src/surf/maxmin.c

   1 /*      $Id$     */
   2
   3 /* Copyright (c) 2004 Arnaud Legrand. All rights reserved.                  */
   4
   5 /* This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the license (GNU LGPL) which comes with this package. */
   7
   8
   9 #include "xbt/sysdep.h"
  10 #include "xbt/log.h"
  11 #include "xbt/mallocator.h"
  12 #include "maxmin_private.h"
  13 #include <stdlib.h>
  14 #include <stdio.h>              /* sprintf */
  15 #include <math.h>
  16 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(surf_maxmin, surf,
  17                                 "Logging specific to SURF (maxmin)");
  18
  19 static void *lmm_variable_mallocator_new_f(void);
  20 static void lmm_variable_mallocator_free_f(void *var);
  21 static void lmm_variable_mallocator_reset_f(void *var);
  22
  23 lmm_system_t lmm_system_new(void)
  24 {
  25   lmm_system_t l = NULL;
  26   s_lmm_variable_t var;
  27   s_lmm_constraint_t cnst;
  28
  29   l = xbt_new0(s_lmm_system_t, 1);
  30
  31   l->modified = 0;
  32   xbt_swag_init(&(l->variable_set),
  33                 xbt_swag_offset(var, variable_set_hookup));
  34   xbt_swag_init(&(l->constraint_set),
  35                 xbt_swag_offset(cnst, constraint_set_hookup));
  36
  37   xbt_swag_init(&(l->active_constraint_set),
  38                 xbt_swag_offset(cnst, active_constraint_set_hookup));
  39
  40   xbt_swag_init(&(l->saturated_variable_set),
  41                 xbt_swag_offset(var, saturated_variable_set_hookup));
  42   xbt_swag_init(&(l->saturated_constraint_set),
  43                 xbt_swag_offset(cnst, saturated_constraint_set_hookup));
  44
  45   l->variable_mallocator = xbt_mallocator_new(64,
  46                                               lmm_variable_mallocator_new_f,
  47                                               lmm_variable_mallocator_free_f,
  48                                               lmm_variable_mallocator_reset_f);
  49
  50   return l;
  51 }
  52
  53 void lmm_system_free(lmm_system_t sys)
  54 {
  55   lmm_variable_t var = NULL;
  56   lmm_constraint_t cnst = NULL;
  57
  58   while ((var = extract_variable(sys)))
  59     lmm_var_free(sys, var);
  60
  61   while ((cnst = extract_constraint(sys)))
  62     lmm_cnst_free(sys, cnst);
  63
  64   xbt_mallocator_free(sys->variable_mallocator);
  65   free(sys);
  66 }
  67
  68 void lmm_variable_disable(lmm_system_t sys, lmm_variable_t var)
  69 {
  70   int i;
  71   lmm_element_t elem = NULL;
  72
  73   XBT_IN2("(sys=%p, var=%p)", sys, var);
  74   sys->modified = 1;
  75
  76   for (i = 0; i < var->cnsts_number; i++) {
  77     elem = &var->cnsts[i];
  78     xbt_swag_remove(elem, &(elem->constraint->element_set));
  79     xbt_swag_remove(elem, &(elem->constraint->active_element_set));
  80     if (!xbt_swag_size(&(elem->constraint->element_set)))
  81       make_constraint_inactive(sys, elem->constraint);
  82   }
  83   var->cnsts_number = 0;
  84   XBT_OUT;
  85 }
  86
  87 static void lmm_var_free(lmm_system_t sys, lmm_variable_t var)
  88 {
  89
  90   lmm_variable_disable(sys, var);
  91   free(var->cnsts);
  92   xbt_mallocator_release(sys->variable_mallocator, var);
  93 }
  94
  95 static void lmm_cnst_free(lmm_system_t sys, lmm_constraint_t cnst)
  96 {
  97 /*   xbt_assert0(xbt_swag_size(&(cnst->element_set)), */
  98 /*            "This list should be empty!"); */
  99   remove_active_constraint(sys, cnst);
 100   free(cnst);
 101 }
 102
 103 lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id,
 104                                     double bound_value)
 105 {
 106   lmm_constraint_t cnst = NULL;
 107   s_lmm_element_t elem;
 108
 109   cnst = xbt_new0(s_lmm_constraint_t, 1);
 110   cnst->id = id;
 111   xbt_swag_init(&(cnst->element_set),
 112                 xbt_swag_offset(elem, element_set_hookup));
 113   xbt_swag_init(&(cnst->active_element_set),
 114                 xbt_swag_offset(elem, active_element_set_hookup));
 115
 116   cnst->bound = bound_value;
 117   cnst->usage = 0;
 118   cnst->shared = 1;
 119   insert_constraint(sys, cnst);
 120
 121   return cnst;
 122 }
 123
 124 void lmm_constraint_shared(lmm_constraint_t cnst)
 125 {
 126   cnst->shared = 0;
 127 }
 128
 129 int lmm_constraint_is_shared(lmm_constraint_t cnst)
 130 {
 131   return (cnst->shared);
 132 }
 133
 134 void lmm_constraint_free(lmm_system_t sys, lmm_constraint_t cnst)
 135 {
 136   remove_constraint(sys, cnst);
 137   lmm_cnst_free(sys, cnst);
 138 }
 139
 140 static void *lmm_variable_mallocator_new_f(void)
 141 {
 142   return xbt_new(s_lmm_variable_t, 1);
 143 }
 144
 145 static void lmm_variable_mallocator_free_f(void *var)
 146 {
 147   xbt_free(var);
 148 }
 149
 150 static void lmm_variable_mallocator_reset_f(void *var)
 151 {
 152   /* memset to zero like calloc */
 153   memset(var, 0, sizeof(s_lmm_variable_t));
 154 }
 155
 156 lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id,
 157                                 double weight,
 158                                 double bound, int number_of_constraints)
 159 {
 160   lmm_variable_t var = NULL;
 161   int i;
 162
 163   XBT_IN5("(sys=%p, id=%p, weight=%f, bound=%f, num_cons =%d)",
 164           sys, id, weight, bound, number_of_constraints);
 165
 166   var = xbt_mallocator_get(sys->variable_mallocator);
 167   var->id = id;
 168   var->cnsts = xbt_new0(s_lmm_element_t, number_of_constraints);
 169   for (i = 0; i < number_of_constraints; i++) {
 170     /* Should be useless because of the
 171        calloc but it seems to help valgrind... */
 172     var->cnsts[i].element_set_hookup.next = NULL;
 173     var->cnsts[i].element_set_hookup.prev = NULL;
 174     var->cnsts[i].active_element_set_hookup.next = NULL;
 175     var->cnsts[i].active_element_set_hookup.prev = NULL;
 176     var->cnsts[i].constraint = NULL;
 177     var->cnsts[i].variable = NULL;
 178     var->cnsts[i].value = 0.0;
 179   }
 180   var->cnsts_size = number_of_constraints;
 181   var->cnsts_number = 0;        /* Should be useless because of the
 182                                    calloc but it seems to help valgrind... */
 183   var->weight = weight;
 184   var->bound = bound;
 185   var->value = 0.0;
 186
 187
 188   var->func_f = func_f_def;
 189   var->func_fp = func_fp_def;
 190   var->func_fpi = func_fpi_def;
 191
 192   if (weight)
 193     xbt_swag_insert_at_head(var, &(sys->variable_set));
 194   else
 195     xbt_swag_insert_at_tail(var, &(sys->variable_set));
 196   XBT_OUT;
 197   return var;
 198 }
 199
 200 void lmm_variable_free(lmm_system_t sys, lmm_variable_t var)
 201 {
 202   remove_variable(sys, var);
 203   lmm_var_free(sys, var);
 204 }
 205
 206 double lmm_variable_getvalue(lmm_variable_t var)
 207 {
 208   return (var->value);
 209 }
 210
 211 double lmm_variable_getbound(lmm_variable_t var)
 212 {
 213   return (var->bound);
 214 }
 215
 216 void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
 217                 lmm_variable_t var, double value)
 218 {
 219   lmm_element_t elem = NULL;
 220
 221   sys->modified = 1;
 222
 223   xbt_assert0(var->cnsts_number < var->cnsts_size, "Too much constraints");
 224
 225   elem = &(var->cnsts[var->cnsts_number++]);
 226
 227   elem->value = value;
 228   elem->constraint = cnst;
 229   elem->variable = var;
 230
 231   if (var->weight)
 232     xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 233   else
 234     xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 235
 236   make_constraint_active(sys, cnst);
 237 }
 238
 239 void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
 240                     lmm_variable_t var, double value)
 241 {
 242   int i;
 243   sys->modified = 1;
 244
 245   for (i = 0; i < var->cnsts_number; i++)
 246     if (var->cnsts[i].constraint == cnst)
 247       break;
 248
 249   if (i < var->cnsts_number) {
 250     if (cnst->shared)
 251       var->cnsts[i].value += value;
 252     else
 253       var->cnsts[i].value = MAX(var->cnsts[i].value, value);
 254   } else
 255     lmm_expand(sys, cnst, var, value);
 256 }
 257
 258 void lmm_elem_set_value(lmm_system_t sys, lmm_constraint_t cnst,
 259                         lmm_variable_t var, double value)
 260 {
 261   int i;
 262
 263   for (i = 0; i < var->cnsts_number; i++)
 264     if (var->cnsts[i].constraint == cnst)
 265       break;
 266
 267   if (i < var->cnsts_number) {
 268     var->cnsts[i].value = value;
 269     sys->modified = 1;
 270   } else
 271     DIE_IMPOSSIBLE;
 272 }
 273
 274 lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t sys,
 275                                        lmm_variable_t var, int num)
 276 {
 277   if (num < var->cnsts_number)
 278     return (var->cnsts[num].constraint);
 279   else
 280     return NULL;
 281 }
 282
 283 int lmm_get_number_of_cnst_from_var(lmm_system_t sys, lmm_variable_t var)
 284 {
 285   return (var->cnsts_number);
 286 }
 287
 288 lmm_variable_t lmm_get_var_from_cnst(lmm_system_t sys,
 289                                      lmm_constraint_t cnst,
 290                                      lmm_element_t * elem)
 291 {
 292   if (!(*elem))
 293     *elem = xbt_swag_getFirst(&(cnst->element_set));
 294   else
 295     *elem = xbt_swag_getNext(*elem, cnst->element_set.offset);
 296   if (*elem)
 297     return (*elem)->variable;
 298   else
 299     return NULL;
 300 }
 301
 302 void *lmm_constraint_id(lmm_constraint_t cnst)
 303 {
 304   return cnst->id;
 305 }
 306
 307 void *lmm_variable_id(lmm_variable_t var)
 308 {
 309   return var->id;
 310 }
 311
 312 static void saturated_constraint_set_update(lmm_system_t sys,
 313                                             lmm_constraint_t cnst,
 314                                             double *min_usage)
 315 {
 316   lmm_constraint_t useless_cnst = NULL;
 317
 318   XBT_IN3("sys=%p, cnst=%p, min_usage=%f", sys, cnst, *min_usage);
 319   if (cnst->usage <= 0) {
 320     XBT_OUT;
 321     return;
 322   }
 323   if (cnst->remaining <= 0) {
 324     XBT_OUT;
 325     return;
 326   }
 327   if ((*min_usage < 0) || (*min_usage > cnst->remaining / cnst->usage)) {
 328     *min_usage = cnst->remaining / cnst->usage;
 329     LOG3(xbt_log_priority_trace,
 330          "min_usage=%f (cnst->remaining=%f, cnst->usage=%f)", *min_usage,
 331          cnst->remaining, cnst->usage);
 332     while ((useless_cnst =
 333             xbt_swag_getFirst(&(sys->saturated_constraint_set))))
 334       xbt_swag_remove(useless_cnst, &(sys->saturated_constraint_set));
 335
 336     xbt_swag_insert(cnst, &(sys->saturated_constraint_set));
 337   } else if (*min_usage == cnst->remaining / cnst->usage) {
 338     xbt_swag_insert(cnst, &(sys->saturated_constraint_set));
 339   }
 340   XBT_OUT;
 341 }
 342
 343 static void saturated_variable_set_update(lmm_system_t sys)
 344 {
 345   lmm_constraint_t cnst = NULL;
 346   xbt_swag_t cnst_list = NULL;
 347   lmm_element_t elem = NULL;
 348   xbt_swag_t elem_list = NULL;
 349
 350   cnst_list = &(sys->saturated_constraint_set);
 351   while ((cnst = xbt_swag_getFirst(cnst_list))) {
 352     elem_list = &(cnst->active_element_set);
 353     xbt_swag_foreach(elem, elem_list) {
 354       if (elem->variable->weight <= 0)
 355         break;
 356       if ((elem->value > 0))
 357         xbt_swag_insert(elem->variable, &(sys->saturated_variable_set));
 358     }
 359     xbt_swag_remove(cnst, cnst_list);
 360   }
 361 }
 362
 363 void lmm_print(lmm_system_t sys)
 364 {
 365   lmm_constraint_t cnst = NULL;
 366   lmm_element_t elem = NULL;
 367   lmm_variable_t var = NULL;
 368   xbt_swag_t cnst_list = NULL;
 369   xbt_swag_t var_list = NULL;
 370   xbt_swag_t elem_list = NULL;
 371   char print_buf[1024];
 372   char *trace_buf = xbt_malloc0(sizeof(char));
 373   double sum = 0.0;
 374
 375   /* Printing Objective */
 376   var_list = &(sys->variable_set);
 377   sprintf(print_buf, "MAX-MIN ( ");
 378   trace_buf =
 379     xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 380   strcat(trace_buf, print_buf);
 381   xbt_swag_foreach(var, var_list) {
 382     sprintf(print_buf, "'%p'(%f) ", var, var->weight);
 383     trace_buf =
 384       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 385     strcat(trace_buf, print_buf);
 386   }
 387   sprintf(print_buf, ")");
 388   trace_buf =
 389     xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 390   strcat(trace_buf, print_buf);
 391   DEBUG1("%s", trace_buf);
 392   trace_buf[0] = '\000';
 393
 394   DEBUG0("Constraints");
 395   /* Printing Constraints */
 396   cnst_list = &(sys->active_constraint_set);
 397   xbt_swag_foreach(cnst, cnst_list) {
 398     sum = 0.0;
 399     elem_list = &(cnst->element_set);
 400     sprintf(print_buf, "\t");
 401     trace_buf =
 402       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 403     strcat(trace_buf, print_buf);
 404     xbt_swag_foreach(elem, elem_list) {
 405       sprintf(print_buf, "%f.'%p'(%f) + ", elem->value,
 406               elem->variable, elem->variable->value);
 407       trace_buf =
 408         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 409       strcat(trace_buf, print_buf);
 410       sum += elem->value * elem->variable->value;
 411     }
 412     sprintf(print_buf, "0 <= %f ('%p')", cnst->bound, cnst);
 413     trace_buf =
 414       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 415     strcat(trace_buf, print_buf);
 416
 417     if (!cnst->shared) {
 418       sprintf(print_buf, " [MAX-Constraint]");
 419       trace_buf =
 420         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 421       strcat(trace_buf, print_buf);
 422     }
 423     DEBUG1("%s", trace_buf);
 424     trace_buf[0] = '\000';
 425     xbt_assert3(!double_positive(sum - cnst->bound),
 426                 "Incorrect value (%f is not smaller than %f): %g",
 427                 sum, cnst->bound, sum - cnst->bound);
 428   }
 429
 430   DEBUG0("Variables");
 431   /* Printing Result */
 432   xbt_swag_foreach(var, var_list) {
 433     if (var->bound > 0) {
 434       DEBUG4("'%p'(%f) : %f (<=%f)", var, var->weight, var->value,
 435              var->bound);
 436       xbt_assert2(!double_positive(var->value - var->bound),
 437                   "Incorrect value (%f is not smaller than %f",
 438                   var->value, var->bound);
 439     } else
 440       DEBUG3("'%p'(%f) : %f", var, var->weight, var->value);
 441   }
 442
 443   free(trace_buf);
 444 }
 445
 446 void lmm_solve(lmm_system_t sys)
 447 {
 448   lmm_variable_t var = NULL;
 449   lmm_constraint_t cnst = NULL;
 450   lmm_element_t elem = NULL;
 451   xbt_swag_t cnst_list = NULL;
 452   xbt_swag_t var_list = NULL;
 453   xbt_swag_t elem_list = NULL;
 454   double min_usage = -1;
 455   double min_bound = -1;
 456
 457   if (!(sys->modified))
 458     return;
 459
 460   /* Init */
 461   var_list = &(sys->variable_set);
 462   DEBUG1("Variable set : %d", xbt_swag_size(var_list));
 463   xbt_swag_foreach(var, var_list) {
 464     int nb = 0;
 465     int i;
 466     if (var->weight <= 0.0)
 467       break;
 468     var->value = 0.0;
 469     for (i = 0; i < var->cnsts_number; i++) {
 470       if (var->cnsts[i].value == 0.0)
 471         nb++;
 472     }
 473     if ((nb == var->cnsts_number) && (var->weight > 0.0))
 474       var->value = 1.0;
 475   }
 476
 477   /*
 478    * Compute Usage and store the variables that reach the maximum.
 479    */
 480   cnst_list = &(sys->active_constraint_set);
 481   DEBUG1("Active constraints : %d", xbt_swag_size(cnst_list));
 482   xbt_swag_foreach(cnst, cnst_list) {
 483     /* INIT */
 484     cnst->remaining = cnst->bound;
 485     cnst->usage = 0;
 486     elem_list = &(cnst->element_set);
 487     cnst->usage = 0.0;
 488     xbt_swag_foreach(elem, elem_list) {
 489       /* 0-weighted elements (ie, sleep actions) are at the end of the swag and we don't want to consider them */
 490       if (elem->variable->weight <= 0)
 491         break;
 492       if ((elem->value > 0)) {
 493         if (cnst->shared)
 494           cnst->usage += elem->value / elem->variable->weight;
 495         else if (cnst->usage < elem->value / elem->variable->weight)
 496           cnst->usage = elem->value / elem->variable->weight;
 497         DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
 498         make_elem_active(elem);
 499       }
 500     }
 501     /* Saturated constraints update */
 502     saturated_constraint_set_update(sys, cnst, &min_usage);
 503   }
 504   saturated_variable_set_update(sys);
 505
 506   /* Saturated variables update */
 507
 508   do {
 509     /* Fix the variables that have to be */
 510     var_list = &(sys->saturated_variable_set);
 511
 512     xbt_swag_foreach(var, var_list) {
 513       if (var->weight <= 0.0)
 514         DIE_IMPOSSIBLE;
 515       /* First check if some of these variables have reach their upper
 516          bound and update min_usage accordingly. */
 517       DEBUG5
 518         ("var=%p, var->bound=%f, var->weight=%f, min_usage=%f, var->bound*var->weight=%f",
 519          var, var->bound, var->weight, min_usage, var->bound * var->weight);
 520       if ((var->bound > 0) && (var->bound * var->weight < min_usage)) {
 521         if (min_bound < 0)
 522           min_bound = var->bound;
 523         else
 524           min_bound = MIN(min_bound, var->bound);
 525         DEBUG1("Updated min_bound=%f", min_bound);
 526       }
 527     }
 528
 529
 530     while ((var = xbt_swag_getFirst(var_list))) {
 531       int i;
 532
 533       if (min_bound < 0) {
 534         var->value = min_usage / var->weight;
 535       } else {
 536         if (min_bound == var->bound)
 537           var->value = var->bound;
 538         else {
 539           xbt_swag_remove(var, var_list);
 540           continue;
 541         }
 542       }
 543       DEBUG5("Min usage: %f, Var(%p)->weight: %f, Var(%p)->value: %f ",
 544              min_usage, var, var->weight, var, var->value);
 545
 546
 547       /* Update usage */
 548
 549       for (i = 0; i < var->cnsts_number; i++) {
 550         elem = &var->cnsts[i];
 551         cnst = elem->constraint;
 552         if (cnst->shared) {
 553           double_update(&(cnst->remaining), elem->value * var->value);
 554           double_update(&(cnst->usage), elem->value / var->weight);
 555           make_elem_inactive(elem);
 556         } else {                /* FIXME one day: We recompute usage.... :( */
 557           cnst->usage = 0.0;
 558           make_elem_inactive(elem);
 559           xbt_swag_foreach(elem, elem_list) {
 560             if (elem->variable->weight <= 0)
 561               break;
 562             if (elem->variable->value > 0)
 563               break;
 564             if ((elem->value > 0)) {
 565               if (cnst->usage < elem->value / elem->variable->weight)
 566                 cnst->usage = elem->value / elem->variable->weight;
 567               DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
 568               make_elem_active(elem);
 569             }
 570           }
 571         }
 572       }
 573       xbt_swag_remove(var, var_list);
 574     }
 575
 576     /* Find out which variables reach the maximum */
 577     cnst_list = &(sys->active_constraint_set);
 578     min_usage = -1;
 579     min_bound = -1;
 580     xbt_swag_foreach(cnst, cnst_list) {
 581       saturated_constraint_set_update(sys, cnst, &min_usage);
 582     }
 583     saturated_variable_set_update(sys);
 584
 585   } while (xbt_swag_size(&(sys->saturated_variable_set)));
 586
 587   sys->modified = 0;
 588   if (XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug)) {
 589     lmm_print(sys);
 590   }
 591 }
 592
 593 /* Not a O(1) function */
 594
 595 void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
 596                 lmm_variable_t var, double value)
 597 {
 598   int i;
 599
 600   sys->modified = 1;
 601   for (i = 0; i < var->cnsts_number; i++)
 602     if (var->cnsts[i].constraint == cnst) {
 603       var->cnsts[i].value = value;
 604       return;
 605     }
 606 }
 607
 608 /** \brief Attribute the value bound to var->bound.
 609  *
 610  *  \param sys the lmm_system_t
 611  *  \param var the lmm_variable_t
 612  *  \param bound the new bound to associate with var
 613  *
 614  *  Makes var->bound equal to bound. Whenever this function is called
 615  *  a change is  signed in the system. To
 616  *  avoid false system changing detection it is a good idea to test
 617  *  (bound != 0) before calling it.
 618  *
 619  */
 620 void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
 621                                double bound)
 622 {
 623   sys->modified = 1;
 624   var->bound = bound;
 625 }
 626
 627
 628 void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
 629                                 double weight)
 630 {
 631   int i;
 632   lmm_element_t elem;
 633
 634   if (weight == var->weight)
 635     return;
 636   XBT_IN3("(sys=%p, var=%p, weight=%f)", sys, var, weight);
 637   sys->modified = 1;
 638   var->weight = weight;
 639   xbt_swag_remove(var, &(sys->variable_set));
 640   if (weight)
 641     xbt_swag_insert_at_head(var, &(sys->variable_set));
 642   else
 643     xbt_swag_insert_at_tail(var, &(sys->variable_set));
 644
 645   for (i = 0; i < var->cnsts_number; i++) {
 646     elem = &var->cnsts[i];
 647     xbt_swag_remove(elem, &(elem->constraint->element_set));
 648     if (weight)
 649       xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 650     else
 651       xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 652   }
 653   if (!weight)
 654     var->value = 0.0;
 655
 656   XBT_OUT;
 657 }
 658
 659 double lmm_get_variable_weight(lmm_variable_t var)
 660 {
 661   return var->weight;
 662 }
 663
 664 void lmm_update_constraint_bound(lmm_system_t sys, lmm_constraint_t cnst,
 665                                  double bound)
 666 {
 667   sys->modified = 1;
 668   cnst->bound = bound;
 669 }
 670
 671 int lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst)
 672 {
 673   return xbt_swag_belongs(cnst, &(sys->active_constraint_set));
 674 }
 675
 676 lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t sys)
 677 {
 678   return xbt_swag_getFirst(&(sys->active_constraint_set));
 679 }
 680
 681 lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t sys,
 682                                                 lmm_constraint_t cnst)
 683 {
 684   return xbt_swag_getNext(cnst, (sys->active_constraint_set).offset);
 685 }