# dlansy.f man page

dlansy.f —

## Synopsis

### Functions/Subroutines

DOUBLE PRECISION functiondlansy(NORM, UPLO, N, A, LDA, WORK)DLANSYreturns the value of the 1-norm, or the Frobenius norm, or the infinity norm, or the element of largest absolute value of a real symmetric matrix.

## Function/Subroutine Documentation

### DOUBLE PRECISION function dlansy (characterNORM, characterUPLO, integerN, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )WORK)

**DLANSY** 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 symmetric matrix.

**Purpose:**

```
DLANSY 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.
```

**Returns:**

DLANSY

```
DLANSY = ( 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.
```

**Parameters:**

*NORM*

```
NORM is CHARACTER*1
Specifies the value to be returned in DLANSY as described
above.
```

*UPLO*

```
UPLO is 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*

```
N is INTEGER
The order of the matrix A. N >= 0. When N = 0, DLANSY is
set to zero.
```

*A*

```
A is DOUBLE PRECISION array, dimension (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*

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

*WORK*

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

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 123 of file dlansy.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

dlansy(3) is an alias of dlansy.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK