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annotate libcruft/lapack/dlapy2.f @ 5915:b2e1be30c8e9 ss-2-9-7

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[project @ 2006-07-28 18:08:56 by jwe]
author jwe
date Fri, 28 Jul 2006 18:08:56 +0000
parents 15cddaacbc2d
children 68db500cb558
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1 DOUBLE PRECISION FUNCTION DLAPY2( X, Y )
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2 *
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3 * -- LAPACK auxiliary routine (version 3.0) --
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4 * Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
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5 * Courant Institute, Argonne National Lab, and Rice University
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6 * October 31, 1992
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7 *
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8 * .. Scalar Arguments ..
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9 DOUBLE PRECISION X, Y
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10 * ..
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11 *
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12 * Purpose
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13 * =======
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14 *
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15 * DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary
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16 * overflow.
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17 *
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18 * Arguments
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19 * =========
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20 *
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21 * X (input) DOUBLE PRECISION
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22 * Y (input) DOUBLE PRECISION
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23 * X and Y specify the values x and y.
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24 *
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25 * =====================================================================
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26 *
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27 * .. Parameters ..
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28 DOUBLE PRECISION ZERO
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29 PARAMETER ( ZERO = 0.0D0 )
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30 DOUBLE PRECISION ONE
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31 PARAMETER ( ONE = 1.0D0 )
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32 * ..
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33 * .. Local Scalars ..
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34 DOUBLE PRECISION W, XABS, YABS, Z
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35 * ..
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36 * .. Intrinsic Functions ..
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37 INTRINSIC ABS, MAX, MIN, SQRT
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38 * ..
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39 * .. Executable Statements ..
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40 *
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41 XABS = ABS( X )
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42 YABS = ABS( Y )
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43 W = MAX( XABS, YABS )
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44 Z = MIN( XABS, YABS )
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45 IF( Z.EQ.ZERO ) THEN
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46 DLAPY2 = W
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47 ELSE
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48 DLAPY2 = W*SQRT( ONE+( Z / W )**2 )
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49 END IF
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50 RETURN
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51 *
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52 * End of DLAPY2
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53 *
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54 END