nsz Git - libfirm/blob - heuristical.c

   1 #include "adt/array.h"
   2 #include "assert.h"
   3 #include "error.h"
   4
   5 #include "bucket.h"
   6 #include "heuristical.h"
   7 #include "html_dumper.h"
   8 #include "kaps.h"
   9 #include "matrix.h"
  10 #include "pbqp_edge.h"
  11 #include "pbqp_edge_t.h"
  12 #include "pbqp_node.h"
  13 #include "pbqp_node_t.h"
  14 #include "vector.h"
  15
  16 static pbqp_edge **edge_bucket;
  17 static pbqp_node **node_buckets[4];
  18 static pbqp_node **reduced_bucket = NULL;
  19 static int         buckets_filled = 0;
  20
  21 /* Forward declarations. */
  22 static void apply_Brute_Force(pbqp *pbqp);
  23
  24 static void insert_into_edge_bucket(pbqp_edge *edge)
  25 {
  26         if (edge_bucket_contains(edge_bucket, edge)) {
  27                 /* Edge is already inserted. */
  28                 return;
  29         }
  30
  31         edge_bucket_insert(&edge_bucket, edge);
  32 }
  33
  34 static void init_buckets(void)
  35 {
  36         int i;
  37
  38         edge_bucket_init(&edge_bucket);
  39         node_bucket_init(&reduced_bucket);
  40
  41         for (i = 0; i < 4; ++i) {
  42                 node_bucket_init(&node_buckets[i]);
  43         }
  44 }
  45
  46 static void free_buckets(void)
  47 {
  48         int i;
  49
  50         for (i = 0; i < 4; ++i) {
  51                 node_bucket_free(&node_buckets[i]);
  52         }
  53
  54         edge_bucket_free(&edge_bucket);
  55         node_bucket_free(&reduced_bucket);
  56
  57         buckets_filled = 0;
  58 }
  59
  60 static void fill_node_buckets(pbqp *pbqp)
  61 {
  62         unsigned node_index;
  63         unsigned node_len;
  64
  65         assert(pbqp);
  66         node_len = pbqp->num_nodes;
  67
  68         for (node_index = 0; node_index < node_len; ++node_index) {
  69                 unsigned   degree;
  70                 pbqp_node *node = get_node(pbqp, node_index);
  71
  72                 if (!node) continue;
  73
  74                 degree = pbqp_node_get_degree(node);
  75
  76                 /* We have only one bucket for nodes with arity >= 3. */
  77                 if (degree > 3) {
  78                         degree = 3;
  79                 }
  80
  81                 node_bucket_insert(&node_buckets[degree], node);
  82         }
  83
  84         buckets_filled = 1;
  85 }
  86
  87 static void normalize_towards_source(pbqp *pbqp, pbqp_edge *edge)
  88 {
  89         pbqp_matrix    *mat;
  90         pbqp_node      *src_node;
  91         pbqp_node      *tgt_node;
  92         vector         *src_vec;
  93         vector         *tgt_vec;
  94         int             src_len;
  95         int             tgt_len;
  96         int             src_index;
  97
  98         assert(pbqp);
  99         assert(edge);
 100
 101         src_node = edge->src;
 102         tgt_node = edge->tgt;
 103         assert(src_node);
 104         assert(tgt_node);
 105
 106         src_vec = src_node->costs;
 107         tgt_vec = tgt_node->costs;
 108         assert(src_vec);
 109         assert(tgt_vec);
 110
 111         src_len = src_vec->len;
 112         tgt_len = tgt_vec->len;
 113         assert(src_len > 0);
 114         assert(tgt_len > 0);
 115
 116         mat = edge->costs;
 117         assert(mat);
 118
 119         /* Normalize towards source node. */
 120         for (src_index = 0; src_index < src_len; ++src_index) {
 121                 num min = pbqp_matrix_get_row_min(mat, src_index, tgt_vec);
 122
 123                 if (min != 0) {
 124                         if (src_vec->entries[src_index].data == INF_COSTS) {
 125                                 pbqp_matrix_set_row_value(mat, src_index, 0);
 126                         } else {
 127                                 pbqp_matrix_sub_row_value(mat, src_index, tgt_vec, min);
 128                         }
 129                         src_vec->entries[src_index].data = pbqp_add(
 130                                         src_vec->entries[src_index].data, min);
 131
 132                         if (min == INF_COSTS) {
 133                                 unsigned edge_index;
 134                                 unsigned edge_len = pbqp_node_get_degree(src_node);
 135
 136                                 for (edge_index = 0; edge_index < edge_len; ++edge_index) {
 137                                         pbqp_edge *edge_candidate = src_node->edges[edge_index];
 138                                         if (edge_candidate != edge) {
 139                                                 insert_into_edge_bucket(edge_candidate);
 140                                         }
 141                                 }
 142                         }
 143                 }
 144         }
 145 }
 146
 147 static void normalize_towards_target(pbqp *pbqp, pbqp_edge *edge)
 148 {
 149         pbqp_matrix    *mat;
 150         pbqp_node      *src_node;
 151         pbqp_node      *tgt_node;
 152         vector         *src_vec;
 153         vector         *tgt_vec;
 154         int             src_len;
 155         int             tgt_len;
 156         int             tgt_index;
 157
 158         assert(pbqp);
 159         assert(edge);
 160
 161         src_node = edge->src;
 162         tgt_node = edge->tgt;
 163         assert(src_node);
 164         assert(tgt_node);
 165
 166         src_vec = src_node->costs;
 167         tgt_vec = tgt_node->costs;
 168         assert(src_vec);
 169         assert(tgt_vec);
 170
 171         src_len = src_vec->len;
 172         tgt_len = tgt_vec->len;
 173         assert(src_len > 0);
 174         assert(tgt_len > 0);
 175
 176         mat = edge->costs;
 177         assert(mat);
 178
 179         for (tgt_index = 0; tgt_index < tgt_len; ++tgt_index) {
 180                 num min = pbqp_matrix_get_col_min(mat, tgt_index, src_vec);
 181
 182                 if (min != 0) {
 183                         if (tgt_vec->entries[tgt_index].data == INF_COSTS) {
 184                                 pbqp_matrix_set_col_value(mat, tgt_index, 0);
 185                         } else {
 186                                 pbqp_matrix_sub_col_value(mat, tgt_index, src_vec, min);
 187                         }
 188                         tgt_vec->entries[tgt_index].data = pbqp_add(
 189                                         tgt_vec->entries[tgt_index].data, min);
 190
 191                         if (min == INF_COSTS) {
 192                                 unsigned edge_index;
 193                                 unsigned edge_len = pbqp_node_get_degree(tgt_node);
 194
 195                                 for (edge_index = 0; edge_index < edge_len; ++edge_index) {
 196                                         pbqp_edge *edge_candidate = tgt_node->edges[edge_index];
 197                                         if (edge_candidate != edge) {
 198                                                 insert_into_edge_bucket(edge_candidate);
 199                                         }
 200                                 }
 201                         }
 202                 }
 203         }
 204 }
 205
 206 static void reorder_node(pbqp_node *node)
 207 {
 208         unsigned    degree     = pbqp_node_get_degree(node);
 209         /* Assume node lost one incident edge. */
 210         unsigned    old_degree = degree + 1;
 211
 212         if (!buckets_filled) return;
 213
 214         /* Same bucket as before */
 215         if (degree > 2) return;
 216
 217         if (!node_bucket_contains(node_buckets[old_degree], node)) {
 218                 /* Old arity is new arity, so we have nothing to do. */
 219                 assert(node_bucket_contains(node_buckets[degree], node));
 220                 return;
 221         }
 222
 223         /* Delete node from old bucket... */
 224         node_bucket_remove(&node_buckets[old_degree], node);
 225
 226         /* ..and add to new one. */
 227         node_bucket_insert(&node_buckets[degree], node);
 228 }
 229
 230 static void check_melting_possibility(pbqp *pbqp, pbqp_edge *edge)
 231 {
 232         pbqp_matrix    *mat;
 233         pbqp_node      *src_node;
 234         pbqp_node      *tgt_node;
 235         vector         *src_vec;
 236         vector         *tgt_vec;
 237         int             src_len;
 238         int             tgt_len;
 239         int             src_index;
 240         int             tgt_index;
 241
 242         assert(pbqp);
 243         assert(edge);
 244
 245         src_node = edge->src;
 246         tgt_node = edge->tgt;
 247         assert(src_node);
 248         assert(tgt_node);
 249
 250         src_vec = src_node->costs;
 251         tgt_vec = tgt_node->costs;
 252         assert(src_vec);
 253         assert(tgt_vec);
 254
 255         src_len = src_vec->len;
 256         tgt_len = tgt_vec->len;
 257         assert(src_len > 0);
 258         assert(tgt_len > 0);
 259
 260         mat = edge->costs;
 261         assert(mat);
 262
 263         if (src_len == 1 && tgt_len == 1) {
 264                 //panic("Something is wrong");
 265         }
 266
 267         int allRowsOk = 1;
 268         for (src_index = 0; src_index < src_len; ++src_index) {
 269                 int onlyOneZero = 0;
 270                 if (src_vec->entries[src_index].data == INF_COSTS) {
 271                         continue;
 272                 }
 273                 for (tgt_index = 0; tgt_index < tgt_len; ++tgt_index) {
 274                         if (tgt_vec->entries[tgt_index].data == INF_COSTS) {
 275                                 continue;
 276                         }
 277                         if (mat->entries[src_index * tgt_len + tgt_index] == 0) {
 278                                 if (onlyOneZero) {
 279                                         onlyOneZero = 0;
 280                                         break;
 281                                 } else {
 282                                         onlyOneZero = 1;
 283                                         continue;
 284                                 }
 285                         }
 286                         if (mat->entries[src_index * tgt_len + tgt_index] == INF_COSTS) {
 287                                 continue;
 288                         }
 289                         onlyOneZero = 0;
 290                         break;
 291                 }
 292                 allRowsOk &= onlyOneZero;
 293         }
 294
 295         int allColsOk = 1;
 296         for (tgt_index = 0; tgt_index < tgt_len; ++tgt_index) {
 297                 int onlyOneZero = 0;
 298                 if (tgt_vec->entries[tgt_index].data == INF_COSTS) {
 299                         continue;
 300                 }
 301                 for (src_index = 0; src_index < src_len; ++src_index) {
 302                         if (src_vec->entries[src_index].data == INF_COSTS) {
 303                                 continue;
 304                         }
 305                         if (mat->entries[src_index * tgt_len + tgt_index] == 0) {
 306                                 if (onlyOneZero) {
 307                                         onlyOneZero = 0;
 308                                         break;
 309                                 } else {
 310                                         onlyOneZero = 1;
 311                                         continue;
 312                                 }
 313                         }
 314                         if (mat->entries[src_index * tgt_len + tgt_index] == INF_COSTS) {
 315                                 continue;
 316                         }
 317                         onlyOneZero = 0;
 318                         break;
 319                 }
 320                 allColsOk &= onlyOneZero;
 321         }
 322
 323         if (allRowsOk && allColsOk) {
 324                 panic("Hurray");
 325         }
 326 }
 327
 328 static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
 329 {
 330         pbqp_matrix    *mat;
 331         pbqp_node      *src_node;
 332         pbqp_node      *tgt_node;
 333         vector         *src_vec;
 334         vector         *tgt_vec;
 335         int             src_len;
 336         int             tgt_len;
 337
 338         assert(pbqp);
 339         assert(edge);
 340
 341         src_node = edge->src;
 342         tgt_node = edge->tgt;
 343         assert(src_node);
 344         assert(tgt_node);
 345
 346         /* If edge are already deleted, we have nothing to do. */
 347         if (!is_connected(src_node, edge) || !is_connected(tgt_node, edge))
 348                 return;
 349
 350         if (pbqp->dump_file) {
 351                 char txt[100];
 352                 sprintf(txt, "Simplification of Edge n%d-n%d", src_node->index, tgt_node->index);
 353                 dump_section(pbqp->dump_file, 3, txt);
 354         }
 355
 356         src_vec = src_node->costs;
 357         tgt_vec = tgt_node->costs;
 358         assert(src_vec);
 359         assert(tgt_vec);
 360
 361         src_len = src_vec->len;
 362         tgt_len = tgt_vec->len;
 363         assert(src_len > 0);
 364         assert(tgt_len > 0);
 365
 366         mat = edge->costs;
 367         assert(mat);
 368
 369         if (pbqp->dump_file) {
 370                 fputs("Input:<br>\n", pbqp->dump_file);
 371                 dump_simplifyedge(pbqp, edge);
 372         }
 373
 374         normalize_towards_source(pbqp, edge);
 375         normalize_towards_target(pbqp, edge);
 376
 377         if (pbqp->dump_file) {
 378                 fputs("<br>\nOutput:<br>\n", pbqp->dump_file);
 379                 dump_simplifyedge(pbqp, edge);
 380         }
 381
 382         if (pbqp_matrix_is_zero(mat, src_vec, tgt_vec)) {
 383                 if (pbqp->dump_file) {
 384                         fputs("edge has been eliminated<br>\n", pbqp->dump_file);
 385                 }
 386
 387                 delete_edge(edge);
 388                 reorder_node(src_node);
 389                 reorder_node(tgt_node);
 390         } else {
 391                 //check_melting_possibility(pbqp, edge);
 392         }
 393 }
 394
 395 static void initial_simplify_edges(pbqp *pbqp)
 396 {
 397         unsigned node_index;
 398         unsigned node_len;
 399
 400         assert(pbqp);
 401
 402         if (pbqp->dump_file) {
 403                 pbqp_dump_input(pbqp);
 404                 dump_section(pbqp->dump_file, 1, "2. Simplification of Cost Matrices");
 405         }
 406
 407         node_len = pbqp->num_nodes;
 408
 409         init_buckets();
 410
 411         /* First simplify all edges. */
 412         for (node_index = 0; node_index < node_len; ++node_index) {
 413                 unsigned    edge_index;
 414                 pbqp_node  *node = get_node(pbqp, node_index);
 415                 pbqp_edge **edges;
 416                 unsigned    edge_len;
 417
 418                 if (!node) continue;
 419
 420                 edges = node->edges;
 421                 edge_len = pbqp_node_get_degree(node);
 422
 423                 for (edge_index = 0; edge_index < edge_len; ++edge_index) {
 424                         pbqp_edge *edge = edges[edge_index];
 425
 426                         /* Simplify only once per edge. */
 427                         if (node != edge->src) continue;
 428
 429                         simplify_edge(pbqp, edge);
 430                 }
 431         }
 432 }
 433
 434 num determine_solution(FILE *file)
 435 {
 436         unsigned node_index;
 437         unsigned node_len;
 438         num      solution;
 439
 440         if (file) {
 441                 dump_section(file, 1, "4. Determine Solution/Minimum");
 442                 dump_section(file, 2, "4.1. Trivial Solution");
 443         }
 444
 445         /* Solve trivial nodes and calculate solution. */
 446         node_len = node_bucket_get_length(node_buckets[0]);
 447         for (node_index = 0; node_index < node_len; ++node_index) {
 448                 pbqp_node *node = node_buckets[0][node_index];
 449                 assert(node);
 450
 451                 node->solution = vector_get_min_index(node->costs);
 452                 solution       = pbqp_add(solution,
 453                                 node->costs->entries[node->solution].data);
 454                 if (file) {
 455                         fprintf(file, "node n%d is set to %d<br>\n", node->index, node->solution);
 456                         dump_node(file, node);
 457                 }
 458         }
 459
 460         if (file) {
 461                 dump_section(file, 2, "Minimum");
 462                 fprintf(file, "Minimum is equal to %lld.", solution);
 463         }
 464
 465         return solution;
 466 }
 467
 468 static void back_propagate(pbqp *pbqp)
 469 {
 470         unsigned node_index;
 471         unsigned node_len   = node_bucket_get_length(reduced_bucket);
 472
 473         assert(pbqp);
 474         if (pbqp->dump_file) {
 475                 dump_section(pbqp->dump_file, 2, "Back Propagation");
 476         }
 477
 478         for (node_index = node_len; node_index > 0; --node_index) {
 479                 pbqp_node *node = reduced_bucket[node_index - 1];
 480
 481                 switch (pbqp_node_get_degree(node)) {
 482                         case 1:
 483                                 back_propagate_RI(pbqp, node);
 484                                 break;
 485                         case 2:
 486                                 back_propagate_RII(pbqp, node);
 487                                 break;
 488                         default:
 489                                 panic("Only nodes with degree one or two should be in this bucket");
 490                                 break;
 491                 }
 492         }
 493 }
 494
 495 static void apply_heuristic_reductions(pbqp *pbqp)
 496 {
 497         for (;;) {
 498                 if (edge_bucket_get_length(edge_bucket) > 0) {
 499                         apply_edge(pbqp);
 500                 } else if (node_bucket_get_length(node_buckets[1]) > 0) {
 501                         apply_RI(pbqp);
 502                 } else if (node_bucket_get_length(node_buckets[2]) > 0) {
 503                         apply_RII(pbqp);
 504                 } else if (node_bucket_get_length(node_buckets[3]) > 0) {
 505                         apply_RN(pbqp);
 506                 } else {
 507                         return;
 508                 }
 509         }
 510 }
 511
 512 void solve_pbqp_heuristical(pbqp *pbqp)
 513 {
 514         /* Reduce nodes degree ... */
 515         initial_simplify_edges(pbqp);
 516
 517         /* ... and put node into bucket representing their degree. */
 518         fill_node_buckets(pbqp);
 519
 520         apply_heuristic_reductions(pbqp);
 521
 522         pbqp->solution = determine_solution(pbqp->dump_file);
 523
 524         /* Solve reduced nodes. */
 525         back_propagate(pbqp);
 526
 527         free_buckets();
 528 }
 529
 530 void apply_edge(pbqp *pbqp)
 531 {
 532         pbqp_edge *edge = edge_bucket_pop(&edge_bucket);
 533
 534         simplify_edge(pbqp, edge);
 535 }
 536
 537 void apply_RI(pbqp *pbqp)
 538 {
 539         pbqp_node   *node       = node_bucket_pop(&node_buckets[1]);
 540         pbqp_edge   *edge       = node->edges[0];
 541         pbqp_matrix *mat        = edge->costs;
 542         int          is_src     = edge->src == node;
 543         pbqp_node   *other_node;
 544
 545         if (is_src) {
 546                 other_node = edge->tgt;
 547         } else {
 548                 other_node = edge->src;
 549         }
 550
 551         if (pbqp->dump_file) {
 552                 char     txt[100];
 553                 sprintf(txt, "RI-Reduction of Node n%d", node->index);
 554                 dump_section(pbqp->dump_file, 2, txt);
 555                 pbqp_dump_graph(pbqp);
 556                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 557                 dump_node(pbqp->dump_file, node);
 558                 dump_node(pbqp->dump_file, other_node);
 559                 dump_edge(pbqp->dump_file, edge);
 560         }
 561
 562         if (is_src) {
 563                 pbqp_matrix_add_to_all_cols(mat, node->costs);
 564                 normalize_towards_target(pbqp, edge);
 565         } else {
 566                 pbqp_matrix_add_to_all_rows(mat, node->costs);
 567                 normalize_towards_source(pbqp, edge);
 568         }
 569         disconnect_edge(other_node, edge);
 570
 571         if (pbqp->dump_file) {
 572                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 573                 dump_node(pbqp->dump_file, other_node);
 574         }
 575
 576         reorder_node(other_node);
 577
 578         /* Add node to back propagation list. */
 579         node_bucket_insert(&reduced_bucket, node);
 580 }
 581
 582 void apply_RII(pbqp *pbqp)
 583 {
 584         pbqp_node   *node       = node_bucket_pop(&node_buckets[2]);
 585         pbqp_edge   *src_edge   = node->edges[0];
 586         pbqp_edge   *tgt_edge   = node->edges[1];
 587         int          src_is_src = src_edge->src == node;
 588         int          tgt_is_src = tgt_edge->src == node;
 589         pbqp_matrix *src_mat;
 590         pbqp_matrix *tgt_mat;
 591         pbqp_node   *src_node;
 592         pbqp_node   *tgt_node;
 593         pbqp_matrix *mat;
 594         vector      *vec;
 595         vector      *node_vec;
 596         vector      *src_vec;
 597         vector      *tgt_vec;
 598         unsigned     col_index;
 599         unsigned     col_len;
 600         unsigned     row_index;
 601         unsigned     row_len;
 602         unsigned     node_len;
 603
 604         assert(pbqp);
 605
 606         if (src_is_src) {
 607                 src_node = src_edge->tgt;
 608         } else {
 609                 src_node = src_edge->src;
 610         }
 611
 612         if (tgt_is_src) {
 613                 tgt_node = tgt_edge->tgt;
 614         } else {
 615                 tgt_node = tgt_edge->src;
 616         }
 617
 618         /* Swap nodes if necessary. */
 619         if (tgt_node->index < src_node->index) {
 620                 pbqp_node *tmp_node;
 621                 pbqp_edge *tmp_edge;
 622
 623                 tmp_node = src_node;
 624                 src_node = tgt_node;
 625                 tgt_node = tmp_node;
 626
 627                 tmp_edge = src_edge;
 628                 src_edge = tgt_edge;
 629                 tgt_edge = tmp_edge;
 630
 631                 src_is_src = src_edge->src == node;
 632                 tgt_is_src = tgt_edge->src == node;
 633         }
 634
 635         if (pbqp->dump_file) {
 636                 char     txt[100];
 637                 sprintf(txt, "RII-Reduction of Node n%d", node->index);
 638                 dump_section(pbqp->dump_file, 2, txt);
 639                 pbqp_dump_graph(pbqp);
 640                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 641                 dump_node(pbqp->dump_file, src_node);
 642                 dump_edge(pbqp->dump_file, src_edge);
 643                 dump_node(pbqp->dump_file, node);
 644                 dump_edge(pbqp->dump_file, tgt_edge);
 645                 dump_node(pbqp->dump_file, tgt_node);
 646         }
 647
 648         src_mat = src_edge->costs;
 649         tgt_mat = tgt_edge->costs;
 650
 651         src_vec  = src_node->costs;
 652         tgt_vec  = tgt_node->costs;
 653         node_vec = node->costs;
 654
 655         row_len  = src_vec->len;
 656         col_len  = tgt_vec->len;
 657         node_len = node_vec->len;
 658
 659         mat = pbqp_matrix_alloc(pbqp, row_len, col_len);
 660
 661         for (row_index = 0; row_index < row_len; ++row_index) {
 662                 for (col_index = 0; col_index < col_len; ++col_index) {
 663                         vec = vector_copy(pbqp, node_vec);
 664
 665                         if (src_is_src) {
 666                                 vector_add_matrix_col(vec, src_mat, row_index);
 667                         } else {
 668                                 vector_add_matrix_row(vec, src_mat, row_index);
 669                         }
 670
 671                         if (tgt_is_src) {
 672                                 vector_add_matrix_col(vec, tgt_mat, col_index);
 673                         } else {
 674                                 vector_add_matrix_row(vec, tgt_mat, col_index);
 675                         }
 676
 677                         mat->entries[row_index * col_len + col_index] = vector_get_min(vec);
 678
 679                         obstack_free(&pbqp->obstack, vec);
 680                 }
 681         }
 682
 683         pbqp_edge *edge = get_edge(pbqp, src_node->index, tgt_node->index);
 684
 685         /* Disconnect node. */
 686         disconnect_edge(src_node, src_edge);
 687         disconnect_edge(tgt_node, tgt_edge);
 688
 689         /* Add node to back propagation list. */
 690         node_bucket_insert(&reduced_bucket, node);
 691
 692         if (edge == NULL) {
 693                 edge = alloc_edge(pbqp, src_node->index, tgt_node->index, mat);
 694         } else {
 695                 pbqp_matrix_add(edge->costs, mat);
 696
 697                 /* Free local matrix. */
 698                 obstack_free(&pbqp->obstack, mat);
 699
 700                 reorder_node(src_node);
 701                 reorder_node(tgt_node);
 702         }
 703
 704         if (pbqp->dump_file) {
 705                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 706                 dump_edge(pbqp->dump_file, edge);
 707         }
 708
 709         /* Edge has changed so we simplify it. */
 710         simplify_edge(pbqp, edge);
 711 }
 712
 713 static void select_alternative(pbqp_node *node, unsigned selected_index)
 714 {
 715         unsigned  edge_index;
 716         unsigned  node_index;
 717         unsigned  node_len;
 718         vector   *node_vec;
 719         unsigned  max_degree = pbqp_node_get_degree(node);
 720
 721         assert(selected_index < max_degree);
 722         assert(node);
 723         node->solution = selected_index;
 724         node_vec = node->costs;
 725         node_len = node_vec->len;
 726
 727         /* Set all other costs to infinity. */
 728         for (node_index = 0; node_index < node_len; ++node_index) {
 729                 if (node_index != selected_index) {
 730                         node_vec->entries[node_index].data = INF_COSTS;
 731                 }
 732         }
 733
 734         /* Add all incident edges to edge bucket, since they are now independent. */
 735         for (edge_index = 0; edge_index < max_degree; ++edge_index) {
 736                 insert_into_edge_bucket(node->edges[edge_index]);
 737         }
 738 }
 739
 740 static pbqp_node *get_node_with_max_degree(void)
 741 {
 742         pbqp_node  **bucket       = node_buckets[3];
 743         unsigned     bucket_len   = node_bucket_get_length(bucket);
 744         unsigned     bucket_index;
 745         unsigned     max_degree   = 0;
 746         pbqp_node   *result       = NULL;
 747
 748         for (bucket_index = 0; bucket_index < bucket_len; ++bucket_index) {
 749                 pbqp_node *candidate = bucket[bucket_index];
 750                 unsigned   degree    = pbqp_node_get_degree(candidate);
 751
 752                 if (degree > max_degree) {
 753                         result = candidate;
 754                         max_degree = degree;
 755                 }
 756         }
 757
 758         return result;
 759 }
 760
 761 static unsigned get_local_minimal_alternative(pbqp *pbqp, pbqp_node *node)
 762 {
 763         pbqp_edge   *edge;
 764         vector      *node_vec;
 765         vector      *vec;
 766         pbqp_matrix *mat;
 767         unsigned     edge_index;
 768         unsigned     max_degree   = 0;
 769         unsigned     node_index;
 770         unsigned     node_len;
 771         unsigned     min_index    = 0;
 772         num          min          = INF_COSTS;
 773         int          is_src;
 774
 775         assert(pbqp);
 776         assert(node);
 777         node_vec = node->costs;
 778         node_len = node_vec->len;
 779
 780         for (node_index = 0; node_index < node_len; ++node_index) {
 781                 num value = node_vec->entries[node_index].data;
 782
 783                 for (edge_index = 0; edge_index < max_degree; ++edge_index) {
 784                         edge   = node->edges[edge_index];
 785                         mat    = edge->costs;
 786                         is_src = edge->src == node;
 787
 788                         if (is_src) {
 789                                 vec = vector_copy(pbqp, edge->tgt->costs);
 790                                 vector_add_matrix_row(vec, mat, node_index);
 791                         } else {
 792                                 vec = vector_copy(pbqp, edge->src->costs);
 793                                 vector_add_matrix_col(vec, mat, node_index);
 794                         }
 795
 796                         value = pbqp_add(value, vector_get_min(vec));
 797
 798                         obstack_free(&pbqp->obstack, vec);
 799                 }
 800
 801                 if (value < min) {
 802                         min = value;
 803                         min_index = node_index;
 804                 }
 805         }
 806
 807         return min_index;
 808 }
 809
 810 void apply_RN(pbqp *pbqp)
 811 {
 812         pbqp_node   *node         = NULL;
 813         unsigned     min_index    = 0;
 814
 815         assert(pbqp);
 816
 817         /* We want to reduce a node with maximum degree. */
 818         node = get_node_with_max_degree();
 819         assert(node);
 820
 821         if (pbqp->dump_file) {
 822                 char     txt[100];
 823                 sprintf(txt, "RN-Reduction of Node n%d", node->index);
 824                 dump_section(pbqp->dump_file, 2, txt);
 825                 pbqp_dump_graph(pbqp);
 826         }
 827
 828         min_index = get_local_minimal_alternative(pbqp, node);
 829
 830         if (pbqp->dump_file) {
 831                 fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
 832                                         node->index, min_index);
 833         }
 834
 835         /* Now that we found the local minimum set all other costs to infinity. */
 836         select_alternative(node, min_index);
 837 }
 838
 839 static void apply_brute_force_reductions(pbqp *pbqp)
 840 {
 841         for (;;) {
 842                 if (edge_bucket_get_length(edge_bucket) > 0) {
 843                         apply_edge(pbqp);
 844                 } else if (node_bucket_get_length(node_buckets[1]) > 0) {
 845                         apply_RI(pbqp);
 846                 } else if (node_bucket_get_length(node_buckets[2]) > 0) {
 847                         apply_RII(pbqp);
 848                 } else if (node_bucket_get_length(node_buckets[3]) > 0) {
 849                         apply_Brute_Force(pbqp);
 850                 } else {
 851                         return;
 852                 }
 853         }
 854 }
 855
 856 static unsigned get_minimal_alternative(pbqp *pbqp, pbqp_node *node)
 857 {
 858         vector      *node_vec;
 859         unsigned     node_index;
 860         unsigned     node_len;
 861         unsigned     min_index    = 0;
 862         num          min          = INF_COSTS;
 863
 864         assert(pbqp);
 865         assert(node);
 866         node_vec = node->costs;
 867         node_len = node_vec->len;
 868
 869         for (node_index = 0; node_index < node_len; ++node_index) {
 870                 num value;
 871
 872                 /* Some node buckets and the edge bucket should be empty. */
 873                 assert(node_bucket_get_length(node_buckets[1]) == 0);
 874                 assert(node_bucket_get_length(node_buckets[2]) == 0);
 875                 assert(edge_bucket_get_length(edge_bucket)     == 0);
 876
 877                 /* Save current PBQP state. */
 878                 pbqp_node_bucket *bucket_deg0 = node_bucket_deep_copy(node_buckets[0]);
 879                 pbqp_node_bucket *bucket_deg3 = node_bucket_deep_copy(node_buckets[3]);
 880                 pbqp_node_bucket *bucket_red  = node_bucket_deep_copy(reduced_bucket);
 881
 882                 /* Select alternative and solve PBQP recursively. */
 883                 select_alternative(node, node_index);
 884                 apply_brute_force_reductions(pbqp);
 885
 886                 value = determine_solution(pbqp->dump_file);
 887
 888                 if (value < min) {
 889                         min = value;
 890                         min_index = node_index;
 891                 }
 892
 893                 /* Some node buckets and the edge bucket should still be empty. */
 894                 assert(node_bucket_get_length(node_buckets[1]) == 0);
 895                 assert(node_bucket_get_length(node_buckets[2]) == 0);
 896                 assert(edge_bucket_get_length(edge_bucket)     == 0);
 897
 898                 /* TODO Restore old PBQP state. */
 899
 900         }
 901
 902         return min_index;
 903 }
 904
 905 void apply_Brute_Force(pbqp *pbqp)
 906 {
 907         pbqp_node   *node         = NULL;
 908         unsigned     min_index    = 0;
 909
 910         assert(pbqp);
 911
 912         /* We want to reduce a node with maximum degree. */
 913         node = get_node_with_max_degree();
 914         assert(node);
 915
 916         if (pbqp->dump_file) {
 917                 char     txt[100];
 918                 sprintf(txt, "BF-Reduction of Node n%d", node->index);
 919                 dump_section(pbqp->dump_file, 2, txt);
 920                 pbqp_dump_graph(pbqp);
 921         }
 922
 923         min_index = get_minimal_alternative(pbqp, node);
 924
 925         if (pbqp->dump_file) {
 926                 fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
 927                                         node->index, min_index);
 928         }
 929
 930         /* Now that we found the minimum set all other costs to infinity. */
 931         select_alternative(node, min_index);
 932 }
 933
 934 void solve_pbqp_brute_force(pbqp *pbqp)
 935 {
 936         /* Reduce nodes degree ... */
 937         initial_simplify_edges(pbqp);
 938
 939         /* ... and put node into bucket representing their degree. */
 940         fill_node_buckets(pbqp);
 941
 942         apply_brute_force_reductions(pbqp);
 943
 944         pbqp->solution = determine_solution(pbqp->dump_file);
 945
 946         /* Solve reduced nodes. */
 947         back_propagate(pbqp);
 948
 949         free_buckets();
 950 }
 951
 952 void back_propagate_RI(pbqp *pbqp, pbqp_node *node)
 953 {
 954         pbqp_edge   *edge;
 955         pbqp_node   *other;
 956         pbqp_matrix *mat;
 957         vector      *vec;
 958         int          is_src;
 959
 960         assert(pbqp);
 961         assert(node);
 962
 963         edge = node->edges[0];
 964         mat = edge->costs;
 965         is_src = edge->src == node;
 966         vec = node->costs;
 967
 968         if (is_src) {
 969                 other = edge->tgt;
 970                 assert(other);
 971                 vector_add_matrix_col(vec, mat, other->solution);
 972         } else {
 973                 other = edge->src;
 974                 assert(other);
 975                 vector_add_matrix_row(vec, mat, other->solution);
 976         }
 977
 978         node->solution = vector_get_min_index(vec);
 979         if (pbqp->dump_file) {
 980                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
 981         }
 982 }
 983
 984 void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
 985 {
 986         pbqp_edge   *src_edge   = node->edges[0];
 987         pbqp_edge   *tgt_edge   = node->edges[1];
 988         int          src_is_src = src_edge->src == node;
 989         int          tgt_is_src = tgt_edge->src == node;
 990         pbqp_matrix *src_mat;
 991         pbqp_matrix *tgt_mat;
 992         pbqp_node   *src_node;
 993         pbqp_node   *tgt_node;
 994         vector      *vec;
 995         vector      *node_vec;
 996         unsigned     col_index;
 997         unsigned     row_index;
 998
 999         assert(pbqp);
1000
1001         if (src_is_src) {
1002                 src_node = src_edge->tgt;
1003         } else {
1004                 src_node = src_edge->src;
1005         }
1006
1007         if (tgt_is_src) {
1008                 tgt_node = tgt_edge->tgt;
1009         } else {
1010                 tgt_node = tgt_edge->src;
1011         }
1012
1013         /* Swap nodes if necessary. */
1014         if (tgt_node->index < src_node->index) {
1015                 pbqp_node *tmp_node;
1016                 pbqp_edge *tmp_edge;
1017
1018                 tmp_node = src_node;
1019                 src_node = tgt_node;
1020                 tgt_node = tmp_node;
1021
1022                 tmp_edge = src_edge;
1023                 src_edge = tgt_edge;
1024                 tgt_edge = tmp_edge;
1025
1026                 src_is_src = src_edge->src == node;
1027                 tgt_is_src = tgt_edge->src == node;
1028         }
1029
1030         src_mat = src_edge->costs;
1031         tgt_mat = tgt_edge->costs;
1032
1033         node_vec = node->costs;
1034
1035         row_index = src_node->solution;
1036         col_index = tgt_node->solution;
1037
1038         vec = vector_copy(pbqp, node_vec);
1039
1040         if (src_is_src) {
1041                 vector_add_matrix_col(vec, src_mat, row_index);
1042         } else {
1043                 vector_add_matrix_row(vec, src_mat, row_index);
1044         }
1045
1046         if (tgt_is_src) {
1047                 vector_add_matrix_col(vec, tgt_mat, col_index);
1048         } else {
1049                 vector_add_matrix_row(vec, tgt_mat, col_index);
1050         }
1051
1052         node->solution = vector_get_min_index(vec);
1053         if (pbqp->dump_file) {
1054                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
1055         }
1056
1057         obstack_free(&pbqp->obstack, vec);
1058 }
1059
1060 int node_is_reduced(pbqp_node *node)
1061 {
1062         if (!reduced_bucket) return 0;
1063
1064         if (pbqp_node_get_degree(node) == 0) return 1;
1065
1066         return node_bucket_contains(reduced_bucket, node);
1067 }