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