static int
autohelperread_attack20(int trans, int move, int color, int action)
{
int a;
UNUSED(color);
a = AFFINE_TRANSFORM(721, trans, move);
if (!action)
return (countlib(a) <= 3 && accuratelib(move, color, MAX_LIBERTIES, NULL) >= 2);
if (countlib(a) == 2) ((read_attack + 20)->value) = 49; else if (countlib(a) == 1 && countstones(a) > 1) ((read_attack + 20)->value) = 79; else if (countlib(a) == 1) ((read_attack + 20)->value) = 48; else if (stackp <= backfill_depth && stackp <= superstring_depth /* || !atari_possible*/) ((read_attack + 20)->value) = 12; else ((read_attack + 20)->value) = 0;;
return 0;
}
/* 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;
}
void
unconditional_life(int unconditional_territory[BOARDMAX], int color)
{
int found_one;
int other = OTHER_COLOR(color);
int libs[MAXLIBS];
int liberties;
int pos;
int k, r;
int moves_played;
int potential_sekis[BOARDMAX];
int none_invincible;
/* Initialize unconditional_territory array. */
memset(unconditional_territory, 0,
sizeof(unconditional_territory[0]) * BOARDMAX);
/* Find isolated two-stone strings which might be involved in the
* kind of seki described in the comments.
*/
memset(potential_sekis, 0, sizeof(potential_sekis));
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
int isolated = 1;
int stones[2];
int pos2;
if (board[pos] != color
|| find_origin(pos) != pos
|| countstones(pos) != 2)
continue;
findstones(pos, 2, stones);
for (k = 0; k < 2 && isolated; k++) {
for (r = 0; r < 8 && isolated; r++) {
pos2 = stones[k] + delta[r];
if (!ON_BOARD(pos2)
|| (board[pos2] == color
&& !same_string(pos, pos2)))
isolated = 0;
}
}
if (isolated) {
potential_sekis[stones[0]] = 1;
potential_sekis[stones[1]] = 1;
}
}
moves_played = capture_non_invincible_strings(color, potential_sekis,
&none_invincible);
/* If there are no invincible strings, nothing can be unconditionally
* settled.
*/
if (none_invincible) {
/* Take back all moves. */
while (moves_played > 0) {
popgo();
moves_played--;
}
return;
}
/* The strings still remaining except those marked in
* potential_sekis[] are uncapturable. Now see which opponent
* strings can survive.
*
* 1. Play opponent stones on all liberties of the unconditionally
* alive strings except where illegal.
*/
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (board[pos] != color || potential_sekis[pos] || find_origin(pos) != pos)
continue;
/* Play as many liberties as we can. */
liberties = findlib(pos, MAXLIBS, libs);
for (k = 0; k < liberties; k++) {
if (trymove(libs[k], other, "unconditional_life", pos))
moves_played++;
}
}
/* 2. Recursively extend opponent strings in atari, except where this
* would be suicide.
*/
found_one = 1;
while (found_one) {
/* Nothing found so far in this turn of the loop. */
found_one = 0;
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (board[pos] != other || countlib(pos) > 1)
continue;
/* Try to extend the string at (m, n). */
findlib(pos, 1, libs);
if (trymove(libs[0], other, "unconditional_life", pos)) {
moves_played++;
found_one = 1;
}
}
}
/* Now see whether there are any significant sekis on the board. */
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (!potential_sekis[pos]
|| board[pos] == EMPTY
|| find_origin(pos) != pos)
continue;
for (r = 0; r < 4; r++) {
int up = delta[r];
int right = delta[(r + 1) % 4];
int locally_played_moves = 0;
if (board[pos + up] != color
|| board[pos + up + up] != EMPTY
|| board[pos - up] != EMPTY)
continue;
for (k = 0; k < 2; k++) {
if (k == 1)
right = -right;
if (board[pos + right] != EMPTY || board[pos + up - right] != EMPTY)
continue;
if (board[pos - right] == EMPTY
&& trymove(pos - right, other, "unconditional_life", pos))
locally_played_moves++;
if (board[pos + up + right] == EMPTY
&& trymove(pos + up + right, other, "unconditional_life", pos))
locally_played_moves++;
if (board[pos - right] == other && board[pos + up + right] == other
&& same_string(pos - right, pos + up + right)) {
/* This is a critical seki. Extend the string with one stone
* in an arbitrary direction to break the seki.
*/
while (locally_played_moves > 0) {
popgo();
locally_played_moves--;
}
trymove(pos - up, color, "unconditional_life", pos);
moves_played++;
break;
}
else {
while (locally_played_moves > 0) {
popgo();
locally_played_moves--;
}
}
}
if (countstones(pos) > 2)
break;
}
}
/* Capture the strings involved in potential sekis. */
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (!potential_sekis[pos] || board[pos] == EMPTY)
continue;
/* Play as many liberties as we can. */
liberties = findlib(pos, MAXLIBS, libs);
for (k = 0; k < liberties; k++) {
if (trymove(libs[k], other, "unconditional_life", pos))
moves_played++;
}
}
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
int apos;
int bpos;
int aopen, bopen;
int alib, blib;
if (board[pos] != other || countlib(pos) != 2)
continue;
findlib(pos, 2, libs);
apos = libs[0];
bpos = libs[1];
if (abs(I(apos) - I(bpos)) + abs(J(apos) - J(bpos)) != 1)
continue;
/* Only two liberties and these are adjacent. Play one. We want
* to maximize the number of open liberties. In this particular
* situation we can count this with approxlib for the opposite
* color. If the number of open liberties is the same, we
* maximize the total number of obtained liberties.
* Two relevant positions:
*
* |XXX.
* |OOXX |XXXXXXX
* |O.OX |OOXOOOX
* |..OX |..OO.OX
* +---- +-------
*/
aopen = approxlib(apos, color, 4, NULL);
bopen = approxlib(bpos, color, 4, NULL);
alib = approxlib(apos, other, 4, NULL);
blib = approxlib(bpos, other, 4, NULL);
if (aopen > bopen || (aopen == bopen && alib >= blib)) {
trymove(apos, other, "unconditional_life", pos);
moves_played++;
}
else {
trymove(bpos, other, "unconditional_life", pos);
moves_played++;
}
}
/* Identify unconditionally alive stones and unconditional territory. */
for (pos = BOARDMIN; pos < BOARDMAX; pos++) {
if (board[pos] == color && !potential_sekis[pos]) {
unconditional_territory[pos] = 1;
if (find_origin(pos) == pos) {
liberties = findlib(pos, MAXLIBS, libs);
for (k = 0; k < liberties; k++)
unconditional_territory[libs[k]] = 2;
}
}
else if (board[pos] == other && countlib(pos) == 1) {
unconditional_territory[pos] = 2;
findlib(pos, 1, libs);
unconditional_territory[libs[0]] = 2;
}
}
/* Take back all moves. */
while (moves_played > 0) {
popgo();
moves_played--;
}
}
