
CTRTRS(l) ) CTRTRS(l)
NAME
CTRTRS  solve a triangular system of the form A * X = B, A**T * X = B, or A**H * X = B,
SYNOPSIS
SUBROUTINE CTRTRS( UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB, INFO )
CHARACTER DIAG, TRANS, UPLO
INTEGER INFO, LDA, LDB, N, NRHS
COMPLEX A( LDA, * ), B( LDB, * )
PURPOSE
CTRTRS solves a triangular system of the form A * X = B, A**T * X = B, or A**H * X = B,
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)
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) COMPLEX 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 trian
gular part of A is not referenced. If UPLO = 'L', the leading NbyN lower trian
gular 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 ele
ments 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 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.
LAPACK version 3.0 15 June 2000 CTRTRS(l) 
