## MA02MD

### Compute norms of a real skew-symmetric matrix

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

To compute the value of the one norm, or the Frobenius norm, or
the infinity norm, or the element of largest absolute value
of a real skew-symmetric matrix.

Note that for this kind of matrices the infinity norm is equal
to the one norm.

Specification
DOUBLE PRECISION FUNCTION MA02MD( NORM, UPLO, N, A, LDA, DWORK )
C     .. Scalar Arguments ..
CHARACTER          NORM, UPLO
INTEGER            LDA, N
C     .. Array Arguments ..
DOUBLE PRECISION   A( LDA, * ), DWORK( * )

Function Value
MA02MD  DOUBLE PRECISION
The computed norm.

Arguments

Mode Parameters

NORM    CHARACTER*1
Specifies the value to be returned in MA02MD:
= '1' or 'O':  one norm of A;
= 'F' or 'E':  Frobenius norm of A;
= 'I':         infinity norm of A;
= 'M':         max(abs(A(i,j)).

UPLO    CHARACTER*1
Specifies whether the upper or lower triangular part of
the skew-symmetric matrix A is to be referenced.
= 'U':  Upper triangular part of A is referenced;
= 'L':  Lower triangular part of A is referenced.

Input/Output Parameters
N       (input) INTEGER
The order of the matrix A.  N >= 0.  When N = 0, MA02MD is
set to zero.

A       (input) DOUBLE PRECISION array, dimension (LDA,N)
The skew-symmetric matrix A.  If UPLO = 'U', the leading
N-by-N strictly upper triangular part of A contains the
strictly upper triangular part of the matrix A, and the
lower triangular part of A is not referenced.
If UPLO = 'L', the leading N-by-N strictly lower
triangular part of A contains the strictly lower
triangular part of the matrix A, and the upper triangular
part of A is not referenced.
The diagonal of A need not be set to zero.

LDA     INTEGER
The leading dimension of the array A.  LDA >= max(1,N).

Workspace
DWORK   DOUBLE PRECISION array, dimension (MAX(1,LDWORK)),
where LDWORK >= N when NORM = 'I' or '1' or 'O';
otherwise, DWORK is not referenced.

Further Comments
None
Example

Program Text

None
Program Data
None
Program Results
None

Return to Supporting Routines index