# dlassq.f - Man Page

## Synopsis

### Functions/Subroutines

subroutine **dlassq** (**N**, X, INCX, SCALE, SUMSQ)**DLASSQ** updates a sum of squares represented in scaled form.

## Function/Subroutine Documentation

### subroutine dlassq (integer N, double precision, dimension( * ) X, integer INCX, double precision SCALE, double precision SUMSQ)

**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:**December 2016

Definition at line 105 of file dlassq.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dlassq(3) is an alias of dlassq.f(3).

Tue Nov 14 2017 Version 3.8.0 LAPACK