CTPCON - Online Linux Manual Page

Section : 1
Updated : November 2008
Source : LAPACK routine (version 3.2)
Note : LAPACK routine (version 3.2)
NAMECTPCON - estimates the reciprocal of the condition number of a packed triangular matrix A, in either the 1-norm or the infinity-norm
SYNOPSISSUBROUTINE CTPCON(  NORM, UPLO, DIAG, N, AP, RCOND, WORK, RWORK, INFO )  CHARACTER DIAG, NORM, UPLO  INTEGER INFO, N  REAL RCOND  REAL RWORK( * )  COMPLEX AP( * ), WORK( * )
PURPOSECTPCON 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)) ).
ARGUMENTSNORM (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) COMPLEX 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) REAL  The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))). WORK (workspace) COMPLEX array, dimension (2*N)  RWORK (workspace) REAL array, dimension (N)  INFO (output) INTEGER  = 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value 0
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