cgttrs(3)

NAME

CGTTRS - solve one of the systems of equations A * X = B,

A**T * X = B, or A**H * X = B,

SYNOPSIS

SUBROUTINE  CGTTRS(  TRANS, N, NRHS, DL, D, DU, DU2, IPIV,
B, LDB, INFO )
    CHARACTER      TRANS
    INTEGER        INFO, LDB, N, NRHS
    INTEGER        IPIV( * )
    COMPLEX        B( LDB, * ), D( * ), DL( * ), DU( *  ),
DU2( * )

PURPOSE

CGTTRS solves one of the systems of equations A * X = B,

A**T * X = B, or A**H * X = B, with a tridiagonal matrix A using

the LU factorization computed by CGTTRF.

ARGUMENTS

TRANS (input) CHARACTER

Specifies the form of the system of equations. =

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

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) COMPLEX array, dimension (N-1)

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

from the LU factorization of A.

D (input) COMPLEX array, dimension (N)

The n diagonal elements of the upper triangular

matrix U from the LU factorization of A.

DU (input) COMPLEX array, dimension (N-1)

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

U.

DU2 (input) COMPLEX 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) COMPLEX 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 = -k, the k-th argument had an ille

gal value

LAPACK version 3.0 15 June 2000

CGTTRS(3)