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annotate libcruft/lapack/slapy3.f @ 9665:1dba57e9d08d

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use blas_trans_type for xgemm
author Jaroslav Hajek <highegg@gmail.com>
date Sat, 26 Sep 2009 10:41:07 +0200
parents 82be108cc558
children
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1 REAL FUNCTION SLAPY3( X, Y, Z )
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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, Z
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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 * SLAPY3 returns sqrt(x**2+y**2+z**2), taking care not to cause
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15 * unnecessary 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 * Z (input) REAL
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23 * X, Y and Z specify the values x, y and z.
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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 REAL ZERO
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29 PARAMETER ( ZERO = 0.0E0 )
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30 * ..
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31 * .. Local Scalars ..
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32 REAL W, XABS, YABS, ZABS
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33 * ..
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34 * .. Intrinsic Functions ..
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35 INTRINSIC ABS, MAX, SQRT
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36 * ..
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37 * .. Executable Statements ..
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38 *
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39 XABS = ABS( X )
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40 YABS = ABS( Y )
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41 ZABS = ABS( Z )
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42 W = MAX( XABS, YABS, ZABS )
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43 IF( W.EQ.ZERO ) THEN
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44 * W can be zero for max(0,nan,0)
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45 * adding all three entries together will make sure
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46 * NaN will not disappear.
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47 SLAPY3 = XABS + YABS + ZABS
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48 ELSE
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49 SLAPY3 = W*SQRT( ( XABS / W )**2+( YABS / W )**2+
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50 $ ( ZABS / W )**2 )
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51 END IF
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52 RETURN
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53 *
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54 * End of SLAPY3
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55 *
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56 END