# strtrs.f(3) [debian man page]

```strtrs.f(3)							      LAPACK							       strtrs.f(3)

NAME
strtrs.f -

SYNOPSIS
Functions/Subroutines
subroutine strtrs (UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB, INFO)
STRTRS

Function/Subroutine Documentation
subroutine strtrs (characterUPLO, characterTRANS, characterDIAG, integerN, integerNRHS, real, dimension( lda, * )A, integerLDA, real,
dimension( ldb, * )B, integerLDB, integerINFO)
STRTRS

Purpose:

STRTRS solves a triangular system of the form

A * X = B  or  A**T * X = B,

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.

Parameters:
UPLO

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

TRANS

TRANS is 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

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

N

N is INTEGER
The order of the matrix A.  N >= 0.

NRHS

NRHS is INTEGER
The number of right hand sides, i.e., the number of columns
of the matrix B.  NRHS >= 0.

A

A is REAL 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

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

B

B is REAL array, dimension (LDB,NRHS)
On entry, the right hand side matrix B.
On exit, if INFO = 0, the solution matrix X.

LDB

LDB is INTEGER
The leading dimension of the array B.  LDB >= max(1,N).

INFO

INFO is 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.

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
November 2011

Definition at line 140 of file strtrs.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.1							  Sun May 26 2013						       strtrs.f(3)```

## Check Out this Related Man Page

```STRTRS(l)								 )								 STRTRS(l)

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

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

CHARACTER	  DIAG, TRANS, UPLO

INTEGER	  INFO, LDA, LDB, N, NRHS

REAL 	  A( LDA, * ), B( LDB, * )

PURPOSE
STRTRS  solves  a triangular system of the form A * X = B or A**T * X = B, 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 = 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) REAL 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) REAL 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.

LAPACK version 3.0						   15 June 2000 							 STRTRS(l)```
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