Provided by: scalapack-doc_1.5-10_all #### NAME

```       ZPTTRSV - solve one of the triangular systems  L * X = B, or L**H * X = B,

```

#### SYNOPSIS

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

CHARACTER       UPLO, TRANS

INTEGER         INFO, LDB, N, NRHS

DOUBLE          PRECISION D( * )

COMPLEX*16      B( LDB, * ), E( * )

```

#### PURPOSE

```       ZPTTRSV solves one of the triangular systems
L * X = B, or  L**H * X = B,
U * X = B, or  U**H * X = B,
where  L or U is the Cholesky factor of a Hermitian positive definite tridiagonal matrix A
such that
A = U**H*D*U or A = L*D*L**H (computed by ZPTTRF).

```

#### ARGUMENTS

```       UPLO    (input) CHARACTER*1
Specifies whether the superdiagonal or the subdiagonal of the tridiagonal matrix A
is stored and the form of the factorization:
= 'U':  E is the superdiagonal of U, and A = U'*D*U;
=  'L':  E is the subdiagonal of L, and A = L*D*L'.  (The two forms are equivalent
if A is real.)

TRANS   (input) CHARACTER
Specifies the form of the system of equations:
= 'N':  L * X = B     (No transpose)
= 'N':  L * X = B     (No transpose)
= 'C':  U**H * X = B  (Conjugate transpose)
= 'C':  L**H * X = B  (Conjugate transpose)

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 computed
by ZPTTRF.

E       (input) COMPLEX array, dimension (N-1)
The (n-1) off-diagonal elements of the unit bidiagonal factor  U  or  L  from  the
factorization computed by ZPTTRF (see UPLO).

B       (input/output) COMPLEX array, dimension (LDB,NRHS)
On entry, the right hand side matrix B.  On exit, the 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
```