annotate Python/pymath.c @ 87690:66c1c9f32567 default tip

Add use_weakref option to functools.lru_cache The use_weakref option makes lru_cache create weak references to the function arguments when creating the cache key, which prevents them from staying in the memory forever even after all other references to them are gone. This is a proof of concept for http://bugs.python.org/issue19859
author Radomir Dopieralski <devel@sheep.art.pl>
date Tue, 03 Dec 2013 16:02:48 +0100
parents 3c9232a684ae
children
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1 #include "Python.h"
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2
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3 #ifdef X87_DOUBLE_ROUNDING
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4 /* On x86 platforms using an x87 FPU, this function is called from the
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5 Py_FORCE_DOUBLE macro (defined in pymath.h) to force a floating-point
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6 number out of an 80-bit x87 FPU register and into a 64-bit memory location,
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7 thus rounding from extended precision to double precision. */
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8 double _Py_force_double(double x)
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9 {
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10 volatile double y;
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11 y = x;
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12 return y;
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13 }
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14 #endif
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15
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16 #ifdef HAVE_GCC_ASM_FOR_X87
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17
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18 /* inline assembly for getting and setting the 387 FPU control word on
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19 gcc/x86 */
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20
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21 unsigned short _Py_get_387controlword(void) {
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22 unsigned short cw;
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23 __asm__ __volatile__ ("fnstcw %0" : "=m" (cw));
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24 return cw;
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25 }
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26
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27 void _Py_set_387controlword(unsigned short cw) {
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28 __asm__ __volatile__ ("fldcw %0" : : "m" (cw));
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29 }
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30
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31 #endif
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32
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33
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34 #ifndef HAVE_HYPOT
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35 double hypot(double x, double y)
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36 {
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37 double yx;
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38
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39 x = fabs(x);
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40 y = fabs(y);
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41 if (x < y) {
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42 double temp = x;
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43 x = y;
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44 y = temp;
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45 }
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46 if (x == 0.)
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47 return 0.;
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48 else {
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49 yx = y/x;
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50 return x*sqrt(1.+yx*yx);
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51 }
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52 }
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53 #endif /* HAVE_HYPOT */
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54
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55 #ifndef HAVE_COPYSIGN
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56 double
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57 copysign(double x, double y)
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58 {
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59 /* use atan2 to distinguish -0. from 0. */
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60 if (y > 0. || (y == 0. && atan2(y, -1.) > 0.)) {
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61 return fabs(x);
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62 } else {
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63 return -fabs(x);
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64 }
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65 }
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66 #endif /* HAVE_COPYSIGN */
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67
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68 #ifndef HAVE_ROUND
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69 double
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70 round(double x)
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71 {
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72 double absx, y;
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73 absx = fabs(x);
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74 y = floor(absx);
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75 if (absx - y >= 0.5)
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76 y += 1.0;
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77 return copysign(y, x);
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78 }
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79 #endif /* HAVE_ROUND */