Revision 16960,
1.1 KB
checked in by ghudson, 22 years ago
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This commit was generated by cvs2svn to compensate for changes in r16959,
which included commits to RCS files with non-trunk default branches.
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1 | #include "f2c.h" |
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2 | |
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3 | #ifdef KR_headers |
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4 | double log(), f__cabs(), atan2(); |
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5 | VOID z_log(r, z) doublecomplex *r, *z; |
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6 | #else |
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7 | #undef abs |
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8 | #include "math.h" |
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9 | extern double f__cabs(double, double); |
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10 | void z_log(doublecomplex *r, doublecomplex *z) |
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11 | #endif |
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12 | { |
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13 | double s, s0, t, t2, u, v; |
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14 | double zi = z->i, zr = z->r; |
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15 | |
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16 | r->i = atan2(zi, zr); |
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17 | #ifdef Pre20000310 |
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18 | r->r = log( f__cabs( zr, zi ) ); |
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19 | #else |
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20 | if (zi < 0) |
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21 | zi = -zi; |
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22 | if (zr < 0) |
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23 | zr = -zr; |
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24 | if (zr < zi) { |
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25 | t = zi; |
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26 | zi = zr; |
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27 | zr = t; |
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28 | } |
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29 | t = zi/zr; |
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30 | s = zr * sqrt(1 + t*t); |
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31 | /* now s = f__cabs(zi,zr), and zr = |zr| >= |zi| = zi */ |
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32 | if ((t = s - 1) < 0) |
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33 | t = -t; |
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34 | if (t > .01) |
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35 | r->r = log(s); |
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36 | else { |
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37 | |
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38 | #ifdef Comment |
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39 | |
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40 | log(1+x) = x - x^2/2 + x^3/3 - x^4/4 + - ... |
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41 | |
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42 | = x(1 - x/2 + x^2/3 -+...) |
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43 | |
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44 | [sqrt(y^2 + z^2) - 1] * [sqrt(y^2 + z^2) + 1] = y^2 + z^2 - 1, so |
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45 | |
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46 | sqrt(y^2 + z^2) - 1 = (y^2 + z^2 - 1) / [sqrt(y^2 + z^2) + 1] |
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47 | |
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48 | #endif /*Comment*/ |
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49 | |
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50 | t = ((zr*zr - 1.) + zi*zi) / (s + 1); |
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51 | t2 = t*t; |
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52 | s = 1. - 0.5*t; |
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53 | u = v = 1; |
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54 | do { |
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55 | s0 = s; |
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56 | u *= t2; |
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57 | v += 2; |
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58 | s += u/v - t*u/(v+1); |
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59 | } while(s > s0); |
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60 | r->r = s*t; |
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61 | } |
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62 | #endif |
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63 | } |
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