uct/uct.c

   1 #include <assert.h>
   2 #include <math.h>
   3 #include <stdio.h>
   4 #include <stdlib.h>
   5 #include <string.h>
   6 #include <time.h>
   7
   8 #define DEBUG
   9
  10 #include "debug.h"
  11 #include "board.h"
  12 #include "gtp.h"
  13 #include "chat.h"
  14 #include "move.h"
  15 #include "mq.h"
  16 #include "joseki/base.h"
  17 #include "playout.h"
  18 #include "playout/moggy.h"
  19 #include "playout/light.h"
  20 #include "tactics/util.h"
  21 #include "timeinfo.h"
  22 #include "uct/dynkomi.h"
  23 #include "uct/internal.h"
  24 #include "uct/plugins.h"
  25 #include "uct/prior.h"
  26 #include "uct/search.h"
  27 #include "uct/slave.h"
  28 #include "uct/tree.h"
  29 #include "uct/uct.h"
  30 #include "uct/walk.h"
  31
  32 struct uct_policy *policy_ucb1_init(struct uct *u, char *arg);
  33 struct uct_policy *policy_ucb1amaf_init(struct uct *u, char *arg, struct board *board);
  34 static void uct_pondering_start(struct uct *u, struct board *b0, struct tree *t, enum stone color);
  35
  36 /* Maximal simulation length. */
  37 #define MC_GAMELEN      MAX_GAMELEN
  38
  39
  40 static void
  41 setup_state(struct uct *u, struct board *b, enum stone color)
  42 {
  43         u->t = tree_init(b, color, u->fast_alloc ? u->max_tree_size : 0,
  44                          u->max_pruned_size, u->pruning_threshold, u->local_tree_aging, u->stats_hbits);
  45         if (u->initial_extra_komi)
  46                 u->t->extra_komi = u->initial_extra_komi;
  47         if (u->force_seed)
  48                 fast_srandom(u->force_seed);
  49         if (UDEBUGL(3))
  50                 fprintf(stderr, "Fresh board with random seed %lu\n", fast_getseed());
  51         if (!u->no_tbook && b->moves == 0) {
  52                 if (color == S_BLACK) {
  53                         tree_load(u->t, b);
  54                 } else if (DEBUGL(0)) {
  55                         fprintf(stderr, "Warning: First move appears to be white\n");
  56                 }
  57         }
  58 }
  59
  60 static void
  61 reset_state(struct uct *u)
  62 {
  63         assert(u->t);
  64         tree_done(u->t); u->t = NULL;
  65 }
  66
  67 static void
  68 setup_dynkomi(struct uct *u, struct board *b, enum stone to_play)
  69 {
  70         if (u->t->use_extra_komi && !u->pondering && u->dynkomi->permove)
  71                 u->t->extra_komi = u->dynkomi->permove(u->dynkomi, b, u->t);
  72         else if (!u->t->use_extra_komi)
  73                 u->t->extra_komi = 0;
  74 }
  75
  76 void
  77 uct_prepare_move(struct uct *u, struct board *b, enum stone color)
  78 {
  79         if (u->t) {
  80                 /* Verify that we have sane state. */
  81                 assert(b->es == u);
  82                 assert(u->t && b->moves);
  83                 if (color != stone_other(u->t->root_color)) {
  84                         fprintf(stderr, "Fatal: Non-alternating play detected %d %d\n",
  85                                 color, u->t->root_color);
  86                         exit(1);
  87                 }
  88                 uct_htable_reset(u->t);
  89
  90         } else {
  91                 /* We need fresh state. */
  92                 b->es = u;
  93                 setup_state(u, b, color);
  94         }
  95
  96         u->ownermap.playouts = 0;
  97         memset(u->ownermap.map, 0, board_size2(b) * sizeof(u->ownermap.map[0]));
  98         u->played_own = u->played_all = 0;
  99 }
 100
 101 static void
 102 dead_group_list(struct uct *u, struct board *b, struct move_queue *mq)
 103 {
 104         enum gj_state gs_array[board_size2(b)];
 105         struct group_judgement gj = { .thres = GJ_THRES, .gs = gs_array };
 106         board_ownermap_judge_groups(b, &u->ownermap, &gj);
 107         groups_of_status(b, &gj, GS_DEAD, mq);
 108 }
 109
 110 bool
 111 uct_pass_is_safe(struct uct *u, struct board *b, enum stone color, bool pass_all_alive)
 112 {
 113         /* Make sure enough playouts are simulated to get a reasonable dead group list. */
 114         while (u->ownermap.playouts < GJ_MINGAMES)
 115                 uct_playout(u, b, color, u->t);
 116
 117         struct move_queue mq = { .moves = 0 };
 118         dead_group_list(u, b, &mq);
 119         if (pass_all_alive) {
 120                 for (unsigned int i = 0; i < mq.moves; i++) {
 121                         if (board_at(b, mq.move[i]) == stone_other(color)) {
 122                                 return false; // We need to remove opponent dead groups first.
 123                         }
 124                 }
 125                 mq.moves = 0; // our dead stones are alive when pass_all_alive is true
 126         }
 127         if (u->allow_losing_pass) {
 128                 foreach_point(b) {
 129                         if (board_at(b, c) == S_OFFBOARD)
 130                                 continue;
 131                         if (board_ownermap_judge_point(&u->ownermap, c, GJ_THRES) == PJ_UNKNOWN) {
 132                                 if (UDEBUGL(3))
 133                                         fprintf(stderr, "uct_pass_is_safe fails at %s[%d]\n", coord2sstr(c, b), c);
 134                                 return false; // Unclear point, clarify first.
 135                         }
 136                 } foreach_point_end;
 137                 return true;
 138         }
 139         return pass_is_safe(b, color, &mq);
 140 }
 141
 142 static char *
 143 uct_printhook_ownermap(struct board *board, coord_t c, char *s, char *end)
 144 {
 145         struct uct *u = board->es;
 146         if (!u) {
 147                 strcat(s, ". ");
 148                 return s + 2;
 149         }
 150         const char chr[] = ":XO,"; // dame, black, white, unclear
 151         const char chm[] = ":xo,";
 152         char ch = chr[board_ownermap_judge_point(&u->ownermap, c, GJ_THRES)];
 153         if (ch == ',') { // less precise estimate then?
 154                 ch = chm[board_ownermap_judge_point(&u->ownermap, c, 0.67)];
 155         }
 156         s += snprintf(s, end - s, "%c ", ch);
 157         return s;
 158 }
 159
 160 static char *
 161 uct_notify_play(struct engine *e, struct board *b, struct move *m, char *enginearg)
 162 {
 163         struct uct *u = e->data;
 164         if (!u->t) {
 165                 /* No state, create one - this is probably game beginning
 166                  * and we need to load the opening tbook right now. */
 167                 uct_prepare_move(u, b, m->color);
 168                 assert(u->t);
 169         }
 170
 171         /* Stop pondering, required by tree_promote_at() */
 172         uct_pondering_stop(u);
 173         if (UDEBUGL(2) && u->slave)
 174                 tree_dump(u->t, u->dumpthres);
 175
 176         if (is_resign(m->coord)) {
 177                 /* Reset state. */
 178                 reset_state(u);
 179                 return NULL;
 180         }
 181
 182         /* Promote node of the appropriate move to the tree root. */
 183         assert(u->t->root);
 184         if (u->t->untrustworthy_tree | !tree_promote_at(u->t, b, m->coord)) {
 185                 if (UDEBUGL(3)) {
 186                         if (u->t->untrustworthy_tree)
 187                                 fprintf(stderr, "Not promoting move node in untrustworthy tree.\n");
 188                         else
 189                                 fprintf(stderr, "Warning: Cannot promote move node! Several play commands in row?\n");
 190                 }
 191                 /* Preserve dynamic komi information, though, that is important. */
 192                 u->initial_extra_komi = u->t->extra_komi;
 193                 reset_state(u);
 194                 return NULL;
 195         }
 196
 197         /* If we are a slave in a distributed engine, start pondering once
 198          * we know which move we actually played. See uct_genmove() about
 199          * the check for pass. */
 200         if (u->pondering_opt && u->slave && m->color == u->my_color && !is_pass(m->coord))
 201                 uct_pondering_start(u, b, u->t, stone_other(m->color));
 202
 203         return NULL;
 204 }
 205
 206 static char *
 207 uct_undo(struct engine *e, struct board *b)
 208 {
 209         struct uct *u = e->data;
 210
 211         if (!u->t) return NULL;
 212         uct_pondering_stop(u);
 213         u->initial_extra_komi = u->t->extra_komi;
 214         reset_state(u);
 215         return NULL;
 216 }
 217
 218 static char *
 219 uct_result(struct engine *e, struct board *b)
 220 {
 221         struct uct *u = e->data;
 222         static char reply[1024];
 223
 224         if (!u->t)
 225                 return NULL;
 226         enum stone color = u->t->root_color;
 227         struct tree_node *n = u->t->root;
 228         snprintf(reply, 1024, "%s %s %d %.2f %.1f",
 229                  stone2str(color), coord2sstr(node_coord(n), b),
 230                  n->u.playouts, tree_node_get_value(u->t, -1, n->u.value),
 231                  u->t->use_extra_komi ? u->t->extra_komi : 0);
 232         return reply;
 233 }
 234
 235 static char *
 236 uct_chat(struct engine *e, struct board *b, bool opponent, char *from, char *cmd)
 237 {
 238         struct uct *u = e->data;
 239
 240         if (!u->t)
 241                 return generic_chat(b, opponent, from, cmd, S_NONE, pass, 0, 1, u->threads, 0.0, 0.0);
 242
 243         struct tree_node *n = u->t->root;
 244         double winrate = tree_node_get_value(u->t, -1, n->u.value);
 245         double extra_komi = u->t->use_extra_komi && abs(u->t->extra_komi) >= 0.5 ? u->t->extra_komi : 0;
 246
 247         return generic_chat(b, opponent, from, cmd, u->t->root_color, node_coord(n), n->u.playouts, 1,
 248                             u->threads, winrate, extra_komi);
 249 }
 250
 251 static void
 252 uct_dead_group_list(struct engine *e, struct board *b, struct move_queue *mq)
 253 {
 254         struct uct *u = e->data;
 255
 256         /* This means the game is probably over, no use pondering on. */
 257         uct_pondering_stop(u);
 258
 259         if (u->pass_all_alive)
 260                 return; // no dead groups
 261
 262         bool mock_state = false;
 263
 264         if (!u->t) {
 265                 /* No state, but we cannot just back out - we might
 266                  * have passed earlier, only assuming some stones are
 267                  * dead, and then re-connected, only to lose counting
 268                  * when all stones are assumed alive. */
 269                 uct_prepare_move(u, b, S_BLACK); assert(u->t);
 270                 mock_state = true;
 271         }
 272         /* Make sure the ownermap is well-seeded. */
 273         while (u->ownermap.playouts < GJ_MINGAMES)
 274                 uct_playout(u, b, S_BLACK, u->t);
 275         /* Show the ownermap: */
 276         if (DEBUGL(2))
 277                 board_print_custom(b, stderr, uct_printhook_ownermap);
 278
 279         dead_group_list(u, b, mq);
 280
 281         if (mock_state) {
 282                 /* Clean up the mock state in case we will receive
 283                  * a genmove; we could get a non-alternating-move
 284                  * error from uct_prepare_move() in that case otherwise. */
 285                 reset_state(u);
 286         }
 287 }
 288
 289 static void
 290 playout_policy_done(struct playout_policy *p)
 291 {
 292         if (p->done) p->done(p);
 293         if (p->data) free(p->data);
 294         free(p);
 295 }
 296
 297 static void
 298 uct_stop(struct engine *e)
 299 {
 300         /* This is called on game over notification. However, an undo
 301          * and game resume can follow, so don't panic yet and just
 302          * relax and stop thinking so that we don't waste CPU. */
 303         struct uct *u = e->data;
 304         uct_pondering_stop(u);
 305 }
 306
 307 static void
 308 uct_done(struct engine *e)
 309 {
 310         /* This is called on engine reset, especially when clear_board
 311          * is received and new game should begin. */
 312         struct uct *u = e->data;
 313         uct_pondering_stop(u);
 314         if (u->t) reset_state(u);
 315         free(u->ownermap.map);
 316
 317         free(u->policy);
 318         free(u->random_policy);
 319         playout_policy_done(u->playout);
 320         uct_prior_done(u->prior);
 321         joseki_done(u->jdict);
 322         pluginset_done(u->plugins);
 323 }
 324
 325
 326
 327 /* Run time-limited MCTS search on foreground. */
 328 static int
 329 uct_search(struct uct *u, struct board *b, struct time_info *ti, enum stone color, struct tree *t, bool print_progress)
 330 {
 331         struct uct_search_state s;
 332         uct_search_start(u, b, color, t, ti, &s);
 333         if (UDEBUGL(2) && s.base_playouts > 0)
 334                 fprintf(stderr, "<pre-simulated %d games>\n", s.base_playouts);
 335
 336         /* The search tree is ctx->t. This is currently == . It is important
 337          * to reference ctx->t directly since the
 338          * thread manager will swap the tree pointer asynchronously. */
 339
 340         /* Now, just periodically poll the search tree. */
 341         /* Note that in case of TD_GAMES, threads will not wait for
 342          * the uct_search_check_stop() signalization. */
 343         while (1) {
 344                 time_sleep(TREE_BUSYWAIT_INTERVAL);
 345                 /* TREE_BUSYWAIT_INTERVAL should never be less than desired time, or the
 346                  * time control is broken. But if it happens to be less, we still search
 347                  * at least 100ms otherwise the move is completely random. */
 348
 349                 int i = uct_search_games(&s);
 350                 /* Print notifications etc. */
 351                 uct_search_progress(u, b, color, t, ti, &s, i);
 352                 /* Check if we should stop the search. */
 353                 if (uct_search_check_stop(u, b, color, t, ti, &s, i))
 354                         break;
 355         }
 356
 357         struct uct_thread_ctx *ctx = uct_search_stop();
 358         if (UDEBUGL(2)) tree_dump(t, u->dumpthres);
 359         if (UDEBUGL(2))
 360                 fprintf(stderr, "(avg score %f/%d; dynkomi's %f/%d value %f/%d)\n",
 361                         t->avg_score.value, t->avg_score.playouts,
 362                         u->dynkomi->score.value, u->dynkomi->score.playouts,
 363                         u->dynkomi->value.value, u->dynkomi->value.playouts);
 364         if (print_progress)
 365                 uct_progress_status(u, t, color, ctx->games, NULL);
 366
 367         if (u->debug_after.playouts > 0) {
 368                 /* Now, start an additional run of playouts, single threaded. */
 369                 struct time_info debug_ti = {
 370                         .period = TT_MOVE,
 371                         .dim = TD_GAMES,
 372                 };
 373                 debug_ti.len.games = t->root->u.playouts + u->debug_after.playouts;
 374
 375                 board_print_custom(b, stderr, uct_printhook_ownermap);
 376                 fprintf(stderr, "--8<-- UCT debug post-run begin (%d:%d) --8<--\n", u->debug_after.level, u->debug_after.playouts);
 377
 378                 int debug_level_save = debug_level;
 379                 int u_debug_level_save = u->debug_level;
 380                 int p_debug_level_save = u->playout->debug_level;
 381                 debug_level = u->debug_after.level;
 382                 u->debug_level = u->debug_after.level;
 383                 u->playout->debug_level = u->debug_after.level;
 384                 uct_halt = false;
 385
 386                 uct_playouts(u, b, color, t, &debug_ti);
 387                 tree_dump(t, u->dumpthres);
 388
 389                 uct_halt = true;
 390                 debug_level = debug_level_save;
 391                 u->debug_level = u_debug_level_save;
 392                 u->playout->debug_level = p_debug_level_save;
 393
 394                 fprintf(stderr, "--8<-- UCT debug post-run finished --8<--\n");
 395         }
 396
 397         u->played_own += ctx->games;
 398         return ctx->games;
 399 }
 400
 401 /* Start pondering background with @color to play. */
 402 static void
 403 uct_pondering_start(struct uct *u, struct board *b0, struct tree *t, enum stone color)
 404 {
 405         if (UDEBUGL(1))
 406                 fprintf(stderr, "Starting to ponder with color %s\n", stone2str(stone_other(color)));
 407         u->pondering = true;
 408
 409         /* We need a local board copy to ponder upon. */
 410         struct board *b = malloc2(sizeof(*b)); board_copy(b, b0);
 411
 412         /* *b0 did not have the genmove'd move played yet. */
 413         struct move m = { node_coord(t->root), t->root_color };
 414         int res = board_play(b, &m);
 415         assert(res >= 0);
 416         setup_dynkomi(u, b, stone_other(m.color));
 417
 418         /* Start MCTS manager thread "headless". */
 419         static struct uct_search_state s;
 420         uct_search_start(u, b, color, t, NULL, &s);
 421 }
 422
 423 /* uct_search_stop() frontend for the pondering (non-genmove) mode, and
 424  * to stop the background search for a slave in the distributed engine. */
 425 void
 426 uct_pondering_stop(struct uct *u)
 427 {
 428         if (!thread_manager_running)
 429                 return;
 430
 431         /* Stop the thread manager. */
 432         struct uct_thread_ctx *ctx = uct_search_stop();
 433         if (UDEBUGL(1)) {
 434                 if (u->pondering) fprintf(stderr, "(pondering) ");
 435                 uct_progress_status(u, ctx->t, ctx->color, ctx->games, NULL);
 436         }
 437         if (u->pondering) {
 438                 free(ctx->b);
 439                 u->pondering = false;
 440         }
 441 }
 442
 443
 444 void
 445 uct_genmove_setup(struct uct *u, struct board *b, enum stone color)
 446 {
 447         if (b->superko_violation) {
 448                 fprintf(stderr, "!!! WARNING: SUPERKO VIOLATION OCCURED BEFORE THIS MOVE\n");
 449                 fprintf(stderr, "Maybe you play with situational instead of positional superko?\n");
 450                 fprintf(stderr, "I'm going to ignore the violation, but note that I may miss\n");
 451                 fprintf(stderr, "some moves valid under this ruleset because of this.\n");
 452                 b->superko_violation = false;
 453         }
 454
 455         uct_prepare_move(u, b, color);
 456
 457         assert(u->t);
 458         u->my_color = color;
 459
 460         /* How to decide whether to use dynkomi in this game? Since we use
 461          * pondering, it's not simple "who-to-play" matter. Decide based on
 462          * the last genmove issued. */
 463         u->t->use_extra_komi = !!(u->dynkomi_mask & color);
 464         setup_dynkomi(u, b, color);
 465
 466         if (b->rules == RULES_JAPANESE)
 467                 u->territory_scoring = true;
 468
 469         /* Make pessimistic assumption about komi for Japanese rules to
 470          * avoid losing by 0.5 when winning by 0.5 with Chinese rules.
 471          * The rules usually give the same winner if the integer part of komi
 472          * is odd so we adjust the komi only if it is even (for a board of
 473          * odd size). We are not trying  to get an exact evaluation for rare
 474          * cases of seki. For details see http://home.snafu.de/jasiek/parity.html */
 475         if (u->territory_scoring && (((int)floor(b->komi) + board_size(b)) & 1)) {
 476                 b->komi += (color == S_BLACK ? 1.0 : -1.0);
 477                 if (UDEBUGL(0))
 478                         fprintf(stderr, "Setting komi to %.1f assuming Japanese rules\n",
 479                                 b->komi);
 480         }
 481 }
 482
 483 static coord_t *
 484 uct_genmove(struct engine *e, struct board *b, struct time_info *ti, enum stone color, bool pass_all_alive)
 485 {
 486         double start_time = time_now();
 487         struct uct *u = e->data;
 488         u->pass_all_alive |= pass_all_alive;
 489         uct_pondering_stop(u);
 490         uct_genmove_setup(u, b, color);
 491
 492         /* Start the Monte Carlo Tree Search! */
 493         int base_playouts = u->t->root->u.playouts;
 494         int played_games = uct_search(u, b, ti, color, u->t, false);
 495
 496         coord_t best_coord;
 497         struct tree_node *best;
 498         best = uct_search_result(u, b, color, u->pass_all_alive, played_games, base_playouts, &best_coord);
 499
 500         if (UDEBUGL(2)) {
 501                 double time = time_now() - start_time + 0.000001; /* avoid divide by zero */
 502                 fprintf(stderr, "genmove in %0.2fs (%d games/s, %d games/s/thread)\n",
 503                         time, (int)(played_games/time), (int)(played_games/time/u->threads));
 504         }
 505
 506         uct_progress_status(u, u->t, color, played_games, &best_coord);
 507
 508         if (!best) {
 509                 /* Pass or resign. */
 510                 if (is_pass(best_coord))
 511                         u->initial_extra_komi = u->t->extra_komi;
 512                 reset_state(u);
 513                 return coord_copy(best_coord);
 514         }
 515
 516         if (!u->t->untrustworthy_tree) {
 517                 tree_promote_node(u->t, &best);
 518         } else {
 519                 /* Throw away an untrustworthy tree. */
 520                 /* Preserve dynamic komi information, though, that is important. */
 521                 u->initial_extra_komi = u->t->extra_komi;
 522                 reset_state(u);
 523         }
 524
 525         /* After a pass, pondering is harmful for two reasons:
 526          * (i) We might keep pondering even when the game is over.
 527          * Of course this is the case for opponent resign as well.
 528          * (ii) More importantly, the ownermap will get skewed since
 529          * the UCT will start cutting off any playouts. */
 530         if (u->pondering_opt && u->t && !is_pass(node_coord(best))) {
 531                 uct_pondering_start(u, b, u->t, stone_other(color));
 532         }
 533         return coord_copy(best_coord);
 534 }
 535
 536
 537 bool
 538 uct_gentbook(struct engine *e, struct board *b, struct time_info *ti, enum stone color)
 539 {
 540         struct uct *u = e->data;
 541         if (!u->t) uct_prepare_move(u, b, color);
 542         assert(u->t);
 543
 544         if (ti->dim == TD_GAMES) {
 545                 /* Don't count in games that already went into the tbook. */
 546                 ti->len.games += u->t->root->u.playouts;
 547         }
 548         uct_search(u, b, ti, color, u->t, true);
 549
 550         assert(ti->dim == TD_GAMES);
 551         tree_save(u->t, b, ti->len.games / 100);
 552
 553         return true;
 554 }
 555
 556 void
 557 uct_dumptbook(struct engine *e, struct board *b, enum stone color)
 558 {
 559         struct uct *u = e->data;
 560         struct tree *t = tree_init(b, color, u->fast_alloc ? u->max_tree_size : 0,
 561                          u->max_pruned_size, u->pruning_threshold, u->local_tree_aging, 0);
 562         tree_load(t, b);
 563         tree_dump(t, 0);
 564         tree_done(t);
 565 }
 566
 567
 568 floating_t
 569 uct_evaluate_one(struct engine *e, struct board *b, struct time_info *ti, coord_t c, enum stone color)
 570 {
 571         struct uct *u = e->data;
 572
 573         struct board b2;
 574         board_copy(&b2, b);
 575         struct move m = { c, color };
 576         int res = board_play(&b2, &m);
 577         if (res < 0)
 578                 return NAN;
 579         color = stone_other(color);
 580
 581         if (u->t) reset_state(u);
 582         uct_prepare_move(u, &b2, color);
 583         assert(u->t);
 584
 585         floating_t bestval;
 586         uct_search(u, &b2, ti, color, u->t, true);
 587         struct tree_node *best = u->policy->choose(u->policy, u->t->root, &b2, color, resign);
 588         if (!best) {
 589                 bestval = NAN; // the opponent has no reply!
 590         } else {
 591                 bestval = tree_node_get_value(u->t, 1, best->u.value);
 592         }
 593
 594         reset_state(u); // clean our junk
 595
 596         return isnan(bestval) ? NAN : 1.0f - bestval;
 597 }
 598
 599 void
 600 uct_evaluate(struct engine *e, struct board *b, struct time_info *ti, floating_t *vals, enum stone color)
 601 {
 602         for (int i = 0; i < b->flen; i++) {
 603                 if (is_pass(b->f[i]))
 604                         vals[i] = NAN;
 605                 else
 606                         vals[i] = uct_evaluate_one(e, b, ti, b->f[i], color);
 607         }
 608 }
 609
 610
 611 struct uct *
 612 uct_state_init(char *arg, struct board *b)
 613 {
 614         struct uct *u = calloc2(1, sizeof(struct uct));
 615         bool pat_setup = false;
 616
 617         u->debug_level = debug_level;
 618         u->reportfreq = 10000;
 619         u->gamelen = MC_GAMELEN;
 620         u->resign_threshold = 0.2;
 621         u->sure_win_threshold = 0.95;
 622         u->mercymin = 0;
 623         u->significant_threshold = 50;
 624         u->expand_p = 8;
 625         u->dumpthres = 0.01;
 626         u->playout_amaf = true;
 627         u->amaf_prior = false;
 628         u->max_tree_size = 1408ULL * 1048576;
 629         u->fast_alloc = true;
 630         u->pruning_threshold = 0;
 631
 632         u->threads = 1;
 633         u->thread_model = TM_TREEVL;
 634         u->virtual_loss = 1;
 635
 636         u->pondering_opt = true;
 637
 638         u->fuseki_end = 20; // max time at 361*20% = 72 moves (our 36th move, still 99 to play)
 639         u->yose_start = 40; // (100-40-25)*361/100/2 = 63 moves still to play by us then
 640         u->bestr_ratio = 0.02;
 641         // 2.5 is clearly too much, but seems to compensate well for overly stern time allocations.
 642         // TODO: Further tuning and experiments with better time allocation schemes.
 643         u->best2_ratio = 2.5;
 644         // Higher values of max_maintime_ratio sometimes cause severe time trouble in tournaments
 645         // It might be necessary to reduce it to 1.5 on large board, but more tuning is needed.
 646         u->max_maintime_ratio = 2.0;
 647
 648         u->val_scale = 0; u->val_points = 40;
 649         u->dynkomi_interval = 1000;
 650         u->dynkomi_mask = S_BLACK | S_WHITE;
 651
 652         u->tenuki_d = 4;
 653         u->local_tree_aging = 80;
 654         u->local_tree_depth_decay = 1.5;
 655         u->local_tree_eval = LTE_ROOT;
 656         u->local_tree_neival = true;
 657
 658         u->max_slaves = -1;
 659         u->slave_index = -1;
 660         u->stats_delay = 0.01; // 10 ms
 661         u->shared_levels = 1;
 662
 663         u->plugins = pluginset_init(b);
 664
 665         u->jdict = joseki_load(b->size);
 666
 667         if (arg) {
 668                 char *optspec, *next = arg;
 669                 while (*next) {
 670                         optspec = next;
 671                         next += strcspn(next, ",");
 672                         if (*next) { *next++ = 0; } else { *next = 0; }
 673
 674                         char *optname = optspec;
 675                         char *optval = strchr(optspec, '=');
 676                         if (optval) *optval++ = 0;
 677
 678                         /** Basic options */
 679
 680                         if (!strcasecmp(optname, "debug")) {
 681                                 if (optval)
 682                                         u->debug_level = atoi(optval);
 683                                 else
 684                                         u->debug_level++;
 685                         } else if (!strcasecmp(optname, "reporting") && optval) {
 686                                 /* The format of output for detailed progress
 687                                  * information (such as current best move and
 688                                  * its value, etc.). */
 689                                 if (!strcasecmp(optval, "text")) {
 690                                         /* Plaintext traditional output. */
 691                                         u->reporting = UR_TEXT;
 692                                 } else if (!strcasecmp(optval, "json")) {
 693                                         /* JSON output. Implies debug=0. */
 694                                         u->reporting = UR_JSON;
 695                                         u->debug_level = 0;
 696                                 } else if (!strcasecmp(optval, "jsonbig")) {
 697                                         /* JSON output, but much more detailed.
 698                                          * Implies debug=0. */
 699                                         u->reporting = UR_JSON_BIG;
 700                                         u->debug_level = 0;
 701                                 } else {
 702                                         fprintf(stderr, "UCT: Invalid reporting format %s\n", optval);
 703                                         exit(1);
 704                                 }
 705                         } else if (!strcasecmp(optname, "reportfreq") && optval) {
 706                                 /* The progress information line will be shown
 707                                  * every <reportfreq> simulations. */
 708                                 u->reportfreq = atoi(optval);
 709                         } else if (!strcasecmp(optname, "dumpthres") && optval) {
 710                                 /* When dumping the UCT tree on output, include
 711                                  * nodes with at least this many playouts.
 712                                  * (A fraction of the total # of playouts at the
 713                                  * tree root.) */
 714                                 /* Use 0 to list all nodes with at least one
 715                                  * simulation, and -1 to list _all_ nodes. */
 716                                 u->dumpthres = atof(optval);
 717                         } else if (!strcasecmp(optname, "resign_threshold") && optval) {
 718                                 /* Resign when this ratio of games is lost
 719                                  * after GJ_MINGAMES sample is taken. */
 720                                 u->resign_threshold = atof(optval);
 721                         } else if (!strcasecmp(optname, "sure_win_threshold") && optval) {
 722                                 /* Stop reading when this ratio of games is won
 723                                  * after PLAYOUT_EARLY_BREAK_MIN sample is
 724                                  * taken. (Prevents stupid time losses,
 725                                  * friendly to human opponents.) */
 726                                 u->sure_win_threshold = atof(optval);
 727                         } else if (!strcasecmp(optname, "force_seed") && optval) {
 728                                 /* Set RNG seed at the tree setup. */
 729                                 u->force_seed = atoi(optval);
 730                         } else if (!strcasecmp(optname, "no_tbook")) {
 731                                 /* Disable UCT opening tbook. */
 732                                 u->no_tbook = true;
 733                         } else if (!strcasecmp(optname, "pass_all_alive")) {
 734                                 /* Whether to consider passing only after all
 735                                  * dead groups were removed from the board;
 736                                  * this is like all genmoves are in fact
 737                                  * kgs-genmove_cleanup. */
 738                                 u->pass_all_alive = !optval || atoi(optval);
 739                         } else if (!strcasecmp(optname, "allow_losing_pass")) {
 740                                 /* Whether to consider passing in a clear
 741                                  * but losing situation, to be scored as a loss
 742                                  * for us. */
 743                                 u->allow_losing_pass = !optval || atoi(optval);
 744                         } else if (!strcasecmp(optname, "territory_scoring")) {
 745                                 /* Use territory scoring (default is area scoring).
 746                                  * An explicit kgs-rules command overrides this. */
 747                                 u->territory_scoring = !optval || atoi(optval);
 748                         } else if (!strcasecmp(optname, "stones_only")) {
 749                                 /* Do not count eyes. Nice to teach go to kids.
 750                                  * http://strasbourg.jeudego.org/regle_strasbourgeoise.htm */
 751                                 b->rules = RULES_STONES_ONLY;
 752                                 u->pass_all_alive = true;
 753                         } else if (!strcasecmp(optname, "debug_after")) {
 754                                 /* debug_after=9:1000 will make Pachi think under
 755                                  * the normal conditions, but at the point when
 756                                  * a move is to be chosen, the tree is dumped and
 757                                  * another 1000 simulations are run single-threaded
 758                                  * with debug level 9, allowing inspection of Pachi's
 759                                  * behavior after it has thought a lot. */
 760                                 if (optval) {
 761                                         u->debug_after.level = atoi(optval);
 762                                         char *playouts = strchr(optval, ':');
 763                                         if (playouts)
 764                                                 u->debug_after.playouts = atoi(playouts+1);
 765                                         else
 766                                                 u->debug_after.playouts = 1000;
 767                                 } else {
 768                                         u->debug_after.level = 9;
 769                                         u->debug_after.playouts = 1000;
 770                                 }
 771                         } else if (!strcasecmp(optname, "banner") && optval) {
 772                                 /* Additional banner string. This must come as the
 773                                  * last engine parameter. You can use '+' instead
 774                                  * of ' ' if you are wrestling with kgsGtp. */
 775                                 if (*next) *--next = ',';
 776                                 u->banner = strdup(optval);
 777                                 for (char *b = u->banner; *b; b++) {
 778                                         if (*b == '+') *b = ' ';
 779                                 }
 780                                 break;
 781                         } else if (!strcasecmp(optname, "plugin") && optval) {
 782                                 /* Load an external plugin; filename goes before the colon,
 783                                  * extra arguments after the colon. */
 784                                 char *pluginarg = strchr(optval, ':');
 785                                 if (pluginarg)
 786                                         *pluginarg++ = 0;
 787                                 plugin_load(u->plugins, optval, pluginarg);
 788
 789                         /** UCT behavior and policies */
 790
 791                         } else if ((!strcasecmp(optname, "policy")
 792                                 /* Node selection policy. ucb1amaf is the
 793                                  * default policy implementing RAVE, while
 794                                  * ucb1 is the simple exploration/exploitation
 795                                  * policy. Policies can take further extra
 796                                  * options. */
 797                                     || !strcasecmp(optname, "random_policy")) && optval) {
 798                                 /* A policy to be used randomly with small
 799                                  * chance instead of the default policy. */
 800                                 char *policyarg = strchr(optval, ':');
 801                                 struct uct_policy **p = !strcasecmp(optname, "policy") ? &u->policy : &u->random_policy;
 802                                 if (policyarg)
 803                                         *policyarg++ = 0;
 804                                 if (!strcasecmp(optval, "ucb1")) {
 805                                         *p = policy_ucb1_init(u, policyarg);
 806                                 } else if (!strcasecmp(optval, "ucb1amaf")) {
 807                                         *p = policy_ucb1amaf_init(u, policyarg, b);
 808                                 } else {
 809                                         fprintf(stderr, "UCT: Invalid tree policy %s\n", optval);
 810                                         exit(1);
 811                                 }
 812                         } else if (!strcasecmp(optname, "playout") && optval) {
 813                                 /* Random simulation (playout) policy.
 814                                  * moggy is the default policy with large
 815                                  * amount of domain-specific knowledge and
 816                                  * heuristics. light is a simple uniformly
 817                                  * random move selection policy. */
 818                                 char *playoutarg = strchr(optval, ':');
 819                                 if (playoutarg)
 820                                         *playoutarg++ = 0;
 821                                 if (!strcasecmp(optval, "moggy")) {
 822                                         u->playout = playout_moggy_init(playoutarg, b, u->jdict);
 823                                 } else if (!strcasecmp(optval, "light")) {
 824                                         u->playout = playout_light_init(playoutarg, b);
 825                                 } else {
 826                                         fprintf(stderr, "UCT: Invalid playout policy %s\n", optval);
 827                                         exit(1);
 828                                 }
 829                         } else if (!strcasecmp(optname, "prior") && optval) {
 830                                 /* Node priors policy. When expanding a node,
 831                                  * it will seed node values heuristically
 832                                  * (most importantly, based on playout policy
 833                                  * opinion, but also with regard to other
 834                                  * things). See uct/prior.c for details.
 835                                  * Use prior=eqex=0 to disable priors. */
 836                                 u->prior = uct_prior_init(optval, b, u);
 837                         } else if (!strcasecmp(optname, "mercy") && optval) {
 838                                 /* Minimal difference of black/white captures
 839                                  * to stop playout - "Mercy Rule". Speeds up
 840                                  * hopeless playouts at the expense of some
 841                                  * accuracy. */
 842                                 u->mercymin = atoi(optval);
 843                         } else if (!strcasecmp(optname, "gamelen") && optval) {
 844                                 /* Maximum length of single simulation
 845                                  * in moves. */
 846                                 u->gamelen = atoi(optval);
 847                         } else if (!strcasecmp(optname, "expand_p") && optval) {
 848                                 /* Expand UCT nodes after it has been
 849                                  * visited this many times. */
 850                                 u->expand_p = atoi(optval);
 851                         } else if (!strcasecmp(optname, "random_policy_chance") && optval) {
 852                                 /* If specified (N), with probability 1/N, random_policy policy
 853                                  * descend is used instead of main policy descend; useful
 854                                  * if specified policy (e.g. UCB1AMAF) can make unduly biased
 855                                  * choices sometimes, you can fall back to e.g.
 856                                  * random_policy=UCB1. */
 857                                 u->random_policy_chance = atoi(optval);
 858
 859                         /** General AMAF behavior */
 860                         /* (Only relevant if the policy supports AMAF.
 861                          * More variables can be tuned as policy
 862                          * parameters.) */
 863
 864                         } else if (!strcasecmp(optname, "playout_amaf")) {
 865                                 /* Whether to include random playout moves in
 866                                  * AMAF as well. (Otherwise, only tree moves
 867                                  * are included in AMAF. Of course makes sense
 868                                  * only in connection with an AMAF policy.) */
 869                                 /* with-without: 55.5% (+-4.1) */
 870                                 if (optval && *optval == '0')
 871                                         u->playout_amaf = false;
 872                                 else
 873                                         u->playout_amaf = true;
 874                         } else if (!strcasecmp(optname, "playout_amaf_cutoff") && optval) {
 875                                 /* Keep only first N% of playout stage AMAF
 876                                  * information. */
 877                                 u->playout_amaf_cutoff = atoi(optval);
 878                         } else if (!strcasecmp(optname, "amaf_prior") && optval) {
 879                                 /* In node policy, consider prior values
 880                                  * part of the real result term or part
 881                                  * of the AMAF term? */
 882                                 u->amaf_prior = atoi(optval);
 883
 884                         /** Performance and memory management */
 885
 886                         } else if (!strcasecmp(optname, "threads") && optval) {
 887                                 /* By default, Pachi will run with only single
 888                                  * tree search thread! */
 889                                 u->threads = atoi(optval);
 890                         } else if (!strcasecmp(optname, "thread_model") && optval) {
 891                                 if (!strcasecmp(optval, "tree")) {
 892                                         /* Tree parallelization - all threads
 893                                          * grind on the same tree. */
 894                                         u->thread_model = TM_TREE;
 895                                         u->virtual_loss = 0;
 896                                 } else if (!strcasecmp(optval, "treevl")) {
 897                                         /* Tree parallelization, but also
 898                                          * with virtual losses - this discou-
 899                                          * rages most threads choosing the
 900                                          * same tree branches to read. */
 901                                         u->thread_model = TM_TREEVL;
 902                                 } else {
 903                                         fprintf(stderr, "UCT: Invalid thread model %s\n", optval);
 904                                         exit(1);
 905                                 }
 906                         } else if (!strcasecmp(optname, "virtual_loss") && optval) {
 907                                 /* Number of virtual losses added before evaluating a node. */
 908                                 u->virtual_loss = atoi(optval);
 909                         } else if (!strcasecmp(optname, "pondering")) {
 910                                 /* Keep searching even during opponent's turn. */
 911                                 u->pondering_opt = !optval || atoi(optval);
 912                         } else if (!strcasecmp(optname, "max_tree_size") && optval) {
 913                                 /* Maximum amount of memory [MiB] consumed by the move tree.
 914                                  * For fast_alloc it includes the temp tree used for pruning.
 915                                  * Default is 3072 (3 GiB). */
 916                                 u->max_tree_size = atol(optval) * 1048576;
 917                         } else if (!strcasecmp(optname, "fast_alloc")) {
 918                                 u->fast_alloc = !optval || atoi(optval);
 919                         } else if (!strcasecmp(optname, "pruning_threshold") && optval) {
 920                                 /* Force pruning at beginning of a move if the tree consumes
 921                                  * more than this [MiB]. Default is 10% of max_tree_size.
 922                                  * Increase to reduce pruning time overhead if memory is plentiful.
 923                                  * This option is meaningful only for fast_alloc. */
 924                                 u->pruning_threshold = atol(optval) * 1048576;
 925
 926                         /** Time control */
 927
 928                         } else if (!strcasecmp(optname, "best2_ratio") && optval) {
 929                                 /* If set, prolong simulating while
 930                                  * first_best/second_best playouts ratio
 931                                  * is less than best2_ratio. */
 932                                 u->best2_ratio = atof(optval);
 933                         } else if (!strcasecmp(optname, "bestr_ratio") && optval) {
 934                                 /* If set, prolong simulating while
 935                                  * best,best_best_child values delta
 936                                  * is more than bestr_ratio. */
 937                                 u->bestr_ratio = atof(optval);
 938                         } else if (!strcasecmp(optname, "max_maintime_ratio") && optval) {
 939                                 /* If set and while not in byoyomi, prolong simulating no more than
 940                                  * max_maintime_ratio times the normal desired thinking time. */
 941                                 u->max_maintime_ratio = atof(optval);
 942                         } else if (!strcasecmp(optname, "fuseki_end") && optval) {
 943                                 /* At the very beginning it's not worth thinking
 944                                  * too long because the playout evaluations are
 945                                  * very noisy. So gradually increase the thinking
 946                                  * time up to maximum when fuseki_end percent
 947                                  * of the board has been played.
 948                                  * This only applies if we are not in byoyomi. */
 949                                 u->fuseki_end = atoi(optval);
 950                         } else if (!strcasecmp(optname, "yose_start") && optval) {
 951                                 /* When yose_start percent of the board has been
 952                                  * played, or if we are in byoyomi, stop spending
 953                                  * more time and spread the remaining time
 954                                  * uniformly.
 955                                  * Between fuseki_end and yose_start, we spend
 956                                  * a constant proportion of the remaining time
 957                                  * on each move. (yose_start should actually
 958                                  * be much earlier than when real yose start,
 959                                  * but "yose" is a good short name to convey
 960                                  * the idea.) */
 961                                 u->yose_start = atoi(optval);
 962
 963                         /** Dynamic komi */
 964
 965                         } else if (!strcasecmp(optname, "dynkomi") && optval) {
 966                                 /* Dynamic komi approach; there are multiple
 967                                  * ways to adjust komi dynamically throughout
 968                                  * play. We currently support two: */
 969                                 char *dynkomiarg = strchr(optval, ':');
 970                                 if (dynkomiarg)
 971                                         *dynkomiarg++ = 0;
 972                                 if (!strcasecmp(optval, "none")) {
 973                                         u->dynkomi = uct_dynkomi_init_none(u, dynkomiarg, b);
 974                                 } else if (!strcasecmp(optval, "linear")) {
 975                                         /* You should set dynkomi_mask=1 or a very low
 976                                          * handicap_value for white. */
 977                                         u->dynkomi = uct_dynkomi_init_linear(u, dynkomiarg, b);
 978                                 } else if (!strcasecmp(optval, "adaptive")) {
 979                                         /* There are many more knobs to
 980                                          * crank - see uct/dynkomi.c. */
 981                                         u->dynkomi = uct_dynkomi_init_adaptive(u, dynkomiarg, b);
 982                                 } else {
 983                                         fprintf(stderr, "UCT: Invalid dynkomi mode %s\n", optval);
 984                                         exit(1);
 985                                 }
 986                         } else if (!strcasecmp(optname, "dynkomi_mask") && optval) {
 987                                 /* Bitmask of colors the player must be
 988                                  * for dynkomi be applied; the default dynkomi_mask=3 allows
 989                                  * dynkomi even in games where Pachi is white. */
 990                                 u->dynkomi_mask = atoi(optval);
 991                         } else if (!strcasecmp(optname, "dynkomi_interval") && optval) {
 992                                 /* If non-zero, re-adjust dynamic komi
 993                                  * throughout a single genmove reading,
 994                                  * roughly every N simulations. */
 995                                 /* XXX: Does not work with tree
 996                                  * parallelization. */
 997                                 u->dynkomi_interval = atoi(optval);
 998                         } else if (!strcasecmp(optname, "extra_komi") && optval) {
 999                                 /* Initial dynamic komi settings. This
1000                                  * is useful for the adaptive dynkomi
1001                                  * policy as the value to start with
1002                                  * (this is NOT kept fixed) in case
1003                                  * there is not enough time in the search
1004                                  * to adjust the value properly (e.g. the
1005                                  * game was interrupted). */
1006                                 u->initial_extra_komi = atof(optval);
1007
1008                         /** Node value result scaling */
1009
1010                         } else if (!strcasecmp(optname, "val_scale") && optval) {
1011                                 /* How much of the game result value should be
1012                                  * influenced by win size. Zero means it isn't. */
1013                                 u->val_scale = atof(optval);
1014                         } else if (!strcasecmp(optname, "val_points") && optval) {
1015                                 /* Maximum size of win to be scaled into game
1016                                  * result value. Zero means boardsize^2. */
1017                                 u->val_points = atoi(optval) * 2; // result values are doubled
1018                         } else if (!strcasecmp(optname, "val_extra")) {
1019                                 /* If false, the score coefficient will be simply
1020                                  * added to the value, instead of scaling the result
1021                                  * coefficient because of it. */
1022                                 u->val_extra = !optval || atoi(optval);
1023                         } else if (!strcasecmp(optname, "val_byavg")) {
1024                                 /* If true, the score included in the value will
1025                                  * be relative to average score in the current
1026                                  * search episode inst. of jigo. */
1027                                 u->val_byavg = !optval || atoi(optval);
1028                         } else if (!strcasecmp(optname, "val_bytemp")) {
1029                                 /* If true, the value scaling coefficient
1030                                  * is different based on value extremity
1031                                  * (dist. from 0.5), linear between
1032                                  * val_bytemp_min, val_scale. */
1033                                 u->val_bytemp = !optval || atoi(optval);
1034                         } else if (!strcasecmp(optname, "val_bytemp_min") && optval) {
1035                                 /* Minimum val_scale in case of val_bytemp. */
1036                                 u->val_bytemp_min = atof(optval);
1037
1038                         /** Local trees */
1039                         /* (Purely experimental. Does not work - yet!) */
1040
1041                         } else if (!strcasecmp(optname, "local_tree")) {
1042                                 /* Whether to bias exploration by local tree values. */
1043                                 u->local_tree = !optval || atoi(optval);
1044                         } else if (!strcasecmp(optname, "tenuki_d") && optval) {
1045                                 /* Tenuki distance at which to break the local tree. */
1046                                 u->tenuki_d = atoi(optval);
1047                                 if (u->tenuki_d > TREE_NODE_D_MAX + 1) {
1048                                         fprintf(stderr, "uct: tenuki_d must not be larger than TREE_NODE_D_MAX+1 %d\n", TREE_NODE_D_MAX + 1);
1049                                         exit(1);
1050                                 }
1051                         } else if (!strcasecmp(optname, "local_tree_aging") && optval) {
1052                                 /* How much to reduce local tree values between moves. */
1053                                 u->local_tree_aging = atof(optval);
1054                         } else if (!strcasecmp(optname, "local_tree_depth_decay") && optval) {
1055                                 /* With value x>0, during the descent the node
1056                                  * contributes 1/x^depth playouts in
1057                                  * the local tree. I.e., with x>1, nodes more
1058                                  * distant from local situation contribute more
1059                                  * than nodes near the root. */
1060                                 u->local_tree_depth_decay = atof(optval);
1061                         } else if (!strcasecmp(optname, "local_tree_allseq")) {
1062                                 /* If disabled, only complete sequences are stored
1063                                  * in the local tree. If this is on, also
1064                                  * subsequences starting at each move are stored. */
1065                                 u->local_tree_allseq = !optval || atoi(optval);
1066                         } else if (!strcasecmp(optname, "local_tree_neival")) {
1067                                 /* If disabled, local node value is not
1068                                  * computed just based on terminal status
1069                                  * of the coordinate, but also its neighbors. */
1070                                 u->local_tree_neival = !optval || atoi(optval);
1071                         } else if (!strcasecmp(optname, "local_tree_eval")) {
1072                                 /* How is the value inserted in the local tree
1073                                  * determined. */
1074                                 if (!strcasecmp(optval, "root"))
1075                                         /* All moves within a tree branch are
1076                                          * considered wrt. their merit
1077                                          * reaching tachtical goal of making
1078                                          * the first move in the branch
1079                                          * survive. */
1080                                         u->local_tree_eval = LTE_ROOT;
1081                                 else if (!strcasecmp(optval, "each"))
1082                                         /* Each move is considered wrt.
1083                                          * its own survival. */
1084                                         u->local_tree_eval = LTE_EACH;
1085                                 else if (!strcasecmp(optval, "total"))
1086                                         /* The tactical goal is the survival
1087                                          * of all the moves of my color and
1088                                          * non-survival of all the opponent
1089                                          * moves. Local values (and their
1090                                          * inverses) are averaged. */
1091                                         u->local_tree_eval = LTE_TOTAL;
1092                                 else {
1093                                         fprintf(stderr, "uct: unknown local_tree_eval %s\n", optval);
1094                                         exit(1);
1095                                 }
1096                         } else if (!strcasecmp(optname, "local_tree_rootchoose")) {
1097                                 /* If disabled, only moves within the local
1098                                  * tree branch are considered; the values
1099                                  * of the branch roots (i.e. root children)
1100                                  * are ignored. This may make sense together
1101                                  * with eval!=each, we consider only moves
1102                                  * that influence the goal, not the "rating"
1103                                  * of the goal itself. (The real solution
1104                                  * will be probably using criticality to pick
1105                                  * local tree branches.) */
1106                                 u->local_tree_rootchoose = !optval || atoi(optval);
1107
1108                         /** Other heuristics */
1109                         } else if (!strcasecmp(optname, "patterns")) {
1110                                 /* Load pattern database. Various modules
1111                                  * (priors, policies etc.) may make use
1112                                  * of this database. They will request
1113                                  * it automatically in that case, but you
1114                                  * can use this option to tweak the pattern
1115                                  * parameters. */
1116                                 patterns_init(&u->pat, optval, false, true);
1117                                 u->want_pat = pat_setup = true;
1118                         } else if (!strcasecmp(optname, "significant_threshold") && optval) {
1119                                 /* Some heuristics (XXX: none in mainline) rely
1120                                  * on the knowledge of the last "significant"
1121                                  * node in the descent. Such a node is
1122                                  * considered reasonably trustworthy to carry
1123                                  * some meaningful information in the values
1124                                  * of the node and its children. */
1125                                 u->significant_threshold = atoi(optval);
1126
1127                         /** Distributed engine slaves setup */
1128
1129                         } else if (!strcasecmp(optname, "slave")) {
1130                                 /* Act as slave for the distributed engine. */
1131                                 u->slave = !optval || atoi(optval);
1132                         } else if (!strcasecmp(optname, "slave_index") && optval) {
1133                                 /* Optional index if per-slave behavior is desired.
1134                                  * Must be given as index/max */
1135                                 u->slave_index = atoi(optval);
1136                                 char *p = strchr(optval, '/');
1137                                 if (p) u->max_slaves = atoi(++p);
1138                         } else if (!strcasecmp(optname, "shared_nodes") && optval) {
1139                                 /* Share at most shared_nodes between master and slave at each genmoves.
1140                                  * Must use the same value in master and slaves. */
1141                                 u->shared_nodes = atoi(optval);
1142                         } else if (!strcasecmp(optname, "shared_levels") && optval) {
1143                                 /* Share only nodes of level <= shared_levels. */
1144                                 u->shared_levels = atoi(optval);
1145                         } else if (!strcasecmp(optname, "stats_hbits") && optval) {
1146                                 /* Set hash table size to 2^stats_hbits for the shared stats. */
1147                                 u->stats_hbits = atoi(optval);
1148                         } else if (!strcasecmp(optname, "stats_delay") && optval) {
1149                                 /* How long to wait in slave for initial stats to build up before
1150                                  * replying to the genmoves command (in ms) */
1151                                 u->stats_delay = 0.001 * atof(optval);
1152
1153                         /** Presets */
1154
1155                         } else if (!strcasecmp(optname, "maximize_score")) {
1156                                 /* A combination of settings that will make
1157                                  * Pachi try to maximize his points (instead
1158                                  * of playing slack yose) or minimize his loss
1159                                  * (and proceed to counting even when losing). */
1160                                 /* Please note that this preset might be
1161                                  * somewhat weaker than normal Pachi, and the
1162                                  * score maximization is approximate; point size
1163                                  * of win/loss still should not be used to judge
1164                                  * strength of Pachi or the opponent. */
1165                                 /* See README for some further notes. */
1166                                 if (!optval || atoi(optval)) {
1167                                         /* Allow scoring a lost game. */
1168                                         u->allow_losing_pass = true;
1169                                         /* Make Pachi keep his calm when losing
1170                                          * and/or maintain winning marging. */
1171                                         /* Do not play games that are losing
1172                                          * by too much. */
1173                                         /* XXX: komi_ratchet_age=40000 is necessary
1174                                          * with losing_komi_ratchet, but 40000
1175                                          * is somewhat arbitrary value. */
1176                                         char dynkomi_args[] = "losing_komi_ratchet:komi_ratchet_age=60000:no_komi_at_game_end=0:max_losing_komi=30";
1177                                         u->dynkomi = uct_dynkomi_init_adaptive(u, dynkomi_args, b);
1178                                         /* XXX: Values arbitrary so far. */
1179                                         /* XXX: Also, is bytemp sensible when
1180                                          * combined with dynamic komi?! */
1181                                         u->val_scale = 0.01;
1182                                         u->val_bytemp = true;
1183                                         u->val_bytemp_min = 0.001;
1184                                         u->val_byavg = true;
1185                                 }
1186
1187                         } else {
1188                                 fprintf(stderr, "uct: Invalid engine argument %s or missing value\n", optname);
1189                                 exit(1);
1190                         }
1191                 }
1192         }
1193
1194         if (!u->policy)
1195                 u->policy = policy_ucb1amaf_init(u, NULL, b);
1196
1197         if (!!u->random_policy_chance ^ !!u->random_policy) {
1198                 fprintf(stderr, "uct: Only one of random_policy and random_policy_chance is set\n");
1199                 exit(1);
1200         }
1201
1202         if (!u->local_tree) {
1203                 /* No ltree aging. */
1204                 u->local_tree_aging = 1.0f;
1205         }
1206
1207         if (u->fast_alloc) {
1208                 if (u->pruning_threshold < u->max_tree_size / 10)
1209                         u->pruning_threshold = u->max_tree_size / 10;
1210                 if (u->pruning_threshold > u->max_tree_size / 2)
1211                         u->pruning_threshold = u->max_tree_size / 2;
1212
1213                 /* Limit pruning temp space to 20% of memory. Beyond this we discard
1214                  * the nodes and recompute them at the next move if necessary. */
1215                 u->max_pruned_size = u->max_tree_size / 5;
1216                 u->max_tree_size -= u->max_pruned_size;
1217         } else {
1218                 /* Reserve 5% memory in case the background free() are slower
1219                  * than the concurrent allocations. */
1220                 u->max_tree_size -= u->max_tree_size / 20;
1221         }
1222
1223         if (!u->prior)
1224                 u->prior = uct_prior_init(NULL, b, u);
1225
1226         if (!u->playout)
1227                 u->playout = playout_moggy_init(NULL, b, u->jdict);
1228         if (!u->playout->debug_level)
1229                 u->playout->debug_level = u->debug_level;
1230
1231         if (u->want_pat && !pat_setup)
1232                 patterns_init(&u->pat, NULL, false, true);
1233
1234         u->ownermap.map = malloc2(board_size2(b) * sizeof(u->ownermap.map[0]));
1235
1236         if (u->slave) {
1237                 if (!u->stats_hbits) u->stats_hbits = DEFAULT_STATS_HBITS;
1238                 if (!u->shared_nodes) u->shared_nodes = DEFAULT_SHARED_NODES;
1239                 assert(u->shared_levels * board_bits2(b) <= 8 * (int)sizeof(path_t));
1240         }
1241
1242         if (!u->dynkomi)
1243                 u->dynkomi = board_small(b) ? uct_dynkomi_init_none(u, NULL, b)
1244                         : uct_dynkomi_init_linear(u, NULL, b);
1245
1246         /* Some things remain uninitialized for now - the opening tbook
1247          * is not loaded and the tree not set up. */
1248         /* This will be initialized in setup_state() at the first move
1249          * received/requested. This is because right now we are not aware
1250          * about any komi or handicap setup and such. */
1251
1252         return u;
1253 }
1254
1255 struct engine *
1256 engine_uct_init(char *arg, struct board *b)
1257 {
1258         struct uct *u = uct_state_init(arg, b);
1259         struct engine *e = calloc2(1, sizeof(struct engine));
1260         e->name = "UCT";
1261         e->printhook = uct_printhook_ownermap;
1262         e->notify_play = uct_notify_play;
1263         e->chat = uct_chat;
1264         e->undo = uct_undo;
1265         e->result = uct_result;
1266         e->genmove = uct_genmove;
1267         e->genmoves = uct_genmoves;
1268         e->evaluate = uct_evaluate;
1269         e->dead_group_list = uct_dead_group_list;
1270         e->stop = uct_stop;
1271         e->done = uct_done;
1272         e->data = u;
1273         if (u->slave)
1274                 e->notify = uct_notify;
1275
1276         const char banner[] = "If you believe you have won but I am still playing, "
1277                 "please help me understand by capturing all dead stones. "
1278                 "Anyone can send me 'winrate' in private chat to get my assessment of the position.";
1279         if (!u->banner) u->banner = "";
1280         e->comment = malloc2(sizeof(banner) + strlen(u->banner) + 1);
1281         sprintf(e->comment, "%s %s", banner, u->banner);
1282
1283         return e;
1284 }