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annotate libcruft/lapack/dlapy3.f @ 4720:e759d01692db ss-2-1-53

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[project @ 2004-01-23 04:13:37 by jwe]
author jwe
date Fri, 23 Jan 2004 04:13:37 +0000
parents 15cddaacbc2d
children 68db500cb558
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1 DOUBLE PRECISION FUNCTION DLAPY3( X, Y, Z )
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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, Z
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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 * DLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
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16 * unnecessary 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 * Z (input) DOUBLE PRECISION
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24 * X, Y and Z specify the values x, y and z.
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25 *
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26 * =====================================================================
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27 *
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28 * .. Parameters ..
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29 DOUBLE PRECISION ZERO
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30 PARAMETER ( ZERO = 0.0D0 )
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31 * ..
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32 * .. Local Scalars ..
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33 DOUBLE PRECISION W, XABS, YABS, ZABS
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34 * ..
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35 * .. Intrinsic Functions ..
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36 INTRINSIC ABS, MAX, 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 ZABS = ABS( Z )
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43 W = MAX( XABS, YABS, ZABS )
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44 IF( W.EQ.ZERO ) THEN
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45 DLAPY3 = ZERO
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46 ELSE
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47 DLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+
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48 $ ( ZABS / 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 DLAPY3
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53 *
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54 END