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

```       LAPACK-3  -  solves  a  tridiagonal  system  of  the  form   A  * X = B using the L*D*L**T
factorization of A computed by SPTTRF

```

#### SYNOPSIS

```       SUBROUTINE SPTTRS( N, NRHS, D, E, B, LDB, INFO )

INTEGER        INFO, LDB, N, NRHS

REAL           B( LDB, * ), D( * ), E( * )

```

#### PURPOSE

```       SPTTRS solves a tridiagonal system of the form
A * X = B using the L*D*L**T factorization of A computed by SPTTRF.  D is a
diagonal matrix specified in the vector D, L is a unit bidiagonal
matrix whose subdiagonal is specified in the vector E, and X and B
are N by NRHS matrices.

```

#### ARGUMENTS

```        N       (input) INTEGER
The order of the tridiagonal 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.

D       (input) REAL array, dimension (N)
The n diagonal elements of the diagonal matrix D from the
L*D*L**T factorization of A.

E       (input) REAL array, dimension (N-1)
The (n-1) subdiagonal elements of the unit bidiagonal factor
L from the L*D*L**T factorization of A.  E can also be regarded
as the superdiagonal of the unit bidiagonal factor U from the
factorization A = U**T*D*U.

B       (input/output) REAL array, dimension (LDB,NRHS)
On entry, the right hand side vectors B for the system of
linear equations.
On exit, 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 illegal value

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