SGTTRS(3)

NAME
SGTTRS - one of the systems of equations A*X = B or A'*X = B,

SYNOPSIS

SUBROUTINE SGTTRS(
    TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )

CHARACTER
    TRANS

INTEGER
    INFO, LDB, N, NRHS

INTEGER
    IPIV( * )

REAL
    B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )

PURPOSE
SGTTRS 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 SGTTRF.

ARGUMENTS

TRANS   (input) CHARACTER*1
    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 = 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) REAL array, dimension (N-1)
    The (n-1) multipliers that define the matrix L from the LU factorization of A.

D       (input) REAL array, dimension (N)
    The n diagonal elements of the upper triangular matrix U from the LU factorization of A.

DU      (input) REAL array, dimension (N-1)
    The (n-1) elements of the first super-diagonal of U.

DU2     (input) REAL 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) REAL 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 illegal value