tactics/nlib.c

   1 #include <assert.h>
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4
   5 #define DEBUG
   6 #include "board.h"
   7 #include "debug.h"
   8 #include "mq.h"
   9 #include "tactics/2lib.h"
  10 #include "tactics/nlib.h"
  11 #include "tactics/selfatari.h"
  12 #include "tactics/goals.h"
  13
  14
  15 void
  16 group_nlib_defense_check(struct board *b, group_t group, enum stone to_play, struct libmap_mq *q, int tag)
  17 {
  18         enum stone color = to_play;
  19         assert(color != S_OFFBOARD && color != S_NONE
  20                && color == board_at(b, group_base(group)));
  21
  22         if (DEBUGL(5))
  23                 fprintf(stderr, "[%s] nlib defense check of color %d\n",
  24                         coord2sstr(group, b), color);
  25
  26 #if 0
  27         /* XXX: The code below is specific for 3-liberty groups. Its impact
  28          * needs to be tested first, and possibly moved to a more appropriate
  29          * place. */
  30
  31         /* First, look at our liberties. */
  32         int continuous = 0, enemy = 0, spacy = 0, eyes = 0;
  33         for (int i = 0; i < 3; i++) {
  34                 coord_t c = board_group_info(b, group).lib[i];
  35                 eyes += board_is_one_point_eye(b, c, to_play);
  36                 continuous += coord_is_adjecent(c, board_group_info(b, group).lib[(i + 1) % 3], b);
  37                 enemy += neighbor_count_at(b, c, stone_other(color));
  38                 spacy += immediate_liberty_count(b, c) > 1;
  39         }
  40
  41         /* Safe groups are boring. */
  42         if (eyes > 1)
  43                 return;
  44
  45         /* If all our liberties are in single line and they are internal,
  46          * this is likely a tiny three-point eyespace that we rather want
  47          * to live at! */
  48         assert(continuous < 3);
  49         if (continuous == 2 && !enemy && spacy == 1) {
  50                 assert(!eyes);
  51                 int i;
  52                 for (i = 0; i < 3; i++)
  53                         if (immediate_liberty_count(b, board_group_info(b, group).lib[i]) == 2)
  54                                 break;
  55                 /* Play at middle point. */
  56                 mq_add(q, board_group_info(b, group).lib[i], tag);
  57                 mq_nodup(q);
  58                 return;
  59         }
  60 #endif
  61
  62         /* "Escaping" (gaining more liberties) with many-liberty group
  63          * is difficult. Do not even try. */
  64
  65         /* There is another way to gain safety - through winning semeai
  66          * with another group. */
  67         /* We will not look at taking liberties of enemy n-groups, since
  68          * we do not try to gain liberties for own n-groups. That would
  69          * be really unbalanced (and most of our liberty-taking moves
  70          * would be really stupid, most likely). */
  71
  72         /* However, it is possible that we must start capturing a 2-lib
  73          * neighbor right now, because of approach liberties. Therefore,
  74          * we will check for this case. If we take a liberty of a group
  75          * even if we could have waited another move, no big harm done
  76          * either. */
  77
  78         foreach_in_group(b, group) {
  79                 foreach_neighbor(b, c, {
  80                         if (board_at(b, c) != stone_other(color))
  81                                 continue;
  82                         group_t g2 = group_at(b, c);
  83                         if (board_group_info(b, g2).libs != 2)
  84                                 continue;
  85                         struct libmap_move_groupinfo lmgi;
  86                         lmgi.group = group;
  87                         lmgi.color = color;
  88                         lmgi.hash = group_to_libmap(b, group);
  89                         lmgi.goal = to_play;
  90                         can_atari_group(b, g2, stone_other(color), to_play, q, tag, lmgi, group_to_libmap(b, g2), true /* XXX */);
  91                 });
  92         } foreach_in_group_end;
  93 }