DTPCON
November 2006
Modified to call DLACN2 in place of DLACON, 5 Feb 03, SJH.
Modified to call DLACN2 in place of DLACON, 5 Feb 03, SJH.
Purpose
DTPCON estimates the reciprocal of the condition number of a packed
triangular matrix A, in either the 1-norm or the infinity-norm.
The norm of A is computed and an estimate is obtained for
norm(inv(A)), then the reciprocal of the condition number is
computed as
RCOND = 1 / ( norm(A) * norm(inv(A)) ).
triangular matrix A, in either the 1-norm or the infinity-norm.
The norm of A is computed and an estimate is obtained for
norm(inv(A)), then the reciprocal of the condition number is
computed as
RCOND = 1 / ( norm(A) * norm(inv(A)) ).
Arguments
| NORM |
(input) CHARACTER*1
Specifies whether the 1-norm condition number or the
infinity-norm condition number is required: = '1' or 'O': 1-norm; = 'I': Infinity-norm. |
| UPLO |
(input) CHARACTER*1
= 'U': A is upper triangular;
= 'L': A is lower triangular. |
| DIAG |
(input) CHARACTER*1
= 'N': A is non-unit triangular;
= 'U': A is unit triangular. |
| N |
(input) INTEGER
The order of the matrix A. N >= 0.
|
| AP |
(input) 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(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for j<=i<=n. If DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be 1. |
| RCOND |
(output) DOUBLE PRECISION
The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(norm(A) * norm(inv(A))). |
| WORK |
(workspace) DOUBLE PRECISION array, dimension (3*N)
|
| IWORK |
(workspace) INTEGER array, dimension (N)
|
| INFO |
(output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value |