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

```       LAPACK-3  - solves a tridiagonal system of the form  A * X = B using the factorization A =
U**H*D*U or A = L*D*L**H computed by CPTTRF

```

#### SYNOPSIS

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

CHARACTER      UPLO

INTEGER        INFO, LDB, N, NRHS

REAL           D( * )

COMPLEX        B( LDB, * ), E( * )

```

#### PURPOSE

```       CPTTRS solves a tridiagonal system of the form
A * X = B using the factorization A = U**H*D*U or A = L*D*L**H computed by CPTTRF.
D is a diagonal matrix specified in the vector D, U (or L) is a unit
bidiagonal matrix whose superdiagonal (subdiagonal) is specified in
the vector E, and X and B are N by NRHS matrices.

```

#### ARGUMENTS

```        UPLO    (input) CHARACTER*1
Specifies the form of the factorization and whether the
vector E is the superdiagonal of the upper bidiagonal factor
U or the subdiagonal of the lower bidiagonal factor L.
= 'U':  A = U**H*D*U, E is the superdiagonal of U
= 'L':  A = L*D*L**H, E is the subdiagonal of L

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
factorization A = U**H*D*U or A = L*D*L**H.

E       (input) COMPLEX array, dimension (N-1)
If UPLO = 'U', the (n-1) superdiagonal elements of the unit
bidiagonal factor U from the factorization A = U**H*D*U.
If UPLO = 'L', the (n-1) subdiagonal elements of the unit
bidiagonal factor L from the factorization A = L*D*L**H.

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                            CPTTRS(3lapack)
```