# dtpt06.f - Man Page

TESTING/LIN/dtpt06.f

## Synopsis

### Functions/Subroutines

subroutine **dtpt06** (rcond, rcondc, uplo, diag, n, ap, work, rat)**DTPT06**

## Function/Subroutine Documentation

### subroutine dtpt06 (double precision rcond, double precision rcondc, character uplo, character diag, integer n, double precision, dimension( * ) ap, double precision, dimension( * ) work, double precision rat)

**DTPT06**

**Purpose:**

DTPT06 computes a test ratio comparing RCOND (the reciprocal condition number of a triangular matrix A) and RCONDC, the estimate computed by DTPCON. 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 DTPCON.

*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.

*AP*AP is DOUBLE PRECISION array, dimension (N*(N+1)/2) The upper or lower triangular matrix A, packed columnwise in a linear array. The j-th column of A is stored in the array AP as follows: if UPLO = 'U', AP((j-1)*j/2 + i) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP((j-1)*(n-j) + j*(j+1)/2 + i-j) = A(i,j) for j<=i<=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 **110** of file **dtpt06.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dtpt06(3) is an alias of dtpt06.f(3).

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