# dlassq.f man page

dlassq.f —

## Synopsis

### Functions/Subroutines

subroutinedlassq(N, X, INCX, SCALE, SUMSQ)DLASSQupdates a sum of squares represented in scaled form.

## Function/Subroutine Documentation

### subroutine dlassq (integerN, double precision, dimension( * )X, integerINCX, double precisionSCALE, double precisionSUMSQ)

**DLASSQ** updates a sum of squares represented in scaled form.

**Purpose:**

```
DLASSQ returns the values scl and smsq such that
( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,
where x( i ) = X( 1 + ( i - 1 )*INCX ). The value of sumsq is
assumed to be non-negative and scl returns the value
scl = max( scale, abs( x( i ) ) ).
scale and sumsq must be supplied in SCALE and SUMSQ and
scl and smsq are overwritten on SCALE and SUMSQ respectively.
The routine makes only one pass through the vector x.
```

**Parameters:**

*N*

```
N is INTEGER
The number of elements to be used from the vector X.
```

*X*

```
X is DOUBLE PRECISION array, dimension (N)
The vector for which a scaled sum of squares is computed.
x( i ) = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n.
```

*INCX*

```
INCX is INTEGER
The increment between successive values of the vector X.
INCX > 0.
```

*SCALE*

```
SCALE is DOUBLE PRECISION
On entry, the value scale in the equation above.
On exit, SCALE is overwritten with scl , the scaling factor
for the sum of squares.
```

*SUMSQ*

```
SUMSQ is DOUBLE PRECISION
On entry, the value sumsq in the equation above.
On exit, SUMSQ is overwritten with smsq , the basic sum of
squares from which scl has been factored out.
```

**Author:**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

**Date:**

September 2012

Definition at line 104 of file dlassq.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

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