# ?lansy

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/complex symmetric matrix.

## Syntax

val = slansy( norm, uplo, n, a, lda, work )

val = dlansy( norm, uplo, n, a, lda, work )

val = clansy( norm, uplo, n, a, lda, work )

val = zlansy( norm, uplo, n, a, lda, work )

• mkl.fi

## Description

The function ?lansy 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/complex symmetric matrix A.

## Input Parameters

The data types are given for the Fortran interface.

norm

CHARACTER*1. Specifies the value to be returned by the routine:

= 'M' or 'm': val = max(abs(Aij)), largest absolute value of the matrix A.

= '1' or 'O' or 'o': val = norm1(A), 1-norm of the matrix A (maximum column sum),

= 'I' or 'i': val = normI(A), infinity norm of the matrix A (maximum row sum),

= 'F', 'f', 'E' or 'e': val = normF(A), Frobenius norm of the matrix A (square root of sum of squares).

uplo

CHARACTER*1.

Specifies whether the upper or lower triangular part of the symmetric matrix A is to be referenced.

= 'U': Upper triangular part of A is referenced.

= 'L': Lower triangular part of A is referenced

n

INTEGER. The order of the matrix A. n 0. When n = 0, ?lansy is set to zero.

a

REAL for slansy

DOUBLE PRECISION for dlansy

COMPLEX for clansy

DOUBLE COMPLEX for zlansy

Array, size (lda,n). The symmetric matrix A.

If uplo = 'U', the leading n-by-n upper triangular part of a contains the upper triangular part of the matrix A, and the strictly lower triangular part of a is not referenced.

If uplo = 'L', the leading n-by-n lower triangular part of a contains the lower triangular part of the matrix A, and the strictly upper triangular part of a is not referenced.

lda

INTEGER. The leading dimension of the array a.

lda max(n,1).

work

REAL for slansy and clansy.

DOUBLE PRECISION for dlansy and zlansy.

Workspace array, DIMENSION(max(1,lwork)), where

lworkn when norm = 'I' or '1' or 'O'; otherwise, work is not referenced.

## Output Parameters

val

REAL for slansy/clansy

DOUBLE PRECISION for dlansy/zlansy

Value returned by the function.

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