uct/uct.c

   1 #include <assert.h>
   2 #include <pthread.h>
   3 #include <signal.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <time.h>
   8
   9 #define DEBUG
  10
  11 #include "debug.h"
  12 #include "board.h"
  13 #include "gtp.h"
  14 #include "move.h"
  15 #include "mq.h"
  16 #include "playout.h"
  17 #include "playout/elo.h"
  18 #include "playout/moggy.h"
  19 #include "playout/light.h"
  20 #include "random.h"
  21 #include "timeinfo.h"
  22 #include "tactics.h"
  23 #include "uct/internal.h"
  24 #include "uct/prior.h"
  25 #include "uct/tree.h"
  26 #include "uct/uct.h"
  27 #include "uct/walk.h"
  28
  29 struct uct_policy *policy_ucb1_init(struct uct *u, char *arg);
  30 struct uct_policy *policy_ucb1amaf_init(struct uct *u, char *arg);
  31 static void uct_pondering_stop(struct uct *u);
  32
  33
  34 /* Default number of simulations to perform per move.
  35  * Note that this is now in total over all threads! (Unless TM_ROOT.) */
  36 #define MC_GAMES        80000
  37 #define MC_GAMELEN      MAX_GAMELEN
  38
  39 /* How big proportion of ownermap counts must be of one color to consider
  40  * the point sure. */
  41 #define GJ_THRES        0.8
  42 /* How many games to consider at minimum before judging groups. */
  43 #define GJ_MINGAMES     500
  44
  45 /* How often to inspect the tree from the main thread to check for playout
  46  * stop, progress reports, etc. (in seconds) */
  47 #define TREE_BUSYWAIT_INTERVAL 0.1 /* 100ms */
  48
  49 /* For safety, use at most 3 times the desired time on a single move
  50  * in main time, and 1.1 times in byoyomi. */
  51 #define MAX_MAIN_TIME_EXTENSION 3.0
  52 #define MAX_BYOYOMI_TIME_EXTENSION 1.1
  53
  54 /* Once per how many simulations (per thread) to show a progress report line. */
  55 #define TREE_SIMPROGRESS_INTERVAL 10000
  56
  57
  58 static void
  59 setup_state(struct uct *u, struct board *b, enum stone color)
  60 {
  61         u->t = tree_init(b, color);
  62         if (u->force_seed)
  63                 fast_srandom(u->force_seed);
  64         if (UDEBUGL(0))
  65                 fprintf(stderr, "Fresh board with random seed %lu\n", fast_getseed());
  66         //board_print(b, stderr);
  67         if (!u->no_book && b->moves == 0) {
  68                 assert(color == S_BLACK);
  69                 tree_load(u->t, b);
  70         }
  71 }
  72
  73 static void
  74 reset_state(struct uct *u)
  75 {
  76         assert(u->t);
  77         tree_done(u->t); u->t = NULL;
  78 }
  79
  80 static void
  81 prepare_move(struct engine *e, struct board *b, enum stone color)
  82 {
  83         struct uct *u = e->data;
  84
  85         if (u->t) {
  86                 /* Verify that we have sane state. */
  87                 assert(b->es == u);
  88                 assert(u->t && b->moves);
  89                 if (color != stone_other(u->t->root_color)) {
  90                         fprintf(stderr, "Fatal: Non-alternating play detected %d %d\n",
  91                                 color, u->t->root_color);
  92                         exit(1);
  93                 }
  94
  95         } else {
  96                 /* We need fresh state. */
  97                 b->es = u;
  98                 setup_state(u, b, color);
  99         }
 100
 101         if (u->dynkomi && u->dynkomi > b->moves && (color & u->dynkomi_mask))
 102                 u->t->extra_komi = uct_get_extra_komi(u, b);
 103
 104         u->ownermap.playouts = 0;
 105         memset(u->ownermap.map, 0, board_size2(b) * sizeof(u->ownermap.map[0]));
 106 }
 107
 108 static void
 109 dead_group_list(struct uct *u, struct board *b, struct move_queue *mq)
 110 {
 111         struct group_judgement gj;
 112         gj.thres = GJ_THRES;
 113         gj.gs = alloca(board_size2(b) * sizeof(gj.gs[0]));
 114         board_ownermap_judge_group(b, &u->ownermap, &gj);
 115         groups_of_status(b, &gj, GS_DEAD, mq);
 116 }
 117
 118 bool
 119 uct_pass_is_safe(struct uct *u, struct board *b, enum stone color, bool pass_all_alive)
 120 {
 121         if (u->ownermap.playouts < GJ_MINGAMES)
 122                 return false;
 123
 124         struct move_queue mq = { .moves = 0 };
 125         if (!pass_all_alive)
 126                 dead_group_list(u, b, &mq);
 127         return pass_is_safe(b, color, &mq);
 128 }
 129
 130
 131 static void
 132 uct_printhook_ownermap(struct board *board, coord_t c, FILE *f)
 133 {
 134         struct uct *u = board->es;
 135         assert(u);
 136         const char chr[] = ":XO,"; // dame, black, white, unclear
 137         const char chm[] = ":xo,";
 138         char ch = chr[board_ownermap_judge_point(&u->ownermap, c, GJ_THRES)];
 139         if (ch == ',') { // less precise estimate then?
 140                 ch = chm[board_ownermap_judge_point(&u->ownermap, c, 0.67)];
 141         }
 142         fprintf(f, "%c ", ch);
 143 }
 144
 145 static char *
 146 uct_notify_play(struct engine *e, struct board *b, struct move *m)
 147 {
 148         struct uct *u = e->data;
 149         if (!u->t) {
 150                 /* No state, create one - this is probably game beginning
 151                  * and we need to load the opening book right now. */
 152                 prepare_move(e, b, m->color);
 153                 assert(u->t);
 154         }
 155
 156         /* Stop pondering. */
 157         /* XXX: If we are about to receive multiple 'play' commands,
 158          * e.g. in a rengo, we will not ponder during the rest of them. */
 159         uct_pondering_stop(u);
 160
 161         if (is_resign(m->coord)) {
 162                 /* Reset state. */
 163                 reset_state(u);
 164                 return NULL;
 165         }
 166
 167         /* Promote node of the appropriate move to the tree root. */
 168         assert(u->t->root);
 169         if (!tree_promote_at(u->t, b, m->coord)) {
 170                 if (UDEBUGL(0))
 171                         fprintf(stderr, "Warning: Cannot promote move node! Several play commands in row?\n");
 172                 reset_state(u);
 173                 return NULL;
 174         }
 175
 176         return NULL;
 177 }
 178
 179 static char *
 180 uct_chat(struct engine *e, struct board *b, char *cmd)
 181 {
 182         struct uct *u = e->data;
 183         static char reply[1024];
 184
 185         cmd += strspn(cmd, " \n\t");
 186         if (!strncasecmp(cmd, "winrate", 7)) {
 187                 if (!u->t)
 188                         return "no game context (yet?)";
 189                 enum stone color = u->t->root_color;
 190                 struct tree_node *n = u->t->root;
 191                 snprintf(reply, 1024, "In %d playouts at %d threads, %s %s can win with %.2f%% probability",
 192                          n->u.playouts, u->threads, stone2str(color), coord2sstr(n->coord, b),
 193                          tree_node_get_value(u->t, -1, n->u.value) * 100);
 194                 if (abs(u->t->extra_komi) >= 0.5) {
 195                         sprintf(reply + strlen(reply), ", while self-imposing extra komi %.1f",
 196                                 u->t->extra_komi);
 197                 }
 198                 strcat(reply, ".");
 199                 return reply;
 200         }
 201         return NULL;
 202 }
 203
 204 static void
 205 uct_dead_group_list(struct engine *e, struct board *b, struct move_queue *mq)
 206 {
 207         struct uct *u = e->data;
 208
 209         /* This means the game is probably over, no use pondering on. */
 210         uct_pondering_stop(u);
 211
 212         if (u->pass_all_alive)
 213                 return; // no dead groups
 214
 215         bool mock_state = false;
 216
 217         if (!u->t) {
 218                 /* No state, but we cannot just back out - we might
 219                  * have passed earlier, only assuming some stones are
 220                  * dead, and then re-connected, only to lose counting
 221                  * when all stones are assumed alive. */
 222                 /* Mock up some state and seed the ownermap by few
 223                  * simulations. */
 224                 prepare_move(e, b, S_BLACK); assert(u->t);
 225                 for (int i = 0; i < GJ_MINGAMES; i++)
 226                         uct_playout(u, b, S_BLACK, u->t);
 227                 mock_state = true;
 228         }
 229
 230         dead_group_list(u, b, mq);
 231
 232         if (mock_state) {
 233                 /* Clean up the mock state in case we will receive
 234                  * a genmove; we could get a non-alternating-move
 235                  * error from prepare_move() in that case otherwise. */
 236                 reset_state(u);
 237         }
 238 }
 239
 240 static void
 241 playout_policy_done(struct playout_policy *p)
 242 {
 243         if (p->done) p->done(p);
 244         if (p->data) free(p->data);
 245         free(p);
 246 }
 247
 248 static void
 249 uct_done(struct engine *e)
 250 {
 251         /* This is called on engine reset, especially when clear_board
 252          * is received and new game should begin. */
 253         struct uct *u = e->data;
 254         uct_pondering_stop(u);
 255         if (u->t) reset_state(u);
 256         free(u->ownermap.map);
 257
 258         free(u->policy);
 259         free(u->random_policy);
 260         playout_policy_done(u->playout);
 261         uct_prior_done(u->prior);
 262 }
 263
 264
 265 /* Pachi threading structure (if uct_playouts_parallel() is used):
 266  *
 267  * main thread
 268  *   |         main(), GTP communication, ...
 269  *   |         starts and stops the search managed by thread_manager
 270  *   |
 271  * thread_manager
 272  *   |         spawns and collects worker threads
 273  *   |
 274  * worker0
 275  * worker1
 276  * ...
 277  * workerK
 278  *             uct_playouts() loop, doing descend-playout until uct_halt
 279  *
 280  * Another way to look at it is by functions (lines denote thread boundaries):
 281  *
 282  * | uct_genmove()
 283  * | uct_search()            (uct_search_start() .. uct_search_stop())
 284  * | -----------------------
 285  * | spawn_thread_manager()
 286  * | -----------------------
 287  * | spawn_worker()
 288  * V uct_playouts() */
 289
 290 /* Set in thread manager in case the workers should stop. */
 291 volatile sig_atomic_t uct_halt = 0;
 292 /* ID of the running worker thread. */
 293 __thread int thread_id = -1;
 294 /* ID of the thread manager. */
 295 static pthread_t thread_manager;
 296 static bool thread_manager_running;
 297
 298 static pthread_mutex_t finish_mutex = PTHREAD_MUTEX_INITIALIZER;
 299 static pthread_cond_t finish_cond = PTHREAD_COND_INITIALIZER;
 300 static volatile int finish_thread;
 301 static pthread_mutex_t finish_serializer = PTHREAD_MUTEX_INITIALIZER;
 302
 303 struct spawn_ctx {
 304         int tid;
 305         struct uct *u;
 306         struct board *b;
 307         enum stone color;
 308         struct tree *t;
 309         unsigned long seed;
 310         int games;
 311 };
 312
 313 static void *
 314 spawn_worker(void *ctx_)
 315 {
 316         struct spawn_ctx *ctx = ctx_;
 317         /* Setup */
 318         fast_srandom(ctx->seed);
 319         thread_id = ctx->tid;
 320         /* Run */
 321         ctx->games = uct_playouts(ctx->u, ctx->b, ctx->color, ctx->t);
 322         /* Finish */
 323         pthread_mutex_lock(&finish_serializer);
 324         pthread_mutex_lock(&finish_mutex);
 325         finish_thread = ctx->tid;
 326         pthread_cond_signal(&finish_cond);
 327         pthread_mutex_unlock(&finish_mutex);
 328         return ctx;
 329 }
 330
 331 /* Thread manager, controlling worker threads. It must be called with
 332  * finish_mutex lock held, but it will unlock it itself before exiting;
 333  * this is necessary to be completely deadlock-free. */
 334 /* The finish_cond can be signalled for it to stop; in that case,
 335  * the caller should set finish_thread = -1. */
 336 /* After it is started, it will update mctx->t to point at some tree
 337  * used for the actual search (matters only for TM_ROOT), on return
 338  * it will set mctx->games to the number of performed simulations. */
 339 static void *
 340 spawn_thread_manager(void *ctx_)
 341 {
 342         /* In thread_manager, we use only some of the ctx fields. */
 343         struct spawn_ctx *mctx = ctx_;
 344         struct uct *u = mctx->u;
 345         struct tree *t = mctx->t;
 346         bool shared_tree = u->parallel_tree;
 347         fast_srandom(mctx->seed);
 348
 349         int played_games = 0;
 350         pthread_t threads[u->threads];
 351         int joined = 0;
 352
 353         uct_halt = 0;
 354
 355         /* Spawn threads... */
 356         for (int ti = 0; ti < u->threads; ti++) {
 357                 struct spawn_ctx *ctx = malloc(sizeof(*ctx));
 358                 ctx->u = u; ctx->b = mctx->b; ctx->color = mctx->color;
 359                 mctx->t = ctx->t = shared_tree ? t : tree_copy(t);
 360                 ctx->tid = ti; ctx->seed = fast_random(65536) + ti;
 361                 pthread_create(&threads[ti], NULL, spawn_worker, ctx);
 362                 if (UDEBUGL(2))
 363                         fprintf(stderr, "Spawned worker %d\n", ti);
 364         }
 365
 366         /* ...and collect them back: */
 367         while (joined < u->threads) {
 368                 /* Wait for some thread to finish... */
 369                 pthread_cond_wait(&finish_cond, &finish_mutex);
 370                 if (finish_thread < 0) {
 371                         /* Stop-by-caller. Tell the workers to wrap up. */
 372                         uct_halt = 1;
 373                         continue;
 374                 }
 375                 /* ...and gather its remnants. */
 376                 struct spawn_ctx *ctx;
 377                 pthread_join(threads[finish_thread], (void **) &ctx);
 378                 played_games += ctx->games;
 379                 joined++;
 380                 if (!shared_tree) {
 381                         if (ctx->t == mctx->t) mctx->t = t;
 382                         tree_merge(t, ctx->t);
 383                         tree_done(ctx->t);
 384                 }
 385                 free(ctx);
 386                 if (UDEBUGL(2))
 387                         fprintf(stderr, "Joined worker %d\n", finish_thread);
 388                 pthread_mutex_unlock(&finish_serializer);
 389         }
 390
 391         pthread_mutex_unlock(&finish_mutex);
 392
 393         if (!shared_tree)
 394                 tree_normalize(mctx->t, u->threads);
 395
 396         mctx->games = played_games;
 397         return mctx;
 398 }
 399
 400 static struct spawn_ctx *
 401 uct_search_start(struct uct *u, struct board *b, enum stone color, struct tree *t)
 402 {
 403         assert(u->threads > 0);
 404         assert(!thread_manager_running);
 405
 406         struct spawn_ctx ctx = { .u = u, .b = b, .color = color, .t = t, .seed = fast_random(65536) };
 407         static struct spawn_ctx mctx; mctx = ctx;
 408         pthread_mutex_lock(&finish_mutex);
 409         pthread_create(&thread_manager, NULL, spawn_thread_manager, &mctx);
 410         thread_manager_running = true;
 411         return &mctx;
 412 }
 413
 414 static struct spawn_ctx *
 415 uct_search_stop(void)
 416 {
 417         assert(thread_manager_running);
 418
 419         /* Signal thread manager to stop the workers. */
 420         pthread_mutex_lock(&finish_mutex);
 421         finish_thread = -1;
 422         pthread_cond_signal(&finish_cond);
 423         pthread_mutex_unlock(&finish_mutex);
 424
 425         /* Collect the thread manager. */
 426         struct spawn_ctx *pctx;
 427         thread_manager_running = false;
 428         pthread_join(thread_manager, (void **) &pctx);
 429         return pctx;
 430 }
 431
 432
 433 /* Search stopping conditions */
 434 union stop_conditions {
 435         struct { // TD_WALLTIME
 436                 double desired_stop; /* stop at that time if possible */
 437                 double worst_stop;   /* stop no later than this */
 438         } t;
 439         struct { // TD_GAMES
 440                 int desired_playouts;
 441                 int worst_playouts;
 442         } p;
 443 };
 444
 445 /* Pre-process time_info for search control and sets the desired stopping conditions. */
 446 static void
 447 time_prep(struct time_info *ti, struct uct *u, struct board *b, union stop_conditions *stop)
 448 {
 449         assert(ti->period != TT_TOTAL);
 450
 451         if (ti->period == TT_NULL) {
 452                 ti->period = TT_MOVE;
 453                 ti->dim = TD_GAMES;
 454                 ti->len.games = MC_GAMES;
 455         }
 456         if (ti->dim == TD_GAMES) {
 457                 stop->p.desired_playouts = ti->len.games;
 458                 stop->p.worst_playouts = ti->len.games * MAX_MAIN_TIME_EXTENSION;
 459         } else {
 460                 double desired_time = ti->len.t.recommended_time;
 461                 double worst_time;
 462                 if (time_in_byoyomi(ti)) {
 463                         worst_time = desired_time * MAX_BYOYOMI_TIME_EXTENSION;
 464                         desired_time *= (2 - MAX_BYOYOMI_TIME_EXTENSION); // make average(desired, worst) == recommended
 465                 } else {
 466                         worst_time = desired_time * MAX_MAIN_TIME_EXTENSION;
 467                 }
 468                 if (worst_time > ti->len.t.max_time)
 469                         worst_time = ti->len.t.max_time;
 470                 if (desired_time > worst_time)
 471                         desired_time = worst_time;
 472
 473                 stop->t.desired_stop = ti->len.t.timer_start + desired_time - ti->len.t.net_lag;
 474                 stop->t.worst_stop = ti->len.t.timer_start + worst_time - ti->len.t.net_lag;
 475                 // Both stop points may be in the past if too much lag.
 476
 477                 if (UDEBUGL(2))
 478                         fprintf(stderr, "desired time %.02f, worst %.02f\n", desired_time, worst_time);
 479         }
 480 }
 481
 482 /* Run time-limited MCTS search on foreground. */
 483 static int
 484 uct_search(struct uct *u, struct board *b, struct time_info *ti, enum stone color, struct tree *t)
 485 {
 486         union stop_conditions stop;
 487         time_prep(ti, u, b, &stop);
 488         if (UDEBUGL(2) && u->t->root->u.playouts > 0)
 489                 fprintf(stderr, "<pre-simulated %d games skipped>\n", u->t->root->u.playouts);
 490
 491         /* Number of last game with progress print. */
 492         int last_print = t->root->u.playouts;
 493         /* Number of simulations to wait before next print. */
 494         int print_interval = TREE_SIMPROGRESS_INTERVAL * (u->thread_model == TM_ROOT ? 1 : u->threads);
 495         /* Printed notification about full memory? */
 496         bool print_fullmem = false;
 497
 498         struct spawn_ctx *ctx = uct_search_start(u, b, color, t);
 499
 500         /* The search tree is ctx->t. This is normally == t, but in case of
 501          * TM_ROOT, it is one of the trees belonging to the independent
 502          * workers. It is important to reference ctx->t directly since the
 503          * thread manager will swap the tree pointer asynchronously. */
 504         /* XXX: This means TM_ROOT support is suboptimal since single stalled
 505          * thread can stall the others in case of limiting the search by game
 506          * count. However, TM_ROOT just does not deserve any more extra code
 507          * right now. */
 508
 509         struct tree_node *best = NULL, *prev_best;
 510         struct tree_node *winner = NULL, *prev_winner;
 511
 512         double busywait_interval = TREE_BUSYWAIT_INTERVAL;
 513
 514         /* Now, just periodically poll the search tree. */
 515         while (1) {
 516                 time_sleep(busywait_interval);
 517                 /* busywait_interval should never be less than desired time, or the
 518                  * time control is broken. But if it happens to be less, we still search
 519                  * at least 100ms otherwise the move is completely random. */
 520
 521                 int i = ctx->t->root->u.playouts;
 522
 523                 /* Print progress? */
 524                 if (i - last_print > print_interval) {
 525                         last_print += print_interval; // keep the numbers tidy
 526                         uct_progress_status(u, ctx->t, color, last_print);
 527                 }
 528                 if (!print_fullmem && ctx->t->nodes_size > u->max_tree_size) {
 529                         if (UDEBUGL(2))
 530                                 fprintf(stderr, "memory limit hit (%ld > %lu)\n", ctx->t->nodes_size, u->max_tree_size);
 531                         print_fullmem = true;
 532                 }
 533
 534                 /* Check against time settings. */
 535                 bool desired_done = false;
 536                 if (ti->dim == TD_WALLTIME) {
 537                         double now = time_now();
 538                         if (now > stop.t.worst_stop) break;
 539                         desired_done = now > stop.t.desired_stop;
 540                 } else {
 541                         assert(ti->dim == TD_GAMES);
 542                         if (i > stop.p.worst_playouts) break;
 543                         desired_done = i > stop.p.desired_playouts;
 544                 }
 545
 546                 /* Early break in won situation. */
 547                 prev_best = best;
 548                 best = u->policy->choose(u->policy, ctx->t->root, b, color);
 549                 if (best && ((best->u.playouts >= 2000 && tree_node_get_value(ctx->t, 1, best->u.value) >= u->loss_threshold)
 550                              || (best->u.playouts >= 500 && tree_node_get_value(ctx->t, 1, best->u.value) >= 0.95)))
 551                         break;
 552
 553                 if (desired_done) {
 554                         if (!u->policy->winner || !u->policy->evaluate)
 555                                 break;
 556                         /* Stop only if best explored has also highest value: */
 557                         prev_winner = winner;
 558                         winner = u->policy->winner(u->policy, ctx->t, ctx->t->root);
 559                         if (best && best == winner)
 560                                 break;
 561                         if (UDEBUGL(3) && (best != prev_best || winner != prev_winner)) {
 562                                 fprintf(stderr, "[%d] best", i);
 563                                 if (best)
 564                                         fprintf(stderr, " %3s [%d] %f", coord2sstr(best->coord, ctx->t->board),
 565                                                 best->u.playouts, tree_node_get_value(ctx->t, 1, best->u.value));
 566                                 fprintf(stderr, " != winner");
 567                                 if (winner)
 568                                         fprintf(stderr, " %3s [%d] %f ", coord2sstr(winner->coord, ctx->t->board),
 569                                                 winner->u.playouts, tree_node_get_value(ctx->t, 1, winner->u.value));
 570                                 fprintf(stderr, "\n");
 571                         }
 572                 }
 573
 574                 /* TODO: Early break if best->variance goes under threshold and we already
 575                  * have enough playouts (possibly thanks to book or to pondering). */
 576                 /* TODO: Early break if second best has no chance to catch up. */
 577         }
 578
 579         ctx = uct_search_stop();
 580
 581         if (UDEBUGL(2))
 582                 tree_dump(t, u->dumpthres);
 583         if (UDEBUGL(0))
 584                 uct_progress_status(u, t, color, ctx->games);
 585
 586         return ctx->games;
 587 }
 588
 589
 590 /* Start pondering background with @color to play. */
 591 static void
 592 uct_pondering_start(struct uct *u, struct board *b0, struct tree *t, enum stone color)
 593 {
 594         if (UDEBUGL(1))
 595                 fprintf(stderr, "Starting to ponder with color %s\n", stone2str(stone_other(color)));
 596
 597         /* We need a local board copy to ponder upon. */
 598         struct board *b = malloc(sizeof(*b)); board_copy(b, b0);
 599
 600         /* *b0 did not have the genmove'd move played yet. */
 601         struct move m = { t->root->coord, t->root_color };
 602         int res = board_play(b, &m);
 603         assert(res >= 0);
 604
 605         /* Start MCTS manager thread "headless". */
 606         uct_search_start(u, b, color, t);
 607 }
 608
 609 /* uct_search_stop() frontend for the pondering (non-genmove) mode. */
 610 static void
 611 uct_pondering_stop(struct uct *u)
 612 {
 613         if (!thread_manager_running)
 614                 return;
 615
 616         /* Stop the thread manager. */
 617         struct spawn_ctx *ctx = uct_search_stop();
 618         if (UDEBUGL(1)) {
 619                 fprintf(stderr, "(pondering) ");
 620                 uct_progress_status(u, ctx->t, ctx->color, ctx->games);
 621         }
 622         free(ctx->b);
 623 }
 624
 625
 626 static coord_t *
 627 uct_genmove(struct engine *e, struct board *b, struct time_info *ti, enum stone color, bool pass_all_alive)
 628 {
 629         struct uct *u = e->data;
 630
 631         if (b->superko_violation) {
 632                 fprintf(stderr, "!!! WARNING: SUPERKO VIOLATION OCCURED BEFORE THIS MOVE\n");
 633                 fprintf(stderr, "Maybe you play with situational instead of positional superko?\n");
 634                 fprintf(stderr, "I'm going to ignore the violation, but note that I may miss\n");
 635                 fprintf(stderr, "some moves valid under this ruleset because of this.\n");
 636                 b->superko_violation = false;
 637         }
 638
 639         /* Seed the tree. */
 640         uct_pondering_stop(u);
 641         prepare_move(e, b, color);
 642         assert(u->t);
 643
 644         /* Perform the Monte Carlo Tree Search! */
 645         int played_games = uct_search(u, b, ti, color, u->t);
 646
 647         /* Choose the best move from the tree. */
 648         struct tree_node *best = u->policy->choose(u->policy, u->t->root, b, color);
 649         if (!best) {
 650                 reset_state(u);
 651                 return coord_copy(pass);
 652         }
 653         if (UDEBUGL(1))
 654                 fprintf(stderr, "*** WINNER is %s (%d,%d) with score %1.4f (%d/%d:%d games)\n",
 655                         coord2sstr(best->coord, b), coord_x(best->coord, b), coord_y(best->coord, b),
 656                         tree_node_get_value(u->t, 1, best->u.value),
 657                         best->u.playouts, u->t->root->u.playouts, played_games);
 658         if (tree_node_get_value(u->t, 1, best->u.value) < u->resign_ratio && !is_pass(best->coord)) {
 659                 reset_state(u);
 660                 return coord_copy(resign);
 661         }
 662
 663         /* If the opponent just passed and we win counting, always
 664          * pass as well. */
 665         if (b->moves > 1 && is_pass(b->last_move.coord)) {
 666                 /* Make sure enough playouts are simulated. */
 667                 while (u->ownermap.playouts < GJ_MINGAMES)
 668                         uct_playout(u, b, color, u->t);
 669                 if (uct_pass_is_safe(u, b, color, u->pass_all_alive || pass_all_alive)) {
 670                         if (UDEBUGL(0))
 671                                 fprintf(stderr, "<Will rather pass, looks safe enough.>\n");
 672                         best->coord = pass;
 673                 }
 674         }
 675
 676         tree_promote_node(u->t, best);
 677         /* After a pass, pondering is harmful for two reasons:
 678          * (i) We might keep pondering even when the game is over.
 679          * Of course this is the case for opponent resign as well.
 680          * (ii) More importantly, the ownermap will get skewed since
 681          * the UCT will start cutting off any playouts. */
 682         if (u->pondering && !is_pass(best->coord)) {
 683                 uct_pondering_start(u, b, u->t, stone_other(color));
 684         }
 685         return coord_copy(best->coord);
 686 }
 687
 688
 689 bool
 690 uct_genbook(struct engine *e, struct board *b, struct time_info *ti, enum stone color)
 691 {
 692         struct uct *u = e->data;
 693         if (!u->t) prepare_move(e, b, color);
 694         assert(u->t);
 695
 696         if (ti->dim == TD_GAMES) {
 697                 /* Don't count in games that already went into the book. */
 698                 ti->len.games += u->t->root->u.playouts;
 699         }
 700         uct_search(u, b, ti, color, u->t);
 701
 702         assert(ti->dim == TD_GAMES);
 703         tree_save(u->t, b, ti->len.games / 100);
 704
 705         return true;
 706 }
 707
 708 void
 709 uct_dumpbook(struct engine *e, struct board *b, enum stone color)
 710 {
 711         struct tree *t = tree_init(b, color);
 712         tree_load(t, b);
 713         tree_dump(t, 0);
 714         tree_done(t);
 715 }
 716
 717
 718 struct uct *
 719 uct_state_init(char *arg, struct board *b)
 720 {
 721         struct uct *u = calloc(1, sizeof(struct uct));
 722
 723         u->debug_level = 1;
 724         u->gamelen = MC_GAMELEN;
 725         u->mercymin = 0;
 726         u->expand_p = 2;
 727         u->dumpthres = 1000;
 728         u->playout_amaf = true;
 729         u->playout_amaf_nakade = false;
 730         u->amaf_prior = false;
 731         u->max_tree_size = 3072ULL * 1048576;
 732
 733         if (board_size(b) - 2 >= 19)
 734                 u->dynkomi = 200;
 735         u->dynkomi_mask = S_BLACK;
 736
 737         u->threads = 1;
 738         u->thread_model = TM_TREEVL;
 739         u->parallel_tree = true;
 740         u->virtual_loss = true;
 741
 742         u->val_scale = 0.02; u->val_points = 20;
 743
 744         if (arg) {
 745                 char *optspec, *next = arg;
 746                 while (*next) {
 747                         optspec = next;
 748                         next += strcspn(next, ",");
 749                         if (*next) { *next++ = 0; } else { *next = 0; }
 750
 751                         char *optname = optspec;
 752                         char *optval = strchr(optspec, '=');
 753                         if (optval) *optval++ = 0;
 754
 755                         if (!strcasecmp(optname, "debug")) {
 756                                 if (optval)
 757                                         u->debug_level = atoi(optval);
 758                                 else
 759                                         u->debug_level++;
 760                         } else if (!strcasecmp(optname, "mercy") && optval) {
 761                                 /* Minimal difference of black/white captures
 762                                  * to stop playout - "Mercy Rule". Speeds up
 763                                  * hopeless playouts at the expense of some
 764                                  * accuracy. */
 765                                 u->mercymin = atoi(optval);
 766                         } else if (!strcasecmp(optname, "gamelen") && optval) {
 767                                 u->gamelen = atoi(optval);
 768                         } else if (!strcasecmp(optname, "expand_p") && optval) {
 769                                 u->expand_p = atoi(optval);
 770                         } else if (!strcasecmp(optname, "dumpthres") && optval) {
 771                                 u->dumpthres = atoi(optval);
 772                         } else if (!strcasecmp(optname, "playout_amaf")) {
 773                                 /* Whether to include random playout moves in
 774                                  * AMAF as well. (Otherwise, only tree moves
 775                                  * are included in AMAF. Of course makes sense
 776                                  * only in connection with an AMAF policy.) */
 777                                 /* with-without: 55.5% (+-4.1) */
 778                                 if (optval && *optval == '0')
 779                                         u->playout_amaf = false;
 780                                 else
 781                                         u->playout_amaf = true;
 782                         } else if (!strcasecmp(optname, "playout_amaf_nakade")) {
 783                                 /* Whether to include nakade moves from playouts
 784                                  * in the AMAF statistics; this tends to nullify
 785                                  * the playout_amaf effect by adding too much
 786                                  * noise. */
 787                                 if (optval && *optval == '0')
 788                                         u->playout_amaf_nakade = false;
 789                                 else
 790                                         u->playout_amaf_nakade = true;
 791                         } else if (!strcasecmp(optname, "playout_amaf_cutoff") && optval) {
 792                                 /* Keep only first N% of playout stage AMAF
 793                                  * information. */
 794                                 u->playout_amaf_cutoff = atoi(optval);
 795                         } else if ((!strcasecmp(optname, "policy") || !strcasecmp(optname, "random_policy")) && optval) {
 796                                 char *policyarg = strchr(optval, ':');
 797                                 struct uct_policy **p = !strcasecmp(optname, "policy") ? &u->policy : &u->random_policy;
 798                                 if (policyarg)
 799                                         *policyarg++ = 0;
 800                                 if (!strcasecmp(optval, "ucb1")) {
 801                                         *p = policy_ucb1_init(u, policyarg);
 802                                 } else if (!strcasecmp(optval, "ucb1amaf")) {
 803                                         *p = policy_ucb1amaf_init(u, policyarg);
 804                                 } else {
 805                                         fprintf(stderr, "UCT: Invalid tree policy %s\n", optval);
 806                                         exit(1);
 807                                 }
 808                         } else if (!strcasecmp(optname, "playout") && optval) {
 809                                 char *playoutarg = strchr(optval, ':');
 810                                 if (playoutarg)
 811                                         *playoutarg++ = 0;
 812                                 if (!strcasecmp(optval, "moggy")) {
 813                                         u->playout = playout_moggy_init(playoutarg);
 814                                 } else if (!strcasecmp(optval, "light")) {
 815                                         u->playout = playout_light_init(playoutarg);
 816                                 } else if (!strcasecmp(optval, "elo")) {
 817                                         u->playout = playout_elo_init(playoutarg);
 818                                 } else {
 819                                         fprintf(stderr, "UCT: Invalid playout policy %s\n", optval);
 820                                         exit(1);
 821                                 }
 822                         } else if (!strcasecmp(optname, "prior") && optval) {
 823                                 u->prior = uct_prior_init(optval, b);
 824                         } else if (!strcasecmp(optname, "amaf_prior") && optval) {
 825                                 u->amaf_prior = atoi(optval);
 826                         } else if (!strcasecmp(optname, "threads") && optval) {
 827                                 /* By default, Pachi will run with only single
 828                                  * tree search thread! */
 829                                 u->threads = atoi(optval);
 830                         } else if (!strcasecmp(optname, "thread_model") && optval) {
 831                                 if (!strcasecmp(optval, "root")) {
 832                                         /* Root parallelization - each thread
 833                                          * does independent search, trees are
 834                                          * merged at the end. */
 835                                         u->thread_model = TM_ROOT;
 836                                         u->parallel_tree = false;
 837                                         u->virtual_loss = false;
 838                                 } else if (!strcasecmp(optval, "tree")) {
 839                                         /* Tree parallelization - all threads
 840                                          * grind on the same tree. */
 841                                         u->thread_model = TM_TREE;
 842                                         u->parallel_tree = true;
 843                                         u->virtual_loss = false;
 844                                 } else if (!strcasecmp(optval, "treevl")) {
 845                                         /* Tree parallelization, but also
 846                                          * with virtual losses - this discou-
 847                                          * rages most threads choosing the
 848                                          * same tree branches to read. */
 849                                         u->thread_model = TM_TREEVL;
 850                                         u->parallel_tree = true;
 851                                         u->virtual_loss = true;
 852                                 } else {
 853                                         fprintf(stderr, "UCT: Invalid thread model %s\n", optval);
 854                                         exit(1);
 855                                 }
 856                         } else if (!strcasecmp(optname, "pondering")) {
 857                                 /* Keep searching even during opponent's turn. */
 858                                 u->pondering = !optval || atoi(optval);
 859                         } else if (!strcasecmp(optname, "force_seed") && optval) {
 860                                 u->force_seed = atoi(optval);
 861                         } else if (!strcasecmp(optname, "no_book")) {
 862                                 u->no_book = true;
 863                         } else if (!strcasecmp(optname, "dynkomi")) {
 864                                 /* Dynamic komi in handicap game; linearly
 865                                  * decreases to basic settings until move
 866                                  * #optval. */
 867                                 u->dynkomi = optval ? atoi(optval) : 150;
 868                         } else if (!strcasecmp(optname, "dynkomi_mask") && optval) {
 869                                 /* Bitmask of colors the player must be
 870                                  * for dynkomi be applied; you may want
 871                                  * to use dynkomi_mask=3 to allow dynkomi
 872                                  * even in games where Pachi is white. */
 873                                 u->dynkomi_mask = atoi(optval);
 874                         } else if (!strcasecmp(optname, "val_scale") && optval) {
 875                                 /* How much of the game result value should be
 876                                  * influenced by win size. Zero means it isn't. */
 877                                 u->val_scale = atof(optval);
 878                         } else if (!strcasecmp(optname, "val_points") && optval) {
 879                                 /* Maximum size of win to be scaled into game
 880                                  * result value. Zero means boardsize^2. */
 881                                 u->val_points = atoi(optval) * 2; // result values are doubled
 882                         } else if (!strcasecmp(optname, "val_extra")) {
 883                                 /* If false, the score coefficient will be simply
 884                                  * added to the value, instead of scaling the result
 885                                  * coefficient because of it. */
 886                                 u->val_extra = !optval || atoi(optval);
 887                         } else if (!strcasecmp(optname, "root_heuristic") && optval) {
 888                                 /* Whether to bias exploration by root node values
 889                                  * (must be supported by the used policy).
 890                                  * 0: Don't.
 891                                  * 1: Do, value = result.
 892                                  * Try to temper the result:
 893                                  * 2: Do, value = 0.5+(result-expected)/2.
 894                                  * 3: Do, value = 0.5+bzz((result-expected)^2). */
 895                                 u->root_heuristic = atoi(optval);
 896                         } else if (!strcasecmp(optname, "pass_all_alive")) {
 897                                 /* Whether to consider all stones alive at the game
 898                                  * end instead of marking dead groupd. */
 899                                 u->pass_all_alive = !optval || atoi(optval);
 900                         } else if (!strcasecmp(optname, "random_policy_chance") && optval) {
 901                                 /* If specified (N), with probability 1/N, random_policy policy
 902                                  * descend is used instead of main policy descend; useful
 903                                  * if specified policy (e.g. UCB1AMAF) can make unduly biased
 904                                  * choices sometimes, you can fall back to e.g.
 905                                  * random_policy=UCB1. */
 906                                 u->random_policy_chance = atoi(optval);
 907                         } else if (!strcasecmp(optname, "max_tree_size") && optval) {
 908                                 /* Maximum amount of memory [MiB] consumed by the move tree.
 909                                  * Default is 3072 (3 GiB). Note that if you use TM_ROOT,
 910                                  * this limits size of only one of the trees, not all of them
 911                                  * together. */
 912                                 u->max_tree_size = atol(optval) * 1048576;
 913                         } else if (!strcasecmp(optname, "banner") && optval) {
 914                                 /* Additional banner string. This must come as the
 915                                  * last engine parameter. */
 916                                 if (*next) *--next = ',';
 917                                 u->banner = strdup(optval);
 918                                 break;
 919                         } else {
 920                                 fprintf(stderr, "uct: Invalid engine argument %s or missing value\n", optname);
 921                                 exit(1);
 922                         }
 923                 }
 924         }
 925
 926         u->resign_ratio = 0.2; /* Resign when most games are lost. */
 927         u->loss_threshold = 0.85; /* Stop reading if after at least 5000 playouts this is best value. */
 928         if (!u->policy)
 929                 u->policy = policy_ucb1amaf_init(u, NULL);
 930
 931         if (!!u->random_policy_chance ^ !!u->random_policy) {
 932                 fprintf(stderr, "uct: Only one of random_policy and random_policy_chance is set\n");
 933                 exit(1);
 934         }
 935
 936         if (!u->prior)
 937                 u->prior = uct_prior_init(NULL, b);
 938
 939         if (!u->playout)
 940                 u->playout = playout_moggy_init(NULL);
 941         u->playout->debug_level = u->debug_level;
 942
 943         u->ownermap.map = malloc(board_size2(b) * sizeof(u->ownermap.map[0]));
 944
 945         /* Some things remain uninitialized for now - the opening book
 946          * is not loaded and the tree not set up. */
 947         /* This will be initialized in setup_state() at the first move
 948          * received/requested. This is because right now we are not aware
 949          * about any komi or handicap setup and such. */
 950
 951         return u;
 952 }
 953
 954 struct engine *
 955 engine_uct_init(char *arg, struct board *b)
 956 {
 957         struct uct *u = uct_state_init(arg, b);
 958         struct engine *e = calloc(1, sizeof(struct engine));
 959         e->name = "UCT Engine";
 960         e->printhook = uct_printhook_ownermap;
 961         e->notify_play = uct_notify_play;
 962         e->chat = uct_chat;
 963         e->genmove = uct_genmove;
 964         e->dead_group_list = uct_dead_group_list;
 965         e->done = uct_done;
 966         e->data = u;
 967
 968         const char banner[] = "I'm playing UCT. When I'm losing, I will resign, "
 969                 "if I think I win, I play until you pass. "
 970                 "Anyone can send me 'winrate' in private chat to get my assessment of the position.";
 971         if (!u->banner) u->banner = "";
 972         e->comment = malloc(sizeof(banner) + strlen(u->banner) + 1);
 973         sprintf(e->comment, "%s %s", banner, u->banner);
 974
 975         return e;
 976 }