private Board solve_dfs(Board b, int depthLimit, int depth) {
if (depth >= depthLimit) { // Cutoff test
return b;
}
Board best = null;
int best_score = -1;
for (int i = 0; i < BOARD_WIDTH; i++) {
Board next = new Board(b);
if (next.move(tileSequence, directions[i])) {
Board candidate = solve_dfs(next, depthLimit, depth + 1);
if (candidate == null && next.finished()) {
candidate = next;
}
if (candidate != null) {
if (candidate.finished()) {
updateBest(candidate);
} else {
int score = evaluate(candidate);
if (score > best_score) {
best_score = score;
best = candidate;
}
}
}
}
}
return best;
}
/**
* Single threaded depth-limited depth first search, with no backtracking.
*
* @param s The tile sequence
* @param b The board to search
* @return The final best board state that it can find.
*/
private Board solve_ldfs(Board b) {
Board input = b;
fbest_score = -1;
fbest = null;
currentfactors = factors;
while (b != null && !b.finished()) {
b = solve_dfs(b, MAX_DEPTH, 0);
if (b != null) {
log_info(b);
}
}
// Super edge-case: The input board can't be moved...
return fbest == null ? input : fbest;
}
/**
* Multi-threaded depth-limited depth first search, with no backtracking.
*
* @param s The tile sequence
* @param b The board to search
* @param pool The thread pool
* @return The final best board state that it can find.
*/
private Board solve_pndfs(Board b, ExecutorService pool) {
Board input = b;
fbest_score = -1;
fbest = null;
currentfactors = factors;
while (b != null && !b.finished()) {
b = solve_pdfs(b, pool);
if (b != null) {
// log_info(b);
}
}
// Super edge-case: The input board can't be moved...
return fbest == null ? input : fbest;
}
/**
* Solves a board game using a depth-limited depth first search. Also makes use of some
* backtracking to further optimise the result. Will also attempt to run multithreadedly.
*
* @param s The tile sequence
* @param b The board to search
* @return The final best board state that it can find.
*/
private Board solve_mdfs(Board b) {
Ringbuffer<Board> rb = new Ringbuffer<>(6);
Board current = b, choke_best = null;
char fc = 0, foff = 0;
// VTEC just kicked in yo
ExecutorService pool = Executors.newFixedThreadPool(nThreads);
fbest_score = -1;
fbest = null;
while (current != null && !current.finished()) {
rb.push(current);
current = solve_pdfs(current, pool);
if (choke_best != null && choke_best != fbest) {
log_info(
"Recovery!: [%d:%s] %d(%d) --> %d(%d)",
(int) fc,
Arrays.toString(currentfactors),
choke_best.score(),
choke_best.nMoves(),
fbest.score(),
fbest.nMoves());
choke_best = null;
// Test: Is it always best to stick to 18,2,2,9 where possible?
// Maybe not, but some factors shouldn't be used for extended periods of time.
if (fc > 3) {
log_info(
"Volatile weights were used; switching back to %s",
Arrays.toString(choicefactors[0]));
fc = 0;
currentfactors = choicefactors[0];
}
}
if (current != null) {
log_info(current);
} else if (fbest != null && fbest.nMoves() < tileSequence.length) {
current = rb.pop();
if (choke_best != fbest) {
choke_best = fbest;
foff = 1;
fc = (char) ((fc + 1) % choicefactors.length);
currentfactors = choicefactors[fc];
log_info("Dead-end, back-tracking two steps and trying with different weights!");
log_info(
"Starting index: %d (current score %d/%d)",
(int) fc, current.score(), current.nMoves());
} else if (foff++ < choicefactors.length - 1) {
fc = (char) ((fc + 1) % choicefactors.length);
currentfactors = choicefactors[fc];
log_info("No improvement, trying factor index %d...", (int) fc);
} else {
current = null;
log_info("Factor exhaustion");
}
}
}
pool.shutdown();
return fbest == null ? b : fbest;
}
