# dlaqsp.f man page

dlaqsp.f —

## Synopsis

### Functions/Subroutines

subroutinedlaqsp(UPLO, N, AP, S, SCOND, AMAX, EQUED)DLAQSPscales a symmetric/Hermitian matrix in packed storage, using scaling factors computed by sppequ.

## Function/Subroutine Documentation

### subroutine dlaqsp (characterUPLO, integerN, double precision, dimension( * )AP, double precision, dimension( * )S, double precisionSCOND, double precisionAMAX, characterEQUED)

**DLAQSP** scales a symmetric/Hermitian matrix in packed storage, using scaling factors computed by sppequ.

**Purpose:**

```
DLAQSP equilibrates a symmetric matrix A using the scaling factors
in the vector S.
```

**Parameters:**

*UPLO*

```
UPLO is CHARACTER*1
Specifies whether the upper or lower triangular part of the
symmetric matrix A is stored.
= 'U': Upper triangular
= 'L': Lower triangular
```

*N*

```
N is INTEGER
The order of the matrix A. N >= 0.
```

*AP*

```
AP is DOUBLE PRECISION array, dimension (N*(N+1)/2)
On entry, 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.
On exit, the equilibrated matrix: diag(S) * A * diag(S), in
the same storage format as A.
```

*S*

```
S is DOUBLE PRECISION array, dimension (N)
The scale factors for A.
```

*SCOND*

```
SCOND is DOUBLE PRECISION
Ratio of the smallest S(i) to the largest S(i).
```

*AMAX*

```
AMAX is DOUBLE PRECISION
Absolute value of largest matrix entry.
```

*EQUED*

```
EQUED is CHARACTER*1
Specifies whether or not equilibration was done.
= 'N': No equilibration.
= 'Y': Equilibration was done, i.e., A has been replaced by
diag(S) * A * diag(S).
```

**Internal Parameters:**

```
THRESH is a threshold value used to decide if scaling should be done
based on the ratio of the scaling factors. If SCOND < THRESH,
scaling is done.
LARGE and SMALL are threshold values used to decide if scaling should
be done based on the absolute size of the largest matrix element.
If AMAX > LARGE or AMAX < SMALL, scaling is done.
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 126 of file dlaqsp.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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