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

6       STPCON  -  estimates the reciprocal of the condition number of a packed
7       triangular matrix A, in either the 1-norm or the infinity-norm
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SYNOPSIS

10       SUBROUTINE STPCON( NORM, UPLO, DIAG, N, AP, RCOND, WORK, IWORK, INFO )
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12           CHARACTER      DIAG, NORM, UPLO
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14           INTEGER        INFO, N
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16           REAL           RCOND
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18           INTEGER        IWORK( * )
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20           REAL           AP( * ), WORK( * )
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PURPOSE

23       STPCON estimates the reciprocal of the condition  number  of  a  packed
24       triangular  matrix  A,  in either the 1-norm or the infinity-norm.  The
25       norm of A is computed and an estimate  is  obtained  for  norm(inv(A)),
26       then the reciprocal of the condition number is computed as
27          RCOND = 1 / ( norm(A) * norm(inv(A)) ).
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ARGUMENTS

30       NORM    (input) CHARACTER*1
31               Specifies  whether the 1-norm condition number or the infinity-
32               norm condition number is required:
33               = '1' or 'O':  1-norm;
34               = 'I':         Infinity-norm.
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36       UPLO    (input) CHARACTER*1
37               = 'U':  A is upper triangular;
38               = 'L':  A is lower triangular.
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40       DIAG    (input) CHARACTER*1
41               = 'N':  A is non-unit triangular;
42               = 'U':  A is unit triangular.
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44       N       (input) INTEGER
45               The order of the matrix A.  N >= 0.
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47       AP      (input) REAL array, dimension (N*(N+1)/2)
48               The upper or lower triangular matrix A, packed columnwise in  a
49               linear  array.   The j-th column of A is stored in the array AP
50               as follows: if UPLO = 'U',  AP(i  +  (j-1)*j/2)  =  A(i,j)  for
51               1<=i<=j;  if  UPLO  =  'L', AP(i + (j-1)*(2n-j)/2) = A(i,j) for
52               j<=i<=n.  If DIAG = 'U', the diagonal elements  of  A  are  not
53               referenced and are assumed to be 1.
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55       RCOND   (output) REAL
56               The  reciprocal  of  the condition number of the matrix A, com‐
57               puted as RCOND = 1/(norm(A) * norm(inv(A))).
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59       WORK    (workspace) REAL array, dimension (3*N)
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61       IWORK   (workspace) INTEGER array, dimension (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 3.2)    November 2008                       STPCON(1)
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