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 ? "final" : "interm");
  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, ", \"ownage\": [");
 143                 int f = 0;
 144                 foreach_point(t->board) {
 145                         if (board_at(t->board, c) != S_NONE) continue;
 146                         fprintf(stderr, "%s{\"%s\":{", f++ > 0 ? "," : "",
 147                                 coord2sstr(c, t->board));
 148                         floating_t drate = (floating_t) u->ownermap.map[c][S_NONE] / u->ownermap.playouts;
 149                         bool p = false;
 150 #define print_rate(color,letter) \
 151                         if (drate >= 0.001 || color == S_BLACK) { \
 152                                 floating_t rate = (floating_t) u->ownermap.map[c][color] / u->ownermap.playouts; \
 153                                 fprintf(stderr, "%s\"%c\":%.3f", p ? "," : "", letter, rate); \
 154                                 p = true; \
 155                         }
 156                         print_rate(S_BLACK, 'b');
 157                         print_rate(S_WHITE, 'w');
 158                         print_rate(S_NONE, 'd');
 159                         fprintf(stderr, "}}");
 160                 } foreach_point_end;
 161                 fprintf(stderr, "]");
 162
 163                 /* Chain status statistics. Each chain is identified
 164                  * by some stone within, and bound to a value in range
 165                  * [0,1] describing likelihood of survival. */
 166                 fprintf(stderr, ", \"chainstatus\": [");
 167                 f = 0;
 168                 foreach_point(t->board) {
 169                         group_t g = group_at(t->board, c);
 170                         if (!g || groupnext_at(t->board, c)) continue;
 171                         /* Last stone in some group. */
 172                         fprintf(stderr, "%s{\"%s\":%.3f}",
 173                                 f++ > 0 ? "," : "",
 174                                 coord2sstr(c, t->board),
 175                                 (floating_t) u->ownermap.map[c][board_at(t->board, c)] / u->ownermap.playouts);
 176                 } foreach_point_end;
 177                 fprintf(stderr, "]");
 178         }
 179
 180         fprintf(stderr, "}}\n");
 181 }
 182
 183 void
 184 uct_progress_status(struct uct *u, struct tree *t, enum stone color, int playouts, bool final)
 185 {
 186         switch (u->reporting) {
 187                 case UR_TEXT:
 188                         uct_progress_text(u, t, color, playouts, final);
 189                         break;
 190                 case UR_JSON:
 191                 case UR_JSON_BIG:
 192                         uct_progress_json(u, t, color, playouts, final,
 193                                           u->reporting == UR_JSON_BIG);
 194                         break;
 195                 default: assert(0);
 196         }
 197 }
 198
 199
 200 static void
 201 record_amaf_move(struct playout_amafmap *amaf, coord_t coord, enum stone color)
 202 {
 203         if (amaf->map[coord] == S_NONE || amaf->map[coord] == color) {
 204                 amaf->map[coord] = color;
 205         } else { // XXX: Respect amaf->record_nakade
 206                 amaf_op(amaf->map[coord], +);
 207         }
 208         amaf->game[amaf->gamelen].coord = coord;
 209         amaf->game[amaf->gamelen].color = color;
 210         amaf->gamelen++;
 211         assert(amaf->gamelen < sizeof(amaf->game) / sizeof(amaf->game[0]));
 212 }
 213
 214
 215 struct uct_playout_callback {
 216         struct uct *uct;
 217         struct tree *tree;
 218         struct tree_node *lnode;
 219 };
 220
 221
 222 static coord_t
 223 uct_playout_hook(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color, int mode)
 224 {
 225         /* XXX: This is used in some non-master branches. */
 226         return pass;
 227 }
 228
 229 static coord_t
 230 uct_playout_prepolicy(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color)
 231 {
 232         return uct_playout_hook(playout, setup, b, color, 0);
 233 }
 234
 235 static coord_t
 236 uct_playout_postpolicy(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color)
 237 {
 238         return uct_playout_hook(playout, setup, b, color, 1);
 239 }
 240
 241
 242 static int
 243 uct_leaf_node(struct uct *u, struct board *b, enum stone player_color,
 244               struct playout_amafmap *amaf,
 245               struct uct_descent *descent, int *dlen,
 246               struct tree_node *significant[2],
 247               struct tree *t, struct tree_node *n, enum stone node_color,
 248               char *spaces)
 249 {
 250         enum stone next_color = stone_other(node_color);
 251         int parity = (next_color == player_color ? 1 : -1);
 252
 253         /* We need to make sure only one thread expands the node. If
 254          * we are unlucky enough for two threads to meet in the same
 255          * node, the latter one will simply do another simulation from
 256          * the node itself, no big deal. t->nodes_size may exceed
 257          * the maximum in multi-threaded case but not by much so it's ok.
 258          * The size test must be before the test&set not after, to allow
 259          * expansion of the node later if enough nodes have been freed. */
 260         if (n->u.playouts >= u->expand_p && t->nodes_size < u->max_tree_size
 261             && !__sync_lock_test_and_set(&n->is_expanded, 1)) {
 262                 tree_expand_node(t, n, b, next_color, u, parity);
 263         }
 264         if (UDEBUGL(7))
 265                 fprintf(stderr, "%s*-- UCT playout #%d start [%s] %f\n",
 266                         spaces, n->u.playouts, coord2sstr(n->coord, t->board),
 267                         tree_node_get_value(t, parity, n->u.value));
 268
 269         struct uct_playout_callback upc = {
 270                 .uct = u,
 271                 .tree = t,
 272                 /* TODO: Don't necessarily restart the sequence walk when
 273                  * entering playout. */
 274                 .lnode = NULL,
 275         };
 276
 277         struct playout_setup ps = {
 278                 .gamelen = u->gamelen,
 279                 .mercymin = u->mercymin,
 280                 .prepolicy_hook = uct_playout_prepolicy,
 281                 .postpolicy_hook = uct_playout_postpolicy,
 282                 .hook_data = &upc,
 283         };
 284         int result = play_random_game(&ps, b, next_color,
 285                                       u->playout_amaf ? amaf : NULL,
 286                                       &u->ownermap, u->playout);
 287         if (next_color == S_WHITE) {
 288                 /* We need the result from black's perspective. */
 289                 result = - result;
 290         }
 291         if (UDEBUGL(7))
 292                 fprintf(stderr, "%s -- [%d..%d] %s random playout result %d\n",
 293                         spaces, player_color, next_color, coord2sstr(n->coord, t->board), result);
 294
 295         return result;
 296 }
 297
 298 static floating_t
 299 scale_value(struct uct *u, struct board *b, int result)
 300 {
 301         floating_t rval = result > 0 ? 1.0 : result < 0 ? 0.0 : 0.5;
 302         if (u->val_scale && result != 0) {
 303                 int vp = u->val_points;
 304                 if (!vp) {
 305                         vp = board_size(b) - 1; vp *= vp; vp *= 2;
 306                 }
 307
 308                 floating_t sval = (floating_t) abs(result) / vp;
 309                 sval = sval > 1 ? 1 : sval;
 310                 if (result < 0) sval = 1 - sval;
 311                 if (u->val_extra)
 312                         rval += u->val_scale * sval;
 313                 else
 314                         rval = (1 - u->val_scale) * rval + u->val_scale * sval;
 315                 // fprintf(stderr, "score %d => sval %f, rval %f\n", result, sval, rval);
 316         }
 317         return rval;
 318 }
 319
 320 static void
 321 record_local_sequence(struct uct *u, struct tree *t,
 322                       struct uct_descent *descent, int dlen, int di,
 323                       enum stone seq_color, floating_t rval)
 324 {
 325 #define LTREE_DEBUG if (UDEBUGL(6))
 326
 327         /* Ignore pass sequences. */
 328         if (is_pass(descent[di].node->coord))
 329                 return;
 330
 331         /* Transform the rval appropriately, based on the expected
 332          * result at the root of the sequence. */
 333         if (u->local_tree_rootseqval) {
 334                 float expval = descent[di - 1].value.value;
 335                 rval = stats_temper_value(rval, expval, u->local_tree);
 336         }
 337
 338         LTREE_DEBUG fprintf(stderr, "recording result %f in local %s sequence: ",
 339                 rval, stone2str(seq_color));
 340
 341         /* Sequences starting deeper are less relevant in general. */
 342         int pval = LTREE_PLAYOUTS_MULTIPLIER;
 343         if (u->local_tree && u->local_tree_depth_decay > 0)
 344                 pval = ((floating_t) pval) / pow(u->local_tree_depth_decay, di - 1);
 345         if (!pval) {
 346                 LTREE_DEBUG fprintf(stderr, "too deep @%d\n", di);
 347                 return;
 348         }
 349
 350         /* Pick the right local tree root... */
 351         struct tree_node *lnode = seq_color == S_BLACK ? t->ltree_black : t->ltree_white;
 352         lnode->u.playouts++;
 353
 354         /* ...and record the sequence. */
 355         int di0 = di;
 356         while (di < dlen && (di == di0 || descent[di].node->d < u->tenuki_d)) {
 357                 LTREE_DEBUG fprintf(stderr, "%s[%d] ",
 358                         coord2sstr(descent[di].node->coord, t->board),
 359                         descent[di].node->d);
 360                 lnode = tree_get_node(t, lnode, descent[di++].node->coord, true);
 361                 assert(lnode);
 362                 stats_add_result(&lnode->u, rval, pval);
 363         }
 364
 365         /* Add lnode for tenuki (pass) if we descended further. */
 366         if (di < dlen) {
 367                 LTREE_DEBUG fprintf(stderr, "pass ");
 368                 lnode = tree_get_node(t, lnode, pass, true);
 369                 assert(lnode);
 370                 stats_add_result(&lnode->u, rval, pval);
 371         }
 372
 373         LTREE_DEBUG fprintf(stderr, "\n");
 374 }
 375
 376
 377 int
 378 uct_playout(struct uct *u, struct board *b, enum stone player_color, struct tree *t)
 379 {
 380         struct board b2;
 381         board_copy(&b2, b);
 382
 383         struct playout_amafmap *amaf = NULL;
 384         if (u->policy->wants_amaf) {
 385                 amaf = calloc2(1, sizeof(*amaf));
 386                 amaf->map = calloc2(board_size2(&b2) + 1, sizeof(*amaf->map));
 387                 amaf->map++; // -1 is pass
 388         }
 389
 390         /* Walk the tree until we find a leaf, then expand it and do
 391          * a random playout. */
 392         struct tree_node *n = t->root;
 393         enum stone node_color = stone_other(player_color);
 394         assert(node_color == t->root_color);
 395
 396         /* Tree descent history. */
 397         /* XXX: This is somewhat messy since @n and descent[dlen-1].node are
 398          * redundant. */
 399         struct uct_descent descent[DESCENT_DLEN];
 400         descent[0].node = n; descent[0].lnode = NULL;
 401         int dlen = 1;
 402         /* Total value of the sequence. */
 403         struct move_stats seq_value = { .playouts = 0 };
 404         /* The last "significant" node along the descent (i.e. node
 405          * with higher than configured number of playouts). For black
 406          * and white. */
 407         struct tree_node *significant[2] = { NULL, NULL };
 408         if (n->u.playouts >= u->significant_threshold)
 409                 significant[node_color - 1] = n;
 410
 411         int result;
 412         int pass_limit = (board_size(&b2) - 2) * (board_size(&b2) - 2) / 2;
 413         int passes = is_pass(b->last_move.coord) && b->moves > 0;
 414
 415         /* debug */
 416         static char spaces[] = "\0                                                      ";
 417         /* /debug */
 418         if (UDEBUGL(8))
 419                 fprintf(stderr, "--- UCT walk with color %d\n", player_color);
 420
 421         while (!tree_leaf_node(n) && passes < 2) {
 422                 spaces[dlen - 1] = ' '; spaces[dlen] = 0;
 423
 424
 425                 /*** Choose a node to descend to: */
 426
 427                 /* Parity is chosen already according to the child color, since
 428                  * it is applied to children. */
 429                 node_color = stone_other(node_color);
 430                 int parity = (node_color == player_color ? 1 : -1);
 431
 432                 assert(dlen < DESCENT_DLEN);
 433                 descent[dlen] = descent[dlen - 1];
 434                 if (u->local_tree && (!descent[dlen].lnode || descent[dlen].node->d >= u->tenuki_d)) {
 435                         /* Start new local sequence. */
 436                         /* Remember that node_color already holds color of the
 437                          * to-be-found child. */
 438                         descent[dlen].lnode = node_color == S_BLACK ? t->ltree_black : t->ltree_white;
 439                 }
 440
 441                 if (!u->random_policy_chance || fast_random(u->random_policy_chance))
 442                         u->policy->descend(u->policy, t, &descent[dlen], parity, b2.moves > pass_limit);
 443                 else
 444                         u->random_policy->descend(u->random_policy, t, &descent[dlen], parity, b2.moves > pass_limit);
 445
 446
 447                 /*** Perform the descent: */
 448
 449                 if (descent[dlen].node->u.playouts >= u->significant_threshold) {
 450                         significant[node_color - 1] = descent[dlen].node;
 451                 }
 452
 453                 seq_value.playouts += descent[dlen].value.playouts;
 454                 seq_value.value += descent[dlen].value.value * descent[dlen].value.playouts;
 455                 n = descent[dlen++].node;
 456                 assert(n == t->root || n->parent);
 457                 if (UDEBUGL(7))
 458                         fprintf(stderr, "%s+-- UCT sent us to [%s:%d] %d,%f\n",
 459                                 spaces, coord2sstr(n->coord, t->board),
 460                                 n->coord, n->u.playouts,
 461                                 tree_node_get_value(t, parity, n->u.value));
 462
 463                 /* Add virtual loss if we need to; this is used to discourage
 464                  * other threads from visiting this node in case of multiple
 465                  * threads doing the tree search. */
 466                 if (u->virtual_loss)
 467                         stats_add_result(&n->u, node_color == S_BLACK ? 0.0 : 1.0, u->virtual_loss);
 468
 469                 assert(n->coord >= -1);
 470                 if (amaf && !is_pass(n->coord))
 471                         record_amaf_move(amaf, n->coord, node_color);
 472
 473                 struct move m = { n->coord, node_color };
 474                 int res = board_play(&b2, &m);
 475
 476                 if (res < 0 || (!is_pass(m.coord) && !group_at(&b2, m.coord)) /* suicide */
 477                     || b2.superko_violation) {
 478                         if (UDEBUGL(4)) {
 479                                 for (struct tree_node *ni = n; ni; ni = ni->parent)
 480                                         fprintf(stderr, "%s<%"PRIhash"> ", coord2sstr(ni->coord, t->board), ni->hash);
 481                                 fprintf(stderr, "marking invalid %s node %d,%d res %d group %d spk %d\n",
 482                                         stone2str(node_color), coord_x(n->coord,b), coord_y(n->coord,b),
 483                                         res, group_at(&b2, m.coord), b2.superko_violation);
 484                         }
 485                         n->hints |= TREE_HINT_INVALID;
 486                         result = 0;
 487                         goto end;
 488                 }
 489
 490                 if (is_pass(n->coord))
 491                         passes++;
 492                 else
 493                         passes = 0;
 494         }
 495
 496         if (amaf) {
 497                 amaf->game_baselen = amaf->gamelen;
 498                 amaf->record_nakade = u->playout_amaf_nakade;
 499         }
 500
 501         if (t->use_extra_komi && u->dynkomi->persim) {
 502                 b2.komi += round(u->dynkomi->persim(u->dynkomi, &b2, t, n));
 503         }
 504
 505         if (passes >= 2) {
 506                 /* XXX: No dead groups support. */
 507                 floating_t score = board_official_score(&b2, NULL);
 508                 /* Result from black's perspective (no matter who
 509                  * the player; black's perspective is always
 510                  * what the tree stores. */
 511                 result = - (score * 2);
 512
 513                 if (UDEBUGL(5))
 514                         fprintf(stderr, "[%d..%d] %s p-p scoring playout result %d (W %f)\n",
 515                                 player_color, node_color, coord2sstr(n->coord, t->board), result, score);
 516                 if (UDEBUGL(6))
 517                         board_print(&b2, stderr);
 518
 519                 board_ownermap_fill(&u->ownermap, &b2);
 520
 521         } else { // assert(tree_leaf_node(n));
 522                 /* In case of parallel tree search, the assertion might
 523                  * not hold if two threads chew on the same node. */
 524                 result = uct_leaf_node(u, &b2, player_color, amaf, descent, &dlen, significant, t, n, node_color, spaces);
 525         }
 526
 527         if (amaf && u->playout_amaf_cutoff) {
 528                 unsigned int cutoff = amaf->game_baselen;
 529                 cutoff += (amaf->gamelen - amaf->game_baselen) * u->playout_amaf_cutoff / 100;
 530                 /* Now, reconstruct the amaf map. */
 531                 memset(amaf->map, 0, board_size2(&b2) * sizeof(*amaf->map));
 532                 for (unsigned int i = 0; i < cutoff; i++) {
 533                         coord_t coord = amaf->game[i].coord;
 534                         enum stone color = amaf->game[i].color;
 535                         if (amaf->map[coord] == S_NONE || amaf->map[coord] == color) {
 536                                 amaf->map[coord] = color;
 537                         /* Nakade always recorded for in-tree part */
 538                         } else if (amaf->record_nakade || i <= amaf->game_baselen) {
 539                                 amaf_op(amaf->map[n->coord], +);
 540                         }
 541                 }
 542         }
 543
 544         /* Record the result. */
 545
 546         assert(n == t->root || n->parent);
 547         floating_t rval = scale_value(u, b, result);
 548         u->policy->update(u->policy, t, n, node_color, player_color, amaf, &b2, rval);
 549
 550         if (t->use_extra_komi) {
 551                 stats_add_result(&u->dynkomi->score, result / 2, 1);
 552                 stats_add_result(&u->dynkomi->value, rval, 1);
 553         }
 554
 555         if (u->local_tree && n->parent && !is_pass(n->coord) && dlen > 0) {
 556                 /* Possibly transform the rval appropriately. */
 557                 if (!u->local_tree_rootseqval) {
 558                         floating_t expval = seq_value.value / seq_value.playouts;
 559                         rval = stats_temper_value(rval, expval, u->local_tree);
 560                 }
 561
 562                 /* Get the local sequences and record them in ltree. */
 563                 /* We will look for sequence starts in our descent
 564                  * history, then run record_local_sequence() for each
 565                  * found sequence start; record_local_sequence() may
 566                  * pick longer sequences from descent history then,
 567                  * which is expected as it will create new lnodes. */
 568                 enum stone seq_color = player_color;
 569                 /* First move always starts a sequence. */
 570                 record_local_sequence(u, t, descent, dlen, 1, seq_color, rval);
 571                 seq_color = stone_other(seq_color);
 572                 for (int dseqi = 2; dseqi < dlen; dseqi++, seq_color = stone_other(seq_color)) {
 573                         if (u->local_tree_allseq) {
 574                                 /* We are configured to record all subsequences. */
 575                                 record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 576                                 continue;
 577                         }
 578                         if (descent[dseqi].node->d >= u->tenuki_d) {
 579                                 /* Tenuki! Record the fresh sequence. */
 580                                 record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 581                                 continue;
 582                         }
 583                         if (descent[dseqi].lnode && !descent[dseqi].lnode) {
 584                                 /* Record result for in-descent picked sequence. */
 585                                 record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 586                                 continue;
 587                         }
 588                 }
 589         }
 590
 591 end:
 592         /* We need to undo the virtual loss we added during descend. */
 593         if (u->virtual_loss) {
 594                 floating_t loss = node_color == S_BLACK ? 0.0 : 1.0;
 595                 for (; n->parent; n = n->parent) {
 596                         stats_rm_result(&n->u, loss, u->virtual_loss);
 597                         loss = 1.0 - loss;
 598                 }
 599         }
 600
 601         if (amaf) {
 602                 free(amaf->map - 1);
 603                 free(amaf);
 604         }
 605         board_done_noalloc(&b2);
 606         return result;
 607 }
 608
 609 int
 610 uct_playouts(struct uct *u, struct board *b, enum stone color, struct tree *t, struct time_info *ti)
 611 {
 612         int i;
 613         if (ti && ti->dim == TD_GAMES) {
 614                 for (i = 0; t->root->u.playouts <= ti->len.games; i++)
 615                         uct_playout(u, b, color, t);
 616         } else {
 617                 for (i = 0; !uct_halt; i++)
 618                         uct_playout(u, b, color, t);
 619         }
 620         return i;
 621 }