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dlapy2.f
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Tue Dec 21 13:53:30 2010 UTC (13 years, 5 months ago) by
bertrand
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rpl-4_1_3,
rpl-4_1_2,
rpl-4_1_1,
rpl-4_1_0,
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Mise à jour de lapack vers la version 3.3.0.
1: DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
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
10: * ..
11: *
12: * Purpose
13: * =======
14: *
15: * DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
16: * overflow.
17: *
18: * Arguments
19: * =========
20: *
21: * X (input) DOUBLE PRECISION
22: * Y (input) DOUBLE PRECISION
23: * X and Y specify the values x and y.
24: *
25: * =====================================================================
26: *
27: * .. Parameters ..
28: DOUBLE PRECISION ZERO
29: PARAMETER ( ZERO = 0.0D0 )
30: DOUBLE PRECISION ONE
31: PARAMETER ( ONE = 1.0D0 )
32: * ..
33: * .. Local Scalars ..
34: DOUBLE PRECISION W, XABS, YABS, Z
35: * ..
36: * .. Intrinsic Functions ..
37: INTRINSIC ABS, MAX, MIN, SQRT
38: * ..
39: * .. Executable Statements ..
40: *
41: XABS = ABS( X )
42: YABS = ABS( Y )
43: W = MAX( XABS, YABS )
44: Z = MIN( XABS, YABS )
45: IF( Z.EQ.ZERO ) THEN
46: DLAPY2 = W
47: ELSE
48: DLAPY2 = W*SQRT( ONE+( Z / W )**2 )
49: END IF
50: RETURN
51: *
52: * End of DLAPY2
53: *
54: END
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