dlapy2()

double precision function dlapy2	(	double precision	x,
		double precision	y
	)

DLAPY2 returns sqrt(x2+y2).

Download DLAPY2 + dependencies [TGZ] [ZIP] [TXT]

Purpose:

 DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
 overflow and unnecessary underflow.

Parameters

[in]	X	X is DOUBLE PRECISION
[in]	Y	Y is DOUBLE PRECISION X and Y specify the values x and y.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 62 of file dlapy2.f.

*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      DOUBLE PRECISION   X, Y
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      DOUBLE PRECISION   ZERO
      parameter( zero = 0.0d0 )
      DOUBLE PRECISION   ONE
      parameter( one = 1.0d0 )
*     ..
*     .. Local Scalars ..
      DOUBLE PRECISION   W, XABS, YABS, Z, HUGEVAL
      LOGICAL            X_IS_NAN, Y_IS_NAN
*     ..
*     .. External Functions ..
      LOGICAL            DISNAN
      EXTERNAL           disnan
*     ..
*     .. External Subroutines ..
      DOUBLE PRECISION   DLAMCH
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          abs, max, min, sqrt
*     ..
*     .. Executable Statements ..
*
      x_is_nan = disnan( x )
      y_is_nan = disnan( y )
      IF ( x_is_nan ) dlapy2 = x
      IF ( y_is_nan ) dlapy2 = y
      hugeval = dlamch( 'Overflow' )
*
      IF ( .NOT.( x_is_nan.OR.y_is_nan ) ) THEN
         xabs = abs( x )
         yabs = abs( y )
         w = max( xabs, yabs )
         z = min( xabs, yabs )
         IF( z.EQ.zero .OR. w.GT.hugeval ) THEN
            dlapy2 = w
         ELSE
            dlapy2 = w*sqrt( one+( z / w )**2 )
         END IF
      END IF
      RETURN
*
*     End of DLAPY2
*

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