1CHECON(1)                LAPACK routine (version 3.2)                CHECON(1)
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NAME

6       CHECON  - estimates the reciprocal of the condition number of a complex
7       Hermitian matrix A using the factorization A = U*D*U**H or A = L*D*L**H
8       computed by CHETRF
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SYNOPSIS

11       SUBROUTINE CHECON( UPLO, N, A, LDA, IPIV, ANORM, RCOND, WORK, INFO )
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13           CHARACTER      UPLO
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15           INTEGER        INFO, LDA, N
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17           REAL           ANORM, RCOND
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19           INTEGER        IPIV( * )
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21           COMPLEX        A( LDA, * ), WORK( * )
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PURPOSE

24       CHECON  estimates  the  reciprocal of the condition number of a complex
25       Hermitian matrix A using the factorization A = U*D*U**H or A = L*D*L**H
26       computed  by CHETRF.  An estimate is obtained for norm(inv(A)), and the
27       reciprocal of the condition number is computed as RCOND = 1 / (ANORM  *
28       norm(inv(A))).
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ARGUMENTS

31       UPLO    (input) CHARACTER*1
32               Specifies  whether  the details of the factorization are stored
33               as an upper or lower triangular matrix.  = 'U':  Upper triangu‐
34               lar, form is A = U*D*U**H;
35               = 'L':  Lower triangular, form is A = L*D*L**H.
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37       N       (input) INTEGER
38               The order of the matrix A.  N >= 0.
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40       A       (input) COMPLEX array, dimension (LDA,N)
41               The  block diagonal matrix D and the multipliers used to obtain
42               the factor U or L as computed by CHETRF.
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44       LDA     (input) INTEGER
45               The leading dimension of the array A.  LDA >= max(1,N).
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47       IPIV    (input) INTEGER array, dimension (N)
48               Details of the interchanges and the block  structure  of  D  as
49               determined by CHETRF.
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51       ANORM   (input) REAL
52               The 1-norm of the original matrix A.
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54       RCOND   (output) REAL
55               The  reciprocal  of  the condition number of the matrix A, com‐
56               puted as RCOND = 1/(ANORM * AINVNM), where AINVNM is  an  esti‐
57               mate of the 1-norm of inv(A) computed in this routine.
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59       WORK    (workspace) COMPLEX array, dimension (2*N)
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61       INFO    (output) INTEGER
62               = 0:  successful exit
63               < 0:  if INFO = -i, the i-th argument had an illegal value
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67 LAPACK routine (version 3.2)    November 2008                       CHECON(1)
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