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 void solve_pbqp_heuristical(pbqp *pbqp)
 432 {
 433         unsigned node_index;
 434         unsigned node_len;
 435
 436         /* Reduce nodes degree ... */
 437         initial_simplify_edges(pbqp);
 438
 439         /* ... and put node into bucket representing their degree. */
 440         fill_node_buckets(pbqp);
 441
 442         for (;;) {
 443                 if (edge_bucket_get_length(edge_bucket) > 0) {
 444                         apply_edge(pbqp);
 445                 } else if (node_bucket_get_length(node_buckets[1]) > 0) {
 446                         apply_RI(pbqp);
 447                 } else if (node_bucket_get_length(node_buckets[2]) > 0) {
 448                         apply_RII(pbqp);
 449                 } else if (node_bucket_get_length(node_buckets[3]) > 0) {
 450                         apply_RN(pbqp);
 451                 } else {
 452                         break;
 453                 }
 454         }
 455
 456         if (pbqp->dump_file) {
 457                 dump_section(pbqp->dump_file, 1, "4. Determine Solution/Minimum");
 458                 dump_section(pbqp->dump_file, 2, "4.1. Trivial Solution");
 459         }
 460
 461         /* Solve trivial nodes and calculate solution. */
 462         node_len = node_bucket_get_length(node_buckets[0]);
 463         for (node_index = 0; node_index < node_len; ++node_index) {
 464                 pbqp_node *node = node_buckets[0][node_index];
 465                 assert(node);
 466
 467                 node->solution = vector_get_min_index(node->costs);
 468                 pbqp->solution = pbqp_add(pbqp->solution,
 469                                 node->costs->entries[node->solution].data);
 470                 if (pbqp->dump_file) {
 471                         fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
 472                         dump_node(pbqp, node);
 473                 }
 474         }
 475
 476         if (pbqp->dump_file) {
 477                 dump_section(pbqp->dump_file, 2, "Minimum");
 478                 fprintf(pbqp->dump_file, "Minimum is equal to %lld.", pbqp->solution);
 479                 dump_section(pbqp->dump_file, 2, "Back Propagation");
 480         }
 481
 482         /* Solve reduced nodes. */
 483         node_len = node_bucket_get_length(reduced_bucket);
 484         for (node_index = node_len; node_index > 0; --node_index) {
 485                 pbqp_node *node = reduced_bucket[node_index - 1];
 486
 487                 switch (pbqp_node_get_degree(node)) {
 488                         case 1:
 489                                 back_propagate_RI(pbqp, node);
 490                                 break;
 491                         case 2:
 492                                 back_propagate_RII(pbqp, node);
 493                                 break;
 494                         default:
 495                                 panic("Only nodes with degree one or two should be in this bucket");
 496                                 break;
 497                 }
 498         }
 499
 500         free_buckets();
 501 }
 502
 503 void apply_edge(pbqp *pbqp)
 504 {
 505         pbqp_edge *edge = edge_bucket_pop(&edge_bucket);
 506
 507         simplify_edge(pbqp, edge);
 508 }
 509
 510 void apply_RI(pbqp *pbqp)
 511 {
 512         pbqp_node   *node       = node_bucket_pop(&node_buckets[1]);
 513         pbqp_edge   *edge       = node->edges[0];
 514         pbqp_matrix *mat        = edge->costs;
 515         int          is_src     = edge->src == node;
 516         pbqp_node   *other_node;
 517
 518         if (is_src) {
 519                 other_node = edge->tgt;
 520         } else {
 521                 other_node = edge->src;
 522         }
 523
 524         if (pbqp->dump_file) {
 525                 char     txt[100];
 526                 sprintf(txt, "RI-Reduction of Node n%d", node->index);
 527                 dump_section(pbqp->dump_file, 2, txt);
 528                 pbqp_dump_graph(pbqp);
 529                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 530                 dump_node(pbqp, node);
 531                 dump_node(pbqp, other_node);
 532                 dump_edge(pbqp, edge);
 533         }
 534
 535         if (is_src) {
 536                 pbqp_matrix_add_to_all_cols(mat, node->costs);
 537                 normalize_towards_target(pbqp, edge);
 538         } else {
 539                 pbqp_matrix_add_to_all_rows(mat, node->costs);
 540                 normalize_towards_source(pbqp, edge);
 541         }
 542         disconnect_edge(other_node, edge);
 543
 544         if (pbqp->dump_file) {
 545                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 546                 dump_node(pbqp, other_node);
 547         }
 548
 549         reorder_node(other_node);
 550
 551         /* Add node to back propagation list. */
 552         node_bucket_insert(&reduced_bucket, node);
 553 }
 554
 555 void apply_RII(pbqp *pbqp)
 556 {
 557         pbqp_node   *node       = node_bucket_pop(&node_buckets[2]);
 558         pbqp_edge   *src_edge   = node->edges[0];
 559         pbqp_edge   *tgt_edge   = node->edges[1];
 560         int          src_is_src = src_edge->src == node;
 561         int          tgt_is_src = tgt_edge->src == node;
 562         pbqp_matrix *src_mat;
 563         pbqp_matrix *tgt_mat;
 564         pbqp_node   *src_node;
 565         pbqp_node   *tgt_node;
 566         pbqp_matrix *mat;
 567         vector      *vec;
 568         vector      *node_vec;
 569         vector      *src_vec;
 570         vector      *tgt_vec;
 571         unsigned     col_index;
 572         unsigned     col_len;
 573         unsigned     row_index;
 574         unsigned     row_len;
 575         unsigned     node_len;
 576
 577         assert(pbqp);
 578
 579         if (src_is_src) {
 580                 src_node = src_edge->tgt;
 581         } else {
 582                 src_node = src_edge->src;
 583         }
 584
 585         if (tgt_is_src) {
 586                 tgt_node = tgt_edge->tgt;
 587         } else {
 588                 tgt_node = tgt_edge->src;
 589         }
 590
 591         /* Swap nodes if necessary. */
 592         if (tgt_node->index < src_node->index) {
 593                 pbqp_node *tmp_node;
 594                 pbqp_edge *tmp_edge;
 595
 596                 tmp_node = src_node;
 597                 src_node = tgt_node;
 598                 tgt_node = tmp_node;
 599
 600                 tmp_edge = src_edge;
 601                 src_edge = tgt_edge;
 602                 tgt_edge = tmp_edge;
 603
 604                 src_is_src = src_edge->src == node;
 605                 tgt_is_src = tgt_edge->src == node;
 606         }
 607
 608         if (pbqp->dump_file) {
 609                 char     txt[100];
 610                 sprintf(txt, "RII-Reduction of Node n%d", node->index);
 611                 dump_section(pbqp->dump_file, 2, txt);
 612                 pbqp_dump_graph(pbqp);
 613                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 614                 dump_node(pbqp, src_node);
 615                 dump_edge(pbqp, src_edge);
 616                 dump_node(pbqp, node);
 617                 dump_edge(pbqp, tgt_edge);
 618                 dump_node(pbqp, tgt_node);
 619         }
 620
 621         src_mat = src_edge->costs;
 622         tgt_mat = tgt_edge->costs;
 623
 624         src_vec  = src_node->costs;
 625         tgt_vec  = tgt_node->costs;
 626         node_vec = node->costs;
 627
 628         row_len  = src_vec->len;
 629         col_len  = tgt_vec->len;
 630         node_len = node_vec->len;
 631
 632         mat = pbqp_matrix_alloc(pbqp, row_len, col_len);
 633
 634         for (row_index = 0; row_index < row_len; ++row_index) {
 635                 for (col_index = 0; col_index < col_len; ++col_index) {
 636                         vec = vector_copy(pbqp, node_vec);
 637
 638                         if (src_is_src) {
 639                                 vector_add_matrix_col(vec, src_mat, row_index);
 640                         } else {
 641                                 vector_add_matrix_row(vec, src_mat, row_index);
 642                         }
 643
 644                         if (tgt_is_src) {
 645                                 vector_add_matrix_col(vec, tgt_mat, col_index);
 646                         } else {
 647                                 vector_add_matrix_row(vec, tgt_mat, col_index);
 648                         }
 649
 650                         mat->entries[row_index * col_len + col_index] = vector_get_min(vec);
 651
 652                         obstack_free(&pbqp->obstack, vec);
 653                 }
 654         }
 655
 656         pbqp_edge *edge = get_edge(pbqp, src_node->index, tgt_node->index);
 657
 658         /* Disconnect node. */
 659         disconnect_edge(src_node, src_edge);
 660         disconnect_edge(tgt_node, tgt_edge);
 661
 662         /* Add node to back propagation list. */
 663         node_bucket_insert(&reduced_bucket, node);
 664
 665         if (edge == NULL) {
 666                 edge = alloc_edge(pbqp, src_node->index, tgt_node->index, mat);
 667         } else {
 668                 pbqp_matrix_add(edge->costs, mat);
 669
 670                 /* Free local matrix. */
 671                 obstack_free(&pbqp->obstack, mat);
 672
 673                 reorder_node(src_node);
 674                 reorder_node(tgt_node);
 675         }
 676
 677         if (pbqp->dump_file) {
 678                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 679                 dump_edge(pbqp, edge);
 680         }
 681
 682         /* Edge has changed so we simplify it. */
 683         simplify_edge(pbqp, edge);
 684 }
 685
 686 void apply_RN(pbqp *pbqp)
 687 {
 688         pbqp_node  **bucket       = node_buckets[3];
 689         unsigned     bucket_len   = node_bucket_get_length(bucket);
 690         unsigned     bucket_index;
 691         pbqp_node   *node         = NULL;
 692         pbqp_edge   *edge;
 693         vector      *node_vec;
 694         vector      *vec;
 695         pbqp_matrix *mat;
 696         unsigned     edge_index;
 697         unsigned     max_degree   = 0;
 698         unsigned     node_index;
 699         unsigned     node_len;
 700         unsigned     min_index    = 0;
 701         num          min          = INF_COSTS;
 702         int          is_src;
 703
 704         assert(pbqp);
 705
 706         /* Search for node with maximum degree. */
 707         for (bucket_index = 0; bucket_index < bucket_len; ++bucket_index) {
 708                 pbqp_node *candidate = bucket[bucket_index];
 709                 unsigned   degree    = pbqp_node_get_degree(candidate);
 710
 711                 if (degree > max_degree) {
 712                         node = candidate;
 713                         max_degree = degree;
 714                 }
 715         }
 716         assert(node);
 717         node_vec = node->costs;
 718         node_len = node_vec->len;
 719
 720         if (pbqp->dump_file) {
 721                 char     txt[100];
 722                 sprintf(txt, "RN-Reduction of Node n%d", node->index);
 723                 dump_section(pbqp->dump_file, 2, txt);
 724                 pbqp_dump_graph(pbqp);
 725         }
 726
 727         for (node_index = 0; node_index < node_len; ++node_index) {
 728                 num value = node_vec->entries[node_index].data;
 729
 730                 for (edge_index = 0; edge_index < max_degree; ++edge_index) {
 731                         edge   = node->edges[edge_index];
 732                         mat    = edge->costs;
 733                         is_src = edge->src == node;
 734
 735                         if (is_src) {
 736                                 vec = vector_copy(pbqp, edge->tgt->costs);
 737                                 vector_add_matrix_row(vec, mat, node_index);
 738                         } else {
 739                                 vec = vector_copy(pbqp, edge->src->costs);
 740                                 vector_add_matrix_col(vec, mat, node_index);
 741                         }
 742
 743                         value = pbqp_add(value, vector_get_min(vec));
 744
 745                         obstack_free(&pbqp->obstack, vec);
 746                 }
 747
 748                 if (value < min) {
 749                         min = value;
 750                         min_index = node_index;
 751                 }
 752         }
 753
 754         if (pbqp->dump_file) {
 755                 fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
 756                                         node->index, min_index);
 757                 fprintf(pbqp->dump_file, "Minimal cost of RN reduction: %lld<br>\n",
 758                                                         min);
 759         }
 760
 761         node->solution = min_index;
 762
 763         /* Now that we found the local minimum set all other costs to infinity. */
 764         for (node_index = 0; node_index < node_len; ++node_index) {
 765                 if (node_index != min_index) {
 766                         node_vec->entries[node_index].data = INF_COSTS;
 767                 }
 768         }
 769
 770         /* Add all incident edges to edge bucket, since they are now independent. */
 771         for (edge_index = 0; edge_index < max_degree; ++edge_index) {
 772                 insert_into_edge_bucket(node->edges[edge_index]);
 773         }
 774 }
 775
 776 void apply_Brute_Force(pbqp *pbqp)
 777 {
 778         pbqp_node  **bucket       = node_buckets[3];
 779         unsigned     bucket_len   = node_bucket_get_length(bucket);
 780         unsigned     bucket_index;
 781         pbqp_node   *node         = NULL;
 782         pbqp_edge   *edge;
 783         vector      *node_vec;
 784         vector      *vec;
 785         pbqp_matrix *mat;
 786         unsigned     edge_index;
 787         unsigned     max_degree   = 0;
 788         unsigned     node_index;
 789         unsigned     node_len;
 790         unsigned     min_index    = 0;
 791         num          min          = INF_COSTS;
 792         int          is_src;
 793
 794         assert(pbqp);
 795
 796         /* Search for node with maximum degree. */
 797         for (bucket_index = 0; bucket_index < bucket_len; ++bucket_index) {
 798                 pbqp_node *candidate = bucket[bucket_index];
 799                 unsigned   degree    = pbqp_node_get_degree(candidate);
 800
 801                 if (degree > max_degree) {
 802                         node = candidate;
 803                         max_degree = degree;
 804                 }
 805         }
 806         assert(node);
 807         node_vec = node->costs;
 808         node_len = node_vec->len;
 809
 810         if (pbqp->dump_file) {
 811                 char     txt[100];
 812                 sprintf(txt, "RN-Reduction of Node n%d", node->index);
 813                 dump_section(pbqp->dump_file, 2, txt);
 814                 pbqp_dump_graph(pbqp);
 815         }
 816
 817         for (node_index = 0; node_index < node_len; ++node_index) {
 818                 num value = node_vec->entries[node_index].data;
 819
 820                 /* TODO Copy PBQP */
 821
 822
 823                 if (value < min) {
 824                         min = value;
 825                         min_index = node_index;
 826                 }
 827         }
 828
 829         if (pbqp->dump_file) {
 830                 fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
 831                                         node->index, min_index);
 832                 fprintf(pbqp->dump_file, "Minimal cost of RN reduction: %lld<br>\n",
 833                                                         min);
 834         }
 835
 836         node->solution = min_index;
 837
 838         /* Now that we found the local minimum set all other costs to infinity. */
 839         for (node_index = 0; node_index < node_len; ++node_index) {
 840                 if (node_index != min_index) {
 841                         node_vec->entries[node_index].data = INF_COSTS;
 842                 }
 843         }
 844
 845         /* Add all incident edges to edge bucket, since they are now independent. */
 846         for (edge_index = 0; edge_index < max_degree; ++edge_index) {
 847                 insert_into_edge_bucket(node->edges[edge_index]);
 848         }
 849 }
 850
 851 void back_propagate_RI(pbqp *pbqp, pbqp_node *node)
 852 {
 853         pbqp_edge   *edge;
 854         pbqp_node   *other;
 855         pbqp_matrix *mat;
 856         vector      *vec;
 857         int          is_src;
 858
 859         assert(pbqp);
 860         assert(node);
 861
 862         edge = node->edges[0];
 863         mat = edge->costs;
 864         is_src = edge->src == node;
 865         vec = node->costs;
 866
 867         if (is_src) {
 868                 other = edge->tgt;
 869                 assert(other);
 870                 vector_add_matrix_col(vec, mat, other->solution);
 871         } else {
 872                 other = edge->src;
 873                 assert(other);
 874                 vector_add_matrix_row(vec, mat, other->solution);
 875         }
 876
 877         node->solution = vector_get_min_index(vec);
 878         if (pbqp->dump_file) {
 879                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
 880         }
 881 }
 882
 883 void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
 884 {
 885         pbqp_edge   *src_edge   = node->edges[0];
 886         pbqp_edge   *tgt_edge   = node->edges[1];
 887         int          src_is_src = src_edge->src == node;
 888         int          tgt_is_src = tgt_edge->src == node;
 889         pbqp_matrix *src_mat;
 890         pbqp_matrix *tgt_mat;
 891         pbqp_node   *src_node;
 892         pbqp_node   *tgt_node;
 893         vector      *vec;
 894         vector      *node_vec;
 895         unsigned     col_index;
 896         unsigned     row_index;
 897
 898         assert(pbqp);
 899
 900         if (src_is_src) {
 901                 src_node = src_edge->tgt;
 902         } else {
 903                 src_node = src_edge->src;
 904         }
 905
 906         if (tgt_is_src) {
 907                 tgt_node = tgt_edge->tgt;
 908         } else {
 909                 tgt_node = tgt_edge->src;
 910         }
 911
 912         /* Swap nodes if necessary. */
 913         if (tgt_node->index < src_node->index) {
 914                 pbqp_node *tmp_node;
 915                 pbqp_edge *tmp_edge;
 916
 917                 tmp_node = src_node;
 918                 src_node = tgt_node;
 919                 tgt_node = tmp_node;
 920
 921                 tmp_edge = src_edge;
 922                 src_edge = tgt_edge;
 923                 tgt_edge = tmp_edge;
 924
 925                 src_is_src = src_edge->src == node;
 926                 tgt_is_src = tgt_edge->src == node;
 927         }
 928
 929         src_mat = src_edge->costs;
 930         tgt_mat = tgt_edge->costs;
 931
 932         node_vec = node->costs;
 933
 934         row_index = src_node->solution;
 935         col_index = tgt_node->solution;
 936
 937         vec = vector_copy(pbqp, node_vec);
 938
 939         if (src_is_src) {
 940                 vector_add_matrix_col(vec, src_mat, row_index);
 941         } else {
 942                 vector_add_matrix_row(vec, src_mat, row_index);
 943         }
 944
 945         if (tgt_is_src) {
 946                 vector_add_matrix_col(vec, tgt_mat, col_index);
 947         } else {
 948                 vector_add_matrix_row(vec, tgt_mat, col_index);
 949         }
 950
 951         node->solution = vector_get_min_index(vec);
 952         if (pbqp->dump_file) {
 953                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
 954         }
 955
 956         obstack_free(&pbqp->obstack, vec);
 957 }
 958
 959 int node_is_reduced(pbqp_node *node)
 960 {
 961         if (!reduced_bucket) return 0;
 962
 963         if (pbqp_node_get_degree(node) == 0) return 1;
 964
 965         return node_bucket_contains(reduced_bucket, node);
 966 }