random.h

   1 #ifndef PACHI_RANDOM_H
   2 #define PACHI_RANDOM_H
   3
   4 #include <stdint.h>
   5
   6 #include "util.h"
   7
   8 void fast_srandom(unsigned long seed);
   9 unsigned long fast_getseed(void);
  10
  11 /* Note that only 16bit numbers can be returned. */
  12 uint16_t fast_random(unsigned int max);
  13 /* Use this one if you want larger numbers. */
  14 static uint32_t fast_irandom(unsigned int max);
  15
  16 /* Get random number in [0..1] range. */
  17 float fast_frandom();
  18
  19
  20 static inline uint32_t
  21 fast_irandom(unsigned int max)
  22 {
  23         if (max <= 65536)
  24                 return fast_random(max);
  25         int himax = (max - 1) / 65536;
  26         uint16_t hi = fast_random(himax + 1);
  27         return ((uint32_t)hi << 16) | fast_random(hi < himax ? 65536 : max % 65536);
  28 }
  29
  30 #endif