uct/walk.c

   1 #include <assert.h>
   2 #include <math.h>
   3 #include <pthread.h>
   4 #include <signal.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <string.h>
   8
   9 #define DEBUG
  10
  11 #include "debug.h"
  12 #include "board.h"
  13 #include "move.h"
  14 #include "playout.h"
  15 #include "probdist.h"
  16 #include "random.h"
  17 #include "uct/dynkomi.h"
  18 #include "uct/internal.h"
  19 #include "uct/search.h"
  20 #include "uct/tree.h"
  21 #include "uct/uct.h"
  22 #include "uct/walk.h"
  23
  24 #define DESCENT_DLEN 512
  25
  26
  27 void
  28 uct_progress_text(struct uct *u, struct tree *t, enum stone color, int playouts, bool final)
  29 {
  30         if (!UDEBUGL(0))
  31                 return;
  32
  33         /* Best move */
  34         struct tree_node *best = u->policy->choose(u->policy, t->root, t->board, color, resign);
  35         if (!best) {
  36                 fprintf(stderr, "... No moves left\n");
  37                 return;
  38         }
  39         fprintf(stderr, "[%d] ", playouts);
  40         fprintf(stderr, "best %f ", tree_node_get_value(t, 1, best->u.value));
  41
  42         /* Dynamic komi */
  43         if (t->use_extra_komi)
  44                 fprintf(stderr, "komi %.1f ", t->extra_komi);
  45
  46         /* Best sequence */
  47         fprintf(stderr, "| seq ");
  48         for (int depth = 0; depth < 4; depth++) {
  49                 if (best && best->u.playouts >= 25) {
  50                         fprintf(stderr, "%3s ", coord2sstr(best->coord, t->board));
  51                         best = u->policy->choose(u->policy, best, t->board, color, resign);
  52                 } else {
  53                         fprintf(stderr, "    ");
  54                 }
  55         }
  56
  57         /* Best candidates */
  58         fprintf(stderr, "| can ");
  59         int cans = 4;
  60         struct tree_node *can[cans];
  61         memset(can, 0, sizeof(can));
  62         best = t->root->children;
  63         while (best) {
  64                 int c = 0;
  65                 while ((!can[c] || best->u.playouts > can[c]->u.playouts) && ++c < cans);
  66                 for (int d = 0; d < c; d++) can[d] = can[d + 1];
  67                 if (c > 0) can[c - 1] = best;
  68                 best = best->sibling;
  69         }
  70         while (--cans >= 0) {
  71                 if (can[cans]) {
  72                         fprintf(stderr, "%3s(%.3f) ",
  73                                 coord2sstr(can[cans]->coord, t->board),
  74                                 tree_node_get_value(t, 1, can[cans]->u.value));
  75                 } else {
  76                         fprintf(stderr, "           ");
  77                 }
  78         }
  79
  80         fprintf(stderr, "\n");
  81 }
  82
  83 void
  84 uct_progress_json(struct uct *u, struct tree *t, enum stone color, int playouts, bool final, bool big)
  85 {
  86         /* Prefix indicating JSON line. */
  87         fprintf(stderr, "{\"%s\": {", final ? "move" : "frame");
  88
  89         /* Plaout count */
  90         fprintf(stderr, "\"playouts\": %d", playouts);
  91
  92         /* Dynamic komi */
  93         if (t->use_extra_komi)
  94                 fprintf(stderr, ", \"extrakomi\": %.1f", t->extra_komi);
  95
  96         struct tree_node *best = u->policy->choose(u->policy, t->root, t->board, color, resign);
  97         if (best) {
  98                 /* Best move */
  99                 fprintf(stderr, ", \"best\": {\"%s\": %f}",
 100                         coord2sstr(best->coord, t->board),
 101                         tree_node_get_value(t, 1, best->u.value));
 102
 103                 /* Best sequence */
 104                 fprintf(stderr, ", \"seq\": [");
 105                 for (int depth = 0; depth < 4; depth++) {
 106                         if (!best || best->u.playouts < 25) break;
 107                         fprintf(stderr, "%s\"%s\"", depth > 0 ? "," : "",
 108                                 coord2sstr(best->coord, t->board));
 109                         best = u->policy->choose(u->policy, best, t->board, color, resign);
 110                 }
 111                 fprintf(stderr, "]");
 112         }
 113
 114         /* Best candidates */
 115         int cans = 4;
 116         struct tree_node *can[cans];
 117         memset(can, 0, sizeof(can));
 118         best = t->root->children;
 119         while (best) {
 120                 int c = 0;
 121                 while ((!can[c] || best->u.playouts > can[c]->u.playouts) && ++c < cans);
 122                 for (int d = 0; d < c; d++) can[d] = can[d + 1];
 123                 if (c > 0) can[c - 1] = best;
 124                 best = best->sibling;
 125         }
 126         fprintf(stderr, ", \"can\": [");
 127         while (--cans >= 0) {
 128                 if (!can[cans]) break;
 129                 fprintf(stderr, "%s{\"%s\":%.3f}",
 130                         cans < 3 ? "," : "",
 131                         coord2sstr(can[cans]->coord, t->board),
 132                         tree_node_get_value(t, 1, can[cans]->u.value));
 133         }
 134         fprintf(stderr, "]");
 135
 136         if (big) {
 137                 /* Ownership statistics. {"b":val,"w":val,"d":val}
 138                  * where each val is in range [0,1] describes likelihood
 139                  * of this point becoming black, white and dame.
 140                  * If dame rate would be 0, only black rate is sent and
 141                  * white rate can be computed as 1-blackrate. */
 142                 fprintf(stderr, ", \"territstatus\": [");
 143                 int f = 0;
 144                 foreach_point(t->board) {
 145                         if (board_at(t->board, c) != S_NONE) continue;
 146                         int rate = u->ownermap.map[c][S_BLACK] * 1000 / u->ownermap.playouts;
 147                         int drate = u->ownermap.map[c][S_NONE] * 1000 / u->ownermap.playouts;
 148                         fprintf(stderr, "%s[%d,%d]", f++ > 0 ? "," : "", rate, drate);
 149                 } foreach_point_end;
 150                 fprintf(stderr, "]");
 151
 152                 /* Chain status statistics. Each chain is identified
 153                  * by some stone within, and bound to a value in range
 154                  * [0,1] describing likelihood of survival. */
 155                 fprintf(stderr, ", \"chainstatus\": [");
 156                 f = 0;
 157                 foreach_point(t->board) {
 158                         group_t g = group_at(t->board, c);
 159                         if (!g || groupnext_at(t->board, c)) continue;
 160                         /* Last stone in some group. */
 161                         fprintf(stderr, "%s{\"%s\":%.3f}",
 162                                 f++ > 0 ? "," : "",
 163                                 coord2sstr(c, t->board),
 164                                 (floating_t) u->ownermap.map[c][board_at(t->board, c)] / u->ownermap.playouts);
 165                 } foreach_point_end;
 166                 fprintf(stderr, "]");
 167         }
 168
 169         fprintf(stderr, "}}\n");
 170 }
 171
 172 void
 173 uct_progress_status(struct uct *u, struct tree *t, enum stone color, int playouts, bool final)
 174 {
 175         switch (u->reporting) {
 176                 case UR_TEXT:
 177                         uct_progress_text(u, t, color, playouts, final);
 178                         break;
 179                 case UR_JSON:
 180                 case UR_JSON_BIG:
 181                         uct_progress_json(u, t, color, playouts, final,
 182                                           u->reporting == UR_JSON_BIG);
 183                         break;
 184                 default: assert(0);
 185         }
 186 }
 187
 188
 189 static void
 190 record_amaf_move(struct playout_amafmap *amaf, coord_t coord, enum stone color)
 191 {
 192         if (amaf->map[coord] == S_NONE || amaf->map[coord] == color) {
 193                 amaf->map[coord] = color;
 194         } else { // XXX: Respect amaf->record_nakade
 195                 amaf_op(amaf->map[coord], +);
 196         }
 197         amaf->game[amaf->gamelen].coord = coord;
 198         amaf->game[amaf->gamelen].color = color;
 199         amaf->gamelen++;
 200         assert(amaf->gamelen < sizeof(amaf->game) / sizeof(amaf->game[0]));
 201 }
 202
 203
 204 struct uct_playout_callback {
 205         struct uct *uct;
 206         struct tree *tree;
 207         struct tree_node *lnode;
 208 };
 209
 210
 211 static coord_t
 212 uct_playout_hook(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color, int mode)
 213 {
 214         /* XXX: This is used in some non-master branches. */
 215         return pass;
 216 }
 217
 218 static coord_t
 219 uct_playout_prepolicy(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color)
 220 {
 221         return uct_playout_hook(playout, setup, b, color, 0);
 222 }
 223
 224 static coord_t
 225 uct_playout_postpolicy(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color)
 226 {
 227         return uct_playout_hook(playout, setup, b, color, 1);
 228 }
 229
 230
 231 static int
 232 uct_leaf_node(struct uct *u, struct board *b, enum stone player_color,
 233               struct playout_amafmap *amaf,
 234               struct uct_descent *descent, int *dlen,
 235               struct tree_node *significant[2],
 236               struct tree *t, struct tree_node *n, enum stone node_color,
 237               char *spaces)
 238 {
 239         enum stone next_color = stone_other(node_color);
 240         int parity = (next_color == player_color ? 1 : -1);
 241
 242         /* We need to make sure only one thread expands the node. If
 243          * we are unlucky enough for two threads to meet in the same
 244          * node, the latter one will simply do another simulation from
 245          * the node itself, no big deal. t->nodes_size may exceed
 246          * the maximum in multi-threaded case but not by much so it's ok.
 247          * The size test must be before the test&set not after, to allow
 248          * expansion of the node later if enough nodes have been freed. */
 249         if (n->u.playouts >= u->expand_p && t->nodes_size < u->max_tree_size
 250             && !__sync_lock_test_and_set(&n->is_expanded, 1)) {
 251                 tree_expand_node(t, n, b, next_color, u, parity);
 252         }
 253         if (UDEBUGL(7))
 254                 fprintf(stderr, "%s*-- UCT playout #%d start [%s] %f\n",
 255                         spaces, n->u.playouts, coord2sstr(n->coord, t->board),
 256                         tree_node_get_value(t, parity, n->u.value));
 257
 258         struct uct_playout_callback upc = {
 259                 .uct = u,
 260                 .tree = t,
 261                 /* TODO: Don't necessarily restart the sequence walk when
 262                  * entering playout. */
 263                 .lnode = NULL,
 264         };
 265
 266         struct playout_setup ps = {
 267                 .gamelen = u->gamelen,
 268                 .mercymin = u->mercymin,
 269                 .prepolicy_hook = uct_playout_prepolicy,
 270                 .postpolicy_hook = uct_playout_postpolicy,
 271                 .hook_data = &upc,
 272         };
 273         int result = play_random_game(&ps, b, next_color,
 274                                       u->playout_amaf ? amaf : NULL,
 275                                       &u->ownermap, u->playout);
 276         if (next_color == S_WHITE) {
 277                 /* We need the result from black's perspective. */
 278                 result = - result;
 279         }
 280         if (UDEBUGL(7))
 281                 fprintf(stderr, "%s -- [%d..%d] %s random playout result %d\n",
 282                         spaces, player_color, next_color, coord2sstr(n->coord, t->board), result);
 283
 284         return result;
 285 }
 286
 287 static floating_t
 288 scale_value(struct uct *u, struct board *b, int result)
 289 {
 290         floating_t rval = result > 0 ? 1.0 : result < 0 ? 0.0 : 0.5;
 291         if (u->val_scale && result != 0) {
 292                 int vp = u->val_points;
 293                 if (!vp) {
 294                         vp = board_size(b) - 1; vp *= vp; vp *= 2;
 295                 }
 296
 297                 floating_t sval = (floating_t) abs(result) / vp;
 298                 sval = sval > 1 ? 1 : sval;
 299                 if (result < 0) sval = 1 - sval;
 300                 if (u->val_extra)
 301                         rval += u->val_scale * sval;
 302                 else
 303                         rval = (1 - u->val_scale) * rval + u->val_scale * sval;
 304                 // fprintf(stderr, "score %d => sval %f, rval %f\n", result, sval, rval);
 305         }
 306         return rval;
 307 }
 308
 309 static void
 310 record_local_sequence(struct uct *u, struct tree *t,
 311                       struct uct_descent *descent, int dlen, int di,
 312                       enum stone seq_color, floating_t rval)
 313 {
 314 #define LTREE_DEBUG if (UDEBUGL(6))
 315
 316         /* Ignore pass sequences. */
 317         if (is_pass(descent[di].node->coord))
 318                 return;
 319
 320         /* Transform the rval appropriately, based on the expected
 321          * result at the root of the sequence. */
 322         if (u->local_tree_rootseqval) {
 323                 float expval = descent[di - 1].value.value;
 324                 rval = stats_temper_value(rval, expval, u->local_tree);
 325         }
 326
 327         LTREE_DEBUG fprintf(stderr, "recording result %f in local %s sequence: ",
 328                 rval, stone2str(seq_color));
 329
 330         /* Sequences starting deeper are less relevant in general. */
 331         int pval = LTREE_PLAYOUTS_MULTIPLIER;
 332         if (u->local_tree && u->local_tree_depth_decay > 0)
 333                 pval = ((floating_t) pval) / pow(u->local_tree_depth_decay, di - 1);
 334         if (!pval) {
 335                 LTREE_DEBUG fprintf(stderr, "too deep @%d\n", di);
 336                 return;
 337         }
 338
 339         /* Pick the right local tree root... */
 340         struct tree_node *lnode = seq_color == S_BLACK ? t->ltree_black : t->ltree_white;
 341         lnode->u.playouts++;
 342
 343         /* ...and record the sequence. */
 344         int di0 = di;
 345         while (di < dlen && (di == di0 || descent[di].node->d < u->tenuki_d)) {
 346                 LTREE_DEBUG fprintf(stderr, "%s[%d] ",
 347                         coord2sstr(descent[di].node->coord, t->board),
 348                         descent[di].node->d);
 349                 lnode = tree_get_node(t, lnode, descent[di++].node->coord, true);
 350                 assert(lnode);
 351                 stats_add_result(&lnode->u, rval, pval);
 352         }
 353
 354         /* Add lnode for tenuki (pass) if we descended further. */
 355         if (di < dlen) {
 356                 LTREE_DEBUG fprintf(stderr, "pass ");
 357                 lnode = tree_get_node(t, lnode, pass, true);
 358                 assert(lnode);
 359                 stats_add_result(&lnode->u, rval, pval);
 360         }
 361
 362         LTREE_DEBUG fprintf(stderr, "\n");
 363 }
 364
 365
 366 int
 367 uct_playout(struct uct *u, struct board *b, enum stone player_color, struct tree *t)
 368 {
 369         struct board b2;
 370         board_copy(&b2, b);
 371
 372         struct playout_amafmap *amaf = NULL;
 373         if (u->policy->wants_amaf) {
 374                 amaf = calloc2(1, sizeof(*amaf));
 375                 amaf->map = calloc2(board_size2(&b2) + 1, sizeof(*amaf->map));
 376                 amaf->map++; // -1 is pass
 377         }
 378
 379         /* Walk the tree until we find a leaf, then expand it and do
 380          * a random playout. */
 381         struct tree_node *n = t->root;
 382         enum stone node_color = stone_other(player_color);
 383         assert(node_color == t->root_color);
 384
 385         /* Tree descent history. */
 386         /* XXX: This is somewhat messy since @n and descent[dlen-1].node are
 387          * redundant. */
 388         struct uct_descent descent[DESCENT_DLEN];
 389         descent[0].node = n; descent[0].lnode = NULL;
 390         int dlen = 1;
 391         /* Total value of the sequence. */
 392         struct move_stats seq_value = { .playouts = 0 };
 393         /* The last "significant" node along the descent (i.e. node
 394          * with higher than configured number of playouts). For black
 395          * and white. */
 396         struct tree_node *significant[2] = { NULL, NULL };
 397         if (n->u.playouts >= u->significant_threshold)
 398                 significant[node_color - 1] = n;
 399
 400         int result;
 401         int pass_limit = (board_size(&b2) - 2) * (board_size(&b2) - 2) / 2;
 402         int passes = is_pass(b->last_move.coord) && b->moves > 0;
 403
 404         /* debug */
 405         static char spaces[] = "\0                                                      ";
 406         /* /debug */
 407         if (UDEBUGL(8))
 408                 fprintf(stderr, "--- UCT walk with color %d\n", player_color);
 409
 410         while (!tree_leaf_node(n) && passes < 2) {
 411                 spaces[dlen - 1] = ' '; spaces[dlen] = 0;
 412
 413
 414                 /*** Choose a node to descend to: */
 415
 416                 /* Parity is chosen already according to the child color, since
 417                  * it is applied to children. */
 418                 node_color = stone_other(node_color);
 419                 int parity = (node_color == player_color ? 1 : -1);
 420
 421                 assert(dlen < DESCENT_DLEN);
 422                 descent[dlen] = descent[dlen - 1];
 423                 if (u->local_tree && (!descent[dlen].lnode || descent[dlen].node->d >= u->tenuki_d)) {
 424                         /* Start new local sequence. */
 425                         /* Remember that node_color already holds color of the
 426                          * to-be-found child. */
 427                         descent[dlen].lnode = node_color == S_BLACK ? t->ltree_black : t->ltree_white;
 428                 }
 429
 430                 if (!u->random_policy_chance || fast_random(u->random_policy_chance))
 431                         u->policy->descend(u->policy, t, &descent[dlen], parity, b2.moves > pass_limit);
 432                 else
 433                         u->random_policy->descend(u->random_policy, t, &descent[dlen], parity, b2.moves > pass_limit);
 434
 435
 436                 /*** Perform the descent: */
 437
 438                 if (descent[dlen].node->u.playouts >= u->significant_threshold) {
 439                         significant[node_color - 1] = descent[dlen].node;
 440                 }
 441
 442                 seq_value.playouts += descent[dlen].value.playouts;
 443                 seq_value.value += descent[dlen].value.value * descent[dlen].value.playouts;
 444                 n = descent[dlen++].node;
 445                 assert(n == t->root || n->parent);
 446                 if (UDEBUGL(7))
 447                         fprintf(stderr, "%s+-- UCT sent us to [%s:%d] %d,%f\n",
 448                                 spaces, coord2sstr(n->coord, t->board),
 449                                 n->coord, n->u.playouts,
 450                                 tree_node_get_value(t, parity, n->u.value));
 451
 452                 /* Add virtual loss if we need to; this is used to discourage
 453                  * other threads from visiting this node in case of multiple
 454                  * threads doing the tree search. */
 455                 if (u->virtual_loss)
 456                         stats_add_result(&n->u, node_color == S_BLACK ? 0.0 : 1.0, u->virtual_loss);
 457
 458                 assert(n->coord >= -1);
 459                 if (amaf && !is_pass(n->coord))
 460                         record_amaf_move(amaf, n->coord, node_color);
 461
 462                 struct move m = { n->coord, node_color };
 463                 int res = board_play(&b2, &m);
 464
 465                 if (res < 0 || (!is_pass(m.coord) && !group_at(&b2, m.coord)) /* suicide */
 466                     || b2.superko_violation) {
 467                         if (UDEBUGL(4)) {
 468                                 for (struct tree_node *ni = n; ni; ni = ni->parent)
 469                                         fprintf(stderr, "%s<%"PRIhash"> ", coord2sstr(ni->coord, t->board), ni->hash);
 470                                 fprintf(stderr, "marking invalid %s node %d,%d res %d group %d spk %d\n",
 471                                         stone2str(node_color), coord_x(n->coord,b), coord_y(n->coord,b),
 472                                         res, group_at(&b2, m.coord), b2.superko_violation);
 473                         }
 474                         n->hints |= TREE_HINT_INVALID;
 475                         result = 0;
 476                         goto end;
 477                 }
 478
 479                 if (is_pass(n->coord))
 480                         passes++;
 481                 else
 482                         passes = 0;
 483         }
 484
 485         if (amaf) {
 486                 amaf->game_baselen = amaf->gamelen;
 487                 amaf->record_nakade = u->playout_amaf_nakade;
 488         }
 489
 490         if (t->use_extra_komi && u->dynkomi->persim) {
 491                 b2.komi += round(u->dynkomi->persim(u->dynkomi, &b2, t, n));
 492         }
 493
 494         if (passes >= 2) {
 495                 /* XXX: No dead groups support. */
 496                 floating_t score = board_official_score(&b2, NULL);
 497                 /* Result from black's perspective (no matter who
 498                  * the player; black's perspective is always
 499                  * what the tree stores. */
 500                 result = - (score * 2);
 501
 502                 if (UDEBUGL(5))
 503                         fprintf(stderr, "[%d..%d] %s p-p scoring playout result %d (W %f)\n",
 504                                 player_color, node_color, coord2sstr(n->coord, t->board), result, score);
 505                 if (UDEBUGL(6))
 506                         board_print(&b2, stderr);
 507
 508                 board_ownermap_fill(&u->ownermap, &b2);
 509
 510         } else { // assert(tree_leaf_node(n));
 511                 /* In case of parallel tree search, the assertion might
 512                  * not hold if two threads chew on the same node. */
 513                 result = uct_leaf_node(u, &b2, player_color, amaf, descent, &dlen, significant, t, n, node_color, spaces);
 514         }
 515
 516         if (amaf && u->playout_amaf_cutoff) {
 517                 unsigned int cutoff = amaf->game_baselen;
 518                 cutoff += (amaf->gamelen - amaf->game_baselen) * u->playout_amaf_cutoff / 100;
 519                 /* Now, reconstruct the amaf map. */
 520                 memset(amaf->map, 0, board_size2(&b2) * sizeof(*amaf->map));
 521                 for (unsigned int i = 0; i < cutoff; i++) {
 522                         coord_t coord = amaf->game[i].coord;
 523                         enum stone color = amaf->game[i].color;
 524                         if (amaf->map[coord] == S_NONE || amaf->map[coord] == color) {
 525                                 amaf->map[coord] = color;
 526                         /* Nakade always recorded for in-tree part */
 527                         } else if (amaf->record_nakade || i <= amaf->game_baselen) {
 528                                 amaf_op(amaf->map[n->coord], +);
 529                         }
 530                 }
 531         }
 532
 533         /* Record the result. */
 534
 535         assert(n == t->root || n->parent);
 536         floating_t rval = scale_value(u, b, result);
 537         u->policy->update(u->policy, t, n, node_color, player_color, amaf, &b2, rval);
 538
 539         if (t->use_extra_komi) {
 540                 stats_add_result(&u->dynkomi->score, result / 2, 1);
 541                 stats_add_result(&u->dynkomi->value, rval, 1);
 542         }
 543
 544         if (u->local_tree && n->parent && !is_pass(n->coord) && dlen > 0) {
 545                 /* Possibly transform the rval appropriately. */
 546                 if (!u->local_tree_rootseqval) {
 547                         floating_t expval = seq_value.value / seq_value.playouts;
 548                         rval = stats_temper_value(rval, expval, u->local_tree);
 549                 }
 550
 551                 /* Get the local sequences and record them in ltree. */
 552                 /* We will look for sequence starts in our descent
 553                  * history, then run record_local_sequence() for each
 554                  * found sequence start; record_local_sequence() may
 555                  * pick longer sequences from descent history then,
 556                  * which is expected as it will create new lnodes. */
 557                 enum stone seq_color = player_color;
 558                 /* First move always starts a sequence. */
 559                 record_local_sequence(u, t, descent, dlen, 1, seq_color, rval);
 560                 seq_color = stone_other(seq_color);
 561                 for (int dseqi = 2; dseqi < dlen; dseqi++, seq_color = stone_other(seq_color)) {
 562                         if (u->local_tree_allseq) {
 563                                 /* We are configured to record all subsequences. */
 564                                 record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 565                                 continue;
 566                         }
 567                         if (descent[dseqi].node->d >= u->tenuki_d) {
 568                                 /* Tenuki! Record the fresh sequence. */
 569                                 record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 570                                 continue;
 571                         }
 572                         if (descent[dseqi].lnode && !descent[dseqi].lnode) {
 573                                 /* Record result for in-descent picked sequence. */
 574                                 record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 575                                 continue;
 576                         }
 577                 }
 578         }
 579
 580 end:
 581         /* We need to undo the virtual loss we added during descend. */
 582         if (u->virtual_loss) {
 583                 floating_t loss = node_color == S_BLACK ? 0.0 : 1.0;
 584                 for (; n->parent; n = n->parent) {
 585                         stats_rm_result(&n->u, loss, u->virtual_loss);
 586                         loss = 1.0 - loss;
 587                 }
 588         }
 589
 590         if (amaf) {
 591                 free(amaf->map - 1);
 592                 free(amaf);
 593         }
 594         board_done_noalloc(&b2);
 595         return result;
 596 }
 597
 598 int
 599 uct_playouts(struct uct *u, struct board *b, enum stone color, struct tree *t, struct time_info *ti)
 600 {
 601         int i;
 602         if (ti && ti->dim == TD_GAMES) {
 603                 for (i = 0; t->root->u.playouts <= ti->len.games; i++)
 604                         uct_playout(u, b, color, t);
 605         } else {
 606                 for (i = 0; !uct_halt; i++)
 607                         uct_playout(u, b, color, t);
 608         }
 609         return i;
 610 }