DTRTRS(3)
solves a triangular system of the form A * X = B or A**T * X = B,
SYNOPSIS
 SUBROUTINE DTRTRS(

UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB,
INFO )

CHARACTER
DIAG, TRANS, UPLO

INTEGER
INFO, LDA, LDB, N, NRHS

DOUBLE
PRECISION A( LDA, * ), B( LDB, * )
PURPOSE
DTRTRS solves a triangular system of the form
where A is a triangular matrix of order N, and B is an NbyNRHS
matrix. A check is made to verify that A is nonsingular.
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 = Transpose)
 DIAG (input) CHARACTER*1

= 'N': A is nonunit 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) DOUBLE PRECISION array, dimension (LDA,N)

The triangular matrix A. If UPLO = 'U', the leading NbyN
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 NbyN 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) DOUBLE PRECISION 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 ith argument had an illegal value
> 0: if INFO = i, the ith diagonal element of A is zero,
indicating that the matrix is singular and the solutions
X have not been computed.