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LAPACK version 3.0
dlangt(3)

PURPOSE
  DLANGT - return the value of the one norm, or the Frobenius norm, or the
  infinity norm, or the element of largest absolute value of a real
  tridiagonal matrix A

SYNTAX
  DOUBLE PRECISION FUNCTION DLANGT( NORM, N, DL, D, DU )

      CHARACTER	   NORM

      INTEGER	   N

      DOUBLE	   PRECISION D( * ), DL( * ), DU( * )

DESCRIPTION
  DLANGT returns the value of the one norm, or the Frobenius norm, or the
  infinity norm, or the element of largest absolute value of a real
  tridiagonal matrix A.

DESCRIPTION
  DLANGT returns the value

     DLANGT = ( 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	 matrix norm.

ARGUMENTS
  NORM	  (input) CHARACTER*1
	  Specifies the value to be returned in DLANGT as described above.

  N	  (input) INTEGER
	  The order of the matrix A.  N >= 0.  When N = 0, DLANGT is set to
	  zero.

  DL	  (input) DOUBLE PRECISION array, dimension (N-1)
	  The (n-1) sub-diagonal elements of A.

  D	  (input) DOUBLE PRECISION array, dimension (N)
	  The diagonal elements of A.

  DU	  (input) DOUBLE PRECISION array, dimension (N-1)
	  The (n-1) super-diagonal elements of A.