# dtrt01.f - Man Page

TESTING/LIN/dtrt01.f

## Synopsis

### Functions/Subroutines

subroutine dtrt01 (uplo, diag, n, a, lda, ainv, ldainv, rcond, work, resid)
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

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

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

NAG Ltd.

Definition at line 122 of file dtrt01.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dtrt01(3) is an alias of dtrt01.f(3).

Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK