sides, i.e., the number

of columns of the matrix B. NRHS >= 0.

DL (input) DOUBLE PRECISION array, dimension (N-1)

The (n-1) multipliers that define the matrix L

from the LU factorization of A.

D (input) DOUBLE PRECISION array, dimension (N)

The n diagonal elements of the upper triangular

matrix U from the LU factorization of A.

DU (input) DOUBLE PRECISION array, dimension (N-1)

The (n-1) elements of the first super-diagonal of

U.

DU2 (input) DOUBLE PRECISION array, dimension (N-2)

The (n-2) elements of the second super-diagonal of

U.

IPIV (input) INTEGER array, dimension (N)

The pivot indices; for 1 <= i <= n, row i of the

matrix was interchanged with row IPIV(i). IPIV(i) will always be

either i or i+1; IPIV(i) = i indicates a row interchange was not

required.

B (input/output) DOUBLE PRECISION array, dimension

(LDB,NRHS)

On entry, the matrix of right hand side vectors B.

On exit, B is overwritten by 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 = -i, the i-th argument had an ille

gal value

LAPACK version 3.0 15 June 2000

DGTTRS(3)