dtrtrs (l)  Linux Man Pages
dtrtrs: solves a triangular system of the form A * X = B or A**T * X = B,
Command to display dtrtrs
manual in Linux: $ man l dtrtrs
NAME
DTRTRS  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

= aqUaq: A is upper triangular;
= aqLaq: A is lower triangular.
 TRANS (input) CHARACTER*1

Specifies the form of the system of equations:
= aqNaq: A * X = B (No transpose)
= aqTaq: A**T * X = B (Transpose)
= aqCaq: A**H * X = B (Conjugate transpose = Transpose)
 DIAG (input) CHARACTER*1

= aqNaq: A is nonunit triangular;
= aqUaq: 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 = aqUaq, 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 = aqLaq, 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 = aqUaq, 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.
Pages related to dtrtrs
 dtrtrs (3)
 dtrtri (l)  computes the inverse of a real upper or lower triangular matrix A
 dtrti2 (l)  computes the inverse of a real upper or lower triangular matrix
 dtrttf (l)  copies a triangular matrix A from standard full format (TR) to rectangular full packed format (TF)
 dtrttp (l)  copies a triangular matrix A from full format (TR) to standard packed format (TP)
 dtrcon (l)  estimates the reciprocal of the condition number of a triangular matrix A, in either the 1norm or the infinitynorm
 dtrevc (l)  computes some or all of the right and/or left eigenvectors of a real upper quasitriangular matrix T
 dtrexc (l)  reorders the real Schur factorization of a real matrix A = Q*T*Q**T, so that the diagonal block of T with row index IFST is moved to row ILST