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DOUBLE PRECISION FUNCTION DLAPY3( X, Y, Z )
*
* -- LAPACK auxiliary routine (version 3.1) --
* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
* November 2006
*
* .. Scalar Arguments ..
DOUBLE PRECISION X, Y, Z
* ..
*
* Purpose
* =======
*
* DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
* unnecessary overflow.
*
* Arguments
* =========
*
* X (input) DOUBLE PRECISION
* Y (input) DOUBLE PRECISION
* Z (input) DOUBLE PRECISION
* X, Y and Z specify the values x, y and z.
*
* =====================================================================
*
* .. Parameters ..
DOUBLE PRECISION ZERO
PARAMETER ( ZERO = 0.0D0 )
* ..
* .. Local Scalars ..
DOUBLE PRECISION W, XABS, YABS, ZABS
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, MAX, SQRT
* ..
* .. Executable Statements ..
*
XABS = ABS( X )
YABS = ABS( Y )
ZABS = ABS( Z )
W = MAX( XABS, YABS, ZABS )
IF( W.EQ.ZERO ) THEN
* W can be zero for max(0,nan,0)
* adding all three entries together will make sure
* NaN will not disappear.
DLAPY3 = XABS + YABS + ZABS
ELSE
DLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+
$ ( ZABS / W )**2 )
END IF
RETURN
*
* End of DLAPY3
*
END
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