More notes on the possible min/max method.
[pachi/pachi-r6144.git] / probdist.h
blob8586786b4b2c245bee5cc62346cd2c175412e548
1 #ifndef PACHI_PROBDIST_H
2 #define PACHI_PROBDIST_H
4 /* Tools for picking an item according to a probability distribution. */
6 /* The probability distribution structure is designed to be once
7 * initialized, then random items assigned a value repeatedly and
8 * random items picked repeatedly as well. */
10 #include "fixp.h"
11 #include "move.h"
12 #include "util.h"
14 struct board;
16 /* The interface looks a bit funny-wrapped since we used to switch
17 * between different probdist representations. */
19 struct probdist {
20 struct board *b;
21 fixp_t *items; // [bsize2], [i] = P(pick==i)
22 fixp_t *rowtotals; // [bsize], [i] = sum of items in row i
23 fixp_t total; // sum of all items
27 /* Declare pd_ corresponding to board b_ in the local scope. */
28 #define probdist_alloca(pd_, b_) \
29 fixp_t pd_ ## __pdi[board_size2(b_)] __attribute__((aligned(32))); memset(pd_ ## __pdi, 0, sizeof(pd_ ## __pdi)); \
30 fixp_t pd_ ## __pdr[board_size(b_)] __attribute__((aligned(32))); memset(pd_ ## __pdr, 0, sizeof(pd_ ## __pdr)); \
31 struct probdist pd_ = { .b = b_, .items = pd_ ## __pdi, .rowtotals = pd_ ## __pdr, .total = 0 };
33 /* Get the value of given item. */
34 #define probdist_one(pd, c) ((pd)->items[c])
36 /* Get the cummulative probability value (normalizing constant). */
37 #define probdist_total(pd) ((pd)->total)
39 /* Set the value of given item. */
40 static void probdist_set(struct probdist *pd, coord_t c, fixp_t val);
42 /* Remove the item from the totals; this is used when you then
43 * pass it in the ignore list to probdist_pick(). Of course you
44 * must restore the totals afterwards. */
45 static void probdist_mute(struct probdist *pd, coord_t c);
47 /* Pick a random item. ignore is a pass-terminated sorted array of items
48 * that are not to be considered (and whose values are not in @total). */
49 coord_t probdist_pick(struct probdist *pd, coord_t *ignore);
52 /* Now, we do something horrible - include board.h for the inline helpers.
53 * Yay for us. */
54 #include "board.h"
57 static inline void
58 probdist_set(struct probdist *pd, coord_t c, fixp_t val)
60 /* We disable the assertions here since this is quite time-critical
61 * part of code, and also the compiler is reluctant to inline the
62 * functions otherwise. */
63 #if 0
64 assert(c >= 0 && c < board_size2(pd->b));
65 assert(val >= 0);
66 #endif
67 pd->total += val - pd->items[c];
68 pd->rowtotals[coord_y(c, pd->b)] += val - pd->items[c];
69 pd->items[c] = val;
72 static inline void
73 probdist_mute(struct probdist *pd, coord_t c)
75 pd->total -= pd->items[c];
76 pd->rowtotals[coord_y(c, pd->b)] -= pd->items[c];
79 #endif