zlangt(3P)

NAME

zlangt - return 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

DOUBLE PRECISION
FUNCTION ZLANGT( NORM, N, DL, D, DU )

double zlangt(char norm, long int n, doublecomplex ∗dl, doublecomplex ∗d, doublecomplex ∗du)

CHARACTER NORM

INTEGER N

COMPLEX∗16 D( ∗ ), DL( ∗ ), DU( ∗ )

PURPOSE

ZLANGT 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

ZLANGT returns the value

   ZLANGT = ( 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 ZLANGT as described above.

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

DL (input) COMPLEX∗16 array, dimension (N-1)
The (n-1) sub-diagonal elements of A.

D (input) COMPLEX∗16 array, dimension (N)
The diagonal elements of A.

DU (input) COMPLEX∗16 array, dimension (N-1)
The (n-1) super-diagonal elements of A.