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    1:       DOUBLE PRECISION FUNCTION DLAPY3( X, Y, Z )
    2: *
    3: *  -- LAPACK auxiliary routine (version 3.2) --
    4: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
    5: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
    6: *     November 2006
    7: *
    8: *     .. Scalar Arguments ..
    9:       DOUBLE PRECISION   X, Y, Z
   10: *     ..
   11: *
   12: *  Purpose
   13: *  =======
   14: *
   15: *  DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
   16: *  unnecessary overflow.
   17: *
   18: *  Arguments
   19: *  =========
   20: *
   21: *  X       (input) DOUBLE PRECISION
   22: *  Y       (input) DOUBLE PRECISION
   23: *  Z       (input) DOUBLE PRECISION
   24: *          X, Y and Z specify the values x, y and z.
   25: *
   26: *  =====================================================================
   27: *
   28: *     .. Parameters ..
   29:       DOUBLE PRECISION   ZERO
   30:       PARAMETER          ( ZERO = 0.0D0 )
   31: *     ..
   32: *     .. Local Scalars ..
   33:       DOUBLE PRECISION   W, XABS, YABS, ZABS
   34: *     ..
   35: *     .. Intrinsic Functions ..
   36:       INTRINSIC          ABS, MAX, SQRT
   37: *     ..
   38: *     .. Executable Statements ..
   39: *
   40:       XABS = ABS( X )
   41:       YABS = ABS( Y )
   42:       ZABS = ABS( Z )
   43:       W = MAX( XABS, YABS, ZABS )
   44:       IF( W.EQ.ZERO ) THEN
   45: *     W can be zero for max(0,nan,0)
   46: *     adding all three entries together will make sure
   47: *     NaN will not disappear.
   48:          DLAPY3 =  XABS + YABS + ZABS
   49:       ELSE
   50:          DLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+
   51:      $            ( ZABS / W )**2 )
   52:       END IF
   53:       RETURN
   54: *
   55: *     End of DLAPY3
   56: *
   57:       END