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  1. // Ranlux24 PRNG. (1.03)
  2. // Chaotic with long period but slow due to discard.
  3.  
  4. #include <stdlib.h>
  5. #include <limits.h>
  6. #include <assert.h>
  7. #include <stdio.h>
  8. #include <time.h>
  9.  
  10. // Utility.
  11.  
  12. #define BITS(x) \
  13.     (sizeof(x) * CHAR_BIT)
  14.  
  15. #define UNLIKELY(cond) \
  16.     __builtin_expect(!!(cond), 0)
  17.  
  18. #define NEW_T(T, n) \
  19.     ((T *) allocate(n * sizeof(T)))
  20.  
  21. void *allocate(size_t n)
  22. {
  23.     void *r = malloc(n);
  24.     assert(r != 0 || n == 0);
  25.     return r;
  26. }
  27.  
  28. // Engine Base.
  29.  
  30. typedef struct EngineBase {
  31.     int  (*next)    (struct EngineBase*);
  32.     void (*discard) (struct EngineBase*, int);
  33.     void (*delete)  (struct EngineBase*);
  34. } EngineBase;
  35.  
  36. int EngineBase_next(EngineBase *self)
  37. {
  38.     return self->next(self);
  39. }
  40.  
  41. void EngineBase_discard(EngineBase *self, int n)
  42. {
  43.     return self->discard(self, n);
  44. }
  45.  
  46. void EngineBase_delete(EngineBase *self)
  47. {
  48.     return self->delete(self);
  49. }
  50.  
  51. // Subtract With Carry.
  52.  
  53. typedef struct {
  54.     EngineBase base;
  55.     int *x, c, i, m, r, s;
  56. } SubtractWithCarryEngine;
  57.  
  58. static inline int next(int *x, int mask, int i_s, int i_r, int *carry)
  59. {
  60.     int y = x[i_s] - x[i_r] - *carry;
  61.     *carry = -(y >> (BITS(int) - 1));
  62.     return y & mask;
  63. }
  64.  
  65. int SubtractWithCarryEngine_next(EngineBase *base)
  66. {
  67.     SubtractWithCarryEngine *self = (SubtractWithCarryEngine *) base;
  68.  
  69.     self->i += 1;
  70.     int *x = self->x, i = self->i, r = self->r;
  71.  
  72.     if (UNLIKELY(i >= r))
  73.     {
  74.         int c = self->c, m = self->m, s = self->s, t = r - s;
  75.  
  76.         for (i = 0; i < s; i++)
  77.             x[i] = next(x, m, i + t, i, &c);
  78.         for (i = s; i < r; i++)
  79.             x[i] = next(x, m, i - s, i, &c);
  80.         self->c = c;
  81.         self->i = i = 0;
  82.     }
  83.     return x[i];
  84. }
  85.  
  86. void SubtractWithCarryEngine_discard(EngineBase *base, int n)
  87. {
  88.     for (int i = 0; i < n; i++)
  89.         SubtractWithCarryEngine_next(base);
  90. }
  91.  
  92. void SubtractWithCarryEngine_delete(EngineBase *base)
  93. {
  94.     SubtractWithCarryEngine *self = (SubtractWithCarryEngine *) base;
  95.  
  96.     if (self != 0)
  97.     {
  98.         free(self->x);
  99.         free(self);
  100.     }
  101. }
  102.  
  103. EngineBase *SubtractWithCarryEngine_new(int w, int s, int r)
  104. {
  105.     assert(0 < w && w < BITS(int));
  106.     assert(0 < s && s < r);
  107.  
  108.     SubtractWithCarryEngine *self = NEW_T(SubtractWithCarryEngine, 1);
  109.  
  110.     self->base.next = SubtractWithCarryEngine_next;
  111.     self->base.discard = SubtractWithCarryEngine_discard;
  112.     self->base.delete = SubtractWithCarryEngine_delete;
  113.     self->x = NEW_T(int, r);
  114.     self->c = 0;
  115.     self->i = r-1;
  116.     self->m = -1U >> (BITS(int) - w);
  117.     self->r = r;
  118.     self->s = s;
  119.  
  120.     for (int i = 0; i < r; i++)
  121.         self->x[i] = rand() & self->m;
  122.     return (EngineBase *) self;
  123. }
  124.  
  125. // Discard Block.
  126.  
  127. typedef struct {
  128.     EngineBase base, *owned;
  129.     int p, r, i;
  130. } DiscardBlockEngine;
  131.  
  132. int DiscardBlockEngine_next(EngineBase *base)
  133. {
  134.     DiscardBlockEngine *self = (DiscardBlockEngine *) base;
  135.  
  136.     if (self->i == 0)
  137.     {
  138.         EngineBase_discard(self->owned, self->p - self->r);
  139.         self->i = self->r;
  140.     }
  141.     self->i -= 1;
  142.     return EngineBase_next(self->owned);
  143. }
  144.  
  145. void DiscardBlockEngine_discard(EngineBase *base, int n)
  146. {
  147.     for (int i = 0; i < n; i++)
  148.         DiscardBlockEngine_next(base);
  149. }
  150.  
  151. void DiscardBlockEngine_delete(EngineBase *base)
  152. {
  153.     DiscardBlockEngine *self = (DiscardBlockEngine *) base;
  154.  
  155.     if (self != 0)
  156.     {
  157.         EngineBase_delete(self->owned);
  158.         free(self);
  159.     }
  160. }
  161.  
  162. EngineBase *DiscardBlockEngine_new(EngineBase **unique, int p, int r)
  163. {
  164.     assert(0 < r && r <= p);
  165.  
  166.     DiscardBlockEngine *self = NEW_T(DiscardBlockEngine, 1);
  167.  
  168.     self->base.next = DiscardBlockEngine_next;
  169.     self->base.discard = DiscardBlockEngine_discard;
  170.     self->base.delete = DiscardBlockEngine_delete;
  171.     self->owned = *unique; *unique = 0; // Transfer ownership.
  172.     self->p = p;
  173.     self->r = r;
  174.     self->i = r;
  175.     return (EngineBase *) self;
  176. }
  177.  
  178. // Ranlux24.
  179.  
  180. EngineBase *Ranlux24_new(void)
  181. {
  182.     EngineBase *ranlux24_base = SubtractWithCarryEngine_new(24, 10, 24);
  183.     return DiscardBlockEngine_new(&ranlux24_base, 223, 23);
  184. }
  185.  
  186. // Main.
  187.  
  188. double clock_now(void)
  189. {
  190.     struct timespec now;
  191.     clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &now);
  192.     return now.tv_sec + now.tv_nsec / 1.0E+09;
  193. }
  194.  
  195. int main(void)
  196. {
  197.     srand(time(0));
  198.     EngineBase *ranlux24 = Ranlux24_new();
  199.  
  200.     for (int i = 0; i < 24; i++)
  201.     {
  202.         int r = EngineBase_next(ranlux24);
  203.         printf("%d\n", r);
  204.     }
  205.  
  206.     int n = 10000000;
  207.     double t = clock_now();
  208.     EngineBase_discard(ranlux24, n);
  209.     printf("Elapsed: %.9fs\n", clock_now() - t);
  210.  
  211.     EngineBase_delete(ranlux24);
  212.     return 0;
  213. }
Success #stdin #stdout 0.26s 5284KB
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3352764
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Elapsed: 0.256149355s
https://ideone.com/pO4PoJ
language:
C (gcc 8.3)
created:
10 days ago
visibility:
public

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