CTRT06
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
November 2006
Purpose
CTRT06 computes a test ratio comparing RCOND (the reciprocal
condition number of a triangular matrix A) and RCONDC, the estimate
computed by CTRCON. 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.
condition number of a triangular matrix A) and RCONDC, the estimate
computed by CTRCON. 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.
Arguments
| RCOND |
(input) REAL
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 |
(input) REAL
The estimate of the reciprocal condition number computed by
CTRCON. |
| UPLO |
(input) CHARACTER
Specifies whether the matrix A is upper or lower triangular.
= 'U': Upper triangular = 'L': Lower triangular |
| DIAG |
(input) CHARACTER
Specifies whether or not the matrix A is unit triangular.
= 'N': Non-unit triangular = 'U': Unit triangular |
| N |
(input) INTEGER
The order of the matrix A. N >= 0.
|
| A |
(input) COMPLEX 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 |
(input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
|
| RWORK |
(workspace) REAL array, dimension (N)
|
| RAT |
(output) REAL
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. |