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         fixp_t total = probdist_total(pd);
  17         fixp_t stab = fast_irandom(total);
  18         if (DEBUGL(6))
  19                 fprintf(stderr, "stab %f / %f\n", fixp_to_double(stab), fixp_to_double(total));
  20
  21         int r = 1;
  22         coord_t c = board_size(pd->b) + 1;
  23         while (stab > pd->rowtotals[r]) {
  24                 if (DEBUGL(6))
  25                         fprintf(stderr, "[%s] skipping row %f (%f)\n", coord2sstr(c, pd->b), fixp_to_double(pd->rowtotals[r]), fixp_to_double(stab));
  26
  27                 stab -= pd->rowtotals[r];
  28                 r++; assert(r < board_size(pd->b));
  29
  30                 c += board_size(pd->b);
  31                 while (!is_pass(*ignore) && *ignore <= c)
  32                         ignore++;
  33         }
  34
  35         for (; c < board_size2(pd->b); c++) {
  36                 if (DEBUGL(6))
  37                         fprintf(stderr, "[%s] %f (%f)\n", coord2sstr(c, pd->b), fixp_to_double(pd->items[c]), fixp_to_double(stab));
  38
  39                 assert(is_pass(*ignore) || c <= *ignore);
  40                 if (c == *ignore) {
  41                         if (DEBUGL(6))
  42                                 fprintf(stderr, "\tignored\n");
  43                         ignore++;
  44                         continue;
  45                 }
  46
  47                 if (stab <= pd->items[c])
  48                         return c;
  49                 stab -= pd->items[c];
  50         }
  51
  52         fprintf(stderr, "overstab %f (total %f)\n", fixp_to_double(stab), fixp_to_double(total));
  53         assert(0);
  54         return -1;
  55 }