# dtrt06.f - Man Page

TESTING/LIN/dtrt06.f

## Synopsis

### Functions/Subroutines

subroutine **dtrt06** (rcond, rcondc, uplo, diag, n, a, lda, work, rat)**DTRT06**

## Function/Subroutine Documentation

### subroutine dtrt06 (double precision rcond, double precision rcondc, character uplo, character diag, integer n, double precision, dimension( lda, * ) a, integer lda, double precision, dimension( * ) work, double precision rat)

**DTRT06**

**Purpose:**

DTRT06 computes a test ratio comparing RCOND (the reciprocal condition number of a triangular matrix A) and RCONDC, the estimate computed by DTRCON. Information about the triangular matrix A is used if one estimate is zero and the other is non-zero to decide if underflow in the estimate is justified.

**Parameters***RCOND*RCOND is DOUBLE PRECISION The estimate of the reciprocal condition number obtained by forming the explicit inverse of the matrix A and computing RCOND = 1/( norm(A) * norm(inv(A)) ).

*RCONDC*RCONDC is DOUBLE PRECISION The estimate of the reciprocal condition number computed by DTRCON.

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

*DIAG*DIAG is CHARACTER 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).

*WORK*WORK is DOUBLE PRECISION array, dimension (N)

*RAT*RAT is DOUBLE PRECISION The test ratio. If both RCOND and RCONDC are nonzero, RAT = MAX( RCOND, RCONDC )/MIN( RCOND, RCONDC ) - 1. If RAT = 0, the two estimates are exactly the same.

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **119** of file **dtrt06.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dtrt06(3) is an alias of dtrt06.f(3).

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