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## clangb()

real function clangb | ( | character | norm,
|  | integer | n,
|  | integer | kl,
|  | integer | ku,
|  | complex, dimension( ldab, * ) | ab,
|  | integer | ldab,
|  | real, dimension( * ) | work )

CLANGB returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of general band matrix.

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

Purpose:

      !>
      !> CLANGB  returns the value of the one norm,  or the Frobenius norm, or
      !> the  infinity norm,  or the element of  largest absolute value  of an
      !> n by n band matrix  A,  with kl sub-diagonals and ku super-diagonals.
      !>

Returns
  CLANGB

      !>
      !>    CLANGB = ( max(abs(A(i,j))), NORM = 'M' or 'm'
      !>             (
      !>             ( norm1(A),         NORM = '1', 'O' or 'o'
      !>             (
      !>             ( normI(A),         NORM = 'I' or 'i'
      !>             (
      !>             ( normF(A),         NORM = 'F', 'f', 'E' or 'e'
      !>
      !> where  norm1  denotes the  one norm of a matrix (maximum column sum),
      !> normI  denotes the  infinity norm  of a matrix  (maximum row sum) and
      !> normF  denotes the  Frobenius norm of a matrix (square root of sum of
      !> squares).  Note that  max(abs(A(i,j)))  is not a consistent matrix norm.
      !>

Parameters

  [in]

  NORM

      !>          NORM is CHARACTER*1
      !>          Specifies the value to be returned in CLANGB as described
      !>          above.
      !>

  [in]

  N

      !>          N is INTEGER
      !>          The order of the matrix A.  N >= 0.  When N = 0, CLANGB is
      !>          set to zero.
      !>

  [in]

  KL

      !>          KL is INTEGER
      !>          The number of sub-diagonals of the matrix A.  KL >= 0.
      !>

  [in]

  KU

      !>          KU is INTEGER
      !>          The number of super-diagonals of the matrix A.  KU >= 0.
      !>

  [in]

  AB

      !>          AB is COMPLEX array, dimension (LDAB,N)
      !>          The band matrix A, stored in rows 1 to KL+KU+1.  The j-th
      !>          column of A is stored in the j-th column of the array AB as
      !>          follows:
      !>          AB(ku+1+i-j,j) = A(i,j) for max(1,j-ku)<=i<=min(n,j+kl).
      !>

  [in]

  LDAB

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

  [out]

  WORK

      !>          WORK is REAL array, dimension (MAX(1,LWORK)),
      !>          where LWORK >= N when NORM = 'I'; otherwise, WORK is not
      !>          referenced.
      !>

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