probdist.c

   1 #include <assert.h>
   2 #include <math.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5
   6 //#define DEBUG
   7 #include "debug.h"
   8 #include "move.h"
   9 #include "probdist.h"
  10 #include "random.h"
  11 #include "board.h"
  12
  13 coord_t
  14 probdist_pick(struct probdist *restrict pd, coord_t *restrict ignore)
  15 {
  16         double total = probdist_total(pd) - PROBDIST_EPSILON;
  17         assert(total >= 0);
  18         double stab = fast_frandom() * total;
  19         if (DEBUGL(6))
  20                 fprintf(stderr, "stab %f / %f\n", stab, total);
  21
  22         int r = 0;
  23         coord_t c = 0;
  24         while (stab > pd->rowtotals[r] + PROBDIST_EPSILON) {
  25                 if (DEBUGL(6))
  26                         fprintf(stderr, "[%s] skipping row %f (%f)\n", coord2sstr(c, pd->b), pd->rowtotals[r], stab);
  27
  28                 stab -= pd->rowtotals[r];
  29                 r++; assert(r < board_size(pd->b));
  30
  31                 c += board_size(pd->b);
  32                 while (!is_pass(*ignore) && *ignore <= c)
  33                         ignore++;
  34         }
  35
  36         for (; c < board_size2(pd->b); c++) {
  37                 if (DEBUGL(6))
  38                         fprintf(stderr, "[%s] %f (%f)\n", coord2sstr(c, pd->b), pd->items[c], stab);
  39
  40                 assert(is_pass(*ignore) || c <= *ignore);
  41                 if (c == *ignore) {
  42                         if (DEBUGL(6))
  43                                 fprintf(stderr, "ignored\n");
  44                         ignore++;
  45                         continue;
  46                 }
  47
  48                 if (stab <= pd->items[c])
  49                         return c;
  50                 stab -= pd->items[c];
  51         }
  52
  53         fprintf(stderr, "overstab %f (total %f)\n", stab, total);
  54         assert(0);
  55         return -1;
  56 }