ZTPT06
Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
November 2006
November 2006
Purpose
ZTPT06 computes a test ratio comparing RCOND (the reciprocal
condition number of the triangular matrix A) and RCONDC, the estimate
computed by ZTPCON. Information about the triangular matrix 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 the triangular matrix A) and RCONDC, the estimate
computed by ZTPCON. Information about the triangular matrix 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) 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 |
(input) DOUBLE PRECISION
The estimate of the reciprocal condition number computed by
ZTPCON. |
| 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.
|
| AP |
(input) COMPLEX*16 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. |
| RWORK |
(workspace) DOUBLE PRECISION array, dimension (N)
|
| RAT |
(output) 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. |