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