Revision 16960,
1.1 KB
checked in by ghudson, 22 years ago
(diff) |
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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[14547] | 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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[16959] | 13 | double s, s0, t, t2, u, v; |
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[14547] | 14 | double zi = z->i, zr = z->r; |
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[16959] | 15 | |
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[14547] | 16 | r->i = atan2(zi, zr); |
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[16959] | 17 | #ifdef Pre20000310 |
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[14547] | 18 | r->r = log( f__cabs( zr, zi ) ); |
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[16959] | 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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[14547] | 63 | } |
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