nsz Git - libfirm/blob - ir/be/becopyilp2.c

   1 /*
   2  * This file is part of libFirm.
   3  * Copyright (C) 2012 University of Karlsruhe.
   4  */
   5
   6 /**
   7  * @file
   8  * @brief       ILP based copy minimization.
   9  * @author      Daniel Grund
  10  * @date        28.02.2006
  11  *
  12  * ILP formalization using G=(V, E, Q):
  13  *  - 2 class of variables: coloring vars x_ic   and   equal color vars y_ij
  14  *  - Path constraints
  15  *  - Clique-star constraints
  16  *
  17  *
  18  * \min \sum_{ (i,j) \in Q }  w_ij y_ij
  19  *
  20  *     \sum_c x_nc           =  1           n \in N, c \in C
  21  *
  22  *     x_nc                  =  0           n \in N, c \not\in C(n)
  23  *
  24  *     \sum x_nc            <=  1           x_nc \in Clique \in AllCliques,  c \in C
  25  *
  26  *     \sum_{e \in p} y_e   >=  1           p \in P      path constraints
  27  *
  28  *     \sum_{e \in cs} y_e  >= |cs| - 1     cs \in CP    clique-star constraints
  29  *
  30  *     x_nc, y_ij \in N,   w_ij \in R^+
  31  */
  32 #include "config.h"
  33
  34 #include "be_t.h"
  35 #include "beintlive_t.h"
  36 #include "beirg.h"
  37 #include "bitset.h"
  38 #include "error.h"
  39 #include "raw_bitset.h"
  40 #include "pdeq.h"
  41
  42 #include "util.h"
  43 #include "irgwalk.h"
  44 #include "becopyilp_t.h"
  45 #include "beifg.h"
  46 #include "besched.h"
  47 #include "bemodule.h"
  48
  49 DEBUG_ONLY(static firm_dbg_module_t *dbg;)
  50
  51 typedef struct local_env_t {
  52         int             first_x_var;
  53         int             last_x_var;
  54         const unsigned *allocatable_colors;
  55 } local_env_t;
  56
  57 static unsigned check_alignment_constraints(ir_node *node)
  58 {
  59         const arch_register_req_t *req = arch_get_irn_register_req(node);
  60         // For larger than 1 variables, support only aligned constraints
  61         assert((arch_register_req_is(req, aligned) || req->width == 1) && "Unaligned large (width > 1) variables not supported");
  62         return arch_register_req_is(req, aligned) && req->width > 1;
  63 }
  64
  65 static void make_color_var_name(char *buf, size_t buf_size,
  66                                 const ir_node *node, unsigned color)
  67 {
  68         unsigned node_idx = get_irn_idx(node);
  69         snprintf(buf, buf_size, "x_%u_%u", node_idx, color);
  70 }
  71
  72 static void build_coloring_cstr(ilp_env_t *ienv)
  73 {
  74         local_env_t    *lenv   = (local_env_t*)ienv->env;
  75         be_ifg_t       *ifg    = ienv->co->cenv->ifg;
  76         unsigned        n_regs = arch_register_class_n_regs(ienv->co->cls);
  77         const unsigned *allocatable_colors = lenv->allocatable_colors;
  78         char            buf[32];
  79
  80         unsigned *const colors = rbitset_alloca(n_regs);
  81         be_ifg_foreach_node(ifg, irn) {
  82                 const arch_register_req_t *req;
  83                 unsigned                   col;
  84                 int                        cst_idx;
  85                 unsigned                   curr_node_color;
  86                 unsigned                   has_alignment_cstr;
  87
  88                 if (sr_is_removed(ienv->sr, irn))
  89                         continue;
  90
  91                 has_alignment_cstr = check_alignment_constraints(irn);
  92
  93                 req = arch_get_irn_register_req(irn);
  94
  95                 /* get assignable colors */
  96                 if (arch_register_req_is(req, limited)) {
  97                         rbitset_copy(colors, req->limited, n_regs);
  98                 } else {
  99                         rbitset_copy(colors, allocatable_colors, n_regs);
 100                 }
 101
 102                 /* add the coloring constraint */
 103                 cst_idx = lpp_add_cst(ienv->lp, NULL, lpp_equal, 1.0);
 104
 105                 curr_node_color = get_irn_col(irn);
 106                 for (col = 0; col < n_regs; ++col) {
 107                         int    var_idx;
 108                         double val;
 109                         if (!rbitset_is_set(colors, col)
 110                                 || (has_alignment_cstr && ((col % req->width) != 0)))
 111                                 continue;
 112
 113                         make_color_var_name(buf, sizeof(buf), irn, col);
 114                         var_idx = lpp_add_var(ienv->lp, buf, lpp_binary, 0.0);
 115                         lpp_set_factor_fast(ienv->lp, cst_idx, var_idx, 1);
 116
 117                         val = (col == curr_node_color) ? 1.0 : 0.0;
 118                         lpp_set_start_value(ienv->lp, var_idx, val);
 119
 120                         lenv->last_x_var = var_idx;
 121                         if (lenv->first_x_var == -1)
 122                                 lenv->first_x_var = var_idx;
 123                 }
 124
 125                 /* add register constraint constraints */
 126                 for (col = 0; col < n_regs; ++col) {
 127                         int cst_idx;
 128                         int var_idx;
 129                         if (rbitset_is_set(colors, col)
 130                                 // for aligned variable, we set the unaligned part to 0
 131                                 && (!has_alignment_cstr || ((col % req->width) == 0)))
 132                                 continue;
 133
 134                         make_color_var_name(buf, sizeof(buf), irn, col);
 135                         cst_idx = lpp_add_cst(ienv->lp, NULL, lpp_equal, 0.0);
 136                         var_idx = lpp_add_var(ienv->lp, buf, lpp_binary, 0.0);
 137                         lpp_set_start_value(ienv->lp, var_idx, 0.0);
 138                         lpp_set_factor_fast(ienv->lp, cst_idx, var_idx, 1);
 139
 140                         lenv->last_x_var = var_idx;
 141                 }
 142         }
 143 }
 144
 145 static void build_interference_cstr(ilp_env_t *ienv)
 146 {
 147         lpp_t          *lpp      = ienv->lp;
 148         local_env_t    *lenv     = (local_env_t*)ienv->env;
 149         be_ifg_t       *ifg      = ienv->co->cenv->ifg;
 150         unsigned        n_colors = arch_register_class_n_regs(ienv->co->cls);
 151         ir_node       **clique   = ALLOCAN(ir_node*, n_colors);
 152         const unsigned *allocatable_colors = lenv->allocatable_colors;
 153         cliques_iter_t iter;
 154         int            size;
 155         unsigned       col;
 156         int            i;
 157
 158         /* for each maximal clique */
 159         be_ifg_foreach_clique(ifg, &iter, clique, &size) {
 160                 unsigned realsize = 0;
 161
 162                 for (i=0; i<size; ++i) {
 163                         if (!sr_is_removed(ienv->sr, clique[i]))
 164                                 ++realsize;
 165                 }
 166
 167                 if (realsize < 2)
 168                         continue;
 169
 170                 /* for all colors */
 171                 for (col=0; col<n_colors; ++col) {
 172                         int cst_idx;
 173                         if (!rbitset_is_set(allocatable_colors, col))
 174                                 continue;
 175
 176                         cst_idx = lpp_add_cst(lpp, NULL, lpp_less_equal, 1.0);
 177
 178                         /* for each member of this clique */
 179                         for (i=0; i<size; ++i) {
 180                                 ir_node *irn = clique[i];
 181                                 char     buf[32];
 182                                 int      var_idx;
 183                                 unsigned aligment_offset = 0;
 184
 185                                 if (sr_is_removed(ienv->sr, irn))
 186                                         continue;
 187
 188                                 // Use the first part of the large registers for all
 189                                 // interference, since it is the only colorable one.
 190                                 if (check_alignment_constraints(irn)) {
 191                                         const arch_register_req_t *req
 192                                                 = arch_get_irn_register_req(irn);
 193                                         aligment_offset = col % req->width;
 194                                 }
 195
 196                                 make_color_var_name(buf, sizeof(buf), irn,
 197                                                                         col - aligment_offset);
 198                                 var_idx = lpp_get_var_idx(lpp, buf);
 199                                 lpp_set_factor_fast(lpp, cst_idx, var_idx, 1);
 200                         }
 201                 }
 202         }
 203 }
 204
 205 static void make_affinity_var_name(char *buf, size_t buf_size,
 206                                    const ir_node *node1, const ir_node *node2)
 207 {
 208         unsigned n1 = get_irn_idx(node1);
 209         unsigned n2 = get_irn_idx(node2);
 210         if (n1 < n2) {
 211                 snprintf(buf, buf_size, "y_%u_%u", n1, n2);
 212         } else {
 213                 snprintf(buf, buf_size, "y_%u_%u", n2, n1);
 214         }
 215 }
 216
 217
 218 /**
 219  * TODO: Remove the dependency of the opt-units data structure
 220  *       by walking over all affinity edges. Graph structure
 221  *       does not provide this walker, yet.
 222  */
 223 static void build_affinity_cstr(ilp_env_t *ienv)
 224 {
 225         unsigned  n_colors = arch_register_class_n_regs(ienv->co->cls);
 226
 227         /* for all optimization units */
 228         list_for_each_entry(unit_t, curr, &ienv->co->units, units) {
 229                 ir_node *root     = curr->nodes[0];
 230                 unsigned root_col = get_irn_col(root);
 231                 int      i;
 232
 233                 for (i = 1; i < curr->node_count; ++i) {
 234                         ir_node *arg     = curr->nodes[i];
 235                         unsigned arg_col = get_irn_col(arg);
 236                         double   val;
 237                         char     buf[32];
 238                         unsigned col;
 239                         int      y_idx;
 240
 241                         /* add a new affinity variable */
 242                         make_affinity_var_name(buf, sizeof(buf), arg, root);
 243                         y_idx = lpp_add_var(ienv->lp, buf, lpp_binary, curr->costs[i]);
 244                         val   = (root_col == arg_col) ? 0.0 : 1.0;
 245                         lpp_set_start_value(ienv->lp, y_idx, val);
 246
 247                         /* add constraints relating the affinity var to the color vars */
 248                         for (col=0; col<n_colors; ++col) {
 249                                 int cst_idx = lpp_add_cst(ienv->lp, NULL, lpp_less_equal, 0.0);
 250                                 int root_idx;
 251                                 int arg_idx;
 252
 253                                 make_color_var_name(buf, sizeof(buf), root, col);
 254                                 root_idx = lpp_get_var_idx(ienv->lp, buf);
 255                                 make_color_var_name(buf, sizeof(buf), arg, col);
 256                                 arg_idx  = lpp_get_var_idx(ienv->lp, buf);
 257
 258                                 lpp_set_factor_fast(ienv->lp, cst_idx, root_idx,  1.0);
 259                                 lpp_set_factor_fast(ienv->lp, cst_idx, arg_idx,  -1.0);
 260                                 lpp_set_factor_fast(ienv->lp, cst_idx, y_idx, -1.0);
 261                         }
 262                 }
 263         }
 264 }
 265
 266 /**
 267  * Helping stuff for build_clique_star_cstr
 268  */
 269 typedef struct edge_t {
 270         ir_node *n1;
 271         ir_node *n2;
 272 } edge_t;
 273
 274 static int compare_edge_t(const void *k1, const void *k2, size_t size)
 275 {
 276         const edge_t *e1 = (const edge_t*)k1;
 277         const edge_t *e2 = (const edge_t*)k2;
 278         (void) size;
 279
 280         return ! (e1->n1 == e2->n1 && e1->n2 == e2->n2);
 281 }
 282
 283 #define HASH_EDGE(e) (hash_irn((e)->n1) ^ hash_irn((e)->n2))
 284
 285 static inline edge_t *add_edge(set *edges, ir_node *n1, ir_node *n2, size_t *counter)
 286 {
 287         edge_t new_edge;
 288
 289         if (PTR_TO_INT(n1) < PTR_TO_INT(n2)) {
 290                 new_edge.n1 = n1;
 291                 new_edge.n2 = n2;
 292         } else {
 293                 new_edge.n1 = n2;
 294                 new_edge.n2 = n1;
 295         }
 296         (*counter)++;
 297         return set_insert(edge_t, edges, &new_edge, sizeof(new_edge), HASH_EDGE(&new_edge));
 298 }
 299
 300 static inline edge_t *find_edge(set *edges, ir_node *n1, ir_node *n2)
 301 {
 302         edge_t new_edge;
 303
 304         if (PTR_TO_INT(n1) < PTR_TO_INT(n2)) {
 305                 new_edge.n1 = n1;
 306                 new_edge.n2 = n2;
 307         } else {
 308                 new_edge.n1 = n2;
 309                 new_edge.n2 = n1;
 310         }
 311         return set_find(edge_t, edges, &new_edge, sizeof(new_edge), HASH_EDGE(&new_edge));
 312 }
 313
 314 static inline void remove_edge(set *edges, ir_node *n1, ir_node *n2, size_t *counter)
 315 {
 316         edge_t new_edge, *e;
 317
 318         if (PTR_TO_INT(n1) < PTR_TO_INT(n2)) {
 319                 new_edge.n1 = n1;
 320                 new_edge.n2 = n2;
 321         } else {
 322                 new_edge.n1 = n2;
 323                 new_edge.n2 = n1;
 324         }
 325         e = set_find(edge_t, edges, &new_edge, sizeof(new_edge), HASH_EDGE(&new_edge));
 326         if (e) {
 327                 e->n1 = NULL;
 328                 e->n2 = NULL;
 329                 (*counter)--;
 330         }
 331 }
 332
 333 #define pset_foreach(pset, irn) foreach_pset((pset), ir_node, (irn))
 334
 335 /**
 336  * Search for an interference clique and an external node
 337  * with affinity edges to all nodes of the clique.
 338  * At most 1 node of the clique can be colored equally with the external node.
 339  */
 340 static void build_clique_star_cstr(ilp_env_t *ienv)
 341 {
 342         /* for each node with affinity edges */
 343         be_lv_t *const lv = be_get_irg_liveness(ienv->co->irg);
 344         co_gs_foreach_aff_node(ienv->co, aff) {
 345                 struct obstack ob;
 346                 const ir_node *center = aff->irn;
 347                 ir_node **nodes;
 348                 set *edges;
 349                 int i, o, n_nodes;
 350                 size_t n_edges;
 351
 352                 if (arch_irn_is_ignore(aff->irn))
 353                         continue;
 354
 355                 obstack_init(&ob);
 356                 edges = new_set(compare_edge_t, 8);
 357
 358                 /* get all affinity neighbours */
 359                 n_nodes = 0;
 360                 co_gs_foreach_neighb(aff, nbr) {
 361                         if (!arch_irn_is_ignore(nbr->irn)) {
 362                                 obstack_ptr_grow(&ob, nbr->irn);
 363                                 ++n_nodes;
 364                         }
 365                 }
 366                 nodes = (ir_node**)obstack_finish(&ob);
 367
 368                 /* get all interference edges between these */
 369                 n_edges = 0;
 370                 for (i=0; i<n_nodes; ++i) {
 371                         for (o=0; o<i; ++o) {
 372                                 if (be_values_interfere(lv, nodes[i], nodes[o]))
 373                                         add_edge(edges, nodes[i], nodes[o], &n_edges);
 374                         }
 375                 }
 376
 377                 /* cover all these interference edges with maximal cliques */
 378                 while (n_edges) {
 379                         edge_t *e;
 380                         pset   *clique = pset_new_ptr(8);
 381                         bool    growed;
 382
 383                         /* get 2 starting nodes to form a clique */
 384                         for (e = set_first(edge_t, edges); !e->n1; e = set_next(edge_t, edges)) {}
 385
 386                         /* we could be stepped out of the loop before the set iterated to the end */
 387                         set_break(edges);
 388
 389                         pset_insert_ptr(clique, e->n1);
 390                         pset_insert_ptr(clique, e->n2);
 391                         remove_edge(edges, e->n1, e->n2, &n_edges);
 392
 393                         /* while the clique is growing */
 394                         do {
 395                                 growed = false;
 396
 397                                 /* search for a candidate to extend the clique */
 398                                 for (i=0; i<n_nodes; ++i) {
 399                                         ir_node *cand = nodes[i];
 400                                         bool     is_cand;
 401
 402                                         /* if its already in the clique try the next */
 403                                         if (pset_find_ptr(clique, cand))
 404                                                 continue;
 405
 406                                         /* are there all necessary interferences? */
 407                                         is_cand = true;
 408                                         pset_foreach(clique, member) {
 409                                                 if (!find_edge(edges, cand, member)) {
 410                                                         is_cand = false;
 411                                                         pset_break(clique);
 412                                                         break;
 413                                                 }
 414                                         }
 415
 416                                         /* now we know if we have a clique extender */
 417                                         if (is_cand) {
 418                                                 /* first remove all covered edges */
 419                                                 pset_foreach(clique, member)
 420                                                         remove_edge(edges, cand, member, &n_edges);
 421
 422                                                 /* insert into clique */
 423                                                 pset_insert_ptr(clique, cand);
 424                                                 growed = true;
 425                                                 break;
 426                                         }
 427                                 }
 428                         } while (growed);
 429
 430                         /* now the clique is maximal. Finally add the constraint */
 431                         {
 432                                 int  var_idx;
 433                                 int  cst_idx;
 434                                 char buf[32];
 435
 436                                 cst_idx = lpp_add_cst(ienv->lp, NULL, lpp_greater_equal, pset_count(clique)-1);
 437
 438                                 pset_foreach(clique, member) {
 439                                         make_affinity_var_name(buf, sizeof(buf), center, member);
 440                                         var_idx = lpp_get_var_idx(ienv->lp, buf);
 441                                         lpp_set_factor_fast(ienv->lp, cst_idx, var_idx, 1.0);
 442                                 }
 443                         }
 444
 445                         del_pset(clique);
 446                 }
 447
 448                 del_set(edges);
 449                 obstack_free(&ob, NULL);
 450         }
 451 }
 452
 453 static void extend_path(ilp_env_t *ienv, pdeq *path, const ir_node *irn)
 454 {
 455         int i, len;
 456         ir_node **curr_path;
 457         affinity_node_t *aff;
 458
 459         /* do not walk backwards or in circles */
 460         if (pdeq_contains(path, irn))
 461                 return;
 462
 463         if (arch_irn_is_ignore(irn))
 464                 return;
 465
 466         /* insert the new irn */
 467         pdeq_putr(path, irn);
 468
 469         /* check for forbidden interferences */
 470         len       = pdeq_len(path);
 471         curr_path = ALLOCAN(ir_node*, len);
 472         pdeq_copyl(path, (const void **)curr_path);
 473
 474         be_lv_t *const lv = be_get_irg_liveness(ienv->co->irg);
 475         for (i=1; i<len; ++i) {
 476                 if (be_values_interfere(lv, irn, curr_path[i]))
 477                         goto end;
 478         }
 479
 480         /* check for terminating interference */
 481         if (be_values_interfere(lv, irn, curr_path[0])) {
 482                 /* One node is not a path. */
 483                 /* And a path of length 2 is covered by a clique star constraint. */
 484                 if (len > 2) {
 485                         /* finally build the constraint */
 486                         int cst_idx = lpp_add_cst(ienv->lp, NULL, lpp_greater_equal, 1.0);
 487                         for (i=1; i<len; ++i) {
 488                                 char buf[32];
 489                                 int  var_idx;
 490
 491                                 make_affinity_var_name(buf, sizeof(buf), curr_path[i-1], curr_path[i]);
 492                                 var_idx = lpp_get_var_idx(ienv->lp, buf);
 493                                 lpp_set_factor_fast(ienv->lp, cst_idx, var_idx, 1.0);
 494                         }
 495                 }
 496
 497                 /* this path cannot be extended anymore */
 498                 goto end;
 499         }
 500
 501         /* recursively extend the path */
 502         aff = get_affinity_info(ienv->co, irn);
 503         co_gs_foreach_neighb(aff, nbr) {
 504                 extend_path(ienv, path, nbr->irn);
 505         }
 506
 507 end:
 508         /* remove the irn */
 509         pdeq_getr(path);
 510 }
 511
 512 /**
 513  * Search a path of affinity edges, whose ends are connected
 514  * by an interference edge and there are no other interference
 515  * edges in between.
 516  * Then at least one of these affinity edges must break.
 517  */
 518 static void build_path_cstr(ilp_env_t *ienv)
 519 {
 520         /* for each node with affinity edges */
 521         co_gs_foreach_aff_node(ienv->co, aff_info) {
 522                 pdeq *path = new_pdeq();
 523
 524                 extend_path(ienv, path, aff_info->irn);
 525
 526                 del_pdeq(path);
 527         }
 528 }
 529
 530 static void ilp2_build(ilp_env_t *ienv)
 531 {
 532         int lower_bound;
 533
 534         ienv->lp = lpp_new(ienv->co->name, lpp_minimize);
 535         build_coloring_cstr(ienv);
 536         build_interference_cstr(ienv);
 537         build_affinity_cstr(ienv);
 538         build_clique_star_cstr(ienv);
 539         build_path_cstr(ienv);
 540
 541         lower_bound = co_get_lower_bound(ienv->co) - co_get_inevit_copy_costs(ienv->co);
 542         lpp_set_bound(ienv->lp, lower_bound);
 543 }
 544
 545 static void ilp2_apply(ilp_env_t *ienv)
 546 {
 547         local_env_t *lenv = (local_env_t*)ienv->env;
 548         ir_graph    *irg  = ienv->co->irg;
 549
 550         /* first check if there was sth. to optimize */
 551         if (lenv->first_x_var >= 0) {
 552                 int              count = lenv->last_x_var - lenv->first_x_var + 1;
 553                 double          *sol   = XMALLOCN(double, count);
 554                 lpp_sol_state_t  state = lpp_get_solution(ienv->lp, sol, lenv->first_x_var, lenv->last_x_var);
 555                 int              i;
 556
 557                 if (state != lpp_optimal) {
 558                         printf("WARNING %s: Solution state is not 'optimal': %d\n",
 559                                ienv->co->name, (int)state);
 560                         if (state < lpp_feasible) {
 561                                 panic("Copy coalescing solution not feasible!");
 562                         }
 563                 }
 564
 565                 for (i=0; i<count; ++i) {
 566                         unsigned nodenr;
 567                         unsigned color;
 568                         char     var_name[32];
 569                         if (sol[i] <= 1-EPSILON)
 570                                 continue;
 571                         /* split variable name into components */
 572                         lpp_get_var_name(ienv->lp, lenv->first_x_var+i, var_name, sizeof(var_name));
 573
 574                         if (sscanf(var_name, "x_%u_%u", &nodenr, &color) == 2) {
 575                                 ir_node *irn = get_idx_irn(irg, nodenr);
 576                                 set_irn_col(ienv->co->cls, irn, color);
 577                         } else {
 578                                 panic("This should be a x-var");
 579                         }
 580                 }
 581
 582                 xfree(sol);
 583         }
 584
 585 #ifdef COPYOPT_STAT
 586         /* TODO adapt to multiple possible ILPs */
 587         copystat_add_ilp_time((int)(1000.0*lpp_get_sol_time(pi->curr_lp)));  //now we have ms
 588         copystat_add_ilp_vars(lpp_get_var_count(pi->curr_lp));
 589         copystat_add_ilp_csts(lpp_get_cst_count(pi->curr_lp));
 590         copystat_add_ilp_iter(lpp_get_iter_cnt(pi->curr_lp));
 591 #endif
 592 }
 593
 594 /**
 595  * Solves the problem using mixed integer programming
 596  * @returns 1 iff solution state was optimal
 597  * Uses the OU and the GRAPH data structure
 598  * Dependency of the OU structure can be removed
 599  */
 600 static int co_solve_ilp2(copy_opt_t *co)
 601 {
 602         unsigned        n_regs = arch_register_class_n_regs(co->cls);
 603         lpp_sol_state_t sol_state;
 604         ilp_env_t      *ienv;
 605         local_env_t     my;
 606
 607         ASSERT_OU_AVAIL(co); //See build_clique_st
 608         ASSERT_GS_AVAIL(co);
 609
 610         my.first_x_var = -1;
 611         my.last_x_var  = -1;
 612         FIRM_DBG_REGISTER(dbg, "firm.be.coilp2");
 613
 614         unsigned *const allocatable_colors = rbitset_alloca(n_regs);
 615         be_set_allocatable_regs(co->irg, co->cls, allocatable_colors);
 616         my.allocatable_colors = allocatable_colors;
 617
 618         ienv = new_ilp_env(co, ilp2_build, ilp2_apply, &my);
 619
 620         sol_state = ilp_go(ienv);
 621
 622         free_ilp_env(ienv);
 623
 624         return sol_state == lpp_optimal;
 625 }
 626
 627 BE_REGISTER_MODULE_CONSTRUCTOR(be_init_copyilp2)
 628 void be_init_copyilp2(void)
 629 {
 630         static co_algo_info copyheur = {
 631                 co_solve_ilp2, 1
 632         };
 633
 634         be_register_copyopt("ilp", &copyheur);
 635 }