/* Change the status and safety of a dragon. In addition, if the new
* status is not DEAD, make all worms of the dragon essential, so that
* results found by semeai code don't get ignored.
*/
static void
update_status(int dr, enum dragon_status new_status,
enum dragon_status new_safety)
{
int pos;
if (dragon[dr].status != new_status
&& (dragon[dr].status != CRITICAL || new_status != DEAD)) {
DEBUG(DEBUG_SEMEAI, "Changing status of %1m from %s to %s.\n", dr,
status_to_string(dragon[dr].status),
status_to_string(new_status));
for (pos = BOARDMIN; pos < BOARDMAX; pos++)
if (IS_STONE(board[pos]) && is_same_dragon(dr, pos)) {
dragon[pos].status = new_status;
if (new_status != DEAD)
worm[pos].inessential = 0;
}
}
if (DRAGON2(dr).safety != new_safety
&& (DRAGON2(dr).safety != CRITICAL || new_safety != DEAD)) {
DEBUG(DEBUG_SEMEAI, "Changing safety of %1m from %s to %s.\n", dr,
status_to_string(DRAGON2(dr).safety), status_to_string(new_safety));
DRAGON2(dr).safety = new_safety;
}
}
int
does_surround(int move, int dr)
{
if (DRAGON2(dr).surround_status)
return 0;
return compute_surroundings(dr, move, 0, NULL);
}
int
compute_surroundings(int pos, int apos, int showboard, int *surround_size)
{
int i, j;
int m, n;
int k;
int dpos;
int surrounded;
int left_corner[MAX_BOARD];
int right_corner[MAX_BOARD];
int corner[BOARDMAX];
int left_corners = 0, right_corners = 0;
int corners = 0;
int top_row, bottom_row;
int color = board[pos];
int other = OTHER_COLOR(color);
int gi = 0;
int gj = 0;
int stones = 0;
int found_some;
signed char mf[BOARDMAX]; /* friendly dragon */
signed char mn[BOARDMAX]; /* neighbor dragons */
int sd[BOARDMAX]; /* distances to the goal */
if (DRAGON2(pos).hostile_neighbors == 0)
return(0);
memset(mf, 0, sizeof(mf));
memset(mn, 0, sizeof(mn));
memset(sd, 0, sizeof(sd));
mark_dragon(pos, mf, 1);
/* mark hostile neighbors */
for (k = 0; k < DRAGON2(pos).neighbors; k++) {
int nd = DRAGON(DRAGON2(pos).adjacent[k]).origin;
if (board[nd] != color) {
if (0)
gprintf("neighbor: %1m\n", nd);
mark_dragon(nd, mn, 1);
}
}
/* descend markings from stones lying on the 2nd and third lines */
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
if (ON_BOARD(dpos) && mn[dpos]) {
for (k = 0; k < 4; k++) {
int d = delta[k];
if (!ON_BOARD(dpos + d))
continue;
if (!ON_BOARD(dpos + 2*d)) {
if (board[dpos + d] == EMPTY)
mn[dpos + d] = 1;
}
else if (!ON_BOARD(dpos + 3*d)) {
if (board[dpos + d] == EMPTY
&& board[dpos + 2*d] == EMPTY)
mn[dpos + 2*d] = 1;
}
}
}
/* compute minimum distances to the goal */
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
if (ON_BOARD(dpos) && mn[dpos])
sd[dpos] = goal_dist(dpos, mf);
/* revise markings */
do {
found_some = 0;
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
if (ON_BOARD(dpos) && mn[dpos] && sd[dpos] > 8) {
/* discard markings if we can find 2 stones
* that verify :
* - it is closer to the goal than we are
* - it is closer to us than the goal is
* - they are closer to each other than we are to the goal
*/
for (i = BOARDMIN; i < BOARDMAX; i++)
if (ON_BOARD(i) && mn[i] && i != dpos
&& sd[i] < sd[dpos]
&& square_dist(i, dpos) < sd[dpos]) {
for (j = i + 1; j < BOARDMAX; j++)
if (ON_BOARD(j) && mn[j] && j != dpos
&& sd[j] < sd[dpos]
&& square_dist(j, dpos) < sd[dpos]
&& square_dist(i, j) < sd[dpos]) {
mn[dpos] = 0;
found_some = 1;
break;
}
if (mn[dpos] == 0)
break;
}
}
} while (found_some);
/* prepare corner array */
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
if (ON_BOARD(dpos) && mn[dpos])
corner[corners++] = dpos;
/* compute gravity center of the goal */
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
if (ON_BOARD(dpos) && mf[dpos]) {
gi += I(dpos);
gj += J(dpos);
stones++;
}
gi /= stones;
gj /= stones;
gg = POS(gi, gj);
/* sort the corner array */
gg_sort(corner, corners, sizeof(int), compare_angles);
/* if apos is not NO_MOVE, mark it. */
if (apos != NO_MOVE) {
ASSERT_ON_BOARD1(apos);
mn[apos] = 1;
}
if (showboard == 1) {
show_surround_map(mf, mn);
}
/* find top row of surrounding polyhedron */
top_row = -1;
for (m = 0; m < board_size; m++) {
if (top_row != -1)
break;
for (n = 0; n < board_size; n++)
if (mn[POS(m, n)]) {
left_corner[0] = POS(m, n);
top_row = m;
break;
}
}
/* find bottom row */
bottom_row = -1;
for (m = board_size - 1; m >= 0; m--) {
if (bottom_row != -1)
break;
for (n = 0; n < board_size; n++)
if (mn[POS(m, n)]) {
bottom_row = m;
break;
}
}
/* find the corners on the left side */
for (left_corners = 1; I(left_corner[left_corners-1]) < bottom_row;
left_corners++) {
int best_found = 0;
float best_slope = 0.;
int m = I(left_corner[left_corners-1]);
int n = J(left_corner[left_corners-1]);
for (i = m + 1; i <= bottom_row; i++)
for (j = 0; j < board_size; j++)
if (mn[POS(i, j)]) {
float slope = ((float) (j - n))/((float) (i - m));
if (0)
gprintf("(left) at %m, last %m, slope=%f\n", i, j, m, n, slope);
if (!best_found || slope < best_slope) {
best_found = POS(i, j);
best_slope = slope;
}
}
ASSERT_ON_BOARD1(best_found);
left_corner[left_corners] = best_found;
}
for (n = board_size-1; n >= 0; n--)
if (mn[POS(top_row, n)]) {
right_corner[0] = POS(top_row, n);
break;
}
/* find the corners on the right side */
for (right_corners = 1; I(right_corner[right_corners-1]) < bottom_row;
right_corners++) {
int best_found = 0;
float best_slope = 0.;
int m = I(right_corner[right_corners-1]);
int n = J(right_corner[right_corners-1]);
for (i = m + 1; i <= bottom_row; i++) {
for (j = board_size - 1; j >= 0; j--) {
if (mn[POS(i, j)]) {
float slope = ((float) (j - n))/((float) (i - m));
if (0)
gprintf("(right) at %m, last %m, slope=%f\n", i, j, m, n, slope);
if (!best_found || slope > best_slope) {
best_found = POS(i, j);
best_slope = slope;
}
}
}
}
ASSERT_ON_BOARD1(best_found);
right_corner[right_corners] = best_found;
}
if (0) {
for (k = 0; k < left_corners; k++)
gprintf("left corner %d: %1m\n", k, left_corner[k]);
for (k = 0; k < right_corners; k++)
gprintf("right corner %d: %1m\n", k, right_corner[k]);
}
/* Now mark the interior of the convex hull */
for (n = J(left_corner[0]); n <= J(right_corner[0]); n++)
mn[POS(top_row, n)] = 1;
for (n = J(left_corner[left_corners-1]);
n <= J(right_corner[right_corners-1]); n++)
mn[POS(bottom_row, n)] = 1;
for (m = top_row+1; m < bottom_row; m++) {
int left_boundary = -1, right_boundary = -1;
for (k = 1; k < left_corners; k++) {
if (I(left_corner[k]) > m) {
float ti = I(left_corner[k-1]);
float tj = J(left_corner[k-1]);
float bi = I(left_corner[k]);
float bj = J(left_corner[k]);
if (0)
gprintf("(left) %d: %1m %1m\n",
m, left_corner[k-1], left_corner[k]);
/* left edge in this row is on segment (ti,tj) -> (bi, bj) */
/* FIXME: Rewrite this to avoid floating point arithmetic */
left_boundary = ceil(tj + (m - ti) * (bj - tj) / (bi - ti));
break;
}
}
for (k = 1; k < right_corners; k++) {
if (I(right_corner[k]) > m) {
float ti = I(right_corner[k-1]);
float tj = J(right_corner[k-1]);
float bi = I(right_corner[k]);
float bj = J(right_corner[k]);
if (0)
gprintf("(right) %d: %1m %1m\n",
m, right_corner[k-1], right_corner[k]);
/* FIXME: Rewrite this to avoid floating point arithmetic */
right_boundary = floor(tj + (m - ti) * (bj - tj) / (bi - ti));
break;
}
}
for (n = left_boundary; n <= right_boundary; n++)
mn[POS(m, n)] = 1;
}
/* mark the expanded region */
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
if (ON_BOARD(dpos) && mn[dpos] == 1)
for (k = 0; k < 4; k++)
if (ON_BOARD(dpos + delta[k]) && !mn[dpos + delta[k]])
mn[dpos + delta[k]] = 2;
/* Mark allied dragons that intersect the (unexpanded) hull.
* These must all lie entirely within the hull for the
* dragon to be considered surrounded.
*
* Only neighbor dragons are considered since dragons that
* are not neighbors are less likely to be helpful.
*/
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++) {
int mpos;
if (ON_BOARD(dpos)
&& mn[dpos] == 1
&& board[dpos] == color
&& are_neighbor_dragons(pos, dpos)
&& !mf[dpos]) {
for (mpos = BOARDMIN; mpos < BOARDMAX; mpos++)
if (ON_BOARD(mpos) && is_same_dragon(mpos, dpos))
mf[mpos] = 2;
}
/* A special case
*
* . X X .
* X O . X
* X . O O
* . O . .
*
* The O stone hasn't been amalgamated and the surround computations
* might think this single stone dragon is surrounded, which in turn
* can generate overvaluation of moves around this stone.
* Consequently, we allow inclusion of the stones at kosumi distance
* in the mf (friendly) array.
*/
if (ON_BOARD(dpos)
&& mn[dpos] == 2
&& board[dpos] == color
&& are_neighbor_dragons(pos, dpos)
&& !mf[dpos]) {
for (k = 4; k < 8; k++)
if (ON_BOARD(dpos + delta[k]) && board[dpos + delta[k]] == color
&& mn[dpos + delta[k]] == 1
&& board[dpos + delta[k-4]] == EMPTY
&& board[dpos + delta[(k-3)%4]] == EMPTY) {
for (mpos = BOARDMIN; mpos < BOARDMAX; mpos++)
if (ON_BOARD(mpos) && is_same_dragon(mpos, dpos))
mf[mpos] = 2;
}
}
}
/* determine the surround status of the dragon */
surrounded = SURROUNDED;
/* Compute the maximum surround status awarded
* If distances between enclosing stones are large, reduce to
* WEAKLY_SURROUNDED. If (really) too large, then reduce to 0
* FIXME: constants chosen completely ad hoc. Possibly better tunings
* can be found.
*/
for (k = 0; k < corners - 1; k++) {
if (is_edge_vertex(corner[k])
&& is_edge_vertex(corner[k+1]))
continue;
if (square_dist(corner[k], corner[k+1]) > 60) {
surrounded = 0;
break;
}
else if (square_dist(corner[k], corner[k+1]) > 27)
surrounded = WEAKLY_SURROUNDED;
}
if (surrounded
&& (!is_edge_vertex(corner[0])
|| !is_edge_vertex(corner[corners-1]))) {
if (square_dist(corner[0], corner[corners-1]) > 60)
surrounded = 0;
else if (square_dist(corner[0], corner[corners-1]) > 27)
surrounded = WEAKLY_SURROUNDED;
}
if (surrounded)
for (dpos = BOARDMIN; dpos < BOARDMAX; dpos++)
if (mf[dpos]) {
if (mn[dpos] == 0) {
surrounded = 0;
break;
}
else if (mn[dpos] == 2)
surrounded = WEAKLY_SURROUNDED;
}
/* revise the status for single stone dragons. */
if (stones == 1
&& surrounded == WEAKLY_SURROUNDED
&& mn[pos] == 2)
surrounded = 0;
/* revise the status if an ikken tobi jumps out. */
if (surrounded) {
for (dpos = BOARDMIN; dpos < BOARDMAX && surrounded; dpos++) {
if (!ON_BOARD(dpos) || !mf[dpos])
continue;
for (k = 0; k < 4; k++) {
int up = delta[k];
int right = delta[(k + 1) % 4];
if (board[dpos + up] == EMPTY
&& board[dpos + 2*up] == color
&& mn[dpos + 2*up] != 1
&& ON_BOARD(dpos + up + right)
&& board[dpos + up + right] != other
&& ON_BOARD(dpos + up - right)
&& board[dpos + up - right] != other) {
surrounded = 0;
break;
}
}
}
}
if (showboard == 1 || (showboard == 2 && surrounded)) {
show_surround_map(mf, mn);
}
if (!apos && surrounded && surround_pointer < MAX_SURROUND) {
memcpy(surroundings[surround_pointer].surround_map, mn, sizeof(mn));
surroundings[surround_pointer].dragon_number = dragon[pos].id;
surround_pointer++;
}
if (surround_size) {
int pos;
*surround_size = 0;
for (pos = BOARDMIN; pos < BOARDMAX; pos++)
if (ON_BOARD(pos) && mn[pos] == 1)
(*surround_size)++;
}
return surrounded;
}
int
is_surrounded(int dr)
{
return(DRAGON2(dr).surround_status);
}
void
decide_position(int color)
{
int pos;
int move = NO_MOVE;
int acode = 0, dcode = 0;
int kworm;
static const char *snames[] = {"dead", "alive", "critical", "unknown"};
SGFTree tree;
/* Prepare pattern matcher and reading code. */
reset_engine();
silent_examine_position(color, EXAMINE_DRAGONS_WITHOUT_OWL);
/* We want to see the reading performed, not just a result picked
* from the cache. Thus we clear the cache here. */
reading_cache_clear();
if (*outfilename)
sgffile_begindump(&tree);
count_variations = 1;
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (!ON_BOARD(pos)
|| dragon[pos].origin != pos
|| board[pos] == EMPTY
|| DRAGON2(pos).escape_route >= 6)
continue;
gprintf("\nanalyzing %1m\n", pos);
gprintf("status=%s, escape=%d\n",
snames[dragon[pos].crude_status], DRAGON2(pos).escape_route);
acode = owl_attack(pos, &move, NULL, &kworm);
if (acode) {
if (acode == WIN) {
if (move == NO_MOVE)
gprintf("%1m is dead as it stands\n", pos);
else
gprintf("%1m can be attacked at %1m (%d variations)\n",
pos, move, count_variations);
}
else if (acode == KO_A)
gprintf("%1m can be attacked with ko (good) at %1m (%d variations)\n",
pos, move, count_variations);
else if (acode == KO_B)
gprintf("%1m can be attacked with ko (bad) at %1m (%d variations)\n",
pos, move, count_variations);
else if (acode == GAIN)
gprintf("%1m can be attacked with gain (captures %1m) at %1m (%d variations)",
pos, kworm, move, count_variations);
count_variations = 1;
dcode = owl_defend(pos, &move, NULL, &kworm);
if (dcode) {
if (dcode == WIN) {
if (move == NO_MOVE)
gprintf("%1m is alive as it stands\n", pos);
else
gprintf("%1m can be defended at %1m (%d variations)\n",
pos, move, count_variations);
}
else if (dcode == KO_A)
gprintf("%1m can be defended with ko (good) at %1m (%d variations)\n",
pos, move, count_variations);
else if (dcode == KO_B)
gprintf("%1m can be defended with ko (bad) at %1m (%d variations)\n",
pos, move, count_variations);
else if (dcode == LOSS)
gprintf("%1m can be defended with loss (loses %1m) at %1m (%d variations)",
pos, kworm, move, count_variations);
}
else
gprintf("%1m cannot be defended (%d variations)\n",
pos, count_variations);
}
else
gprintf("%1m cannot be attacked (%d variations)\n",
pos, count_variations);
if (acode) {
if (dcode)
gprintf("status of %1m revised to CRITICAL\n", pos);
else
gprintf("status of %1m revised to DEAD\n", pos);
}
else
gprintf("status of %1m revised to ALIVE\n", pos);
}
sgffile_enddump(outfilename);
count_variations = 0;
}
void
semeai()
{
int semeai_results_first[MAX_DRAGONS][MAX_DRAGONS];
int semeai_results_second[MAX_DRAGONS][MAX_DRAGONS];
int semeai_move[MAX_DRAGONS][MAX_DRAGONS];
char semeai_certain[MAX_DRAGONS][MAX_DRAGONS];
int d1, d2;
int k;
int num_dragons = number_of_dragons;
if (num_dragons > MAX_DRAGONS) {
TRACE("Too many dragons!!! Might disregard some semeais.");
num_dragons = MAX_DRAGONS;
}
for (d1 = 0; d1 < num_dragons; d1++)
for (d2 = 0; d2 < num_dragons; d2++) {
semeai_results_first[d1][d2] = -1;
semeai_results_second[d1][d2] = -1;
}
for (d1 = 0; d1 < num_dragons; d1++)
for (k = 0; k < dragon2[d1].neighbors; k++) {
int apos = DRAGON(d1).origin;
int bpos = DRAGON(dragon2[d1].adjacent[k]).origin;
int result_certain;
d2 = dragon[bpos].id;
/* Look for semeais */
if (dragon[apos].color == dragon[bpos].color
|| (dragon[apos].status != DEAD
&& dragon[apos].status != CRITICAL)
|| (dragon[bpos].status != DEAD
&& dragon[bpos].status != CRITICAL))
continue;
/* Ignore inessential worms or dragons */
if (worm[apos].inessential
|| DRAGON2(apos).safety == INESSENTIAL
|| worm[bpos].inessential
|| DRAGON2(bpos).safety == INESSENTIAL)
continue;
/* Sometimes the dragons are considered neighbors but are too
* distant to constitute a proper semeai, e.g. in nngs4:650, P2
* vs. R3. Then the result of semeai reading may be meaningless
* and can confuse the analysis. In order to avoid this we check
* that the dragons either are directly adjacent or at least
* have one common liberty.
*/
if (!close_enough_for_proper_semeai(apos, bpos))
continue;
/* The array semeai_results_first[d1][d2] will contain the status
* of d1 after the d1 d2 semeai, giving d1 the first move.
* The array semeai_results_second[d1][d2] will contain the status
* of d1 after the d1 d2 semeai, giving d2 the first move.
*/
DEBUG(DEBUG_SEMEAI, "Considering semeai between %1m and %1m\n",
apos, bpos);
owl_analyze_semeai(apos, bpos,
&(semeai_results_first[d1][d2]),
&(semeai_results_second[d1][d2]),
&(semeai_move[d1][d2]), 1, &result_certain);
DEBUG(DEBUG_SEMEAI, "results if %s moves first: %s %s, %1m%s\n",
board[apos] == BLACK ? "black" : "white",
result_to_string(semeai_results_first[d1][d2]),
result_to_string(semeai_results_second[d1][d2]),
semeai_move[d1][d2], result_certain ? "" : " (uncertain)");
semeai_certain[d1][d2] = result_certain;
}
/* Look for dragons which lose all their semeais outright. The
* winners in those semeais are considered safe and further semeais
* they are involved in are disregarded. See semeai:81-86 and
* nicklas5:1211 for examples of where this is useful.
*
* Note: To handle multiple simultaneous semeais properly we would
* have to make simultaneous semeai reading. Lacking that we can
* only get rough guesses of the correct status of the involved
* dragons. This code is not guaranteed to be correct in all
* situations but should usually be an improvement.
*/
for (d1 = 0; d1 < num_dragons; d1++) {
int involved_in_semeai = 0;
int all_lost = 1;
for (d2 = 0; d2 < num_dragons; d2++) {
if (semeai_results_first[d1][d2] != -1) {
involved_in_semeai = 1;
if (semeai_results_first[d1][d2] != 0) {
all_lost = 0;
break;
}
}
}
if (involved_in_semeai && all_lost) {
/* Leave the status changes to the main loop below. Here we just
* remove the presumably irrelevant semeai results.
*/
for (d2 = 0; d2 < num_dragons; d2++) {
if (semeai_results_first[d1][d2] == 0) {
int d3;
for (d3 = 0; d3 < num_dragons; d3++) {
if (semeai_results_second[d3][d2] > 0) {
semeai_results_first[d3][d2] = -1;
semeai_results_second[d3][d2] = -1;
semeai_results_first[d2][d3] = -1;
semeai_results_second[d2][d3] = -1;
}
}
}
}
}
}
for (d1 = 0; d1 < num_dragons; d1++) {
int semeais_found = 0;
int best_defense = 0;
int best_attack = 0;
int defense_move = PASS_MOVE;
int attack_move = PASS_MOVE;
int defense_certain = 0;
int attack_certain = 0;
int semeai_attack_target = NO_MOVE;
int semeai_defense_target = NO_MOVE;
for (d2 = 0; d2 < num_dragons; d2++) {
if (semeai_results_first[d1][d2] == -1)
continue;
gg_assert(semeai_results_second[d1][d2] != -1);
semeais_found++;
if (best_defense < semeai_results_first[d1][d2]
|| (best_defense == semeai_results_first[d1][d2]
&& defense_certain < semeai_certain[d1][d2])) {
best_defense = semeai_results_first[d1][d2];
defense_move = semeai_move[d1][d2];
defense_certain = semeai_certain[d1][d2];
semeai_defense_target = dragon2[d2].origin;
}
if (best_attack < semeai_results_second[d2][d1]
|| (best_attack == semeai_results_second[d2][d1]
&& attack_certain < semeai_certain[d2][d1])) {
best_attack = semeai_results_second[d2][d1];
attack_move = semeai_move[d2][d1];
attack_certain = semeai_certain[d2][d1];
semeai_attack_target = dragon2[d2].origin;
}
}
if (semeais_found) {
dragon2[d1].semeais = semeais_found;
if (best_defense != 0 && best_attack != 0)
update_status(DRAGON(d1).origin, CRITICAL, CRITICAL);
else if (best_attack == 0 && attack_certain)
update_status(DRAGON(d1).origin, ALIVE, ALIVE);
dragon2[d1].semeai_defense_point = defense_move;
dragon2[d1].semeai_defense_certain = defense_certain;
dragon2[d1].semeai_defense_target = semeai_defense_target;
dragon2[d1].semeai_attack_point = attack_move;
dragon2[d1].semeai_attack_certain = attack_certain;
dragon2[d1].semeai_attack_target = semeai_attack_target;
}
}
find_moves_to_make_seki();
}
/* Find moves turning supposed territory into seki. This is not
* detected above since it either involves an ALIVE dragon adjacent to
* a CRITICAL dragon, or an ALIVE dragon whose eyespace can be invaded
* and turned into a seki.
*
* Currently we only search for tactically critical strings with
* dragon status dead, which are neighbors of only one opponent
* dragon, which is alive. Through semeai analysis we then determine
* whether such a string can in fact live in seki. Relevant testcases
* include gunnar:42 and gifu03:2.
*/
static void
find_moves_to_make_seki()
{
int str;
int defend_move;
int resulta, resultb;
for (str = BOARDMIN; str < BOARDMAX; str++) {
if (IS_STONE(board[str]) && is_worm_origin(str, str)
&& attack_and_defend(str, NULL, NULL, NULL, &defend_move)
&& dragon[str].status == DEAD
&& DRAGON2(str).hostile_neighbors == 1) {
int k;
int color = board[str];
int opponent = NO_MOVE;
int certain;
struct eyevalue reduced_genus;
for (k = 0; k < DRAGON2(str).neighbors; k++) {
opponent = dragon2[DRAGON2(str).adjacent[k]].origin;
if (board[opponent] != color)
break;
}
ASSERT1(opponent != NO_MOVE, opponent);
if (dragon[opponent].status != ALIVE)
continue;
/* FIXME: These heuristics are used for optimization. We don't
* want to call expensive semeai code if the opponent
* dragon has more than one eye elsewhere. However, the
* heuristics might still need improvement.
*/
compute_dragon_genus(opponent, &reduced_genus, str);
if (DRAGON2(opponent).moyo_size > 10 || min_eyes(&reduced_genus) > 1)
continue;
owl_analyze_semeai_after_move(defend_move, color, opponent, str,
&resulta, &resultb, NULL, 1, &certain, 0);
/* Do not trust uncertain results. In fact it should only take a
* few nodes to determine the semeai result, if it is a proper
* potential seki position.
*/
if (resultb != WIN && certain) {
int d = dragon[str].id;
DEBUG(DEBUG_SEMEAI, "Move to make seki at %1m (%1m vs %1m)\n",
defend_move, str, opponent);
dragon2[d].semeais++;
update_status(str, CRITICAL, CRITICAL);
dragon2[d].semeai_defense_point = defend_move;
dragon2[d].semeai_defense_certain = certain;
dragon2[d].semeai_defense_target = opponent;
/* We need to determine a proper attack move (the one that
* prevents seki). Currently we try the defense move first,
* and if it doesn't work -- all liberties of the string.
*/
owl_analyze_semeai_after_move(defend_move, OTHER_COLOR(color),
str, opponent, &resulta, NULL,
NULL, 1, NULL, 0);
if (resulta != WIN)
dragon2[d].semeai_attack_point = defend_move;
else {
int k;
int libs[MAXLIBS];
int liberties = findlib(str, MAXLIBS, libs);
for (k = 0; k < liberties; k++) {
owl_analyze_semeai_after_move(libs[k], OTHER_COLOR(color),
str, opponent, &resulta, NULL,
NULL, 1, NULL, 0);
if (resulta != WIN) {
dragon2[d].semeai_attack_point = libs[k];
break;
}
}
/* FIXME: What should we do if none of the tried attacks worked? */
if (k == liberties)
dragon2[d].semeai_attack_point = defend_move;
}
DEBUG(DEBUG_SEMEAI, "Move to prevent seki at %1m (%1m vs %1m)\n",
dragon2[d].semeai_attack_point, opponent, str);
dragon2[d].semeai_attack_certain = certain;
dragon2[d].semeai_attack_target = opponent;
}
}
}
}
/* Find moves turning supposed territory into seki. This is not
* detected above since it either involves an ALIVE dragon adjacent to
* a CRITICAL dragon, or an ALIVE dragon whose eyespace can be invaded
* and turned into a seki.
*
* Currently we only search for tactically critical strings with
* dragon status dead, which are neighbors of only one opponent
* dragon, which is alive. Through semeai analysis we then determine
* whether such a string can in fact live in seki. Relevant testcases
* include gunnar:42 and gifu03:2.
*/
static void
find_moves_to_make_seki()
{
int str;
int defend_move;
int resulta, resultb;
for (str = BOARDMIN; str < BOARDMAX; str++) {
if (IS_STONE(board[str]) && is_worm_origin(str, str)
&& attack_and_defend(str, NULL, NULL, NULL, &defend_move)
&& dragon[str].status == DEAD
&& DRAGON2(str).hostile_neighbors == 1) {
int k;
int color = board[str];
int opponent = NO_MOVE;
int certain;
struct eyevalue reduced_genus;
for (k = 0; k < DRAGON2(str).neighbors; k++) {
opponent = dragon2[DRAGON2(str).adjacent[k]].origin;
if (board[opponent] != color)
break;
}
ASSERT1(opponent != NO_MOVE, opponent);
if (dragon[opponent].status != ALIVE)
continue;
/* FIXME: These heuristics are used for optimization. We don't
* want to call expensive semeai code if the opponent
* dragon has more than one eye elsewhere. However, the
* heuristics might still need improvement.
*/
compute_dragon_genus(opponent, &reduced_genus, str);
if (min_eyes(&reduced_genus) > 1
|| DRAGON2(opponent).moyo_size > 10
|| DRAGON2(opponent).moyo_territorial_value > 2.999
|| DRAGON2(opponent).escape_route > 0
|| DRAGON2(str).escape_route > 0)
continue;
owl_analyze_semeai_after_move(defend_move, color, opponent, str,
&resulta, &resultb, NULL, 1, &certain, 0);
if (resultb == WIN) {
owl_analyze_semeai(str, opponent, &resultb, &resulta,
&defend_move, 1, &certain);
resulta = REVERSE_RESULT(resulta);
resultb = REVERSE_RESULT(resultb);
}
/* Do not trust uncertain results. In fact it should only take a
* few nodes to determine the semeai result, if it is a proper
* potential seki position.
*/
if (resultb != WIN && certain) {
int d = dragon[str].id;
DEBUG(DEBUG_SEMEAI, "Move to make seki at %1m (%1m vs %1m)\n",
defend_move, str, opponent);
dragon2[d].semeais++;
update_status(str, CRITICAL, CRITICAL);
dragon2[d].semeai_defense_code = REVERSE_RESULT(resultb);
dragon2[d].semeai_defense_point = defend_move;
dragon2[d].semeai_defense_certain = certain;
gg_assert(board[opponent] == OTHER_COLOR(board[dragon2[d].origin]));
dragon2[d].semeai_defense_target = opponent;
/* We need to determine a proper attack move (the one that
* prevents seki). Currently we try the defense move first,
* and if it doesn't work -- all liberties of the string.
*/
owl_analyze_semeai_after_move(defend_move, OTHER_COLOR(color),
str, opponent, &resulta, NULL,
NULL, 1, NULL, 0);
if (resulta != WIN) {
dragon2[d].semeai_attack_code = REVERSE_RESULT(resulta);
dragon2[d].semeai_attack_point = defend_move;
}
else {
int k;
int libs[MAXLIBS];
int liberties = findlib(str, MAXLIBS, libs);
for (k = 0; k < liberties; k++) {
owl_analyze_semeai_after_move(libs[k], OTHER_COLOR(color),
str, opponent, &resulta, NULL,
NULL, 1, NULL, 0);
if (resulta != WIN) {
dragon2[d].semeai_attack_code = REVERSE_RESULT(resulta);
dragon2[d].semeai_attack_point = libs[k];
break;
}
}
if (k == liberties) {
DEBUG(DEBUG_SEMEAI,
"No move to attack in semeai (%1m vs %1m), seki assumed.\n",
str, opponent);
dragon2[d].semeai_attack_code = 0;
dragon2[d].semeai_attack_point = NO_MOVE;
update_status(str, ALIVE, ALIVE_IN_SEKI);
}
}
DEBUG(DEBUG_SEMEAI, "Move to prevent seki at %1m (%1m vs %1m)\n",
dragon2[d].semeai_attack_point, opponent, str);
dragon2[d].semeai_attack_certain = certain;
dragon2[d].semeai_attack_target = opponent;
}
}
}
/* Now look for dead strings inside a single eyespace of a living dragon.
*
* FIXME: Clearly this loop should share most of its code with the
* one above. It would also be good to reimplement so that
* moves invading a previously empty single eyespace to make
* seki can be found.
*/
for (str = BOARDMIN; str < BOARDMAX; str++) {
if (IS_STONE(board[str]) && is_worm_origin(str, str)
&& !find_defense(str, NULL)
&& dragon[str].status == DEAD
&& DRAGON2(str).hostile_neighbors == 1) {
int k;
int color = board[str];
int opponent = NO_MOVE;
int certain;
struct eyevalue reduced_genus;
for (k = 0; k < DRAGON2(str).neighbors; k++) {
opponent = dragon2[DRAGON2(str).adjacent[k]].origin;
if (board[opponent] != color)
break;
}
ASSERT1(opponent != NO_MOVE, opponent);
if (dragon[opponent].status != ALIVE)
continue;
/* FIXME: These heuristics are used for optimization. We don't
* want to call expensive semeai code if the opponent
* dragon has more than one eye elsewhere. However, the
* heuristics might still need improvement.
*/
compute_dragon_genus(opponent, &reduced_genus, str);
if (DRAGON2(opponent).moyo_size > 10 || min_eyes(&reduced_genus) > 1)
continue;
owl_analyze_semeai(str, opponent, &resulta, &resultb,
&defend_move, 1, &certain);
/* Do not trust uncertain results. In fact it should only take a
* few nodes to determine the semeai result, if it is a proper
* potential seki position.
*/
if (resulta != 0 && certain) {
int d = dragon[str].id;
DEBUG(DEBUG_SEMEAI, "Move to make seki at %1m (%1m vs %1m)\n",
defend_move, str, opponent);
dragon2[d].semeais++;
update_status(str, CRITICAL, CRITICAL);
dragon2[d].semeai_defense_code = resulta;
dragon2[d].semeai_defense_point = defend_move;
dragon2[d].semeai_defense_certain = certain;
gg_assert(board[opponent] == OTHER_COLOR(board[dragon2[d].origin]));
dragon2[d].semeai_defense_target = opponent;
/* We need to determine a proper attack move (the one that
* prevents seki). Currently we try the defense move first,
* and if it doesn't work -- all liberties of the string.
*/
owl_analyze_semeai_after_move(defend_move, OTHER_COLOR(color),
str, opponent, &resulta, NULL,
NULL, 1, NULL, 0);
if (resulta != WIN) {
dragon2[d].semeai_attack_code = REVERSE_RESULT(resulta);
dragon2[d].semeai_attack_point = defend_move;
}
else {
int k;
int libs[MAXLIBS];
int liberties = findlib(str, MAXLIBS, libs);
for (k = 0; k < liberties; k++) {
owl_analyze_semeai_after_move(libs[k], OTHER_COLOR(color),
str, opponent, &resulta, NULL,
NULL, 1, NULL, 0);
if (resulta != WIN) {
dragon2[d].semeai_attack_code = REVERSE_RESULT(resulta);
dragon2[d].semeai_attack_point = libs[k];
break;
}
}
if (k == liberties) {
DEBUG(DEBUG_SEMEAI,
"No move to attack in semeai (%1m vs %1m), seki assumed.\n",
str, opponent);
dragon2[d].semeai_attack_code = 0;
dragon2[d].semeai_attack_point = NO_MOVE;
update_status(str, ALIVE, ALIVE_IN_SEKI);
}
}
DEBUG(DEBUG_SEMEAI, "Move to prevent seki at %1m (%1m vs %1m)\n",
dragon2[d].semeai_attack_point, opponent, str);
dragon2[d].semeai_attack_certain = certain;
dragon2[d].semeai_attack_target = opponent;
}
}
}
}
/* Generate a move to definitely settle the position after the game
* has been finished. The purpose of this is to robustly determine
* life and death status and to distinguish between life in seki and
* life with territory.
*
* The strategy is basically to turn all own living stones into
* invincible ones and remove from the board all dead opponent stones.
* Stones which cannot be removed, nor turned invincible, are alive in
* seki.
*
* If do_capture_dead_stones is 0, opponent stones are not necessarily
* removed from the board. This happens if they become unconditionally
* dead anyway.
*
* Moves are generated in the following order of priority:
* 0. Play edge liberties in certain positions. This is not really
* necessary, but often it can simplify the tactical and strategical
* reading substantially, making subsequent moves faster to generate.
* 1. Capture an opponent string in atari and adjacent to own
* invincible string. Moves leading to ko or snapback are excluded.
* 2. Extend an invincible string to a liberty of an opponent string.
* 3. Connect a non-invincible string to an invincible string.
* 4. Extend an invincible string towards an opponent string or an own
* non-invincible string.
* 5. Split a big eyespace of an alive own dragon without invincible
* strings into smaller pieces.
* 6. Play a liberty of a dead opponent dragon.
*
* Steps 2--4 are interleaved to try to optimize the efficiency of the
* moves. In step 5 too, efforts are made to play efficient moves. By
* efficient we here mean moves which are effectively settling the
* position and simplify the tactical and strategical reading for
* subsequent moves.
*
* Steps 1--4 are guaranteed to be completely safe. Step 0 and 5
* should also be risk-free. Step 6 on the other hand definitely
* isn't. Consider for example this position:
*
* .XXXXX.
* XXOOOXX
* XOO.OOX
* XOXXXOX
* XO.XXOX
* -------
*
* In order to remove the O stones, it is necessary to play on one of
* the inner liberties, but one of them lets O live. Thus we have to
* check carefully for blunders at this step.
*
* Update: Step 0 is only safe against blunders if care is taken not
* to get into a shortage of liberties.
* Step 5 also has some risks. Consider this position:
*
* |XXXXX.
* |OOOOXX
* |..O.OX
* |OX*OOX
* +------
*
* Playing at * allows X to make seki.
*
* IMPORTANT RESTRICTION:
* Before calling this function it is mandatory to call genmove() or
* genmove_conservative(). For this function to be meaningful, the
* genmove() call should return pass.
*/
int
aftermath_genmove(int *aftermath_move, int color,
int under_control[BOARDMAX],
int do_capture_dead_stones)
{
int k;
int other = OTHER_COLOR(color);
int distance[BOARDMAX];
int score[BOARDMAX];
float owl_hotspot[BOARDMAX];
float reading_hotspot[BOARDMAX];
int dragons[BOARDMAX];
int something_found;
int closest_opponent = NO_MOVE;
int closest_own = NO_MOVE;
int d;
int move = NO_MOVE;
int pos = NO_MOVE;
int best_score;
int best_scoring_move;
owl_hotspots(owl_hotspot);
reading_hotspots(reading_hotspot);
/* As a preparation we compute a distance map to the invincible strings. */
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (!ON_BOARD(pos))
continue;
else if (board[pos] == color && worm[pos].invincible)
distance[pos] = 0;
else if (!do_capture_dead_stones
&& ((board[pos] == other
&& worm[pos].unconditional_status == DEAD)
|| (board[pos] == color
&& worm[pos].unconditional_status == ALIVE)))
distance[pos] = 0;
else
distance[pos] = -1;
}
d = 0;
do {
something_found = 0;
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (ON_BOARD(pos) && distance[pos] == -1) {
for (k = 0; k < 4; k++) {
int pos2 = pos + delta[k];
if (!ON_BOARD(pos2))
continue;
if ((d == 0 || board[pos2] == EMPTY)
&& distance[pos2] == d) {
if (d > 0 && board[pos] == other) {
distance[pos] = d + 1;
if (closest_opponent == NO_MOVE)
closest_opponent = pos;
}
else if (d > 0 && board[pos] == color) {
distance[pos] = d + 1;
if (closest_own == NO_MOVE)
closest_own = pos;
}
else if (board[pos] == EMPTY) {
distance[pos] = d + 1;
something_found = 1;
}
break;
}
}
}
}
d++;
} while (something_found);
if (under_control) {
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (!ON_BOARD(pos))
continue;
else if (distance[pos] == -1)
under_control[pos] = 0;
else
under_control[pos] = 1;
}
}
if (debug & DEBUG_AFTERMATH) {
int m, n;
for (m = 0; m < board_size; m++) {
for (n = 0; n < board_size; n++) {
pos = POS(m, n);
if (distance[pos] > 0)
fprintf(stderr, "%2d", distance[pos]);
else if (distance[pos] == 0) {
if (board[pos] == WHITE)
gprintf(" o");
else if (board[pos] == BLACK)
gprintf(" x");
else
gprintf(" ?");
}
else {
if (board[pos] == WHITE)
gprintf(" O");
else if (board[pos] == BLACK)
gprintf(" X");
else
gprintf(" .");
}
}
gprintf("\n");
}
gprintf("Closest opponent %1m", closest_opponent);
if (closest_opponent != NO_MOVE)
gprintf(", distance %d\n", distance[closest_opponent]);
else
gprintf("\n");
gprintf("Closest own %1m", closest_own);
if (closest_own != NO_MOVE)
gprintf(", distance %d\n", distance[closest_own]);
else
gprintf("\n");
}
/* Case 0. This is a special measure to avoid a certain kind of
* tactical reading inefficiency.
*
* Here we play on edge liberties in the configuration
*
* XO.
* .*.
* ---
*
* to stop X from "leaking" out along the edge. Sometimes this can
* save huge amounts of tactical reading for later moves.
*/
best_scoring_move = NO_MOVE;
best_score = 5;
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
int libs;
if (board[pos] != EMPTY
|| distance[pos] == 0)
continue;
libs = approxlib(pos, color, 3, NULL);
if (libs < 3)
continue;
if (is_self_atari(pos, other))
continue;
for (k = 0; k < 4; k++) {
int dir = delta[k];
int right = delta[(k+1)%4];
if (!ON_BOARD(pos - dir)
&& board[pos + dir] == color
&& board[pos + dir + right] == other
&& board[pos + dir - right] == other
&& (libs > countlib(pos + dir)
|| (libs > 4
&& libs == countlib(pos + dir)))
&& (DRAGON2(pos + dir).safety == INVINCIBLE
|| DRAGON2(pos + dir).safety == STRONGLY_ALIVE)) {
int this_score = 20 * (owl_hotspot[pos] + reading_hotspot[pos]);
if (this_score > best_score) {
best_score = this_score;
best_scoring_move = pos;
}
}
}
}
if (best_scoring_move != NO_MOVE
&& safe_move(best_scoring_move, color) == WIN) {
*aftermath_move = best_scoring_move;
DEBUG(DEBUG_AFTERMATH, "Closing edge at %1m\n", best_scoring_move);
return 1;
}
/* Case 1. */
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
int lib;
if (board[pos] == other
&& worm[pos].unconditional_status != DEAD
&& countlib(pos) == 1
&& ((ON_BOARD(SOUTH(pos)) && distance[SOUTH(pos)] == 0)
|| (ON_BOARD(WEST(pos)) && distance[WEST(pos)] == 0)
|| (ON_BOARD(NORTH(pos)) && distance[NORTH(pos)] == 0)
|| (ON_BOARD(EAST(pos)) && distance[EAST(pos)] == 0))) {
findlib(pos, 1, &lib);
/* Make sure we don't play into a ko or a (proper) snapback. */
if (countstones(pos) > 1 || !is_self_atari(lib, color)) {
*aftermath_move = lib;
return 1;
}
}
}
/* Cases 2--4. */
if (closest_opponent != NO_MOVE || closest_own != NO_MOVE) {
if (closest_own == NO_MOVE)
move = closest_opponent;
else
move = closest_own;
/* if we're about to play at distance 1, try to optimize the move. */
if (distance[move] == 2) {
char mx[BOARDMAX];
char mark = 0;
memset(mx, 0, sizeof(mx));
best_score = 0;
best_scoring_move = move;
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
int score = 0;
int move_ok = 0;
if (!ON_BOARD(pos) || distance[pos] != 1)
continue;
mark++;
for (k = 0; k < 4; k++) {
int pos2 = pos + delta[k];
if (!ON_BOARD(pos2))
continue;
if (distance[pos2] < 1)
score--;
else if (board[pos2] == EMPTY)
score++;
else if (mx[pos2] == mark)
score--;
else {
if (board[pos2] == color) {
move_ok = 1;
score += 7;
if (countstones(pos2) > 2)
score++;
if (countstones(pos2) > 4)
score++;
if (countlib(pos2) < 4)
score++;
if (countlib(pos2) < 3)
score++;
}
else {
int deltalib = (approxlib(pos, other, MAXLIBS, NULL)
- countlib(pos2));
move_ok = 1;
score++;
if (deltalib >= 0)
score++;
if (deltalib > 0)
score++;
}
mark_string(pos2, mx, mark);
}
}
if (is_suicide(pos, other))
score -= 3;
if (0)
gprintf("Score %1m = %d\n", pos, score);
if (move_ok && score > best_score) {
best_score = score;
best_scoring_move = pos;
}
}
move = best_scoring_move;
}
while (distance[move] > 1) {
for (k = 0; k < 4; k++) {
int pos2 = move + delta[k];
if (ON_BOARD(pos2)
&& board[pos2] == EMPTY
&& distance[pos2] == distance[move] - 1) {
move = pos2;
break;
}
}
}
*aftermath_move = move;
return 1;
}
/* Case 5.
* If we reach here, either all strings of a dragon are invincible
* or no string is. Next we try to make alive dragons invincible by
* splitting big eyes into smaller ones. Our strategy is to search
* for an empty vertex with as many eye points as possible adjacent
* and with at least one alive but not invincible stone adjacent or
* diagonal.
*/
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
int eyespace_neighbors = 0;
int own_neighbors = 0;
int own_diagonals = 0;
int opponent_dragons = 0;
int own_worms = 0;
int safety = UNKNOWN;
int bonus = 0;
int mx[BOARDMAX];
score[pos] = 0;
if (board[pos] != EMPTY || distance[pos] != -1)
continue;
memset(mx, 0, sizeof(mx));
for (k = 0; k < 8; k++) {
int pos2 = pos + delta[k];
if (!ON_BOARD(pos2))
continue;
if (board[pos2] == EMPTY) {
if (k < 4)
eyespace_neighbors++;
continue;
}
if (board[pos2] == other) {
int origin = dragon[pos2].origin;
if (k < 4) {
if (dragon[pos2].status == ALIVE) {
safety = DEAD;
break;
}
else if (!mx[origin]) {
eyespace_neighbors++;
opponent_dragons++;
}
}
if (!mx[origin] && dragon[pos2].status == DEAD) {
bonus++;
if (k < 4
&& countlib(pos2) <= 2
&& countstones(pos2) >= 3)
bonus++;
if (k < 4 && countlib(pos2) == 1)
bonus += 3;
}
mx[origin] = 1;
}
else if (board[pos2] == color) {
dragons[pos] = pos2;
if (safety == UNKNOWN && dragon[pos2].status == ALIVE)
safety = ALIVE;
if (DRAGON2(pos2).safety == INVINCIBLE)
safety = INVINCIBLE;
if (k < 4) {
int apos = worm[pos2].origin;
if (!mx[apos]) {
own_worms++;
if (countstones(apos) == 1)
bonus += 2;
if (countlib(apos) < 6
&& approxlib(pos, color, 5, NULL) < countlib(apos))
bonus -= 5;
mx[apos] = 1;
}
if (countlib(apos) <= 2) {
int r;
int important = 0;
int safe_atari = 0;
for (r = 0; r < 4; r++) {
d = delta[r];
if (!ON_BOARD(apos+d))
continue;
if (board[apos+d] == other
&& dragon[apos+d].status == DEAD)
important = 1;
else if (board[apos+d] == EMPTY
&& !is_self_atari(apos+d, other))
safe_atari = 1;
}
if (approxlib(pos, color, 3, NULL) > 2) {
bonus++;
if (important) {
bonus += 2;
if (safe_atari)
bonus += 2;
}
}
}
own_neighbors++;
}
else
own_diagonals++;
}
}
if (safety == DEAD || safety == UNKNOWN
|| eyespace_neighbors == 0
|| (own_neighbors + own_diagonals) == 0)
continue;
if (bonus < 0)
bonus = 0;
score[pos] = 4 * eyespace_neighbors + bonus;
if (safety == INVINCIBLE) {
score[pos] += own_neighbors;
if (own_neighbors < 2)
score[pos] += own_diagonals;
if (own_worms > 1 && eyespace_neighbors >= 1)
score[pos] += 10 + 5 * (own_worms - 2);
}
else if (eyespace_neighbors > 2)
score[pos] += own_diagonals;
/* Splitting bonus. */
if (opponent_dragons > 1)
score[pos] += 10 * (opponent_dragons - 1);
/* Hotspot bonus. */
{
int owl_hotspot_bonus = (int) (20.0 * owl_hotspot[pos]);
int reading_hotspot_bonus = (int) (20.0 * reading_hotspot[pos]);
int hotspot_bonus = owl_hotspot_bonus + reading_hotspot_bonus;
/* Don't allow the hotspot bonus to turn a positive score into
* a non-positive one.
*/
if (score[pos] > 0 && score[pos] + hotspot_bonus <= 0)
hotspot_bonus = 1 - score[pos];
score[pos] += hotspot_bonus;
if (1 && (debug & DEBUG_AFTERMATH))
gprintf("Score %1M = %d (hotspot bonus %d + %d)\n", pos, score[pos],
owl_hotspot_bonus, reading_hotspot_bonus);
}
/* Avoid taking ko. */
if (is_ko(pos, color, NULL))
score[pos] = (score[pos] + 1) / 2;
}
while (1) {
int bb;
best_score = 0;
move = NO_MOVE;
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (ON_BOARD(pos) && score[pos] > best_score) {
best_score = score[pos];
move = pos;
}
}
if (move == NO_MOVE)
break;
bb = dragons[move];
if (is_illegal_ko_capture(move, color)
|| !safe_move(move, color)
|| (DRAGON2(bb).safety != INVINCIBLE
&& DRAGON2(bb).safety != STRONGLY_ALIVE
&& owl_does_defend(move, bb, NULL) != WIN)
|| (!confirm_safety(move, color, NULL, NULL))) {
score[move] = 0;
}
else {
/* If we're getting short of liberties, we must be more careful.
* Check that no adjacent string or dragon gets more alive by
* the move.
*/
int libs = approxlib(move, color, 5, NULL);
int move_ok = 1;
if (libs < 5) {
for (k = 0; k < 4; k++) {
if (board[move + delta[k]] == color
&& countlib(move + delta[k]) > libs)
break;
}
if (k < 4) {
if (trymove(move, color, "aftermath-B", move + delta[k])) {
int adjs[MAXCHAIN];
int neighbors;
int r;
neighbors = chainlinks(move, adjs);
for (r = 0; r < neighbors; r++) {
if (worm[adjs[r]].attack_codes[0] != 0
&& (find_defense(adjs[r], NULL)
> worm[adjs[r]].defense_codes[0])) {
DEBUG(DEBUG_AFTERMATH,
"Blunder: %1m becomes tactically safer after %1m\n",
adjs[r], move);
move_ok = 0;
}
}
popgo();
for (r = 0; r < neighbors && move_ok; r++) {
if (dragon[adjs[r]].status == DEAD
&& !owl_does_attack(move, adjs[r], NULL)) {
DEBUG(DEBUG_AFTERMATH,
"Blunder: %1m becomes more alive after %1m\n",
adjs[r], move);
move_ok = 0;
}
}
}
}
}
if (!move_ok)
score[move] = 0;
else {
*aftermath_move = move;
DEBUG(DEBUG_AFTERMATH, "Splitting eyespace at %1m\n", move);
return 1;
}
}
}
/* Case 6.
* Finally we try to play on liberties of remaining DEAD opponent
* dragons, carefully checking against mistakes.
*/
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
int target;
int cc = NO_MOVE;
int self_atari_ok = 0;
if (board[pos] != EMPTY || distance[pos] != -1)
continue;
target = NO_MOVE;
for (k = 0; k < 4; k++) {
int pos2 = pos + delta[k];
if (!ON_BOARD(pos2))
continue;
if (board[pos2] == other
&& dragon[pos2].status != ALIVE
&& (do_capture_dead_stones
|| worm[pos2].unconditional_status != DEAD)
&& DRAGON2(pos2).safety != INESSENTIAL) {
target = pos2;
break;
}
}
if (target == NO_MOVE)
continue;
/* At this point, (pos) is a move that potentially may capture
* a dead opponent string at (target).
*/
if (!trymove(pos, color, "aftermath-A", target))
continue;
/* It is frequently necessary to sacrifice own stones in order
* to force the opponent's stones to be removed from the board,
* e.g. by adding stones to fill up a nakade shape. However, we
* should only play into a self atari if the sacrificed stones
* are classified as INESSENTIAL. Thus it would be ok for O to
* try a self atari in this position:
*
* |OOOO
* |XXXO
* |..XO
* |OOXO
* +----
*
* but not in this one:
*
* |XXX..
* |OOXX.
* |.OOXX
* |XXOOX
* |.O.OX
* +-----
*/
self_atari_ok = 1;
for (k = 0; k < 4; k++) {
if (board[pos + delta[k]] == color
&& DRAGON2(pos + delta[k]).safety != INESSENTIAL) {
self_atari_ok = 0;
cc = pos + delta[k];
break;
}
}
/* Copy the potential move to (move). */
move = pos;
/* If the move is a self atari, but that isn't okay, try to
* recursively find a backfilling move which later makes the
* potential move possible.
*/
if (!self_atari_ok) {
while (countlib(pos) == 1) {
int lib;
findlib(pos, 1, &lib);
move = lib;
if (!trymove(move, color, "aftermath-B", target))
break;
}
if (countlib(pos) == 1)
move = NO_MOVE;
}
while (stackp > 0)
popgo();
if (move == NO_MOVE)
continue;
/* Make sure that the potential move really isn't a self
* atari. In the case of a move found after backfilling this
* could happen (because the backfilling moves happened to
* capture some stones).
*/
if (!self_atari_ok && is_self_atari(move, color))
continue;
/* Consult the owl code to determine whether the considered move
* really is effective. Blunders should be detected here.
*/
if (owl_does_attack(move, target, NULL) == WIN) {
/* If we have an adjacent own dragon, which is not inessential,
* verify that it remains safe.
*/
if (cc != NO_MOVE && !owl_does_defend(move, cc, NULL))
continue;
/* If we don't allow self atari, also call confirm safety to
* avoid setting up combination attacks.
*/
if (!self_atari_ok && !confirm_safety(move, color, NULL, NULL))
continue;
*aftermath_move = move;
DEBUG(DEBUG_AFTERMATH, "Filling opponent liberty at %1m\n", move);
return 1;
}
}
/* Case 7.
* In very rare cases it turns out we need yet another pass. An
* example is this position:
*
* |.....
* |OOOO.
* |XXXO.
* |.OXO.
* |O.XO.
* +-----
*
* Here the X stones are found tactically dead and therefore the
* corner O stones have been amalgamated with the surrounding
* stones. Since the previous case only allows sacrificing
* INESSENTIAL stones, it fails to take X off the board.
*
* The solution is to look for tactically attackable opponent stones
* that still remain on the board but should be removed.
*/
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (board[pos] == other
&& (worm[pos].unconditional_status == UNKNOWN
|| do_capture_dead_stones)
&& (DRAGON2(pos).safety == DEAD
|| DRAGON2(pos).safety == TACTICALLY_DEAD)
&& worm[pos].attack_codes[0] != 0
&& !is_illegal_ko_capture(worm[pos].attack_points[0], color)) {
*aftermath_move = worm[pos].attack_points[0];
DEBUG(DEBUG_AFTERMATH, "Tactically attack %1m at %1m\n",
pos, *aftermath_move);
return 1;
}
}
/* No move found. */
return -1;
}
