DLASSQ (3lapack)

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

  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.

ARGUMENTS

  N       (input) INTEGER
          The number of elements to be used from the vector X.

  X       (input) DOUBLE PRECISION
          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.