1CHECON(1)                LAPACK routine (version 3.1)                CHECON(1)
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NAME

6       CHECON  - the reciprocal of the condition number of a complex Hermitian
7       matrix A using the factorization A = U*D*U**H or A = L*D*L**H  computed
8       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.
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28       An  estimate  is  obtained  for norm(inv(A)), and the reciprocal of the
29       condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
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ARGUMENTS

33       UPLO    (input) CHARACTER*1
34               Specifies whether the details of the factorization  are  stored
35               as an upper or lower triangular matrix.  = 'U':  Upper triangu‐
36               lar, form is A = U*D*U**H;
37               = 'L':  Lower triangular, form is A = L*D*L**H.
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39       N       (input) INTEGER
40               The order of the matrix A.  N >= 0.
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42       A       (input) COMPLEX array, dimension (LDA,N)
43               The block diagonal matrix D and the multipliers used to  obtain
44               the factor U or L as computed by CHETRF.
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46       LDA     (input) INTEGER
47               The leading dimension of the array A.  LDA >= max(1,N).
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49       IPIV    (input) INTEGER array, dimension (N)
50               Details  of  the  interchanges  and the block structure of D as
51               determined by CHETRF.
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53       ANORM   (input) REAL
54               The 1-norm of the original matrix A.
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56       RCOND   (output) REAL
57               The reciprocal of the condition number of the  matrix  A,  com‐
58               puted  as  RCOND = 1/(ANORM * AINVNM), where AINVNM is an esti‐
59               mate of the 1-norm of inv(A) computed in this routine.
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61       WORK    (workspace) COMPLEX array, dimension (2*N)
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63       INFO    (output) INTEGER
64               = 0:  successful exit
65               < 0:  if INFO = -i, the i-th argument had an illegal value
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69 LAPACK routine (version 3.1)    November 2006                       CHECON(1)
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