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

6       SSYCON  -  the  reciprocal of the condition number (in the 1-norm) of a
7       real symmetric matrix A using the factorization A =  U*D*U**T  or  A  =
8       L*D*L**T computed by SSYTRF
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SYNOPSIS

11       SUBROUTINE SSYCON( UPLO,  N,  A,  LDA, IPIV, ANORM, RCOND, WORK, IWORK,
12                          INFO )
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14           CHARACTER      UPLO
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16           INTEGER        INFO, LDA, N
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18           REAL           ANORM, RCOND
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20           INTEGER        IPIV( * ), IWORK( * )
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22           REAL           A( LDA, * ), WORK( * )
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PURPOSE

25       SSYCON estimates the reciprocal of the condition number (in the 1-norm)
26       of  a real symmetric matrix A using the factorization A = U*D*U**T or A
27       = L*D*L**T computed by SSYTRF.
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29       An estimate is obtained for norm(inv(A)), and  the  reciprocal  of  the
30       condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
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ARGUMENTS

34       UPLO    (input) CHARACTER*1
35               Specifies  whether  the details of the factorization are stored
36               as an upper or lower triangular matrix.  = 'U':  Upper triangu‐
37               lar, form is A = U*D*U**T;
38               = 'L':  Lower triangular, form is A = L*D*L**T.
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40       N       (input) INTEGER
41               The order of the matrix A.  N >= 0.
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43       A       (input) REAL array, dimension (LDA,N)
44               The  block diagonal matrix D and the multipliers used to obtain
45               the factor U or L as computed by SSYTRF.
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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       IPIV    (input) INTEGER array, dimension (N)
51               Details of the interchanges and the block  structure  of  D  as
52               determined by SSYTRF.
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54       ANORM   (input) REAL
55               The 1-norm of the original matrix A.
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57       RCOND   (output) REAL
58               The  reciprocal  of  the condition number of the matrix A, com‐
59               puted as RCOND = 1/(ANORM * AINVNM), where AINVNM is  an  esti‐
60               mate of the 1-norm of inv(A) computed in this routine.
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62       WORK    (workspace) REAL array, dimension (2*N)
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64       IWORK    (workspace) INTEGER array, dimension (N)
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66       INFO    (output) INTEGER
67               = 0:  successful exit
68               < 0:  if INFO = -i, the i-th argument had an illegal value
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72 LAPACK routine (version 3.1)    November 2006                       SSYCON(1)
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