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## cgbcon()

subroutine cgbcon | ( | character | norm,
|  | integer | n,
|  | integer | kl,
|  | integer | ku,
|  | complex, dimension( ldab, * ) | ab,
|  | integer | ldab,
|  | integer, dimension( * ) | ipiv,
|  | real | anorm,
|  | real | rcond,
|  | complex, dimension( * ) | work,
|  | real, dimension( * ) | rwork,
|  | integer | info )

CGBCON

Download CGBCON + dependencies [TGZ] [ZIP] [TXT]

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 reciprocal of the
      !> condition number is computed as
      !>    RCOND = 1 / ( norm(A) * norm(inv(A)) ).
      !>

Parameters

  [in]

  NORM

      !>          NORM is 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.
      !>

  [in]

  N

      !>          N is INTEGER
      !>          The order of the matrix A.  N >= 0.
      !>

  [in]

  KL

      !>          KL is INTEGER
      !>          The number of subdiagonals within the band of A.  KL >= 0.
      !>

  [in]

  KU

      !>          KU is INTEGER
      !>          The number of superdiagonals within the band of A.  KU >= 0.
      !>

  [in]

  AB

      !>          AB is 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 in rows 1 to KL+KU+1, and
      !>          the multipliers used during the factorization are stored in
      !>          rows KL+KU+2 to 2*KL+KU+1.
      !>

  [in]

  LDAB

      !>          LDAB is INTEGER
      !>          The leading dimension of the array AB.  LDAB >= 2*KL+KU+1.
      !>

  [in]

  IPIV

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

  [in]

  ANORM

      !>          ANORM is 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.
      !>

  [out]

  RCOND

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

  [out]

  WORK

      !>          WORK is COMPLEX array, dimension (2*N)
      !>

  [out]

  RWORK

      !>          RWORK is REAL array, dimension (N)
      !>

  [out]

  INFO

      !>          INFO is INTEGER
      !>          = 0:  successful exit
      !>          < 0: if INFO = -i, the i-th argument had an illegal value
      !>

Author
  Univ. of Tennessee
  Univ. of California Berkeley
  Univ. of Colorado Denver
  NAG Ltd.