# dlangt(3) [centos man page]

```dlangt.f(3)							      LAPACK							       dlangt.f(3)

NAME
dlangt.f -

SYNOPSIS
Functions/Subroutines
DOUBLE PRECISION function dlangt (NORM, N, DL, D, DU)
DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general
tridiagonal matrix.

Function/Subroutine Documentation
DOUBLE PRECISION function dlangt (characterNORM, integerN, double precision, dimension( * )DL, double precision, dimension( * )D, double
precision, dimension( * )DU)
DLANGT returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value of any element of a general
tridiagonal matrix.

Purpose:

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.

Returns:
DLANGT

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 consistent matrix norm.

Parameters:
NORM

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

N

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

DL

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

D

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

DU

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

Author:
Univ. of Tennessee

Univ. of California Berkeley

NAG Ltd.

Date:
September 2012

Definition at line 107 of file dlangt.f.

Author
Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2							  Tue Sep 25 2012						       dlangt.f(3)```

## Check Out this Related Man Page

```dlanst.f(3)							      LAPACK							       dlanst.f(3)

NAME
dlanst.f -

SYNOPSIS
Functions/Subroutines
DOUBLE PRECISION function dlanst (NORM, N, D, E)
DLANST returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real
symmetric tridiagonal matrix.

Function/Subroutine Documentation
DOUBLE PRECISION function dlanst (characterNORM, integerN, double precision, dimension( * )D, double precision, dimension( * )E)
DLANST returns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real
symmetric tridiagonal matrix.

Purpose:

DLANST  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 symmetric tridiagonal matrix A.

Returns:
DLANST

DLANST = ( 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:
NORM

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

N

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

D

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

E

E is DOUBLE PRECISION array, dimension (N-1)
The (n-1) sub-diagonal or super-diagonal elements of A.

Author:
Univ. of Tennessee

Univ. of California Berkeley