 CLANGT(3) returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a complex tridiagonal matrix A

## SYNOPSIS

REAL FUNCTION
CLANGT( NORM, N, DL, D, DU )

CHARACTER NORM

INTEGER N

COMPLEX D( * ), DL( * ), DU( * )

## PURPOSE

CLANGT returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a complex tridiagonal matrix A.

## DESCRIPTION

CLANGT returns the value

CLANGT = ( 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.

## ARGUMENTS

NORM (input) CHARACTER*1
Specifies the value to be returned in CLANGT as described above.
N (input) INTEGER
The order of the matrix A. N >= 0. When N = 0, CLANGT is set to zero.
DL (input) COMPLEX array, dimension (N-1)
The (n-1) sub-diagonal elements of A.
D (input) COMPLEX array, dimension (N)
The diagonal elements of A.
DU (input) COMPLEX array, dimension (N-1)
The (n-1) super-diagonal elements of A.