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         assert(pbqp_node_get_degree(node) == 1);
 546
 547         if (is_src) {
 548                 other_node = edge->tgt;
 549         } else {
 550                 other_node = edge->src;
 551         }
 552
 553         if (pbqp->dump_file) {
 554                 char     txt[100];
 555                 sprintf(txt, "RI-Reduction of Node n%d", node->index);
 556                 dump_section(pbqp->dump_file, 2, txt);
 557                 pbqp_dump_graph(pbqp);
 558                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 559                 dump_node(pbqp->dump_file, node);
 560                 dump_node(pbqp->dump_file, other_node);
 561                 dump_edge(pbqp->dump_file, edge);
 562         }
 563
 564         if (is_src) {
 565                 pbqp_matrix_add_to_all_cols(mat, node->costs);
 566                 normalize_towards_target(pbqp, edge);
 567         } else {
 568                 pbqp_matrix_add_to_all_rows(mat, node->costs);
 569                 normalize_towards_source(pbqp, edge);
 570         }
 571         disconnect_edge(other_node, edge);
 572
 573         if (pbqp->dump_file) {
 574                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 575                 dump_node(pbqp->dump_file, other_node);
 576         }
 577
 578         reorder_node(other_node);
 579
 580         /* Add node to back propagation list. */
 581         node_bucket_insert(&reduced_bucket, node);
 582 }
 583
 584 void apply_RII(pbqp *pbqp)
 585 {
 586         pbqp_node   *node       = node_bucket_pop(&node_buckets[2]);
 587         pbqp_edge   *src_edge   = node->edges[0];
 588         pbqp_edge   *tgt_edge   = node->edges[1];
 589         int          src_is_src = src_edge->src == node;
 590         int          tgt_is_src = tgt_edge->src == node;
 591         pbqp_matrix *src_mat;
 592         pbqp_matrix *tgt_mat;
 593         pbqp_node   *src_node;
 594         pbqp_node   *tgt_node;
 595         pbqp_matrix *mat;
 596         vector      *vec;
 597         vector      *node_vec;
 598         vector      *src_vec;
 599         vector      *tgt_vec;
 600         unsigned     col_index;
 601         unsigned     col_len;
 602         unsigned     row_index;
 603         unsigned     row_len;
 604         unsigned     node_len;
 605
 606         assert(pbqp);
 607         assert(pbqp_node_get_degree(node) == 2);
 608
 609         if (src_is_src) {
 610                 src_node = src_edge->tgt;
 611         } else {
 612                 src_node = src_edge->src;
 613         }
 614
 615         if (tgt_is_src) {
 616                 tgt_node = tgt_edge->tgt;
 617         } else {
 618                 tgt_node = tgt_edge->src;
 619         }
 620
 621         /* Swap nodes if necessary. */
 622         if (tgt_node->index < src_node->index) {
 623                 pbqp_node *tmp_node;
 624                 pbqp_edge *tmp_edge;
 625
 626                 tmp_node = src_node;
 627                 src_node = tgt_node;
 628                 tgt_node = tmp_node;
 629
 630                 tmp_edge = src_edge;
 631                 src_edge = tgt_edge;
 632                 tgt_edge = tmp_edge;
 633
 634                 src_is_src = src_edge->src == node;
 635                 tgt_is_src = tgt_edge->src == node;
 636         }
 637
 638         if (pbqp->dump_file) {
 639                 char     txt[100];
 640                 sprintf(txt, "RII-Reduction of Node n%d", node->index);
 641                 dump_section(pbqp->dump_file, 2, txt);
 642                 pbqp_dump_graph(pbqp);
 643                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 644                 dump_node(pbqp->dump_file, src_node);
 645                 dump_edge(pbqp->dump_file, src_edge);
 646                 dump_node(pbqp->dump_file, node);
 647                 dump_edge(pbqp->dump_file, tgt_edge);
 648                 dump_node(pbqp->dump_file, tgt_node);
 649         }
 650
 651         src_mat = src_edge->costs;
 652         tgt_mat = tgt_edge->costs;
 653
 654         src_vec  = src_node->costs;
 655         tgt_vec  = tgt_node->costs;
 656         node_vec = node->costs;
 657
 658         row_len  = src_vec->len;
 659         col_len  = tgt_vec->len;
 660         node_len = node_vec->len;
 661
 662         mat = pbqp_matrix_alloc(pbqp, row_len, col_len);
 663
 664         for (row_index = 0; row_index < row_len; ++row_index) {
 665                 for (col_index = 0; col_index < col_len; ++col_index) {
 666                         vec = vector_copy(pbqp, node_vec);
 667
 668                         if (src_is_src) {
 669                                 vector_add_matrix_col(vec, src_mat, row_index);
 670                         } else {
 671                                 vector_add_matrix_row(vec, src_mat, row_index);
 672                         }
 673
 674                         if (tgt_is_src) {
 675                                 vector_add_matrix_col(vec, tgt_mat, col_index);
 676                         } else {
 677                                 vector_add_matrix_row(vec, tgt_mat, col_index);
 678                         }
 679
 680                         mat->entries[row_index * col_len + col_index] = vector_get_min(vec);
 681
 682                         obstack_free(&pbqp->obstack, vec);
 683                 }
 684         }
 685
 686         pbqp_edge *edge = get_edge(pbqp, src_node->index, tgt_node->index);
 687
 688         /* Disconnect node. */
 689         disconnect_edge(src_node, src_edge);
 690         disconnect_edge(tgt_node, tgt_edge);
 691
 692         /* Add node to back propagation list. */
 693         node_bucket_insert(&reduced_bucket, node);
 694
 695         if (edge == NULL) {
 696                 edge = alloc_edge(pbqp, src_node->index, tgt_node->index, mat);
 697         } else {
 698                 pbqp_matrix_add(edge->costs, mat);
 699
 700                 /* Free local matrix. */
 701                 obstack_free(&pbqp->obstack, mat);
 702
 703                 reorder_node(src_node);
 704                 reorder_node(tgt_node);
 705         }
 706
 707         if (pbqp->dump_file) {
 708                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 709                 dump_edge(pbqp->dump_file, edge);
 710         }
 711
 712         /* Edge has changed so we simplify it. */
 713         simplify_edge(pbqp, edge);
 714 }
 715
 716 static void select_alternative(pbqp_node *node, unsigned selected_index)
 717 {
 718         unsigned  edge_index;
 719         unsigned  node_index;
 720         unsigned  node_len;
 721         vector   *node_vec;
 722         unsigned  max_degree = pbqp_node_get_degree(node);
 723
 724         assert(node);
 725         node->solution = selected_index;
 726         node_vec = node->costs;
 727         node_len = node_vec->len;
 728         assert(selected_index < node_len);
 729
 730         /* Set all other costs to infinity. */
 731         for (node_index = 0; node_index < node_len; ++node_index) {
 732                 if (node_index != selected_index) {
 733                         node_vec->entries[node_index].data = INF_COSTS;
 734                 }
 735         }
 736
 737         /* Add all incident edges to edge bucket, since they are now independent. */
 738         for (edge_index = 0; edge_index < max_degree; ++edge_index) {
 739                 insert_into_edge_bucket(node->edges[edge_index]);
 740         }
 741 }
 742
 743 static pbqp_node *get_node_with_max_degree(void)
 744 {
 745         pbqp_node  **bucket       = node_buckets[3];
 746         unsigned     bucket_len   = node_bucket_get_length(bucket);
 747         unsigned     bucket_index;
 748         unsigned     max_degree   = 0;
 749         pbqp_node   *result       = NULL;
 750
 751         for (bucket_index = 0; bucket_index < bucket_len; ++bucket_index) {
 752                 pbqp_node *candidate = bucket[bucket_index];
 753                 unsigned   degree    = pbqp_node_get_degree(candidate);
 754
 755                 if (degree > max_degree) {
 756                         result = candidate;
 757                         max_degree = degree;
 758                 }
 759         }
 760
 761         return result;
 762 }
 763
 764 static unsigned get_local_minimal_alternative(pbqp *pbqp, pbqp_node *node)
 765 {
 766         pbqp_edge   *edge;
 767         vector      *node_vec;
 768         vector      *vec;
 769         pbqp_matrix *mat;
 770         unsigned     edge_index;
 771         unsigned     max_degree   = 0;
 772         unsigned     node_index;
 773         unsigned     node_len;
 774         unsigned     min_index    = 0;
 775         num          min          = INF_COSTS;
 776         int          is_src;
 777
 778         assert(pbqp);
 779         assert(node);
 780         node_vec = node->costs;
 781         node_len = node_vec->len;
 782
 783         for (node_index = 0; node_index < node_len; ++node_index) {
 784                 num value = node_vec->entries[node_index].data;
 785
 786                 for (edge_index = 0; edge_index < max_degree; ++edge_index) {
 787                         edge   = node->edges[edge_index];
 788                         mat    = edge->costs;
 789                         is_src = edge->src == node;
 790
 791                         if (is_src) {
 792                                 vec = vector_copy(pbqp, edge->tgt->costs);
 793                                 vector_add_matrix_row(vec, mat, node_index);
 794                         } else {
 795                                 vec = vector_copy(pbqp, edge->src->costs);
 796                                 vector_add_matrix_col(vec, mat, node_index);
 797                         }
 798
 799                         value = pbqp_add(value, vector_get_min(vec));
 800
 801                         obstack_free(&pbqp->obstack, vec);
 802                 }
 803
 804                 if (value < min) {
 805                         min = value;
 806                         min_index = node_index;
 807                 }
 808         }
 809
 810         return min_index;
 811 }
 812
 813 void apply_RN(pbqp *pbqp)
 814 {
 815         pbqp_node   *node         = NULL;
 816         unsigned     min_index    = 0;
 817
 818         assert(pbqp);
 819
 820         /* We want to reduce a node with maximum degree. */
 821         node = get_node_with_max_degree();
 822         assert(node);
 823         assert(pbqp_node_get_degree(node) > 2);
 824
 825         if (pbqp->dump_file) {
 826                 char     txt[100];
 827                 sprintf(txt, "RN-Reduction of Node n%d", node->index);
 828                 dump_section(pbqp->dump_file, 2, txt);
 829                 pbqp_dump_graph(pbqp);
 830         }
 831
 832         min_index = get_local_minimal_alternative(pbqp, node);
 833
 834         if (pbqp->dump_file) {
 835                 fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
 836                                         node->index, min_index);
 837         }
 838
 839         /* Now that we found the local minimum set all other costs to infinity. */
 840         select_alternative(node, min_index);
 841 }
 842
 843 static void apply_brute_force_reductions(pbqp *pbqp)
 844 {
 845         for (;;) {
 846                 if (edge_bucket_get_length(edge_bucket) > 0) {
 847                         apply_edge(pbqp);
 848                 } else if (node_bucket_get_length(node_buckets[1]) > 0) {
 849                         apply_RI(pbqp);
 850                 } else if (node_bucket_get_length(node_buckets[2]) > 0) {
 851                         apply_RII(pbqp);
 852                 } else if (node_bucket_get_length(node_buckets[3]) > 0) {
 853                         apply_Brute_Force(pbqp);
 854                 } else {
 855                         return;
 856                 }
 857         }
 858 }
 859
 860 static unsigned get_minimal_alternative(pbqp *pbqp, pbqp_node *node)
 861 {
 862         vector      *node_vec;
 863         unsigned     node_index;
 864         unsigned     node_len;
 865         unsigned     min_index    = 0;
 866         num          min          = INF_COSTS;
 867
 868         assert(pbqp);
 869         assert(node);
 870         node_vec = node->costs;
 871         node_len = node_vec->len;
 872
 873         for (node_index = 0; node_index < node_len; ++node_index) {
 874                 pbqp_node_bucket bucket_deg0;
 875                 pbqp_node_bucket bucket_deg3;
 876                 pbqp_node_bucket bucket_red;
 877                 num              value;
 878
 879                 /* Some node buckets and the edge bucket should be empty. */
 880                 assert(node_bucket_get_length(node_buckets[1]) == 0);
 881                 assert(node_bucket_get_length(node_buckets[2]) == 0);
 882                 assert(edge_bucket_get_length(edge_bucket)     == 0);
 883
 884                 char *tmp = obstack_finish(&pbqp->obstack);
 885
 886                 /* Save current PBQP state. */
 887                 node_bucket_deep_copy(pbqp, &bucket_deg0, node_buckets[0]);
 888                 node_bucket_deep_copy(pbqp, &bucket_deg3, node_buckets[3]);
 889                 node_bucket_deep_copy(pbqp, &bucket_red, reduced_bucket);
 890
 891                 /* Select alternative and solve PBQP recursively. */
 892                 select_alternative(node, node_index);
 893                 apply_brute_force_reductions(pbqp);
 894
 895                 value = determine_solution(pbqp->dump_file);
 896
 897                 if (value < min) {
 898                         min = value;
 899                         min_index = node_index;
 900                 }
 901
 902                 /* Some node buckets and the edge bucket should still be empty. */
 903                 assert(node_bucket_get_length(node_buckets[1]) == 0);
 904                 assert(node_bucket_get_length(node_buckets[2]) == 0);
 905                 assert(edge_bucket_get_length(edge_bucket)     == 0);
 906
 907                 /* Clear modified buckets... */
 908                 node_bucket_clear(&node_buckets[0]);
 909                 node_bucket_clear(&node_buckets[3]);
 910                 node_bucket_clear(&reduced_bucket);
 911
 912                 /* ... and restore old PBQP state. */
 913                 node_bucket_copy(&node_buckets[0], bucket_deg0);
 914                 node_bucket_copy(&node_buckets[3], bucket_deg3);
 915                 node_bucket_copy(&reduced_bucket, bucket_red);
 916
 917                 /* Free copies. */
 918                 obstack_free(&pbqp->obstack, tmp);
 919                 node_bucket_free(&bucket_deg0);
 920                 node_bucket_free(&bucket_deg3);
 921                 node_bucket_free(&bucket_red);
 922         }
 923
 924         return min_index;
 925 }
 926
 927 void apply_Brute_Force(pbqp *pbqp)
 928 {
 929         pbqp_node   *node         = NULL;
 930         unsigned     min_index    = 0;
 931
 932         assert(pbqp);
 933
 934         /* We want to reduce a node with maximum degree. */
 935         node = get_node_with_max_degree();
 936         assert(node);
 937         assert(pbqp_node_get_degree(node) > 2);
 938
 939         if (pbqp->dump_file) {
 940                 char     txt[100];
 941                 sprintf(txt, "BF-Reduction of Node n%d", node->index);
 942                 dump_section(pbqp->dump_file, 2, txt);
 943                 pbqp_dump_graph(pbqp);
 944         }
 945
 946         min_index = get_minimal_alternative(pbqp, node);
 947
 948         if (pbqp->dump_file) {
 949                 fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
 950                                         node->index, min_index);
 951         }
 952
 953         /* Now that we found the minimum set all other costs to infinity. */
 954         select_alternative(node, min_index);
 955 }
 956
 957 void solve_pbqp_brute_force(pbqp *pbqp)
 958 {
 959         /* Reduce nodes degree ... */
 960         initial_simplify_edges(pbqp);
 961
 962         /* ... and put node into bucket representing their degree. */
 963         fill_node_buckets(pbqp);
 964
 965         apply_brute_force_reductions(pbqp);
 966
 967         pbqp->solution = determine_solution(pbqp->dump_file);
 968
 969         /* Solve reduced nodes. */
 970         back_propagate(pbqp);
 971
 972         free_buckets();
 973 }
 974
 975 void back_propagate_RI(pbqp *pbqp, pbqp_node *node)
 976 {
 977         pbqp_edge   *edge;
 978         pbqp_node   *other;
 979         pbqp_matrix *mat;
 980         vector      *vec;
 981         int          is_src;
 982
 983         assert(pbqp);
 984         assert(node);
 985
 986         edge = node->edges[0];
 987         mat = edge->costs;
 988         is_src = edge->src == node;
 989         vec = node->costs;
 990
 991         if (is_src) {
 992                 other = edge->tgt;
 993                 assert(other);
 994                 vector_add_matrix_col(vec, mat, other->solution);
 995         } else {
 996                 other = edge->src;
 997                 assert(other);
 998                 vector_add_matrix_row(vec, mat, other->solution);
 999         }
1000
1001         node->solution = vector_get_min_index(vec);
1002         if (pbqp->dump_file) {
1003                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
1004         }
1005 }
1006
1007 void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
1008 {
1009         pbqp_edge   *src_edge   = node->edges[0];
1010         pbqp_edge   *tgt_edge   = node->edges[1];
1011         int          src_is_src = src_edge->src == node;
1012         int          tgt_is_src = tgt_edge->src == node;
1013         pbqp_matrix *src_mat;
1014         pbqp_matrix *tgt_mat;
1015         pbqp_node   *src_node;
1016         pbqp_node   *tgt_node;
1017         vector      *vec;
1018         vector      *node_vec;
1019         unsigned     col_index;
1020         unsigned     row_index;
1021
1022         assert(pbqp);
1023
1024         if (src_is_src) {
1025                 src_node = src_edge->tgt;
1026         } else {
1027                 src_node = src_edge->src;
1028         }
1029
1030         if (tgt_is_src) {
1031                 tgt_node = tgt_edge->tgt;
1032         } else {
1033                 tgt_node = tgt_edge->src;
1034         }
1035
1036         /* Swap nodes if necessary. */
1037         if (tgt_node->index < src_node->index) {
1038                 pbqp_node *tmp_node;
1039                 pbqp_edge *tmp_edge;
1040
1041                 tmp_node = src_node;
1042                 src_node = tgt_node;
1043                 tgt_node = tmp_node;
1044
1045                 tmp_edge = src_edge;
1046                 src_edge = tgt_edge;
1047                 tgt_edge = tmp_edge;
1048
1049                 src_is_src = src_edge->src == node;
1050                 tgt_is_src = tgt_edge->src == node;
1051         }
1052
1053         src_mat = src_edge->costs;
1054         tgt_mat = tgt_edge->costs;
1055
1056         node_vec = node->costs;
1057
1058         row_index = src_node->solution;
1059         col_index = tgt_node->solution;
1060
1061         vec = vector_copy(pbqp, node_vec);
1062
1063         if (src_is_src) {
1064                 vector_add_matrix_col(vec, src_mat, row_index);
1065         } else {
1066                 vector_add_matrix_row(vec, src_mat, row_index);
1067         }
1068
1069         if (tgt_is_src) {
1070                 vector_add_matrix_col(vec, tgt_mat, col_index);
1071         } else {
1072                 vector_add_matrix_row(vec, tgt_mat, col_index);
1073         }
1074
1075         node->solution = vector_get_min_index(vec);
1076         if (pbqp->dump_file) {
1077                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
1078         }
1079
1080         obstack_free(&pbqp->obstack, vec);
1081 }
1082
1083 int node_is_reduced(pbqp_node *node)
1084 {
1085         if (!reduced_bucket) return 0;
1086
1087         if (pbqp_node_get_degree(node) == 0) return 1;
1088
1089         return node_bucket_contains(reduced_bucket, node);
1090 }