dlassq (l)  Linux Manuals
dlassq: returns the values scl and smsq such that ( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,
NAME
DLASSQ  returns 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 where x( i ) = X( 1 + ( i  1 )*INCX ). The value of sumsq is assumed to be nonnegative and scl returns the valuescl
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.
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.