CGBCON  -  estimate the reciprocal of the condition number
       of a complex general band matrix A, in either  the  1-norm
       or the infinity-norm,


SYNOPSIS

       SUBROUTINE CGBCON( NORM, N, KL, KU, AB, LDAB, IPIV, ANORM,
                          RCOND, WORK, RWORK, INFO )

           CHARACTER      NORM

           INTEGER        INFO, KL, KU, LDAB, N

           REAL           ANORM, RCOND

           INTEGER        IPIV( * )

           REAL           RWORK( * )

           COMPLEX        AB( LDAB, * ), WORK( * )


PURPOSE

       CGBCON estimates the reciprocal of the condition number of
       a  complex  general band matrix A, in either the 1-norm or
       the infinity-norm, using the LU factorization computed  by
       CGBTRF.

       An estimate is obtained for norm(inv(A)), and the recipro­
       cal 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.

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

       KL      (input) INTEGER
               The  number  of subdiagonals within the band of A.
               KL >= 0.

       KU      (input) INTEGER
               The number of superdiagonals within the band of A.
               KU >= 0.

       AB      (input) COMPLEX array, dimension (LDAB,N)
               Details of the LU factorization of the band matrix
               A, as computed by CGBTRF.  U is stored as an upper
               triangular  band  matrix with KL+KU superdiagonals

               during   the  factorization  are  stored  in  rows
               KL+KU+2 to 2*KL+KU+1.

       LDAB    (input) INTEGER
               The leading dimension of the array  AB.   LDAB  >=
               2*KL+KU+1.

       IPIV    (input) INTEGER array, dimension (N)
               The  pivot  indices; for 1 <= i <= N, row i of the
               matrix was interchanged with row IPIV(i).

       ANORM   (input) REAL
               If NORM = '1' or 'O', the 1-norm of  the  original
               matrix A.  If NORM = 'I', the infinity-norm of the
               original matrix A.

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

       WORK    (workspace) COMPLEX array, dimension (2*N)

       RWORK   (workspace) REAL 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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