man dlantr (Fonctions bibliothèques) - return the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a trapezoidal or triangular matrix A

NAME

DLANTR - return the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a trapezoidal or triangular matrix A

SYNOPSIS

DOUBLE PRECISION
FUNCTION DLANTR( NORM, UPLO, DIAG, M, N, A, LDA, WORK )
CHARACTER DIAG, NORM, UPLO
INTEGER LDA, M, N
DOUBLE PRECISION A( LDA, * ), WORK( * )

PURPOSE

DLANTR returns the value of the one norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a trapezoidal or triangular matrix A.

DESCRIPTION

DLANTR returns the value

DLANTR = ( 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 DLANTR as described above.
UPLO (input) CHARACTER*1
Specifies whether the matrix A is upper or lower trapezoidal. = 'U': Upper trapezoidal

= 'L': Lower trapezoidal Note that A is triangular instead of trapezoidal if M = N.
DIAG (input) CHARACTER*1
Specifies whether or not the matrix A has unit diagonal. = 'N': Non-unit diagonal

= 'U': Unit diagonal
M (input) INTEGER
The number of rows of the matrix A. M >= 0, and if UPLO = 'U', M <= N. When M = 0, DLANTR is set to zero.
N (input) INTEGER
The number of columns of the matrix A. N >= 0, and if UPLO = 'L', N <= M. When N = 0, DLANTR is set to zero.
A (input) DOUBLE PRECISION array, dimension (LDA,N)
The trapezoidal matrix A (A is triangular if M = N). If UPLO = 'U', the leading m by n upper trapezoidal part of the array A contains the upper trapezoidal matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading m by n lower trapezoidal part of the array A contains the lower trapezoidal matrix, and the strictly upper triangular part of A is not referenced. Note that when DIAG = 'U', the diagonal elements of A are not referenced and are assumed to be one.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(M,1).
WORK (workspace) DOUBLE PRECISION array, dimension (LWORK),
where LWORK >= M when NORM = 'I'; otherwise, WORK is not referenced.