DLANSP - return the value of the one norm, or the Frobe
nius norm, or the infinity norm, or the element of largest
absolute value of a real symmetric matrix A, supplied in
packed form
SYNOPSIS
DOUBLE PRECISION FUNCTION DLANSP( NORM, UPLO, N, AP, WORK
)
CHARACTER NORM, UPLO
INTEGER N
DOUBLE PRECISION AP( * ), WORK( * )
PURPOSE
DLANSP 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 matrix A, supplied in
packed form.
DESCRIPTION
DLANSP returns the value
DLANSP = ( 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 Frobe
nius 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 DLANSP as
described above.
UPLO (input) CHARACTER*1
Specifies whether the upper or lower triangular
part of the symmetric matrix A is supplied. =
'U': Upper triangular part of A is supplied
= 'L': Lower triangular part of A is supplied
N (input) INTEGER
The order of the matrix A. N >= 0. When N = 0,
AP (input) DOUBLE PRECISION array, dimension
(N*(N+1)/2)
The upper or lower triangle of the symmetric
matrix A, packed columnwise in a linear array.
The j-th column of A is stored in the array AP as
follows: if UPLO = 'U', AP(i + (j-1)*j/2) = A(i,j)
for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2)
= A(i,j) for j<=i<=n.
WORK (workspace) DOUBLE PRECISION array, dimension
(LWORK),
where LWORK >= N when NORM = 'I' or '1' or 'O';
otherwise, WORK is not referenced.
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