Provided by: liblapack-doc_3.3.1-1_all

#### NAME

```       LAPACK-3 - solves one of the systems of equations  A*X = B or A**T*X = B,

```

#### SYNOPSIS

```       SUBROUTINE DGTTS2( ITRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB )

INTEGER        ITRANS, LDB, N, NRHS

INTEGER        IPIV( * )

DOUBLE         PRECISION B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )

```

#### PURPOSE

```       DGTTS2 solves one of the systems of equations
A*X = B  or  A**T*X = B,
with a tridiagonal matrix A using the LU factorization computed
by DGTTRF.

```

#### ARGUMENTS

```        ITRANS  (input) INTEGER
Specifies the form of the system of equations.
= 0:  A * X = B  (No transpose)
= 1:  A**T* X = B  (Transpose)
= 2:  A**T* 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) 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).

LAPACK auxiliary routine (version 3.2)     April 2011                            DGTTS2(3lapack)
```