probdist.c

   1 #include <assert.h>
   2 #include <math.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5
   6 #include "move.h"
   7 #include "probdist.h"
   8 #include "random.h"
   9
  10 struct probdist *
  11 probdist_init(struct probdist *pd, int n)
  12 {
  13         if (!pd) pd = malloc(sizeof(*pd));
  14         pd->n = n;
  15         pd->items = calloc(n, sizeof(pd->items[0]));
  16         pd->items[0] = 0; // probdist_set() requires [0] to be initialized
  17         return pd;
  18 }
  19
  20 int
  21 probdist_pick(struct probdist *pd)
  22 {
  23         assert(pd->items[pd->n - 1] >= 0);
  24         /* TODO: float random */
  25         float stab = (float) fast_random(65536) / 65536 * pd->items[pd->n - 1];
  26         //fprintf(stderr, "stab %f / %f\n", stab, pd->items[pd->n - 1]);
  27         for (int i = 0; i < pd->n; i++) {
  28                 if (stab <= pd->items[i])
  29                         return i;
  30         }
  31         //fprintf(stderr, "overstab %f (total %f, sum %f)\n", stab, pd->items[pd->n - 1], sum);
  32         assert(0);
  33         return -1;
  34 }
  35
  36 void
  37 probdist_done(struct probdist *pd) {
  38         free(pd->items);
  39 }