ZLASSQ (3lapack)

return the values scl and ssq such that ( scl**2 )*ssq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq,

SYNOPSIS

  SUBROUTINE ZLASSQ( N, X, INCX, SCALE, SUMSQ )

      INTEGER        INCX, N

      DOUBLE         PRECISION SCALE, SUMSQ

      COMPLEX*16     X( * )

PURPOSE

  ZLASSQ returns the values scl and ssq such that

  where x( i ) = abs( X( 1 + ( i - 1 )*INCX ) ). The value of sumsq is
  assumed to be at least unity and the value of ssq will then satisfy

     1.0 .le. ssq .le. ( sumsq + 2*n ).

  scale is assumed to be non-negative and scl returns the value

     scl = max( scale, abs( real( x( i ) ) ), abs( aimag( x( i ) ) ) ),
            i

  scale and sumsq must be supplied in SCALE and SUMSQ respectively.  SCALE
  and SUMSQ are overwritten by scl and ssq 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 x as described above.  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 the value  scl .

  SUMSQ   (input/output) DOUBLE PRECISION
          On entry, the value  sumsq  in the equation above.  On exit, SUMSQ
          is overwritten with the value  ssq .