dtrt01.f3

Usage

Functions/Subroutines

DTRT01

Function/Subroutine Documentation

subroutine dtrt01 (character uplo, character diag, integer n, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( ldainv, * ) ainv, integer ldainv, double precision rcond, double precision, dimension( * ) work, double precision resid)

DTRT01

Purpose:

!>
!> DTRT01 computes the residual for a triangular matrix A times its
!> inverse:
!>    RESID = norm( A*AINV - I ) / ( N * norm(A) * norm(AINV) * EPS ),
!> where EPS is the machine epsilon.
!>

Parameters

UPLO

!>          UPLO is CHARACTER*1
!>          Specifies whether the matrix A is upper or lower triangular.
!>          = 'U':  Upper triangular
!>          = 'L':  Lower triangular
!>

DIAG

!>          DIAG is CHARACTER*1
!>          Specifies whether or not the matrix A is unit triangular.
!>          = 'N':  Non-unit triangular
!>          = 'U':  Unit triangular
!>

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

!>          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).
!>

AINV

!>          AINV is DOUBLE PRECISION array, dimension (LDAINV,N)
!>          On entry, the (triangular) inverse of the matrix A, in the
!>          same storage format as A.
!>          On exit, the contents of AINV are destroyed.
!>

LDAINV

!>          LDAINV is INTEGER
!>          The leading dimension of the array AINV.  LDAINV >= max(1,N).
!>

RCOND

!>          RCOND is DOUBLE PRECISION
!>          The reciprocal condition number of A, computed as
!>          1/(norm(A) * norm(AINV)).
!>

WORK

!>          WORK is DOUBLE PRECISION array, dimension (N)
!>

RESID

!>          RESID is DOUBLE PRECISION
!>          norm(A*AINV - I) / ( N * norm(A) * norm(AINV) * EPS )
!>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 122 of file dtrt01.f.