dtpcon (l)  Linux Man Pages
dtpcon: estimates the reciprocal of the condition number of a packed triangular matrix A, in either the 1norm or the infinitynorm
NAME
DTPCON  estimates the reciprocal of the condition number of a packed triangular matrix A, in either the 1norm or the infinitynormSYNOPSIS
 SUBROUTINE DTPCON(
 NORM, UPLO, DIAG, N, AP, RCOND, WORK, IWORK, INFO )
 CHARACTER DIAG, NORM, UPLO
 INTEGER INFO, N
 DOUBLE PRECISION RCOND
 INTEGER IWORK( * )
 DOUBLE PRECISION AP( * ), WORK( * )
PURPOSE
DTPCON estimates the reciprocal of the condition number of a packed triangular matrix A, in either the 1norm or the infinitynorm. The norm of A is computed and an estimate is obtained for norm(inv(A)), then the reciprocal of the condition number is computed asRCOND
ARGUMENTS
 NORM (input) CHARACTER*1

Specifies whether the 1norm condition number or the
infinitynorm condition number is required:
= aq1aq or aqOaq: 1norm;
= aqIaq: Infinitynorm.  UPLO (input) CHARACTER*1

= aqUaq: A is upper triangular;
= aqLaq: A is lower triangular.  DIAG (input) CHARACTER*1

= aqNaq: A is nonunit triangular;
= aqUaq: 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 jth column of A is stored in the array AP as follows: if UPLO = aqUaq, AP(i + (j1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = aqLaq, AP(i + (j1)*(2nj)/2) = A(i,j) for j<=i<=n. If DIAG = aqUaq, 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 ith argument had an illegal value