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annotate libcruft/lapack/slapy2.f @ 9122:8ca06fd9c6ef

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test lazy copying in structures
author Thorsten Meyer <thorsten.meyier@gmx.de>
date Wed, 15 Apr 2009 12:29:31 +0200
parents 82be108cc558
children
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1 REAL FUNCTION SLAPY2( X, Y )
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2 *
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3 * -- LAPACK auxiliary routine (version 3.1) --
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4 * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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5 * November 2006
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6 *
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7 * .. Scalar Arguments ..
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8 REAL X, Y
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9 * ..
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10 *
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11 * Purpose
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12 * =======
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13 *
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14 * SLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
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15 * overflow.
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16 *
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17 * Arguments
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18 * =========
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19 *
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20 * X (input) REAL
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21 * Y (input) REAL
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22 * X and Y specify the values x and y.
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23 *
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24 * =====================================================================
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25 *
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26 * .. Parameters ..
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27 REAL ZERO
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28 PARAMETER ( ZERO = 0.0E0 )
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29 REAL ONE
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30 PARAMETER ( ONE = 1.0E0 )
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31 * ..
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32 * .. Local Scalars ..
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33 REAL W, XABS, YABS, Z
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34 * ..
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35 * .. Intrinsic Functions ..
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36 INTRINSIC ABS, MAX, MIN, SQRT
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37 * ..
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38 * .. Executable Statements ..
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39 *
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40 XABS = ABS( X )
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41 YABS = ABS( Y )
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42 W = MAX( XABS, YABS )
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43 Z = MIN( XABS, YABS )
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44 IF( Z.EQ.ZERO ) THEN
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45 SLAPY2 = W
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46 ELSE
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47 SLAPY2 = W*SQRT( ONE+( Z / W )**2 )
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48 END IF
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49 RETURN
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50 *
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51 * End of SLAPY2
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52 *
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53 END