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ztrtrs

```
NAME
ZTRTRS - solve a triangular system of the form   A * X = B,
A**T * X = B, or A**H * X = B,

SYNOPSIS
SUBROUTINE ZTRTRS( UPLO, TRANS, DIAG, N, NRHS, A, LDA, B,
LDB, INFO )

CHARACTER      DIAG, TRANS, UPLO

INTEGER        INFO, LDA, LDB, N, NRHS

COMPLEX*16     A( LDA, * ), B( LDB, * )

PURPOSE
ZTRTRS solves a triangular system of the form

where A is a triangular matrix of order N, and B is an N-
by-NRHS matrix.  A check is made to verify that A is non-
singular.

ARGUMENTS
UPLO    (input) CHARACTER*1
= 'U':  A is upper triangular;
= 'L':  A is lower triangular.

TRANS   (input) CHARACTER*1
Specifies the form of the system of equations:
= 'N':  A * X = B     (No transpose)
= 'T':  A**T * X = B  (Transpose)
= 'C':  A**H * X = B  (Conjugate transpose)

DIAG    (input) CHARACTER*1
= 'N':  A is non-unit triangular;
= 'U':  A is unit triangular.

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.

A       (input) COMPLEX*16 array, dimension (LDA,N)
The triangular matrix A.  If UPLO = 'U', the leading
N-by-N upper triangular part of the array A contains
the upper triangular matrix, and the strictly lower
triangular part of A is not referenced.  If UPLO =
'L', the leading N-by-N lower triangular part of the
array A contains the lower triangular matrix, and
the strictly upper triangular part of A is not

referenced.  If DIAG = 'U', the diagonal elements of
A are also not referenced and are assumed to be 1.

LDA     (input) INTEGER
The leading dimension of the array A.  LDA >=
max(1,N).

B       (input/output) COMPLEX*16 array, dimension (LDB,NRHS)
On entry, the right hand side matrix B.  On exit, if
INFO = 0, 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
> 0: if INFO = i, the i-th diagonal element of A is
zero, indicating that the matrix is singular and the
solutions X have not been computed.
```