dcombnrm2()

subroutine dcombnrm2	(	double precision	x,
		double precision	y
	)

Definition at line 306 of file pdtreecomb.f.

*
*  -- ScaLAPACK tools routine (version 1.7) --
*     University of Tennessee, Knoxville, Oak Ridge National Laboratory,
*     and University of California, Berkeley.
*     May 1, 1997
*
*     .. Scalar Arguments ..
      DOUBLE PRECISION   X, Y
*     ..
*
*  Purpose
*  =======
*
*  DCOMBNRM2 combines local norm 2 results, taking care not to cause
*  unnecessary overflow.
*
*  Arguments
*  =========
*
*  X       (local input) DOUBLE PRECISION
*  Y       (local input) DOUBLE PRECISION
*          X and Y specify the values x and y. X and Y are supposed to
*          be >= 0.
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION   ONE, ZERO
      parameter( one = 1.0d+0, zero = 0.0d+0 )
*     ..
*     .. Local Scalars ..
      DOUBLE PRECISION   W, Z
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          max, min, sqrt
*     ..
*     .. Executable Statements ..
*
      w = max( x, y )
      z = min( x, y )
*
      IF( z.EQ.zero ) THEN
         x = w
      ELSE
         x = w*sqrt( one+( z / w )**2 )
      END IF
*
      RETURN
*
*     End of DCOMBNRM2
*

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