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   var->df = 0.0;
 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 double lmm_variable_getdf(lmm_variable_t var)
 217 {
 218   return (var->df);
 219 }
 220
 221 void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
 222                 lmm_variable_t var, double value)
 223 {
 224   lmm_element_t elem = NULL;
 225
 226   sys->modified = 1;
 227
 228   xbt_assert0(var->cnsts_number < var->cnsts_size, "Too much constraints");
 229
 230   elem = &(var->cnsts[var->cnsts_number++]);
 231
 232   elem->value = value;
 233   elem->constraint = cnst;
 234   elem->variable = var;
 235
 236   if (var->weight)
 237     xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 238   else
 239     xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 240
 241   make_constraint_active(sys, cnst);
 242 }
 243
 244 void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
 245                     lmm_variable_t var, double value)
 246 {
 247   int i;
 248   sys->modified = 1;
 249
 250   for (i = 0; i < var->cnsts_number; i++)
 251     if (var->cnsts[i].constraint == cnst)
 252       break;
 253
 254   if (i < var->cnsts_number) {
 255     if(cnst->shared) var->cnsts[i].value += value;
 256     else var->cnsts[i].value = MAX(var->cnsts[i].value,value);
 257   }  else
 258     lmm_expand(sys, cnst, var, value);
 259 }
 260
 261 void lmm_elem_set_value(lmm_system_t sys, lmm_constraint_t cnst,
 262                         lmm_variable_t var, double value)
 263 {
 264   int i;
 265
 266   for (i = 0; i < var->cnsts_number; i++)
 267     if (var->cnsts[i].constraint == cnst)
 268       break;
 269
 270   if (i < var->cnsts_number) {
 271     var->cnsts[i].value = value;
 272     sys->modified = 1;
 273   } else
 274     DIE_IMPOSSIBLE;
 275 }
 276
 277 lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t sys,
 278                                        lmm_variable_t var, int num)
 279 {
 280   if (num < var->cnsts_number)
 281     return (var->cnsts[num].constraint);
 282   else
 283     return NULL;
 284 }
 285
 286 int lmm_get_number_of_cnst_from_var(lmm_system_t sys, lmm_variable_t var)
 287 {
 288   return (var->cnsts_number);
 289 }
 290
 291 lmm_variable_t lmm_get_var_from_cnst(lmm_system_t sys,
 292                                      lmm_constraint_t cnst,
 293                                      lmm_element_t * elem)
 294 {
 295   if (!(*elem))
 296     *elem = xbt_swag_getFirst(&(cnst->element_set));
 297   else
 298     *elem = xbt_swag_getNext(*elem, cnst->element_set.offset);
 299   if(*elem)
 300     return (*elem)->variable;
 301   else
 302     return NULL;
 303 }
 304
 305 void *lmm_constraint_id(lmm_constraint_t cnst)
 306 {
 307   return cnst->id;
 308 }
 309
 310 void *lmm_variable_id(lmm_variable_t var)
 311 {
 312   return var->id;
 313 }
 314
 315 static void saturated_constraint_set_update(lmm_system_t sys,
 316                                             lmm_constraint_t cnst,
 317                                             double *min_usage)
 318 {
 319   lmm_constraint_t useless_cnst = NULL;
 320
 321   XBT_IN3("sys=%p, cnst=%p, min_usage=%f", sys, cnst, *min_usage);
 322   if (cnst->usage <= 0) {
 323     XBT_OUT;
 324     return;
 325   }
 326   if (cnst->remaining <= 0) {
 327     XBT_OUT;
 328     return;
 329   }
 330   if ((*min_usage < 0) || (*min_usage > cnst->remaining / cnst->usage)) {
 331     *min_usage = cnst->remaining / cnst->usage;
 332     LOG3(xbt_log_priority_trace,
 333          "min_usage=%f (cnst->remaining=%f, cnst->usage=%f)", *min_usage,
 334          cnst->remaining, cnst->usage);
 335     while ((useless_cnst =
 336             xbt_swag_getFirst(&(sys->saturated_constraint_set))))
 337       xbt_swag_remove(useless_cnst, &(sys->saturated_constraint_set));
 338
 339     xbt_swag_insert(cnst, &(sys->saturated_constraint_set));
 340   } else if (*min_usage == cnst->remaining / cnst->usage) {
 341     xbt_swag_insert(cnst, &(sys->saturated_constraint_set));
 342   }
 343   XBT_OUT;
 344 }
 345
 346 static void saturated_variable_set_update(lmm_system_t sys)
 347 {
 348   lmm_constraint_t cnst = NULL;
 349   xbt_swag_t cnst_list = NULL;
 350   lmm_element_t elem = NULL;
 351   xbt_swag_t elem_list = NULL;
 352
 353   cnst_list = &(sys->saturated_constraint_set);
 354   while ((cnst = xbt_swag_getFirst(cnst_list))) {
 355     elem_list = &(cnst->active_element_set);
 356     xbt_swag_foreach(elem, elem_list) {
 357       if (elem->variable->weight <= 0)
 358         break;
 359       if ((elem->value > 0))
 360         xbt_swag_insert(elem->variable, &(sys->saturated_variable_set));
 361     }
 362     xbt_swag_remove(cnst, cnst_list);
 363   }
 364 }
 365
 366 void lmm_print(lmm_system_t sys)
 367 {
 368   lmm_constraint_t cnst = NULL;
 369   lmm_element_t elem = NULL;
 370   lmm_variable_t var = NULL;
 371   xbt_swag_t cnst_list = NULL;
 372   xbt_swag_t var_list = NULL;
 373   xbt_swag_t elem_list = NULL;
 374   char print_buf[1024];
 375   char *trace_buf = xbt_malloc0(sizeof(char));
 376   double sum = 0.0;
 377
 378   /* Printing Objective */
 379   var_list = &(sys->variable_set);
 380   sprintf(print_buf, "MAX-MIN ( ");
 381   trace_buf =
 382       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 383   strcat(trace_buf, print_buf);
 384   xbt_swag_foreach(var, var_list) {
 385     sprintf(print_buf, "'%p'(%f) ", var, var->weight);
 386     trace_buf =
 387         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 388     strcat(trace_buf, print_buf);
 389   }
 390   sprintf(print_buf, ")");
 391   trace_buf =
 392       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 393   strcat(trace_buf, print_buf);
 394   DEBUG1("%s", trace_buf);
 395   trace_buf[0] = '\000';
 396
 397   DEBUG0("Constraints");
 398   /* Printing Constraints */
 399   cnst_list = &(sys->active_constraint_set);
 400   xbt_swag_foreach(cnst, cnst_list) {
 401     sum = 0.0;
 402     elem_list = &(cnst->element_set);
 403     sprintf(print_buf, "\t");
 404     trace_buf =
 405         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 406     strcat(trace_buf, print_buf);
 407     xbt_swag_foreach(elem, elem_list) {
 408       sprintf(print_buf, "%f.'%p'(%f) + ", elem->value,
 409               elem->variable, elem->variable->value);
 410       trace_buf =
 411           xbt_realloc(trace_buf,
 412                       strlen(trace_buf) + strlen(print_buf) + 1);
 413       strcat(trace_buf, print_buf);
 414       sum += elem->value * elem->variable->value;
 415     }
 416     sprintf(print_buf, "0 <= %f ('%p')", cnst->bound, cnst);
 417     trace_buf =
 418         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 419     strcat(trace_buf, print_buf);
 420
 421     if (!cnst->shared) {
 422       sprintf(print_buf, " [MAX-Constraint]");
 423       trace_buf =
 424           xbt_realloc(trace_buf,
 425                       strlen(trace_buf) + strlen(print_buf) + 1);
 426       strcat(trace_buf, print_buf);
 427     }
 428     DEBUG1("%s", trace_buf);
 429     trace_buf[0] = '\000';
 430     xbt_assert3(!double_positive(sum - cnst->bound),
 431                 "Incorrect value (%f is not smaller than %f): %g",
 432                 sum, cnst->bound, sum - cnst->bound);
 433   }
 434
 435   DEBUG0("Variables");
 436   /* Printing Result */
 437   xbt_swag_foreach(var, var_list) {
 438     if (var->bound > 0) {
 439       DEBUG4("'%p'(%f) : %f (<=%f)", var, var->weight, var->value,
 440              var->bound);
 441       xbt_assert2(!double_positive(var->value - var->bound),
 442                   "Incorrect value (%f is not smaller than %f",
 443                   var->value, var->bound);
 444     } else
 445       DEBUG3("'%p'(%f) : %f", var, var->weight, var->value);
 446   }
 447
 448   free(trace_buf);
 449 }
 450
 451 void lmm_solve(lmm_system_t sys)
 452 {
 453   lmm_variable_t var = NULL;
 454   lmm_constraint_t cnst = NULL;
 455   lmm_element_t elem = NULL;
 456   xbt_swag_t cnst_list = NULL;
 457   xbt_swag_t var_list = NULL;
 458   xbt_swag_t elem_list = NULL;
 459   double min_usage = -1;
 460
 461   if (!(sys->modified))
 462     return;
 463
 464   /* Init */
 465   var_list = &(sys->variable_set);
 466   DEBUG1("Variable set : %d", xbt_swag_size(var_list));
 467   xbt_swag_foreach(var, var_list) {
 468     int nb=0;
 469     int i;
 470     if(var->weight<=0.0) break;
 471     var->value = 0.0;
 472     for (i = 0; i < var->cnsts_number; i++) {
 473       if(var->cnsts[i].value==0.0) nb++;
 474     }
 475     if((nb==var->cnsts_number) && (var->weight>0.0))
 476       var->value = 1.0;
 477   }
 478
 479   /*
 480    * Compute Usage and store the variables that reach the maximum.
 481    */
 482   cnst_list = &(sys->active_constraint_set);
 483   DEBUG1("Active constraints : %d", xbt_swag_size(cnst_list));
 484   xbt_swag_foreach(cnst, cnst_list) {
 485     /* INIT */
 486     cnst->remaining = cnst->bound;
 487     cnst->usage = 0;
 488     elem_list = &(cnst->element_set);
 489     cnst->usage = 0.0;
 490     xbt_swag_foreach(elem, elem_list) {
 491       if (elem->variable->weight <= 0)
 492         break;
 493       if ((elem->value > 0)) {
 494         if (cnst->shared)
 495           cnst->usage += elem->value / elem->variable->weight;
 496         else if (cnst->usage < elem->value / elem->variable->weight)
 497           cnst->usage = elem->value / elem->variable->weight;
 498         DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
 499         make_elem_active(elem);
 500       }
 501     }
 502     /* Saturated constraints update */
 503     saturated_constraint_set_update(sys, cnst, &min_usage);
 504   }
 505   saturated_variable_set_update(sys);
 506
 507   /* Saturated variables update */
 508
 509   do {
 510     /* Fix the variables that have to be */
 511     var_list = &(sys->saturated_variable_set);
 512
 513     xbt_swag_foreach(var, var_list) {
 514       if(var->weight<=0.0) 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,
 520            var->bound * var->weight);
 521       if ((var->bound > 0) && (var->bound * var->weight < min_usage)) {
 522         min_usage = var->bound * var->weight;
 523         DEBUG1("Updated min_usage=%f", min_usage);
 524       }
 525     }
 526
 527
 528     while ((var = xbt_swag_getFirst(var_list))) {
 529       int i;
 530
 531       var->value = min_usage / var->weight;
 532       DEBUG5("Min usage: %f, Var(%p)->weight: %f, Var(%p)->value: %f ",
 533              min_usage, var, var->weight, var, var->value);
 534
 535
 536       /* Update usage */
 537
 538       for (i = 0; i < var->cnsts_number; i++) {
 539         elem = &var->cnsts[i];
 540         cnst = elem->constraint;
 541         if (cnst->shared) {
 542           double_update(&(cnst->remaining), elem->value * var->value);
 543           double_update(&(cnst->usage), elem->value / var->weight);
 544           make_elem_inactive(elem);
 545         } else {                /* FIXME one day: We recompute usage.... :( */
 546           cnst->usage = 0.0;
 547           make_elem_inactive(elem);
 548           xbt_swag_foreach(elem, elem_list) {
 549             if (elem->variable->weight <= 0)
 550               break;
 551             if (elem->variable->value > 0)
 552               break;
 553             if ((elem->value > 0)) {
 554               if (cnst->usage < elem->value / elem->variable->weight)
 555                 cnst->usage = elem->value / elem->variable->weight;
 556               DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
 557               make_elem_active(elem);
 558             }
 559           }
 560         }
 561       }
 562       xbt_swag_remove(var, var_list);
 563     }
 564
 565     /* Find out which variables reach the maximum */
 566     cnst_list = &(sys->active_constraint_set);
 567     min_usage = -1;
 568     xbt_swag_foreach(cnst, cnst_list) {
 569       saturated_constraint_set_update(sys, cnst, &min_usage);
 570     }
 571     saturated_variable_set_update(sys);
 572
 573   } while (xbt_swag_size(&(sys->saturated_variable_set)));
 574
 575   sys->modified = 0;
 576   if (XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug)) {
 577     lmm_print(sys);
 578   }
 579 }
 580
 581 /* Not a O(1) function */
 582
 583 void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
 584                 lmm_variable_t var, double value)
 585 {
 586   int i;
 587
 588   sys->modified = 1;
 589   for (i = 0; i < var->cnsts_number; i++)
 590     if (var->cnsts[i].constraint == cnst) {
 591       var->cnsts[i].value = value;
 592       return;
 593     }
 594 }
 595
 596 /** \brief Attribute the value bound to var->bound.
 597  *
 598  *  \param sys the lmm_system_t
 599  *  \param var the lmm_variable_t
 600  *  \param bound the new bound to associate with var
 601  *
 602  *  Makes var->bound equal to bound. Whenever this function is called
 603  *  a change is  signed in the system. To
 604  *  avoid false system changing detection it is a good idea to test
 605  *  (bound != 0) before calling it.
 606  *
 607  */
 608 void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
 609                                double bound)
 610 {
 611   sys->modified = 1;
 612   var->bound = bound;
 613 }
 614
 615 /** \brief Add the value delta to var->df (the sum of latencies).
 616  *
 617  *  \param sys the lmm_system_t associated
 618  *  \param var the lmm_variable_t which need to updated
 619  *  \param delta the variation of the latency
 620  *
 621  *  Add the value delta to var->df (the sum of latencys associated to the
 622  *  flow). Whenever this function is called a change is  signed in the system. To
 623  *  avoid false system changing detection it is a good idea to test
 624  *  (delta != 0) before calling it.
 625  *
 626  */
 627 void lmm_update_variable_latency(lmm_system_t sys, lmm_variable_t var,
 628                                  double delta)
 629 {
 630   sys->modified = 1;
 631   var->df += delta;
 632 }
 633
 634 void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
 635                                 double weight)
 636 {
 637   int i;
 638   lmm_element_t elem;
 639
 640   if(weight==var->weight) return;
 641   XBT_IN3("(sys=%p, var=%p, weight=%f)", sys, var, weight);
 642   sys->modified = 1;
 643   var->weight = weight;
 644   xbt_swag_remove(var, &(sys->variable_set));
 645   if (weight)
 646     xbt_swag_insert_at_head(var, &(sys->variable_set));
 647   else
 648     xbt_swag_insert_at_tail(var, &(sys->variable_set));
 649
 650   for (i = 0; i < var->cnsts_number; i++) {
 651     elem = &var->cnsts[i];
 652     xbt_swag_remove(elem, &(elem->constraint->element_set));
 653     if (weight)
 654       xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 655     else
 656       xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 657   }
 658   if(!weight)
 659     var->value = 0.0;
 660
 661   XBT_OUT;
 662 }
 663
 664 double lmm_get_variable_weight(lmm_variable_t var)
 665 {
 666   return var->weight;
 667 }
 668
 669 void lmm_update_constraint_bound(lmm_system_t sys, lmm_constraint_t cnst,
 670                                  double bound)
 671 {
 672   sys->modified = 1;
 673   cnst->bound = bound;
 674 }
 675
 676 int lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst)
 677 {
 678   return xbt_swag_belongs(cnst, &(sys->active_constraint_set));
 679 }
 680
 681 lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t sys)
 682 {
 683   return xbt_swag_getFirst(&(sys->active_constraint_set));
 684 }
 685
 686 lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t sys,
 687                                                 lmm_constraint_t cnst)
 688 {
 689   return xbt_swag_getNext(cnst, (sys->active_constraint_set).offset);
 690 }