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


SYNOPSIS

       SUBROUTINE STBCON( NORM,  UPLO,  DIAG,  N,  KD,  AB, LDAB,
                          RCOND, WORK, IWORK, INFO )

           CHARACTER      DIAG, NORM, UPLO

           INTEGER        INFO, KD, LDAB, N

           REAL           RCOND

           INTEGER        IWORK( * )

           REAL           AB( LDAB, * ), WORK( * )


PURPOSE

       STBCON estimates the reciprocal of the condition number of
       a  triangular  band  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.

       KD      (input) INTEGER
               The  number  of  superdiagonals or subdiagonals of
               the triangular band matrix A.  KD >= 0.

       AB      (input) REAL array, dimension (LDAB,N)
               The upper  or  lower  triangular  band  matrix  A,
               stored in the first kd+1 rows of the array. The j-
               th column of A is stored in the j-th column of the

               = A(i,j) for max(1,j-kd)<=i<=j;  if  UPLO  =  'L',
               AB(1+i-j,j)    = A(i,j) for j<=i<=min(n,j+kd).  If
               DIAG = 'U', the diagonal elements  of  A  are  not
               referenced and are assumed to be 1.

       LDAB    (input) INTEGER
               The  leading  dimension  of the array AB.  LDAB >=
               KD+1.

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

       WORK    (workspace) REAL 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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