dlassq(3)

NAME

DLASSQ - return the values scl and smsq such that (

scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,

SYNOPSIS

SUBROUTINE DLASSQ( N, X, INCX, SCALE, SUMSQ )
    INTEGER        INCX, N
    DOUBLE         PRECISION SCALE, SUMSQ
    DOUBLE         PRECISION X( * )

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 respec

tively.

The routine makes only one pass through the vector x.

ARGUMENTS

N (input) INTEGER

The number of elements to be used from the vector

X.

X (input) 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 (input) INTEGER

The increment between successive values of the

vector X. INCX > 0.

SCALE (input/output) 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 (input/output) 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.

LAPACK version 3.0 15 June 2000

DLASSQ(3)