nsz Git - libfirm/blob - heuristical.c

   1 #include "adt/array.h"
   2 #include "assert.h"
   3 #include "error.h"
   4
   5 #include "heuristical.h"
   6 #include "html_dumper.h"
   7 #include "kaps.h"
   8 #include "matrix.h"
   9 #include "pbqp_edge.h"
  10 #include "pbqp_edge_t.h"
  11 #include "pbqp_node.h"
  12 #include "pbqp_node_t.h"
  13 #include "vector.h"
  14
  15 static pbqp_edge **edge_bucket;
  16 static pbqp_node **node_buckets[4];
  17 static pbqp_node **reduced_bucket = NULL;
  18 static int         buckets_filled = 0;
  19
  20 static void insert_into_edge_bucket(pbqp_edge *edge)
  21 {
  22         unsigned bucket_len = ARR_LEN(edge_bucket);
  23
  24         if (edge->bucket_index < bucket_len && edge_bucket[edge->bucket_index]
  25                         == edge)
  26                 /* Edge is already inserted. */
  27                 return;
  28
  29         edge->bucket_index = bucket_len;
  30         ARR_APP1(pbqp_edge *, edge_bucket, edge);
  31 }
  32
  33 static void init_buckets(void)
  34 {
  35         int i;
  36
  37         edge_bucket = NEW_ARR_F(pbqp_edge *, 0);
  38         reduced_bucket = NEW_ARR_F(pbqp_node *, 0);
  39
  40         for (i = 0; i < 4; ++i) {
  41                 node_buckets[i] = NEW_ARR_F(pbqp_node *, 0);
  42         }
  43 }
  44
  45 static void free_buckets(void)
  46 {
  47         int i;
  48
  49         for (i = 0; i < 4; ++i) {
  50                 DEL_ARR_F(node_buckets[i]);
  51                 node_buckets[i] = NULL;
  52         }
  53
  54         DEL_ARR_F(edge_bucket);
  55         edge_bucket = NULL;
  56
  57         DEL_ARR_F(reduced_bucket);
  58         reduced_bucket = NULL;
  59
  60         buckets_filled = 0;
  61 }
  62
  63 static void fill_node_buckets(pbqp *pbqp)
  64 {
  65         unsigned node_index;
  66         unsigned node_len;
  67
  68         assert(pbqp);
  69         node_len = pbqp->num_nodes;
  70
  71         for (node_index = 0; node_index < node_len; ++node_index) {
  72                 unsigned   arity;
  73                 pbqp_node *node = get_node(pbqp, node_index);
  74
  75                 if (!node) continue;
  76
  77                 arity = ARR_LEN(node->edges);
  78
  79                 /* We have only one bucket for nodes with arity >= 3. */
  80                 if (arity > 3) {
  81                         arity = 3;
  82                 }
  83
  84                 node->bucket_index = ARR_LEN(node_buckets[arity]);
  85
  86                 ARR_APP1(pbqp_node *, node_buckets[arity], node);
  87         }
  88
  89         buckets_filled = 1;
  90 }
  91
  92 static void normalize_towards_source(pbqp *pbqp, pbqp_edge *edge)
  93 {
  94         pbqp_matrix    *mat;
  95         pbqp_node      *src_node;
  96         pbqp_node      *tgt_node;
  97         vector         *src_vec;
  98         vector         *tgt_vec;
  99         int             src_len;
 100         int             tgt_len;
 101         int             src_index;
 102
 103         assert(pbqp);
 104         assert(edge);
 105
 106         src_node = edge->src;
 107         tgt_node = edge->tgt;
 108         assert(src_node);
 109         assert(tgt_node);
 110
 111         src_vec = src_node->costs;
 112         tgt_vec = tgt_node->costs;
 113         assert(src_vec);
 114         assert(tgt_vec);
 115
 116         src_len = src_vec->len;
 117         tgt_len = tgt_vec->len;
 118         assert(src_len > 0);
 119         assert(tgt_len > 0);
 120
 121         mat = edge->costs;
 122         assert(mat);
 123
 124         /* Normalize towards source node. */
 125         for (src_index = 0; src_index < src_len; ++src_index) {
 126                 num min = pbqp_matrix_get_row_min(mat, src_index, tgt_vec);
 127
 128                 if (min != 0) {
 129                         pbqp_matrix_sub_row_value(mat, src_index, tgt_vec, min);
 130                         src_vec->entries[src_index].data = pbqp_add(
 131                                         src_vec->entries[src_index].data, min);
 132
 133                         if (min == INF_COSTS) {
 134                                 insert_into_edge_bucket(edge);
 135                         }
 136                 }
 137         }
 138 }
 139
 140 static void normalize_towards_target(pbqp *pbqp, pbqp_edge *edge)
 141 {
 142         pbqp_matrix    *mat;
 143         pbqp_node      *src_node;
 144         pbqp_node      *tgt_node;
 145         vector         *src_vec;
 146         vector         *tgt_vec;
 147         int             src_len;
 148         int             tgt_len;
 149         int             tgt_index;
 150
 151         assert(pbqp);
 152         assert(edge);
 153
 154         src_node = edge->src;
 155         tgt_node = edge->tgt;
 156         assert(src_node);
 157         assert(tgt_node);
 158
 159         src_vec = src_node->costs;
 160         tgt_vec = tgt_node->costs;
 161         assert(src_vec);
 162         assert(tgt_vec);
 163
 164         src_len = src_vec->len;
 165         tgt_len = tgt_vec->len;
 166         assert(src_len > 0);
 167         assert(tgt_len > 0);
 168
 169         mat = edge->costs;
 170         assert(mat);
 171
 172         for (tgt_index = 0; tgt_index < tgt_len; ++tgt_index) {
 173                 num min = pbqp_matrix_get_col_min(mat, tgt_index, src_vec);
 174
 175                 if (min != 0) {
 176                         pbqp_matrix_sub_col_value(mat, tgt_index, src_vec, min);
 177                         tgt_vec->entries[tgt_index].data = pbqp_add(
 178                                         tgt_vec->entries[tgt_index].data, min);
 179
 180                         if (min == INF_COSTS) {
 181                                 insert_into_edge_bucket(edge);
 182                         }
 183                 }
 184         }
 185 }
 186
 187 static void reorder_node(pbqp_node *node)
 188 {
 189         unsigned    arity;
 190         unsigned    old_arity;
 191         unsigned    old_bucket_len;
 192         unsigned    old_bucket_index;
 193         pbqp_node **old_bucket;
 194         pbqp_node  *other;
 195
 196         if (!buckets_filled) return;
 197
 198         assert(node);
 199
 200         arity = ARR_LEN(node->edges);
 201
 202         /* Same bucket as before */
 203         if (arity > 2) return;
 204
 205         /* Assume node lost one incident edge. */
 206         old_arity        = arity + 1;
 207         old_bucket       = node_buckets[old_arity];
 208         old_bucket_len   = ARR_LEN(old_bucket);
 209         old_bucket_index = node->bucket_index;
 210
 211         if (old_bucket_len <= old_bucket_index || old_bucket[old_bucket_index]
 212                         != node) {
 213                 unsigned bucket_len = ARR_LEN(node_buckets[arity]);
 214
 215                 /* Old arity is new arity, so we have nothing to do. */
 216                 assert(old_bucket_index < bucket_len);
 217                 assert(node_buckets[arity][old_bucket_index] == node);
 218                 return;
 219         }
 220
 221         assert(old_bucket[old_bucket_index] == node);
 222
 223         /* Delete node from old bucket... */
 224         other                        = old_bucket[old_bucket_len - 1];
 225         other->bucket_index          = old_bucket_index;
 226         old_bucket[old_bucket_index] = other;
 227         ARR_SHRINKLEN(node_buckets[old_arity], old_bucket_len - 1);
 228
 229         /* ..and add to new one. */
 230         node->bucket_index = ARR_LEN(node_buckets[arity]);
 231         ARR_APP1(pbqp_node*, node_buckets[arity], node);
 232 }
 233
 234 static void simplify_edge(pbqp *pbqp, pbqp_edge *edge)
 235 {
 236         pbqp_matrix    *mat;
 237         pbqp_node      *src_node;
 238         pbqp_node      *tgt_node;
 239         vector         *src_vec;
 240         vector         *tgt_vec;
 241         int             src_len;
 242         int             tgt_len;
 243
 244         assert(pbqp);
 245         assert(edge);
 246
 247         src_node = edge->src;
 248         tgt_node = edge->tgt;
 249         assert(src_node);
 250         assert(tgt_node);
 251
 252         /* If edge are already deleted, we have nothing to do. */
 253         if (!is_connected(src_node, edge) || !is_connected(tgt_node, edge))
 254                 return;
 255
 256         if (pbqp->dump_file) {
 257                 char txt[100];
 258                 sprintf(txt, "Simplification of Edge n%d-n%d", src_node->index, tgt_node->index);
 259                 dump_section(pbqp->dump_file, 3, txt);
 260         }
 261
 262         src_vec = src_node->costs;
 263         tgt_vec = tgt_node->costs;
 264         assert(src_vec);
 265         assert(tgt_vec);
 266
 267         src_len = src_vec->len;
 268         tgt_len = tgt_vec->len;
 269         assert(src_len > 0);
 270         assert(tgt_len > 0);
 271
 272         mat = edge->costs;
 273         assert(mat);
 274
 275         if (pbqp->dump_file) {
 276                 fputs("Input:<br>\n", pbqp->dump_file);
 277                 dump_simplifyedge(pbqp, edge);
 278         }
 279
 280         normalize_towards_source(pbqp, edge);
 281         normalize_towards_target(pbqp, edge);
 282
 283         if (pbqp->dump_file) {
 284                 fputs("<br>\nOutput:<br>\n", pbqp->dump_file);
 285                 dump_simplifyedge(pbqp, edge);
 286         }
 287
 288         if (pbqp_matrix_is_zero(mat, src_vec, tgt_vec)) {
 289                 if (pbqp->dump_file) {
 290                         fputs("edge has been eliminated<br>\n", pbqp->dump_file);
 291                 }
 292
 293                 delete_edge(edge);
 294                 reorder_node(src_node);
 295                 reorder_node(tgt_node);
 296         }
 297 }
 298
 299 void solve_pbqp_heuristical(pbqp *pbqp)
 300 {
 301         unsigned node_index;
 302         unsigned node_len;
 303
 304         assert(pbqp);
 305
 306         if (pbqp->dump_file) {
 307                 pbqp_dump_input(pbqp);
 308                 dump_section(pbqp->dump_file, 1, "2. Simplification of Cost Matrices");
 309         }
 310
 311         node_len = pbqp->num_nodes;
 312
 313         init_buckets();
 314
 315         /* First simplify all edges. */
 316         for (node_index = 0; node_index < node_len; ++node_index) {
 317                 unsigned    edge_index;
 318                 pbqp_node  *node = get_node(pbqp, node_index);
 319                 pbqp_edge **edges;
 320                 unsigned    edge_len;
 321
 322                 if (!node) continue;
 323
 324                 edges = node->edges;
 325                 edge_len = ARR_LEN(edges);
 326
 327                 for (edge_index = 0; edge_index < edge_len; ++edge_index) {
 328                         pbqp_edge *edge = edges[edge_index];
 329
 330                         /* Simplify only once per edge. */
 331                         if (node != edge->src) continue;
 332
 333                         simplify_edge(pbqp, edge);
 334                 }
 335         }
 336
 337         /* Put node into bucket representing their arity. */
 338         fill_node_buckets(pbqp);
 339
 340         for (;;) {
 341                 if (ARR_LEN(edge_bucket) > 0) {
 342                         apply_edge(pbqp);
 343                 } else if (ARR_LEN(node_buckets[1]) > 0) {
 344                         apply_RI(pbqp);
 345                 } else if (ARR_LEN(node_buckets[2]) > 0) {
 346                         apply_RII(pbqp);
 347                 } else if (ARR_LEN(node_buckets[3]) > 0) {
 348                         apply_RN(pbqp);
 349                 } else {
 350                         break;
 351                 }
 352         }
 353
 354         if (pbqp->dump_file) {
 355                 dump_section(pbqp->dump_file, 1, "4. Determine Solution/Minimum");
 356                 dump_section(pbqp->dump_file, 2, "4.1. Trivial Solution");
 357         }
 358
 359         /* Solve trivial nodes and calculate solution. */
 360         node_len = ARR_LEN(node_buckets[0]);
 361         for (node_index = 0; node_index < node_len; ++node_index) {
 362                 pbqp_node *node = node_buckets[0][node_index];
 363                 assert(node);
 364
 365                 node->solution = vector_get_min_index(node->costs);
 366                 pbqp->solution = pbqp_add(pbqp->solution,
 367                                 node->costs->entries[node->solution].data);
 368                 if (pbqp->dump_file) {
 369                         fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
 370                         dump_node(pbqp, node);
 371                 }
 372         }
 373
 374         if (pbqp->dump_file) {
 375                 dump_section(pbqp->dump_file, 2, "Minimum");
 376                 fprintf(pbqp->dump_file, "Minimum is equal to %d.", pbqp->solution);
 377                 dump_section(pbqp->dump_file, 2, "Back Propagation");
 378         }
 379
 380         /* Solve reduced nodes. */
 381         node_len = ARR_LEN(reduced_bucket);
 382         for (node_index = node_len; node_index > 0; --node_index) {
 383                 pbqp_node *node = reduced_bucket[node_index - 1];
 384                 assert(node);
 385
 386                 switch (ARR_LEN(node->edges)) {
 387                         case 1:
 388                                 back_propagate_RI(pbqp, node);
 389                                 break;
 390                         case 2:
 391                                 back_propagate_RII(pbqp, node);
 392                                 break;
 393                         default:
 394                                 panic("Only nodes with degree one or two should be in this bucket");
 395                                 break;
 396                 }
 397         }
 398
 399         free_buckets();
 400 }
 401
 402 void apply_edge(pbqp *pbqp)
 403 {
 404         unsigned   bucket_len = ARR_LEN(edge_bucket);
 405         pbqp_edge *edge       = edge_bucket[bucket_len - 1];
 406
 407         ARR_SHRINKLEN(edge_bucket, (int)bucket_len - 1);
 408
 409         simplify_edge(pbqp, edge);
 410 }
 411
 412 void apply_RI(pbqp *pbqp)
 413 {
 414         pbqp_node  **bucket     = node_buckets[1];
 415         unsigned     bucket_len = ARR_LEN(bucket);
 416         pbqp_node   *node       = bucket[bucket_len - 1];
 417         pbqp_edge   *edge       = node->edges[0];
 418         pbqp_matrix *mat        = edge->costs;
 419         int          is_src     = edge->src == node;
 420         pbqp_node   *other_node;
 421
 422         if (is_src) {
 423                 other_node = edge->tgt;
 424         } else {
 425                 other_node = edge->src;
 426         }
 427
 428         if (pbqp->dump_file) {
 429                 char     txt[100];
 430                 sprintf(txt, "RI-Reduction of Node n%d", node->index);
 431                 dump_section(pbqp->dump_file, 2, txt);
 432                 pbqp_dump_graph(pbqp);
 433                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 434                 dump_node(pbqp, node);
 435                 dump_node(pbqp, other_node);
 436                 dump_edge(pbqp, edge);
 437         }
 438
 439         if (is_src) {
 440                 pbqp_matrix_add_to_all_cols(mat, node->costs);
 441                 normalize_towards_target(pbqp, edge);
 442         } else {
 443                 pbqp_matrix_add_to_all_rows(mat, node->costs);
 444                 normalize_towards_source(pbqp, edge);
 445         }
 446         disconnect_edge(other_node, edge);
 447
 448         if (pbqp->dump_file) {
 449                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 450                 dump_node(pbqp, other_node);
 451         }
 452
 453         /* Remove node from bucket... */
 454         ARR_SHRINKLEN(bucket, (int)bucket_len - 1);
 455         reorder_node(other_node);
 456
 457         /* ...and add it to back propagation list. */
 458         node->bucket_index = ARR_LEN(reduced_bucket);
 459         ARR_APP1(pbqp_node *, reduced_bucket, node);
 460 }
 461
 462 void apply_RII(pbqp *pbqp)
 463 {
 464         pbqp_node  **bucket     = node_buckets[2];
 465         unsigned     bucket_len = ARR_LEN(bucket);
 466         pbqp_node   *node       = bucket[bucket_len - 1];
 467         pbqp_edge   *src_edge   = node->edges[0];
 468         pbqp_edge   *tgt_edge   = node->edges[1];
 469         int          src_is_src = src_edge->src == node;
 470         int          tgt_is_src = tgt_edge->src == node;
 471         pbqp_matrix *src_mat;
 472         pbqp_matrix *tgt_mat;
 473         pbqp_node   *src_node;
 474         pbqp_node   *tgt_node;
 475         pbqp_matrix *mat;
 476         vector      *vec;
 477         vector      *node_vec;
 478         vector      *src_vec;
 479         vector      *tgt_vec;
 480         unsigned     col_index;
 481         unsigned     col_len;
 482         unsigned     row_index;
 483         unsigned     row_len;
 484         unsigned     node_len;
 485
 486         assert(pbqp);
 487
 488         if (src_is_src) {
 489                 src_node = src_edge->tgt;
 490         } else {
 491                 src_node = src_edge->src;
 492         }
 493
 494         if (tgt_is_src) {
 495                 tgt_node = tgt_edge->tgt;
 496         } else {
 497                 tgt_node = tgt_edge->src;
 498         }
 499
 500         /* Swap nodes if necessary. */
 501         if (tgt_node->index < src_node->index) {
 502                 pbqp_node *tmp_node;
 503                 pbqp_edge *tmp_edge;
 504
 505                 tmp_node = src_node;
 506                 src_node = tgt_node;
 507                 tgt_node = tmp_node;
 508
 509                 tmp_edge = src_edge;
 510                 src_edge = tgt_edge;
 511                 tgt_edge = tmp_edge;
 512
 513                 src_is_src = src_edge->src == node;
 514                 tgt_is_src = tgt_edge->src == node;
 515         }
 516
 517         if (pbqp->dump_file) {
 518                 char     txt[100];
 519                 sprintf(txt, "RII-Reduction of Node n%d", node->index);
 520                 dump_section(pbqp->dump_file, 2, txt);
 521                 pbqp_dump_graph(pbqp);
 522                 fputs("<br>\nBefore reduction:<br>\n", pbqp->dump_file);
 523                 dump_node(pbqp, src_node);
 524                 dump_edge(pbqp, src_edge);
 525                 dump_node(pbqp, node);
 526                 dump_edge(pbqp, tgt_edge);
 527                 dump_node(pbqp, tgt_node);
 528         }
 529
 530         src_mat = src_edge->costs;
 531         tgt_mat = tgt_edge->costs;
 532
 533         src_vec  = src_node->costs;
 534         tgt_vec  = tgt_node->costs;
 535         node_vec = node->costs;
 536
 537         row_len  = src_vec->len;
 538         col_len  = tgt_vec->len;
 539         node_len = node_vec->len;
 540
 541         mat = pbqp_matrix_alloc(pbqp, row_len, col_len);
 542
 543         for (row_index = 0; row_index < row_len; ++row_index) {
 544                 for (col_index = 0; col_index < col_len; ++col_index) {
 545                         vec = vector_copy(pbqp, node_vec);
 546
 547                         if (src_is_src) {
 548                                 vector_add_matrix_col(vec, src_mat, row_index);
 549                         } else {
 550                                 vector_add_matrix_row(vec, src_mat, row_index);
 551                         }
 552
 553                         if (tgt_is_src) {
 554                                 vector_add_matrix_col(vec, tgt_mat, col_index);
 555                         } else {
 556                                 vector_add_matrix_row(vec, tgt_mat, col_index);
 557                         }
 558
 559                         mat->entries[row_index * col_len + col_index] = vector_get_min(vec);
 560
 561                         obstack_free(&pbqp->obstack, vec);
 562                 }
 563         }
 564
 565         pbqp_edge *edge = get_edge(pbqp, src_node->index, tgt_node->index);
 566
 567         /* Disconnect node. */
 568         disconnect_edge(src_node, src_edge);
 569         disconnect_edge(tgt_node, tgt_edge);
 570
 571         /* Remove node from bucket... */
 572         ARR_SHRINKLEN(bucket, (int)bucket_len - 1);
 573
 574         /* ...and add it to back propagation list. */
 575         node->bucket_index = ARR_LEN(reduced_bucket);
 576         ARR_APP1(pbqp_node *, reduced_bucket, node);
 577
 578         if (edge == NULL) {
 579                 edge = alloc_edge(pbqp, src_node->index, tgt_node->index, mat);
 580         } else {
 581                 pbqp_matrix_add(edge->costs, mat);
 582
 583                 /* Free local matrix. */
 584                 obstack_free(&pbqp->obstack, mat);
 585
 586                 reorder_node(src_node);
 587                 reorder_node(tgt_node);
 588         }
 589
 590         if (pbqp->dump_file) {
 591                 fputs("<br>\nAfter reduction:<br>\n", pbqp->dump_file);
 592                 dump_edge(pbqp, edge);
 593         }
 594
 595         /* Edge has changed so we simplify it. */
 596         simplify_edge(pbqp, edge);
 597 }
 598
 599 void apply_RN(pbqp *pbqp)
 600 {
 601         pbqp_node  **bucket     = node_buckets[3];
 602         unsigned     bucket_len = ARR_LEN(bucket);
 603         pbqp_node   *node       = bucket[bucket_len - 1];
 604         pbqp_edge   *edge;
 605         vector      *node_vec   = node->costs;
 606         vector      *vec;
 607         pbqp_matrix *mat;
 608         unsigned     edge_index;
 609         unsigned     edge_len   = ARR_LEN(node->edges);
 610         unsigned     node_index;
 611         unsigned     node_len   = node_vec->len;
 612         unsigned     min_index  = 0;
 613         num          min        = INF_COSTS;
 614         int          is_src;
 615
 616         assert(pbqp);
 617
 618         if (pbqp->dump_file) {
 619                 char     txt[100];
 620                 sprintf(txt, "RN-Reduction of Node n%d", node->index);
 621                 dump_section(pbqp->dump_file, 2, txt);
 622                 pbqp_dump_graph(pbqp);
 623         }
 624
 625         for (node_index = 0; node_index < node_len; ++node_index) {
 626                 num value = 0;
 627
 628                 for (edge_index = 0; edge_index < edge_len; ++edge_index) {
 629                         edge   = node->edges[edge_index];
 630                         mat    = edge->costs;
 631                         is_src = edge->src == node;
 632
 633                         if (is_src) {
 634                                 vec = vector_copy(pbqp, edge->tgt->costs);
 635                                 vector_add_matrix_row(vec, mat, node_index);
 636                         } else {
 637                                 vec = vector_copy(pbqp, edge->src->costs);
 638                                 vector_add_matrix_col(vec, mat, node_index);
 639                         }
 640
 641                         value = pbqp_add(value, vector_get_min(vec));
 642
 643                         obstack_free(&pbqp->obstack, vec);
 644                 }
 645
 646                 if (value < min) {
 647                         min = value;
 648                         min_index = node_index;
 649                 }
 650         }
 651
 652         if (pbqp->dump_file) {
 653                 fprintf(pbqp->dump_file, "node n%d is set to %d<br><br>\n",
 654                                         node->index, min_index);
 655                 fprintf(pbqp->dump_file, "Minimal cost of RN reduction: %d<br>\n",
 656                                                         min);
 657         }
 658
 659         node->solution = min_index;
 660
 661         /* Now that we found the local minimum set all other costs to infinity. */
 662         for (node_index = 0; node_index < node_len; ++node_index) {
 663                 if (node_index != min_index) {
 664                         node_vec->entries[node_index].data = INF_COSTS;
 665                 }
 666         }
 667
 668         /* Add all incident edges to edge bucket, since they are now independent. */
 669         for (edge_index = 0; edge_index < edge_len; ++edge_index) {
 670                 insert_into_edge_bucket(node->edges[edge_index]);
 671         }
 672 }
 673
 674 void back_propagate_RI(pbqp *pbqp, pbqp_node *node)
 675 {
 676         pbqp_edge   *edge;
 677         pbqp_node   *other;
 678         pbqp_matrix *mat;
 679         vector      *vec;
 680         int          is_src;
 681
 682         assert(pbqp);
 683         assert(node);
 684
 685         edge = node->edges[0];
 686         mat = edge->costs;
 687         is_src = edge->src == node;
 688         vec = node->costs;
 689
 690         if (is_src) {
 691                 other = edge->tgt;
 692                 assert(other);
 693                 vector_add_matrix_col(vec, mat, other->solution);
 694         } else {
 695                 other = edge->src;
 696                 assert(other);
 697                 vector_add_matrix_row(vec, mat, other->solution);
 698         }
 699
 700         node->solution = vector_get_min_index(vec);
 701         if (pbqp->dump_file) {
 702                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
 703         }
 704 }
 705
 706 void back_propagate_RII(pbqp *pbqp, pbqp_node *node)
 707 {
 708         pbqp_edge   *src_edge   = node->edges[0];
 709         pbqp_edge   *tgt_edge   = node->edges[1];
 710         int          src_is_src = src_edge->src == node;
 711         int          tgt_is_src = tgt_edge->src == node;
 712         pbqp_matrix *src_mat;
 713         pbqp_matrix *tgt_mat;
 714         pbqp_node   *src_node;
 715         pbqp_node   *tgt_node;
 716         vector      *vec;
 717         vector      *node_vec;
 718         unsigned     col_index;
 719         unsigned     row_index;
 720
 721         assert(pbqp);
 722
 723         if (src_is_src) {
 724                 src_node = src_edge->tgt;
 725         } else {
 726                 src_node = src_edge->src;
 727         }
 728
 729         if (tgt_is_src) {
 730                 tgt_node = tgt_edge->tgt;
 731         } else {
 732                 tgt_node = tgt_edge->src;
 733         }
 734
 735         /* Swap nodes if necessary. */
 736         if (tgt_node->index < src_node->index) {
 737                 pbqp_node *tmp_node;
 738                 pbqp_edge *tmp_edge;
 739
 740                 tmp_node = src_node;
 741                 src_node = tgt_node;
 742                 tgt_node = tmp_node;
 743
 744                 tmp_edge = src_edge;
 745                 src_edge = tgt_edge;
 746                 tgt_edge = tmp_edge;
 747
 748                 src_is_src = src_edge->src == node;
 749                 tgt_is_src = tgt_edge->src == node;
 750         }
 751
 752         src_mat = src_edge->costs;
 753         tgt_mat = tgt_edge->costs;
 754
 755         node_vec = node->costs;
 756
 757         row_index = src_node->solution;
 758         col_index = tgt_node->solution;
 759
 760         vec = vector_copy(pbqp, node_vec);
 761
 762         if (src_is_src) {
 763                 vector_add_matrix_col(vec, src_mat, row_index);
 764         } else {
 765                 vector_add_matrix_row(vec, src_mat, row_index);
 766         }
 767
 768         if (tgt_is_src) {
 769                 vector_add_matrix_col(vec, tgt_mat, col_index);
 770         } else {
 771                 vector_add_matrix_row(vec, tgt_mat, col_index);
 772         }
 773
 774         node->solution = vector_get_min_index(vec);
 775         if (pbqp->dump_file) {
 776                 fprintf(pbqp->dump_file, "node n%d is set to %d<br>\n", node->index, node->solution);
 777         }
 778
 779         obstack_free(&pbqp->obstack, vec);
 780 }
 781
 782 int node_is_reduced(pbqp_node *node)
 783 {
 784         if (!reduced_bucket) return 0;
 785
 786         assert(node);
 787         if (ARR_LEN(node->edges) == 0) return 1;
 788
 789         unsigned bucket_length = ARR_LEN(reduced_bucket);
 790         unsigned bucket_index  = node->bucket_index;
 791
 792         return bucket_index < bucket_length && reduced_bucket[bucket_index] == node;
 793 }