root / src / lapack / double / dlapy2.f @ 1
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| 1 | 1 | equemene | DOUBLE PRECISION FUNCTION DLAPY2( X, Y ) |
|---|---|---|---|
| 2 | 1 | equemene | * |
| 3 | 1 | equemene | * -- LAPACK auxiliary routine (version 3.2) -- |
| 4 | 1 | equemene | * -- LAPACK is a software package provided by Univ. of Tennessee, -- |
| 5 | 1 | equemene | * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
| 6 | 1 | equemene | * November 2006 |
| 7 | 1 | equemene | * |
| 8 | 1 | equemene | * .. Scalar Arguments .. |
| 9 | 1 | equemene | DOUBLE PRECISION X, Y |
| 10 | 1 | equemene | * .. |
| 11 | 1 | equemene | * |
| 12 | 1 | equemene | * Purpose |
| 13 | 1 | equemene | * ======= |
| 14 | 1 | equemene | * |
| 15 | 1 | equemene | * DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary |
| 16 | 1 | equemene | * overflow. |
| 17 | 1 | equemene | * |
| 18 | 1 | equemene | * Arguments |
| 19 | 1 | equemene | * ========= |
| 20 | 1 | equemene | * |
| 21 | 1 | equemene | * X (input) DOUBLE PRECISION |
| 22 | 1 | equemene | * Y (input) DOUBLE PRECISION |
| 23 | 1 | equemene | * X and Y specify the values x and y. |
| 24 | 1 | equemene | * |
| 25 | 1 | equemene | * ===================================================================== |
| 26 | 1 | equemene | * |
| 27 | 1 | equemene | * .. Parameters .. |
| 28 | 1 | equemene | DOUBLE PRECISION ZERO |
| 29 | 1 | equemene | PARAMETER ( ZERO = 0.0D0 ) |
| 30 | 1 | equemene | DOUBLE PRECISION ONE |
| 31 | 1 | equemene | PARAMETER ( ONE = 1.0D0 ) |
| 32 | 1 | equemene | * .. |
| 33 | 1 | equemene | * .. Local Scalars .. |
| 34 | 1 | equemene | DOUBLE PRECISION W, XABS, YABS, Z |
| 35 | 1 | equemene | * .. |
| 36 | 1 | equemene | * .. Intrinsic Functions .. |
| 37 | 1 | equemene | INTRINSIC ABS, MAX, MIN, SQRT |
| 38 | 1 | equemene | * .. |
| 39 | 1 | equemene | * .. Executable Statements .. |
| 40 | 1 | equemene | * |
| 41 | 1 | equemene | XABS = ABS( X ) |
| 42 | 1 | equemene | YABS = ABS( Y ) |
| 43 | 1 | equemene | W = MAX( XABS, YABS ) |
| 44 | 1 | equemene | Z = MIN( XABS, YABS ) |
| 45 | 1 | equemene | IF( Z.EQ.ZERO ) THEN |
| 46 | 1 | equemene | DLAPY2 = W |
| 47 | 1 | equemene | ELSE |
| 48 | 1 | equemene | DLAPY2 = W*SQRT( ONE+( Z / W )**2 ) |
| 49 | 1 | equemene | END IF |
| 50 | 1 | equemene | RETURN |
| 51 | 1 | equemene | * |
| 52 | 1 | equemene | * End of DLAPY2 |
| 53 | 1 | equemene | * |
| 54 | 1 | equemene | END |