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.
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