version 1.3, 2010/08/06 15:28:41
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version 1.18, 2018/05/29 07:17:58
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*> \brief \b DLAPY2 returns sqrt(x2+y2). |
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* |
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* =========== DOCUMENTATION =========== |
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* |
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* Online html documentation available at |
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* http://www.netlib.org/lapack/explore-html/ |
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* |
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*> \htmlonly |
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*> Download DLAPY2 + dependencies |
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dlapy2.f"> |
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*> [TGZ]</a> |
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dlapy2.f"> |
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*> [ZIP]</a> |
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dlapy2.f"> |
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*> [TXT]</a> |
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*> \endhtmlonly |
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* |
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* Definition: |
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* =========== |
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* |
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* DOUBLE PRECISION FUNCTION DLAPY2( X, Y ) |
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* |
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* .. Scalar Arguments .. |
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* DOUBLE PRECISION X, Y |
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* .. |
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* |
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* |
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*> \par Purpose: |
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* ============= |
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*> |
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*> \verbatim |
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*> |
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*> DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary |
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*> overflow. |
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*> \endverbatim |
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* |
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* Arguments: |
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* ========== |
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* |
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*> \param[in] X |
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*> \verbatim |
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*> X is DOUBLE PRECISION |
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*> \endverbatim |
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*> |
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*> \param[in] Y |
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*> \verbatim |
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*> Y is DOUBLE PRECISION |
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*> X and Y specify the values x and y. |
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*> \endverbatim |
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* |
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* Authors: |
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* ======== |
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* |
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*> \author Univ. of Tennessee |
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*> \author Univ. of California Berkeley |
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*> \author Univ. of Colorado Denver |
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*> \author NAG Ltd. |
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* |
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*> \date June 2017 |
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* |
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*> \ingroup OTHERauxiliary |
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* |
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* ===================================================================== |
DOUBLE PRECISION FUNCTION DLAPY2( X, Y ) |
DOUBLE PRECISION FUNCTION DLAPY2( X, Y ) |
* |
* |
* -- LAPACK auxiliary routine (version 3.2) -- |
* -- LAPACK auxiliary routine (version 3.7.1) -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- LAPACK is a software package provided by Univ. of Tennessee, -- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
* November 2006 |
* June 2017 |
* |
* |
* .. Scalar Arguments .. |
* .. Scalar Arguments .. |
DOUBLE PRECISION X, Y |
DOUBLE PRECISION X, Y |
* .. |
* .. |
* |
* |
* Purpose |
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* ======= |
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* |
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* DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary |
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* overflow. |
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* |
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* Arguments |
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* ========= |
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* |
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* X (input) DOUBLE PRECISION |
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* Y (input) DOUBLE PRECISION |
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* X and Y specify the values x and y. |
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* |
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* ===================================================================== |
* ===================================================================== |
* |
* |
* .. Parameters .. |
* .. Parameters .. |
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* .. |
* .. |
* .. Local Scalars .. |
* .. Local Scalars .. |
DOUBLE PRECISION W, XABS, YABS, Z |
DOUBLE PRECISION W, XABS, YABS, Z |
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LOGICAL X_IS_NAN, Y_IS_NAN |
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* .. |
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* .. External Functions .. |
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LOGICAL DISNAN |
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EXTERNAL DISNAN |
* .. |
* .. |
* .. Intrinsic Functions .. |
* .. Intrinsic Functions .. |
INTRINSIC ABS, MAX, MIN, SQRT |
INTRINSIC ABS, MAX, MIN, SQRT |
* .. |
* .. |
* .. Executable Statements .. |
* .. Executable Statements .. |
* |
* |
XABS = ABS( X ) |
X_IS_NAN = DISNAN( X ) |
YABS = ABS( Y ) |
Y_IS_NAN = DISNAN( Y ) |
W = MAX( XABS, YABS ) |
IF ( X_IS_NAN ) DLAPY2 = X |
Z = MIN( XABS, YABS ) |
IF ( Y_IS_NAN ) DLAPY2 = Y |
IF( Z.EQ.ZERO ) THEN |
* |
DLAPY2 = W |
IF ( .NOT.( X_IS_NAN.OR.Y_IS_NAN ) ) THEN |
ELSE |
XABS = ABS( X ) |
DLAPY2 = W*SQRT( ONE+( Z / W )**2 ) |
YABS = ABS( Y ) |
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W = MAX( XABS, YABS ) |
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Z = MIN( XABS, YABS ) |
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IF( Z.EQ.ZERO ) THEN |
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DLAPY2 = W |
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ELSE |
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DLAPY2 = W*SQRT( ONE+( Z / W )**2 ) |
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END IF |
END IF |
END IF |
RETURN |
RETURN |
* |
* |