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  1. // Ranlux24 PRNG. (1.02)
  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 (int i = 0; i < s; i++)
  77.             x[i] = next_(x, m, i + t, i, c);
  78.         for (int i = s; i < r; i++)
  79.             x[i] = next_(x, m, i - s, i, c);
  80.         self->i = i = 0;
  81.     }
  82.     return x[i];
  83. }
  84.  
  85. void SubtractWithCarryEngine_discard(EngineBase *base, int n)
  86. {
  87.     for (int i = 0; i < n; i++)
  88.         SubtractWithCarryEngine_next(base);
  89. }
  90.  
  91. void SubtractWithCarryEngine_delete(EngineBase *base)
  92. {
  93.     SubtractWithCarryEngine *self = (SubtractWithCarryEngine *) base;
  94.  
  95.     if (self != 0)
  96.     {
  97.         free(self->x);
  98.         free(self);
  99.     }
  100. }
  101.  
  102. EngineBase *SubtractWithCarryEngine_new(int w, int s, int r)
  103. {
  104.     assert(0 < w && w < BITS(int));
  105.     assert(0 < s && s < r);
  106.  
  107.     SubtractWithCarryEngine *self = NEW_T(SubtractWithCarryEngine, 1);
  108.  
  109.     self->base.next = SubtractWithCarryEngine_next;
  110.     self->base.discard = SubtractWithCarryEngine_discard;
  111.     self->base.delete = SubtractWithCarryEngine_delete;
  112.     self->x = NEW_T(int, r);
  113.     self->c = 0;
  114.     self->i = r-1;
  115.     self->m = -1U >> (BITS(int) - w);
  116.     self->r = r;
  117.     self->s = s;
  118.  
  119.     for (int i = 0; i < r; i++)
  120.         self->x[i] = rand() & self->m;
  121.     return (EngineBase *) self;
  122. }
  123.  
  124. // Discard Block.
  125.  
  126. typedef struct {
  127.     EngineBase base, *owned;
  128.     int p, r, i;
  129. } DiscardBlockEngine;
  130.  
  131. int DiscardBlockEngine_next(EngineBase *base)
  132. {
  133.     DiscardBlockEngine *self = (DiscardBlockEngine *) base;
  134.  
  135.     if (self->i == 0)
  136.     {
  137.         EngineBase_discard(self->owned, self->p - self->r);
  138.         self->i = self->r;
  139.     }
  140.     self->i -= 1;
  141.     return EngineBase_next(self->owned);
  142. }
  143.  
  144. void DiscardBlockEngine_discard(EngineBase *base, int n)
  145. {
  146.     for (int i = 0; i < n; i++)
  147.         DiscardBlockEngine_next(base);
  148. }
  149.  
  150. void DiscardBlockEngine_delete(EngineBase *base)
  151. {
  152.     DiscardBlockEngine *self = (DiscardBlockEngine *) base;
  153.  
  154.     if (self != 0)
  155.     {
  156.         EngineBase_delete(self->owned);
  157.         free(self);
  158.     }
  159. }
  160.  
  161. EngineBase *DiscardBlockEngine_new(EngineBase **unique, int p, int r)
  162. {
  163.     assert(0 < r <= p);
  164.  
  165.     DiscardBlockEngine *self = NEW_T(DiscardBlockEngine, 1);
  166.  
  167.     self->base.next = DiscardBlockEngine_next;
  168.     self->base.discard = DiscardBlockEngine_discard;
  169.     self->base.delete = DiscardBlockEngine_delete;
  170.     self->owned = *unique; *unique = 0; // Transfer ownership.
  171.     self->p = p;
  172.     self->r = r;
  173.     self->i = r;
  174.     return (EngineBase *) self;
  175. }
  176.  
  177. // Ranlux24.
  178.  
  179. EngineBase *Ranlux24_new(void)
  180. {
  181.     EngineBase *ranlux24_base = SubtractWithCarryEngine_new(24, 10, 24);
  182.     return DiscardBlockEngine_new(&ranlux24_base, 223, 23);
  183. }
  184.  
  185. // Main.
  186.  
  187. double clock_now(void)
  188. {
  189.     struct timespec now;
  190.     clock_gettime(CLOCK_PROCESS_CPUTIME_ID, &now);
  191.     return now.tv_sec + now.tv_nsec / 1.0E+09;
  192. }
  193.  
  194. int main(void)
  195. {
  196.     srand(time(0));
  197.     EngineBase *ranlux24 = Ranlux24_new();
  198.  
  199.     for (int i = 0; i < 24; i++)
  200.     {
  201.         int r = EngineBase_next(ranlux24);
  202.         printf("%d\n", r);
  203.     }
  204.  
  205.     int n = 10000000;
  206.     double t = clock_now();
  207.     EngineBase_discard(ranlux24, n);
  208.     printf("Elapsed: %.9fs\n", clock_now() - t);
  209.  
  210.     EngineBase_delete(ranlux24);
  211.     return 0;
  212. }
Success #stdin #stdout 0.33s 5284KB
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Elapsed: 0.322370179s
https://ideone.com/cz7dKW
language:
C (gcc 8.3)
created:
10 days ago
visibility:
public

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