LAPACK
3.4.2
LAPACK: Linear Algebra PACKage

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Functions/Subroutines  
DOUBLE PRECISION function  dlangt (NORM, N, DL, D, DU) 
DLANGT returns the value of the 1norm, Frobenius norm, infinitynorm, or the largest absolute value of any element of a general tridiagonal matrix. 
DOUBLE PRECISION function dlangt  (  character  NORM, 
integer  N,  
double precision, dimension( * )  DL,  
double precision, dimension( * )  D,  
double precision, dimension( * )  DU  
) 
DLANGT returns the value of the 1norm, Frobenius norm, infinitynorm, or the largest absolute value of any element of a general tridiagonal matrix.
Download DLANGT + dependencies [TGZ] [ZIP] [TXT]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.
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.
[in]  NORM  NORM is CHARACTER*1 Specifies the value to be returned in DLANGT as described above. 
[in]  N  N is INTEGER The order of the matrix A. N >= 0. When N = 0, DLANGT is set to zero. 
[in]  DL  DL is DOUBLE PRECISION array, dimension (N1) The (n1) subdiagonal elements of A. 
[in]  D  D is DOUBLE PRECISION array, dimension (N) The diagonal elements of A. 
[in]  DU  DU is DOUBLE PRECISION array, dimension (N1) The (n1) superdiagonal elements of A. 
Definition at line 107 of file dlangt.f.