Provided by: liblapack-doc_3.3.1-1_all #### NAME

```       LAPACK-3 - solves the equation   A*X = B,

```

#### SYNOPSIS

```       SUBROUTINE DGTSV( N, NRHS, DL, D, DU, B, LDB, INFO )

INTEGER       INFO, LDB, N, NRHS

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

```

#### PURPOSE

```       DGTSV  solves the equation
where A is an n by n tridiagonal matrix, by Gaussian elimination with
partial pivoting.
Note that the equation  A**T*X = B  may be solved by interchanging the
order of the arguments DU and DL.

```

#### 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.

DL      (input/output) DOUBLE PRECISION array, dimension (N-1)
On entry, DL must contain the (n-1) sub-diagonal elements of
A.
On exit, DL is overwritten by the (n-2) elements of the
second super-diagonal of the upper triangular matrix U from
the LU factorization of A, in DL(1), ..., DL(n-2).

D       (input/output) DOUBLE PRECISION array, dimension (N)
On entry, D must contain the diagonal elements of A.
On exit, D is overwritten by the n diagonal elements of U.

DU      (input/output) DOUBLE PRECISION array, dimension (N-1)
On entry, DU must contain the (n-1) super-diagonal elements
of A.
On exit, DU is overwritten by the (n-1) elements of the first
super-diagonal of U.

B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
On entry, the N by NRHS matrix of 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 illegal value
> 0: if INFO = i, U(i,i) is exactly zero, and the solution
has not been computed.  The factorization has not been
completed unless i = N.

LAPACK routine (version 3.3.1)             April 2011                             DGTSV(3lapack)
```