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

6       DPPCON  -  estimates  the  reciprocal  of  the condition number (in the
7       1-norm) of a real symmetric positive definite packed matrix  using  the
8       Cholesky factorization A = U**T*U or A = L*L**T computed by DPPTRF
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SYNOPSIS

11       SUBROUTINE DPPCON( UPLO, N, AP, ANORM, RCOND, WORK, IWORK, INFO )
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13           CHARACTER      UPLO
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15           INTEGER        INFO, N
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17           DOUBLE         PRECISION ANORM, RCOND
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19           INTEGER        IWORK( * )
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21           DOUBLE         PRECISION AP( * ), WORK( * )
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PURPOSE

24       DPPCON estimates the reciprocal of the condition number (in the 1-norm)
25       of a real symmetric positive definite packed matrix using the  Cholesky
26       factorization A = U**T*U or A = L*L**T computed by DPPTRF.  An estimate
27       is obtained for norm(inv(A)), and the reciprocal of the condition  num‐
28       ber is computed as RCOND = 1 / (ANORM * norm(inv(A))).
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ARGUMENTS

31       UPLO    (input) CHARACTER*1
32               = 'U':  Upper triangle of A is stored;
33               = 'L':  Lower triangle of A is stored.
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35       N       (input) INTEGER
36               The order of the matrix A.  N >= 0.
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38       AP      (input) DOUBLE PRECISION array, dimension (N*(N+1)/2)
39               The  triangular factor U or L from the Cholesky factorization A
40               = U**T*U or A = L*L**T, packed columnwise in  a  linear  array.
41               The j-th column of U or L is stored in the array AP as follows:
42               if UPLO = 'U', AP(i + (j-1)*j/2) = U(i,j) for 1<=i<=j; if  UPLO
43               = 'L', AP(i + (j-1)*(2n-j)/2) = L(i,j) for j<=i<=n.
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45       ANORM   (input) DOUBLE PRECISION
46               The 1-norm (or infinity-norm) of the symmetric matrix A.
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48       RCOND   (output) DOUBLE PRECISION
49               The  reciprocal  of  the condition number of the matrix A, com‐
50               puted as RCOND = 1/(ANORM * AINVNM), where AINVNM is  an  esti‐
51               mate of the 1-norm of inv(A) computed in this routine.
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53       WORK    (workspace) DOUBLE PRECISION array, dimension (3*N)
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55       IWORK   (workspace) INTEGER array, dimension (N)
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57       INFO    (output) INTEGER
58               = 0:  successful exit
59               < 0:  if INFO = -i, the i-th argument had an illegal value
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63 LAPACK routine (version 3.2)    November 2008                       DPPCON(1)
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