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NAME
     dtrcon - estimate the reciprocal of the condition number  of
     a   triangular  matrix  A,  in  either  the  1-norm  or  the
     infinity-norm

SYNOPSIS
     SUBROUTINE DTRCON( NORM, UPLO, DIAG, N, A, LDA, RCOND, WORK,
               IWORK, INFO )

     CHARACTER DIAG, NORM, UPLO

     INTEGER INFO, LDA, N

     DOUBLE PRECISION RCOND

     INTEGER IWORK( * )

     DOUBLE PRECISION A( LDA, * ), WORK( * )



     #include <sunperf.h>

     void dtrcon(char norm, char uplo, char diag, int  n,  double
               *da, int lda, double *drcond, int *info);

PURPOSE
     DTRCON estimates the reciprocal of the condition number of a
     triangular  matrix  A, in either the 1-norm or the infinity-
     norm.

     The norm of A is computed and an estimate  is  obtained  for
     norm(inv(A)), then the reciprocal of the condition number is
     computed as
        RCOND = 1 / ( norm(A) * norm(inv(A)) ).


ARGUMENTS
     NORM      (input) CHARACTER*1
               Specifies whether the 1-norm condition  number  or
               the infinity-norm condition number is required:
               = '1' or 'O':  1-norm;
               = 'I':         Infinity-norm.

     UPLO      (input) CHARACTER*1
               = 'U':  A is upper triangular;
               = 'L':  A is lower triangular.

     DIAG      (input) CHARACTER*1
               = 'N':  A is non-unit triangular;
               = 'U':  A is unit triangular.

     N         (input) INTEGER
               The order of the matrix A.  N >= 0.

     A         (input) DOUBLE PRECISION array, dimension (LDA,N)
               The triangular matrix A.  If UPLO = 'U', the lead-
               ing  N-by-N  upper  triangular part of the array A
               contains the  upper  triangular  matrix,  and  the
               strictly  lower triangular part of A is not refer-
               enced.  If UPLO = 'L', the  leading  N-by-N  lower
               triangular  part of the array A contains the lower
               triangular matrix, and the strictly upper triangu-
               lar  part  of A is not referenced.  If DIAG = 'U',
               the diagonal elements of A are also not referenced
               and are assumed to be 1.

     LDA       (input) INTEGER
               The leading dimension of  the  array  A.   LDA  >=
               max(1,N).

     RCOND     (output) DOUBLE PRECISION
               The reciprocal of  the  condition  number  of  the
               matrix   A,  computed  as  RCOND  =  1/(norm(A)  *
               norm(inv(A))).

     WORK      (workspace)  DOUBLE  PRECISION  array,   dimension
               (3*N)

     IWORK     (workspace) INTEGER array, dimension (N)

     INFO      (output) INTEGER
               = 0:  successful exit
               < 0:  if INFO = -i, the i-th argument had an ille-
               gal value

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