uct/policy/ucb1amaf.c

   1 #include <assert.h>
   2 #include <limits.h>
   3 #include <math.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7
   8 //#define DEBUG
   9
  10 #include "board.h"
  11 #include "debug.h"
  12 #include "move.h"
  13 #include "random.h"
  14 #include "tactics/util.h"
  15 #include "uct/internal.h"
  16 #include "uct/tree.h"
  17 #include "uct/policy/generic.h"
  18
  19 /* This implements the UCB1 policy with an extra AMAF heuristics. */
  20
  21 struct ucb1_policy_amaf {
  22         /* This is what the Modification of UCT with Patterns in Monte Carlo Go
  23          * paper calls 'p'. Original UCB has this on 2, but this seems to
  24          * produce way too wide searches; reduce this to get deeper and
  25          * narrower readouts - try 0.2. */
  26         floating_t explore_p;
  27         /* Rescale virtual loss value to square root of #threads. This mitigates
  28          * the number of virtual losses added in case of a large amount of
  29          * threads; it seems that with linear virtual losses, overly diverse
  30          * exploration caused by this may cause a wrong mean value computed
  31          * for the parent node. */
  32         bool vloss_sqrt;
  33         /* In distributed mode, encourage different slaves to work on different
  34          * parts of the tree by adding virtual wins to different nodes. */
  35         int virtual_win;
  36         int root_virtual_win;
  37         int vwin_min_playouts;
  38         /* First Play Urgency - if set to less than infinity (the MoGo paper
  39          * above reports 1.0 as the best), new branches are explored only
  40          * if none of the existing ones has higher urgency than fpu. */
  41         floating_t fpu;
  42         unsigned int equiv_rave;
  43         bool sylvain_rave;
  44         /* Give more weight to moves played earlier. */
  45         int distance_rave;
  46         /* Give 0 or negative rave bonus to ko threats before taking the ko.
  47            1=normal bonus, 0=no bonus, -1=invert rave bonus, -2=double penalty... */
  48         int threat_rave;
  49         /* Coefficient of local tree values embedded in RAVE. */
  50         floating_t ltree_rave;
  51         /* Coefficient of criticality embedded in RAVE. */
  52         floating_t crit_rave;
  53         int crit_min_playouts;
  54         floating_t crit_plthres_coef;
  55         bool crit_negative;
  56         bool crit_negflip;
  57         bool crit_amaf;
  58         bool crit_lvalue;
  59 };
  60
  61
  62 static inline floating_t fast_sqrt(unsigned int x)
  63 {
  64         static const floating_t table[] = {
  65                 0, 1, 1.41421356237309504880, 1.73205080756887729352,
  66                 2.00000000000000000000, 2.23606797749978969640,
  67                 2.44948974278317809819, 2.64575131106459059050,
  68                 2.82842712474619009760, 3.00000000000000000000,
  69                 3.16227766016837933199, 3.31662479035539984911,
  70                 3.46410161513775458705, 3.60555127546398929311,
  71                 3.74165738677394138558, 3.87298334620741688517,
  72                 4.00000000000000000000, 4.12310562561766054982,
  73                 4.24264068711928514640, 4.35889894354067355223,
  74                 4.47213595499957939281, 4.58257569495584000658,
  75                 4.69041575982342955456, 4.79583152331271954159,
  76                 4.89897948556635619639, 5.00000000000000000000,
  77                 5.09901951359278483002, 5.19615242270663188058,
  78                 5.29150262212918118100, 5.38516480713450403125,
  79                 5.47722557505166113456, 5.56776436283002192211,
  80                 5.65685424949238019520, 5.74456264653802865985,
  81                 5.83095189484530047087, 5.91607978309961604256,
  82                 6.00000000000000000000, 6.08276253029821968899,
  83                 6.16441400296897645025, 6.24499799839839820584,
  84                 6.32455532033675866399, 6.40312423743284868648,
  85                 6.48074069840786023096, 6.55743852430200065234,
  86                 6.63324958071079969822, 6.70820393249936908922,
  87                 6.78232998312526813906, 6.85565460040104412493,
  88                 6.92820323027550917410, 7.00000000000000000000,
  89                 7.07106781186547524400, 7.14142842854284999799,
  90                 7.21110255092797858623, 7.28010988928051827109,
  91                 7.34846922834953429459, 7.41619848709566294871,
  92                 7.48331477354788277116, 7.54983443527074969723,
  93                 7.61577310586390828566, 7.68114574786860817576,
  94                 7.74596669241483377035, 7.81024967590665439412,
  95                 7.87400787401181101968, 7.93725393319377177150,
  96         };
  97         if (x < sizeof(table) / sizeof(*table)) {
  98                 return table[x];
  99         } else {
 100                 return sqrt(x);
 101         }
 102 }
 103
 104 #define URAVE_DEBUG if (0)
 105 static inline floating_t
 106 ucb1rave_evaluate(struct uct_policy *p, struct tree *tree, struct uct_descent *descent, int parity)
 107 {
 108         struct ucb1_policy_amaf *b = p->data;
 109         struct tree_node *node = descent->node;
 110         struct tree_node *lnode = descent->lnode;
 111
 112         struct move_stats n = node->u, r = node->amaf;
 113         if (p->uct->amaf_prior) {
 114                 stats_merge(&r, &node->prior);
 115         } else {
 116                 stats_merge(&n, &node->prior);
 117         }
 118
 119         if (p->uct->virtual_loss) {
 120                 /* Add virtual loss if we need to; this is used to discourage
 121                  * other threads from visiting this node in case of multiple
 122                  * threads doing the tree search. */
 123                 floating_t vloss_coeff = b->vloss_sqrt ? sqrt(p->uct->threads) / p->uct->threads : 1.;
 124                 struct move_stats c = { .value = parity > 0 ? 0. : 1., .playouts = node->descents * vloss_coeff };
 125                 stats_merge(&n, &c);
 126         }
 127
 128         /* Local tree heuristics. */
 129         assert(!lnode || lnode->parent);
 130         if (p->uct->local_tree && b->ltree_rave > 0 && lnode
 131             && (p->uct->local_tree_rootchoose || lnode->parent->parent)) {
 132                 struct move_stats l = lnode->u;
 133                 l.playouts = ((floating_t) l.playouts) * b->ltree_rave / LTREE_PLAYOUTS_MULTIPLIER;
 134                 URAVE_DEBUG fprintf(stderr, "[ltree] adding [%s] %f%%%d to [%s] RAVE %f%%%d\n",
 135                         coord2sstr(node_coord(lnode), tree->board), l.value, l.playouts,
 136                         coord2sstr(node_coord(node), tree->board), r.value, r.playouts);
 137                 stats_merge(&r, &l);
 138         }
 139
 140         /* Criticality heuristics. */
 141         if (b->crit_rave > 0 && (b->crit_plthres_coef > 0
 142                                  ? node->u.playouts > tree->root->u.playouts * b->crit_plthres_coef
 143                                  : node->u.playouts > b->crit_min_playouts)) {
 144                 floating_t crit = tree_node_criticality(tree, node);
 145                 if (b->crit_negative || crit > 0) {
 146                         floating_t val = 1.0f;
 147                         if (b->crit_negflip && crit < 0) {
 148                                 val = 0;
 149                                 crit = -crit;
 150                         }
 151                         struct move_stats c = {
 152                                 .value = tree_node_get_value(tree, parity, val),
 153                                 .playouts = crit * r.playouts * b->crit_rave
 154                         };
 155                         URAVE_DEBUG fprintf(stderr, "[crit] adding %f%%%d to [%s] RAVE %f%%%d\n",
 156                                 c.value, c.playouts,
 157                                 coord2sstr(node_coord(node), tree->board), r.value, r.playouts);
 158                         stats_merge(&r, &c);
 159                 }
 160         }
 161
 162         floating_t value = 0;
 163         if (n.playouts) {
 164                 if (r.playouts) {
 165                         /* At the beginning, beta is at 1 and RAVE is used.
 166                          * At b->equiv_rate, beta is at 1/3 and gets steeper on. */
 167                         floating_t beta;
 168                         if (b->sylvain_rave) {
 169                                 beta = (floating_t) r.playouts / (r.playouts + n.playouts
 170                                         + (floating_t) n.playouts * r.playouts / b->equiv_rave);
 171                         } else {
 172                                 /* XXX: This can be cached in descend; but we don't use this by default. */
 173                                 beta = sqrt(b->equiv_rave / (3 * node->parent->u.playouts + b->equiv_rave));
 174                         }
 175
 176                         value = beta * r.value + (1.f - beta) * n.value;
 177                         URAVE_DEBUG fprintf(stderr, "\t%s value = %f * %f + (1 - %f) * %f (prior %f)\n",
 178                                 coord2sstr(node_coord(node), tree->board), beta, r.value, beta, n.value, node->prior.value);
 179                 } else {
 180                         value = n.value;
 181                         URAVE_DEBUG fprintf(stderr, "\t%s value = %f (prior %f)\n",
 182                                 coord2sstr(node_coord(node), tree->board), n.value, node->prior.value);
 183                 }
 184         } else if (r.playouts) {
 185                 value = r.value;
 186                 URAVE_DEBUG fprintf(stderr, "\t%s value = rave %f (prior %f)\n",
 187                         coord2sstr(node_coord(node), tree->board), r.value, node->prior.value);
 188         }
 189         descent->value.playouts = r.playouts + n.playouts;
 190         descent->value.value = value;
 191
 192         return tree_node_get_value(tree, parity, value);
 193 }
 194
 195 void
 196 ucb1rave_descend(struct uct_policy *p, struct tree *tree, struct uct_descent *descent, int parity, bool allow_pass)
 197 {
 198         struct ucb1_policy_amaf *b = p->data;
 199         floating_t nconf = 1.f;
 200         if (b->explore_p > 0)
 201                 nconf = sqrt(log(descent->node->u.playouts + descent->node->prior.playouts));
 202         struct uct *u = p->uct;
 203         int vwin = 0;
 204         if (u->max_slaves > 0 && u->slave_index >= 0)
 205                 vwin = descent->node == tree->root ? b->root_virtual_win : b->virtual_win;
 206         int child = 0;
 207
 208         uctd_try_node_children(tree, descent, allow_pass, parity, u->tenuki_d, di, urgency) {
 209                 struct tree_node *ni = di.node;
 210                 urgency = ucb1rave_evaluate(p, tree, &di, parity);
 211
 212                 /* In distributed mode, encourage different slaves to work on different
 213                  * parts of the tree. We rely on the fact that children (if they exist)
 214                  * are the same and in the same order in all slaves. */
 215                 if (vwin > 0 && ni->u.playouts > b->vwin_min_playouts && (child - u->slave_index) % u->max_slaves == 0)
 216                         urgency += vwin / (ni->u.playouts + vwin);
 217
 218                 if (ni->u.playouts > 0 && b->explore_p > 0) {
 219                         urgency += b->explore_p * nconf / fast_sqrt(ni->u.playouts);
 220
 221                 } else if (ni->u.playouts + ni->amaf.playouts + ni->prior.playouts == 0) {
 222                         /* assert(!u->even_eqex); */
 223                         urgency = b->fpu;
 224                 }
 225         } uctd_set_best_child(di, urgency);
 226
 227         uctd_get_best_child(descent);
 228 }
 229
 230
 231 /* Return the length of the current ko (number of moves up to to the last ko capture),
 232  * 0 if the sequence is empty or doesn't start with a ko capture.
 233  *   B captures a ko
 234  *   W plays a ko threat
 235  *   B answers ko threat
 236  *   W re-captures the ko  <- return 4
 237  *   B plays a ko threat
 238  *   W connects the ko */
 239 static inline int ko_length(bool *ko_capture_map, int map_length)
 240 {
 241         if (map_length <= 0 || !ko_capture_map[0]) return 0;
 242         int length = 1;
 243         while (length + 2 < map_length && ko_capture_map[length + 2]) length += 3;
 244         return length;
 245 }
 246
 247 void
 248 ucb1amaf_update(struct uct_policy *p, struct tree *tree, struct tree_node *node,
 249                 enum stone node_color, enum stone player_color,
 250                 struct playout_amafmap *map, struct board *final_board,
 251                 floating_t result)
 252 {
 253         struct ucb1_policy_amaf *b = p->data;
 254         enum stone winner_color = result > 0.5 ? S_BLACK : S_WHITE;
 255
 256         /* Record of the random playout - for each intersection coord,
 257          * first_move[coord] is the index map->game of the first move
 258          * at this coordinate, or INT_MAX if the move was not played.
 259          * The parity gives the color of this move.
 260          */
 261         int first_map[board_size2(final_board)+1];
 262         int *first_move = &first_map[1]; // +1 for pass
 263
 264 #if 0
 265         struct board bb; bb.size = 9+2;
 266         for (struct tree_node *ni = node; ni; ni = ni->parent)
 267                 fprintf(stderr, "%s ", coord2sstr(node_coord(ni), &bb));
 268         fprintf(stderr, "[color %d] update result %d (color %d)\n",
 269                         node_color, result, player_color);
 270 #endif
 271
 272         /* Initialize first_move */
 273         for (int i = pass; i < board_size2(final_board); i++) first_move[i] = INT_MAX;
 274         int move;
 275         assert(map->gamelen > 0);
 276         for (move = map->gamelen - 1; move >= map->game_baselen; move--)
 277                 first_move[map->game[move]] = move;
 278
 279         while (node) {
 280                 if (!b->crit_amaf && !is_pass(node_coord(node))) {
 281                         stats_add_result(&node->winner_owner, board_local_value(b->crit_lvalue, final_board, node_coord(node), winner_color), 1);
 282                         stats_add_result(&node->black_owner, board_local_value(b->crit_lvalue, final_board, node_coord(node), S_BLACK), 1);
 283                 }
 284                 stats_add_result(&node->u, result, 1);
 285
 286                 bool *ko_capture_map = &map->is_ko_capture[move+1];
 287                 int max_threat_dist = b->threat_rave <= 0 ? ko_length(ko_capture_map, map->gamelen - (move+1)) : -1;
 288
 289                 /* This loop ignores symmetry considerations, but they should
 290                  * matter only at a point when AMAF doesn't help much. */
 291                 assert(map->game_baselen >= 0);
 292                 for (struct tree_node *ni = node->children; ni; ni = ni->sibling) {
 293                         if (is_pass(node_coord(ni))) continue;
 294
 295                         /* Use the child move only if it was first played by the same color. */
 296                         int first = first_move[node_coord(ni)];
 297                         if (first == INT_MAX) continue;
 298                         assert(first > move && first < map->gamelen);
 299                         int distance = first - (move + 1);
 300                         if (distance & 1) continue;
 301
 302                         int weight = 1;
 303                         floating_t res = result;
 304
 305                         /* Don't give amaf bonus to a ko threat before taking the ko.
 306                          * http://www.grappa.univ-lille3.fr/~coulom/Aja_PhD_Thesis.pdf
 307                          */
 308                         if (distance <= max_threat_dist && distance % 6 == 4) {
 309                                 weight = - b->threat_rave;
 310                                 res = 1.0 - res;
 311                         } else if (b->distance_rave != 0) {
 312                                 /* Give more weight to moves played earlier */
 313                                 weight += b->distance_rave * (map->gamelen - first) / (map->gamelen - move);
 314                         }
 315                         stats_add_result(&ni->amaf, res, weight);
 316
 317                         if (b->crit_amaf) {
 318                                 stats_add_result(&ni->winner_owner, board_local_value(b->crit_lvalue, final_board, node_coord(ni), winner_color), 1);
 319                                 stats_add_result(&ni->black_owner, board_local_value(b->crit_lvalue, final_board, node_coord(ni), S_BLACK), 1);
 320                         }
 321 #if 0
 322                         struct board bb; bb.size = 9+2;
 323                         fprintf(stderr, "* %s<%"PRIhash"> -> %s<%"PRIhash"> [%d/%f => %d/%f]\n",
 324                                 coord2sstr(node_coord(node), &bb), node->hash,
 325                                 coord2sstr(node_coord(ni), &bb), ni->hash,
 326                                 player_color, result, move, res);
 327 #endif
 328                 }
 329                 if (node->parent) {
 330                         assert(move >= 0 && map->game[move] == node_coord(node) && first_move[node_coord(node)] > move);
 331                         first_move[node_coord(node)] = move;
 332                         move--;
 333                 }
 334                 node = node->parent;
 335         }
 336 }
 337
 338
 339 struct uct_policy *
 340 policy_ucb1amaf_init(struct uct *u, char *arg, struct board *board)
 341 {
 342         struct uct_policy *p = calloc2(1, sizeof(*p));
 343         struct ucb1_policy_amaf *b = calloc2(1, sizeof(*b));
 344         p->uct = u;
 345         p->data = b;
 346         p->choose = uctp_generic_choose;
 347         p->winner = uctp_generic_winner;
 348         p->evaluate = ucb1rave_evaluate;
 349         p->descend = ucb1rave_descend;
 350         p->update = ucb1amaf_update;
 351         p->wants_amaf = true;
 352
 353         b->explore_p = 0;
 354         b->equiv_rave = board_large(board) ? 4000 : 3000;
 355         b->fpu = INFINITY;
 356         b->sylvain_rave = true;
 357         b->distance_rave = 3;
 358         b->threat_rave = 0;
 359         b->ltree_rave = 0.75f;
 360
 361         b->crit_rave = 1.1f;
 362         b->crit_min_playouts = 2000;
 363         b->crit_negative = 1;
 364         b->crit_amaf = 0;
 365
 366         b->vloss_sqrt = true;
 367
 368         b->virtual_win = 5;
 369         b->root_virtual_win = 30;
 370         b->vwin_min_playouts = 1000;
 371
 372         if (arg) {
 373                 char *optspec, *next = arg;
 374                 while (*next) {
 375                         optspec = next;
 376                         next += strcspn(next, ":");
 377                         if (*next) { *next++ = 0; } else { *next = 0; }
 378
 379                         char *optname = optspec;
 380                         char *optval = strchr(optspec, '=');
 381                         if (optval) *optval++ = 0;
 382
 383                         if (!strcasecmp(optname, "explore_p")) {
 384                                 b->explore_p = atof(optval);
 385                         } else if (!strcasecmp(optname, "fpu") && optval) {
 386                                 b->fpu = atof(optval);
 387                         } else if (!strcasecmp(optname, "equiv_rave") && optval) {
 388                                 b->equiv_rave = atof(optval);
 389                         } else if (!strcasecmp(optname, "sylvain_rave")) {
 390                                 b->sylvain_rave = !optval || *optval == '1';
 391                         } else if (!strcasecmp(optname, "distance_rave") && optval) {
 392                                 b->distance_rave = atoi(optval);
 393                         } else if (!strcasecmp(optname, "threat_rave") && optval) {
 394                                 b->threat_rave = atoi(optval);
 395                         } else if (!strcasecmp(optname, "ltree_rave") && optval) {
 396                                 b->ltree_rave = atof(optval);
 397                         } else if (!strcasecmp(optname, "crit_rave") && optval) {
 398                                 b->crit_rave = atof(optval);
 399                         } else if (!strcasecmp(optname, "crit_min_playouts") && optval) {
 400                                 b->crit_min_playouts = atoi(optval);
 401                         } else if (!strcasecmp(optname, "crit_plthres_coef") && optval) {
 402                                 b->crit_plthres_coef = atof(optval);
 403                         } else if (!strcasecmp(optname, "crit_negative")) {
 404                                 b->crit_negative = !optval || *optval == '1';
 405                         } else if (!strcasecmp(optname, "crit_negflip")) {
 406                                 b->crit_negflip = !optval || *optval == '1';
 407                         } else if (!strcasecmp(optname, "crit_amaf")) {
 408                                 b->crit_amaf = !optval || *optval == '1';
 409                         } else if (!strcasecmp(optname, "crit_lvalue")) {
 410                                 b->crit_lvalue = !optval || *optval == '1';
 411                         } else if (!strcasecmp(optname, "virtual_win") && optval) {
 412                                 b->virtual_win = atoi(optval);
 413                         } else if (!strcasecmp(optname, "root_virtual_win") && optval) {
 414                                 b->root_virtual_win = atoi(optval);
 415                         } else if (!strcasecmp(optname, "vwin_min_playouts") && optval) {
 416                                 b->vwin_min_playouts = atoi(optval);
 417                         } else if (!strcasecmp(optname, "vloss_sqrt")) {
 418                                 b->vloss_sqrt = !optval || *optval == '1';
 419                         } else {
 420                                 fprintf(stderr, "ucb1amaf: Invalid policy argument %s or missing value\n",
 421                                         optname);
 422                                 exit(1);
 423                         }
 424                 }
 425         }
 426
 427         return p;
 428 }