dtrtrs.f (3) Linux Manual Page

dtrtrs.f –

Synopsis

Functions/Subroutines

subroutine dtrtrs (UPLO, TRANS, DIAG, N, NRHS, A, LDA, B, LDB, INFO)
DTRTRS

Function/Subroutine Documentation

subroutine dtrtrs (characterUPLO, characterTRANS, characterDIAG, integerN, integerNRHS, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( ldb, * )B, integerLDB, integerINFO)

DTRTRS

Purpose:

 DTRTRS 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 DOUBLE PRECISION 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 DOUBLE PRECISION 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

Univ. of Colorado Denver

NAG Ltd.

Date:

November 2011

Definition at line 140 of file dtrtrs.f.

Author

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