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

6       DGECON  -  the  reciprocal  of  the  condition number of a general real
7       matrix A, in either the 1-norm or the infinity-norm, using the LU  fac‐
8       torization computed by DGETRF
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SYNOPSIS

11       SUBROUTINE DGECON( NORM, N, A, LDA, ANORM, RCOND, WORK, IWORK, INFO )
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13           CHARACTER      NORM
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15           INTEGER        INFO, LDA, N
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17           DOUBLE         PRECISION ANORM, RCOND
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19           INTEGER        IWORK( * )
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21           DOUBLE         PRECISION A( LDA, * ), WORK( * )
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PURPOSE

24       DGECON  estimates  the  reciprocal of the condition number of a general
25       real matrix A, in either the 1-norm or the infinity-norm, using the  LU
26       factorization computed by DGETRF.
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28       An  estimate  is  obtained  for norm(inv(A)), and the reciprocal of the
29       condition number is computed as
30          RCOND = 1 / ( norm(A) * norm(inv(A)) ).
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ARGUMENTS

34       NORM    (input) CHARACTER*1
35               Specifies whether the 1-norm condition number or the  infinity-
36               norm condition number is required:
37               = '1' or 'O':  1-norm;
38               = 'I':         Infinity-norm.
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40       N       (input) INTEGER
41               The order of the matrix A.  N >= 0.
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43       A       (input) DOUBLE PRECISION array, dimension (LDA,N)
44               The  factors  L  and U from the factorization A = P*L*U as com‐
45               puted by DGETRF.
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47       LDA     (input) INTEGER
48               The leading dimension of the array A.  LDA >= max(1,N).
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50       ANORM   (input) DOUBLE PRECISION
51               If NORM = '1' or 'O', the 1-norm of the original matrix A.   If
52               NORM = 'I', the infinity-norm of the original matrix A.
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54       RCOND   (output) DOUBLE PRECISION
55               The  reciprocal  of  the condition number of the matrix A, com‐
56               puted as RCOND = 1/(norm(A) * norm(inv(A))).
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58       WORK    (workspace) DOUBLE PRECISION array, dimension (4*N)
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60       IWORK   (workspace) INTEGER array, dimension (N)
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62       INFO    (output) INTEGER
63               = 0:  successful exit
64               < 0:  if INFO = -i, the i-th argument had an illegal value
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68 LAPACK routine (version 3.1)    November 2006                       DGECON(1)
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