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 "playout/elo.h"
  16 #include "probdist.h"
  17 #include "random.h"
  18 #include "uct/dynkomi.h"
  19 #include "uct/internal.h"
  20 #include "uct/search.h"
  21 #include "uct/tree.h"
  22 #include "uct/uct.h"
  23 #include "uct/walk.h"
  24
  25 void
  26 uct_progress_status(struct uct *u, struct tree *t, enum stone color, int playouts)
  27 {
  28         if (!UDEBUGL(0))
  29                 return;
  30
  31         /* Best move */
  32         struct tree_node *best = u->policy->choose(u->policy, t->root, t->board, color, resign);
  33         if (!best) {
  34                 fprintf(stderr, "... No moves left\n");
  35                 return;
  36         }
  37         fprintf(stderr, "[%d] ", playouts);
  38         fprintf(stderr, "best %f ", tree_node_get_value(t, 1, best->u.value));
  39
  40         /* Dynamic komi */
  41         if (t->use_extra_komi)
  42                 fprintf(stderr, "komi %.1f ", t->extra_komi);
  43
  44         /* Best sequence */
  45         fprintf(stderr, "| seq ");
  46         for (int depth = 0; depth < 4; depth++) {
  47                 if (best && best->u.playouts >= 25) {
  48                         fprintf(stderr, "%3s ", coord2sstr(best->coord, t->board));
  49                         best = u->policy->choose(u->policy, best, t->board, color, resign);
  50                 } else {
  51                         fprintf(stderr, "    ");
  52                 }
  53         }
  54
  55         /* Best candidates */
  56         fprintf(stderr, "| can ");
  57         int cans = 4;
  58         struct tree_node *can[cans];
  59         memset(can, 0, sizeof(can));
  60         best = t->root->children;
  61         while (best) {
  62                 int c = 0;
  63                 while ((!can[c] || best->u.playouts > can[c]->u.playouts) && ++c < cans);
  64                 for (int d = 0; d < c; d++) can[d] = can[d + 1];
  65                 if (c > 0) can[c - 1] = best;
  66                 best = best->sibling;
  67         }
  68         while (--cans >= 0) {
  69                 if (can[cans]) {
  70                         fprintf(stderr, "%3s(%.3f) ",
  71                                 coord2sstr(can[cans]->coord, t->board),
  72                                 tree_node_get_value(t, 1, can[cans]->u.value));
  73                 } else {
  74                         fprintf(stderr, "           ");
  75                 }
  76         }
  77
  78         fprintf(stderr, "\n");
  79 }
  80
  81
  82 static void
  83 record_amaf_move(struct playout_amafmap *amaf, coord_t coord, enum stone color)
  84 {
  85         if (amaf->map[coord] == S_NONE || amaf->map[coord] == color) {
  86                 amaf->map[coord] = color;
  87         } else { // XXX: Respect amaf->record_nakade
  88                 amaf_op(amaf->map[coord], +);
  89         }
  90         amaf->game[amaf->gamelen].coord = coord;
  91         amaf->game[amaf->gamelen].color = color;
  92         amaf->gamelen++;
  93         assert(amaf->gamelen < sizeof(amaf->game) / sizeof(amaf->game[0]));
  94 }
  95
  96 static double
  97 ltree_node_gamma(struct tree_node *li, enum stone color)
  98 {
  99         /* TODO: How to do this? */
 100         #define li_value(color, li) (li->u.playouts * (color == S_BLACK ? li->u.value : (1 - li->u.value)))
 101         return 0.5 + li_value(color, li);
 102 }
 103
 104
 105 struct uct_playout_callback {
 106         struct uct *uct;
 107         struct tree *tree;
 108         struct tree_node *lnode;
 109
 110         coord_t *treepool[2];
 111         int treepool_n[2];
 112 };
 113
 114 static void
 115 uct_playout_probdist(void *data, struct board *b, enum stone to_play, struct probdist *pd)
 116 {
 117         /* Create probability distribution according to found local tree
 118          * sequence. */
 119         struct uct_playout_callback *upc = data;
 120         assert(upc && upc->tree && pd && b);
 121         coord_t c = b->last_move.coord;
 122         enum stone color = b->last_move.color;
 123
 124         if (is_pass(c)) {
 125                 /* Break local sequence. */
 126                 upc->lnode = NULL;
 127         } else if (upc->lnode) {
 128                 /* Try to follow local sequence. */
 129                 upc->lnode = tree_get_node(upc->tree, upc->lnode, c, false);
 130         }
 131
 132         if (!upc->lnode || !upc->lnode->children) {
 133                 /* There's no local sequence, start new one! */
 134                 upc->lnode = color == S_BLACK ? upc->tree->ltree_black : upc->tree->ltree_white;
 135                 upc->lnode = tree_get_node(upc->tree, upc->lnode, c, false);
 136         }
 137
 138         if (!upc->lnode || !upc->lnode->children) {
 139                 /* We have no local sequence and we cannot find any starting
 140                  * by node corresponding to last move. */
 141                 if (!upc->uct->local_tree_pseqroot) {
 142                         /* Give up then, we have nothing to contribute. */
 143                         return;
 144                 }
 145                 /* Construct probability distribution from possible first
 146                  * sequence move. Remember that @color is color of the
 147                  * *last* move. */
 148                 upc->lnode = color == S_BLACK ? upc->tree->ltree_white : upc->tree->ltree_black;
 149                 if (!upc->lnode->children) {
 150                         /* We don't even have anything in our tree yet. */
 151                         return;
 152                 }
 153         }
 154
 155         /* The probdist has the right structure only if BOARD_GAMMA is defined. */
 156 #ifndef BOARD_GAMMA
 157         assert(0);
 158 #endif
 159
 160         /* Construct probability distribution from lnode children. */
 161         struct tree_node *li = upc->lnode->children;
 162         assert(li);
 163         if (is_pass(li->coord)) {
 164                 /* Tenuki. */
 165                 /* TODO: Spread tenuki gamma over all moves we don't touch. */
 166                 li = li->sibling;
 167         }
 168         for (; li; li = li->sibling) {
 169                 if (board_at(b, li->coord) != S_NONE)
 170                         continue;
 171                 double gamma = fixp_to_double(pd->items[li->coord]) * ltree_node_gamma(li, to_play);
 172                 probdist_set(pd, li->coord, double_to_fixp(gamma));
 173         }
 174 }
 175
 176
 177 static coord_t
 178 uct_playout_hook(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color, int mode)
 179 {
 180         struct uct_playout_callback *upc = setup->hook_data;
 181         struct uct *u = upc->uct;
 182
 183         if (u->treepool_chance[mode] > fast_random(100) && upc->treepool[color - 1]) {
 184                 assert(upc->treepool_n[color - 1] > 0);
 185                 coord_t treepool_move = upc->treepool[color - 1][fast_random(upc->treepool_n[color - 1])];
 186                 if (board_is_valid_play(b, color, treepool_move))
 187                         return treepool_move;
 188         }
 189         return pass;
 190 }
 191
 192 static coord_t
 193 uct_playout_prepolicy(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color)
 194 {
 195         return uct_playout_hook(playout, setup, b, color, 0);
 196 }
 197
 198 static coord_t
 199 uct_playout_postpolicy(struct playout_policy *playout, struct playout_setup *setup, struct board *b, enum stone color)
 200 {
 201         return uct_playout_hook(playout, setup, b, color, 1);
 202 }
 203
 204 double
 205 treepool_node_value(struct uct *u, struct tree *tree, int parity, struct tree_node *node)
 206 {
 207         /* XXX: Playouts get cast to double */
 208         switch (u->treepool_type) {
 209                 case UTT_RAVE_PLAYOUTS:
 210                         return node->amaf.playouts;
 211                 case UTT_RAVE_VALUE:
 212                         return tree_node_get_value(tree, parity, node->amaf.value);
 213                 case UTT_UCT_PLAYOUTS:
 214                         return node->u.playouts;
 215                 case UTT_UCT_VALUE:
 216                         return tree_node_get_value(tree, parity, node->u.value);
 217                 case UTT_EVALUATE:
 218                 {
 219                         struct uct_descent d = { .node = node };
 220                         assert(u->policy->evaluate);
 221                         return u->policy->evaluate(u->policy, tree, &d, parity);
 222                 }
 223                 default: assert(0);
 224         }
 225         return -1;
 226 }
 227
 228 static void
 229 treepool_setup(struct uct_playout_callback *upc, struct tree_node *node, int color)
 230 {
 231         struct uct *u = upc->uct;
 232         int parity = ((node->depth ^ upc->tree->root->depth) & 1) ? -1 : 1;
 233
 234         /* XXX: Naive O(N^2) way. */
 235         for (int i = 0; i < u->treepool_size; i++) {
 236                 /* For each item, find the highest
 237                  * node not in the pool yet. */
 238                 struct tree_node *best = NULL;
 239                 double best_val = -1;
 240
 241                 // first comes pass which we skip
 242                 for (struct tree_node *ni = node->children->sibling; ni; ni = ni->sibling) {
 243                         /* Do we already have it? */
 244                         bool have = false;
 245                         for (int j = 0; j < upc->treepool_n[color]; j++)
 246                                 if (upc->treepool[color][j] == ni->coord) {
 247                                         have = true;
 248                                         break;
 249                                 }
 250                         if (have)
 251                                 continue;
 252
 253                         double i_val = treepool_node_value(u, upc->tree, parity, ni);
 254                         if (i_val > best_val) {
 255                                 best = node;
 256                                 best_val = i_val;
 257                         }
 258                 }
 259
 260                 if (!best) break;
 261                 upc->treepool[color][upc->treepool_n[color]++] = best->coord;
 262         }
 263 }
 264
 265
 266 static int
 267 uct_leaf_node(struct uct *u, struct board *b, enum stone player_color,
 268               struct playout_amafmap *amaf, struct uct_descent *descent,
 269               struct tree *t, struct tree_node *n, enum stone node_color,
 270               char *spaces)
 271 {
 272         enum stone next_color = stone_other(node_color);
 273         int parity = (next_color == player_color ? 1 : -1);
 274
 275         /* We need to make sure only one thread expands the node. If
 276          * we are unlucky enough for two threads to meet in the same
 277          * node, the latter one will simply do another simulation from
 278          * the node itself, no big deal. t->nodes_size may exceed
 279          * the maximum in multi-threaded case but not by much so it's ok.
 280          * The size test must be before the test&set not after, to allow
 281          * expansion of the node later if enough nodes have been freed. */
 282         if (n->u.playouts >= u->expand_p && t->nodes_size < u->max_tree_size
 283             && !__sync_lock_test_and_set(&n->is_expanded, 1)) {
 284                 tree_expand_node(t, n, b, next_color, u, parity);
 285         }
 286         if (UDEBUGL(7))
 287                 fprintf(stderr, "%s*-- UCT playout #%d start [%s] %f\n",
 288                         spaces, n->u.playouts, coord2sstr(n->coord, t->board),
 289                         tree_node_get_value(t, parity, n->u.value));
 290
 291         struct uct_playout_callback upc = {
 292                 .uct = u,
 293                 .tree = t,
 294                 /* TODO: Don't necessarily restart the sequence walk when
 295                  * entering playout. */
 296                 .lnode = NULL,
 297         };
 298
 299         if (u->local_tree_playout) {
 300                 /* N.B.: We know this is ELO playout. */
 301                 playout_elo_callback(u->playout, uct_playout_probdist, &upc);
 302         }
 303
 304         coord_t pool[2][u->treepool_size];
 305         if (u->treepool_chance[0] + u->treepool_chance[1] > 0) {
 306                 for (int color = 0; color < 2; color++) {
 307                         /* Prepare tree-based pool of moves to try forcing
 308                          * during the playout. */
 309                         /* We consider the children of the last significant
 310                          * node, picking top N choices. */
 311                         struct tree_node *n = descent->significant[color];
 312                         if (!n || !n->children || !n->children->sibling) {
 313                                 /* No significant node, or it's childless or has
 314                                  * only pass as its child. */
 315                                 upc.treepool[color] = NULL;
 316                                 upc.treepool_n[color] = 0;
 317                         } else {
 318                                 upc.treepool[color] = (coord_t *) &pool[color];
 319                                 treepool_setup(&upc, n, color);
 320                         }
 321                 }
 322         }
 323
 324         struct playout_setup ps = {
 325                 .gamelen = u->gamelen,
 326                 .mercymin = u->mercymin,
 327                 .prepolicy_hook = uct_playout_prepolicy,
 328                 .postpolicy_hook = uct_playout_postpolicy,
 329                 .hook_data = &upc,
 330         };
 331         int result = play_random_game(&ps, b, next_color,
 332                                       u->playout_amaf ? amaf : NULL,
 333                                       &u->ownermap, u->playout);
 334         if (next_color == S_WHITE) {
 335                 /* We need the result from black's perspective. */
 336                 result = - result;
 337         }
 338         if (UDEBUGL(7))
 339                 fprintf(stderr, "%s -- [%d..%d] %s random playout result %d\n",
 340                         spaces, player_color, next_color, coord2sstr(n->coord, t->board), result);
 341
 342         return result;
 343 }
 344
 345 static float
 346 scale_value(struct uct *u, struct board *b, int result)
 347 {
 348         float rval = result > 0;
 349         if (u->val_scale) {
 350                 int vp = u->val_points;
 351                 if (!vp) {
 352                         vp = board_size(b) - 1; vp *= vp; vp *= 2;
 353                 }
 354
 355                 float sval = (float) abs(result) / vp;
 356                 sval = sval > 1 ? 1 : sval;
 357                 if (result < 0) sval = 1 - sval;
 358                 if (u->val_extra)
 359                         rval += u->val_scale * sval;
 360                 else
 361                         rval = (1 - u->val_scale) * rval + u->val_scale * sval;
 362                 // fprintf(stderr, "score %d => sval %f, rval %f\n", result, sval, rval);
 363         }
 364         return rval;
 365 }
 366
 367 static void
 368 record_local_sequence(struct uct *u, struct tree *t,
 369                       struct uct_descent *descent, int dlen, int di,
 370                       enum stone seq_color, float rval)
 371 {
 372         /* Ignore pass sequences. */
 373         if (is_pass(descent[di].node->coord))
 374                 return;
 375
 376 #define LTREE_DEBUG if (UDEBUGL(6))
 377         LTREE_DEBUG fprintf(stderr, "recording result %f in local %s sequence: ",
 378                 rval, stone2str(seq_color));
 379         int di0 = di;
 380
 381         /* Pick the right local tree root... */
 382         struct tree_node *lnode = seq_color == S_BLACK ? t->ltree_black : t->ltree_white;
 383         lnode->u.playouts++;
 384
 385         /* ...and record the sequence. */
 386         while (di < dlen && (di == di0 || descent[di].node->d < u->tenuki_d)) {
 387                 LTREE_DEBUG fprintf(stderr, "%s[%d] ",
 388                         coord2sstr(descent[di].node->coord, t->board),
 389                         descent[di].node->d);
 390                 lnode = tree_get_node(t, lnode, descent[di++].node->coord, true);
 391                 assert(lnode);
 392                 stats_add_result(&lnode->u, rval, 1);
 393         }
 394
 395         /* Add lnode for tenuki (pass) if we descended further. */
 396         if (di < dlen) {
 397                 LTREE_DEBUG fprintf(stderr, "pass ");
 398                 lnode = tree_get_node(t, lnode, pass, true);
 399                 assert(lnode);
 400                 stats_add_result(&lnode->u, rval, 1);
 401         }
 402
 403         LTREE_DEBUG fprintf(stderr, "\n");
 404 }
 405
 406
 407 int
 408 uct_playout(struct uct *u, struct board *b, enum stone player_color, struct tree *t)
 409 {
 410         struct board b2;
 411         board_copy(&b2, b);
 412
 413         struct playout_amafmap *amaf = NULL;
 414         if (u->policy->wants_amaf) {
 415                 amaf = calloc2(1, sizeof(*amaf));
 416                 amaf->map = calloc2(board_size2(&b2) + 1, sizeof(*amaf->map));
 417                 amaf->map++; // -1 is pass
 418         }
 419
 420         /* Walk the tree until we find a leaf, then expand it and do
 421          * a random playout. */
 422         struct tree_node *n = t->root;
 423         enum stone node_color = stone_other(player_color);
 424         assert(node_color == t->root_color);
 425
 426         /* Tree descent history. */
 427         /* XXX: This is somewhat messy since @n and descent[dlen-1].node are
 428          * redundant. */
 429         #define DLEN 512
 430         struct uct_descent descent[DLEN];
 431         descent[0].node = n; descent[0].lnode = NULL;
 432         descent[0].significant[0] = descent[0].significant[1] = NULL;
 433         int dlen = 1;
 434         /* Total value of the sequence. */
 435         struct move_stats seq_value = { .playouts = 0 };
 436
 437         int result;
 438         int pass_limit = (board_size(&b2) - 2) * (board_size(&b2) - 2) / 2;
 439         int passes = is_pass(b->last_move.coord) && b->moves > 0;
 440
 441         /* debug */
 442         int depth = 0;
 443         static char spaces[] = "\0                                                      ";
 444         /* /debug */
 445         if (UDEBUGL(8))
 446                 fprintf(stderr, "--- UCT walk with color %d\n", player_color);
 447
 448         while (!tree_leaf_node(n) && passes < 2) {
 449                 spaces[depth++] = ' '; spaces[depth] = 0;
 450
 451
 452                 /*** Choose a node to descend to: */
 453
 454                 /* Parity is chosen already according to the child color, since
 455                  * it is applied to children. */
 456                 node_color = stone_other(node_color);
 457                 int parity = (node_color == player_color ? 1 : -1);
 458
 459                 assert(dlen < DLEN);
 460                 descent[dlen] = descent[dlen - 1];
 461                 if (u->local_tree && (!descent[dlen].lnode || descent[dlen].node->d >= u->tenuki_d)) {
 462                         /* Start new local sequence. */
 463                         /* Remember that node_color already holds color of the
 464                          * to-be-found child. */
 465                         descent[dlen].lnode = node_color == S_BLACK ? t->ltree_black : t->ltree_white;
 466                 }
 467
 468                 if (!u->random_policy_chance || fast_random(u->random_policy_chance))
 469                         u->policy->descend(u->policy, t, &descent[dlen], parity, b2.moves > pass_limit);
 470                 else
 471                         u->random_policy->descend(u->random_policy, t, &descent[dlen], parity, b2.moves > pass_limit);
 472
 473
 474                 /*** Perform the descent: */
 475
 476                 if (descent[dlen].node->u.playouts >= u->significant_threshold) {
 477                         descent[dlen].significant[node_color - 1] = n;
 478                 }
 479
 480                 seq_value.playouts += descent[dlen].value.playouts;
 481                 seq_value.value += descent[dlen].value.value * descent[dlen].value.playouts;
 482                 n = descent[dlen++].node;
 483                 assert(n == t->root || n->parent);
 484                 if (UDEBUGL(7))
 485                         fprintf(stderr, "%s+-- UCT sent us to [%s:%d] %f\n",
 486                                 spaces, coord2sstr(n->coord, t->board), n->coord,
 487                                 tree_node_get_value(t, parity, n->u.value));
 488
 489                 /* Add virtual loss if we need to; this is used to discourage
 490                  * other threads from visiting this node in case of multiple
 491                  * threads doing the tree search. */
 492                 if (u->virtual_loss)
 493                         stats_add_result(&n->u, tree_parity(t, parity) > 0 ? 0 : 1, 1);
 494
 495                 assert(n->coord >= -1);
 496                 if (amaf && !is_pass(n->coord))
 497                         record_amaf_move(amaf, n->coord, node_color);
 498
 499                 struct move m = { n->coord, node_color };
 500                 int res = board_play(&b2, &m);
 501
 502                 if (res < 0 || (!is_pass(m.coord) && !group_at(&b2, m.coord)) /* suicide */
 503                     || b2.superko_violation) {
 504                         if (UDEBUGL(4)) {
 505                                 for (struct tree_node *ni = n; ni; ni = ni->parent)
 506                                         fprintf(stderr, "%s<%"PRIhash"> ", coord2sstr(ni->coord, t->board), ni->hash);
 507                                 fprintf(stderr, "marking invalid %s node %d,%d res %d group %d spk %d\n",
 508                                         stone2str(node_color), coord_x(n->coord,b), coord_y(n->coord,b),
 509                                         res, group_at(&b2, m.coord), b2.superko_violation);
 510                         }
 511                         n->hints |= TREE_HINT_INVALID;
 512                         result = 0;
 513                         goto end;
 514                 }
 515
 516                 if (is_pass(n->coord))
 517                         passes++;
 518                 else
 519                         passes = 0;
 520         }
 521
 522         if (amaf) {
 523                 amaf->game_baselen = amaf->gamelen;
 524                 amaf->record_nakade = u->playout_amaf_nakade;
 525         }
 526
 527         if (t->use_extra_komi && u->dynkomi->persim) {
 528                 b2.komi += round(u->dynkomi->persim(u->dynkomi, &b2, t, n));
 529         }
 530
 531         if (passes >= 2) {
 532                 /* XXX: No dead groups support. */
 533                 float score = board_official_score(&b2, NULL);
 534                 /* Result from black's perspective (no matter who
 535                  * the player; black's perspective is always
 536                  * what the tree stores. */
 537                 result = - (score * 2);
 538
 539                 if (UDEBUGL(5))
 540                         fprintf(stderr, "[%d..%d] %s p-p scoring playout result %d (W %f)\n",
 541                                 player_color, node_color, coord2sstr(n->coord, t->board), result, score);
 542                 if (UDEBUGL(6))
 543                         board_print(&b2, stderr);
 544
 545                 board_ownermap_fill(&u->ownermap, &b2);
 546
 547         } else { // assert(tree_leaf_node(n));
 548                 /* In case of parallel tree search, the assertion might
 549                  * not hold if two threads chew on the same node. */
 550                 result = uct_leaf_node(u, &b2, player_color, amaf, &descent[dlen - 1], t, n, node_color, spaces);
 551         }
 552
 553         if (amaf && u->playout_amaf_cutoff) {
 554                 unsigned int cutoff = amaf->game_baselen;
 555                 cutoff += (amaf->gamelen - amaf->game_baselen) * u->playout_amaf_cutoff / 100;
 556                 /* Now, reconstruct the amaf map. */
 557                 memset(amaf->map, 0, board_size2(&b2) * sizeof(*amaf->map));
 558                 for (unsigned int i = 0; i < cutoff; i++) {
 559                         coord_t coord = amaf->game[i].coord;
 560                         enum stone color = amaf->game[i].color;
 561                         if (amaf->map[coord] == S_NONE || amaf->map[coord] == color) {
 562                                 amaf->map[coord] = color;
 563                         /* Nakade always recorded for in-tree part */
 564                         } else if (amaf->record_nakade || i <= amaf->game_baselen) {
 565                                 amaf_op(amaf->map[n->coord], +);
 566                         }
 567                 }
 568         }
 569
 570         assert(n == t->root || n->parent);
 571         if (result != 0) {
 572                 float rval = scale_value(u, b, result);
 573                 u->policy->update(u->policy, t, n, node_color, player_color, amaf, rval);
 574
 575                 if (t->use_extra_komi) {
 576                         stats_add_result(&u->dynkomi->score, result / 2, 1);
 577                         stats_add_result(&u->dynkomi->value, rval, 1);
 578                 }
 579
 580                 if (u->local_tree && n->parent && !is_pass(n->coord) && dlen > 0) {
 581                         /* Possibly transform the rval appropriately. */
 582                         float expval = seq_value.value / seq_value.playouts;
 583                         rval = stats_temper_value(rval, expval, u->local_tree);
 584
 585                         /* Get the local sequences and record them in ltree. */
 586                         /* We will look for sequence starts in our descent
 587                          * history, then run record_local_sequence() for each
 588                          * found sequence start; record_local_sequence() may
 589                          * pick longer sequences from descent history then,
 590                          * which is expected as it will create new lnodes. */
 591                         enum stone seq_color = player_color;
 592                         /* First move always starts a sequence. */
 593                         record_local_sequence(u, t, descent, dlen, 1, seq_color, rval);
 594                         seq_color = stone_other(seq_color);
 595                         for (int dseqi = 2; dseqi < dlen; dseqi++, seq_color = stone_other(seq_color)) {
 596                                 if (u->local_tree_allseq) {
 597                                         /* We are configured to record all subsequences. */
 598                                         record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 599                                         continue;
 600                                 }
 601                                 if (descent[dseqi].node->d >= u->tenuki_d) {
 602                                         /* Tenuki! Record the fresh sequence. */
 603                                         record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 604                                         continue;
 605                                 }
 606                                 if (descent[dseqi].lnode && !descent[dseqi].lnode) {
 607                                         /* Record result for in-descent picked sequence. */
 608                                         record_local_sequence(u, t, descent, dlen, dseqi, seq_color, rval);
 609                                         continue;
 610                                 }
 611                         }
 612                 }
 613         }
 614
 615 end:
 616         /* We need to undo the virtual loss we added during descend. */
 617         if (u->virtual_loss) {
 618                 int parity = (node_color == player_color ? 1 : -1);
 619                 for (; n->parent; n = n->parent) {
 620                         stats_rm_result(&n->u, tree_parity(t, parity) > 0 ? 0 : 1, 1);
 621                         parity = -parity;
 622                 }
 623         }
 624
 625         if (amaf) {
 626                 free(amaf->map - 1);
 627                 free(amaf);
 628         }
 629         board_done_noalloc(&b2);
 630         return result;
 631 }
 632
 633 int
 634 uct_playouts(struct uct *u, struct board *b, enum stone color, struct tree *t, struct time_info *ti)
 635 {
 636         int i;
 637         if (ti && ti->dim == TD_GAMES) {
 638                 for (i = 0; t->root->u.playouts <= ti->len.games; i++)
 639                         uct_playout(u, b, color, t);
 640         } else {
 641                 for (i = 0; !uct_halt; i++)
 642                         uct_playout(u, b, color, t);
 643         }
 644         return i;
 645 }