ZTRTRS(1) LAPACK routine (version 3.2) ZTRTRS(1)NAME
ZTRTRS - solves 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 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 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 trian‐
gular matrix, and the strictly lower triangular part of A is
not referenced. If UPLO = 'L', the leading N-by-N 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 elements of A are also not refer‐
enced 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, indi‐
cating that the matrix is singular and the solutions X have not
been computed.
LAPACK routine (version 3.2) November 2008 ZTRTRS(1)