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 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     if (double_positive(sum - cnst->bound))
 426       WARN3("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       if (double_positive(var->value - var->bound))
 437         WARN2("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
 456   if (!(sys->modified))
 457     return;
 458
 459   /* Init */
 460   var_list = &(sys->variable_set);
 461   DEBUG1("Variable set : %d", xbt_swag_size(var_list));
 462   xbt_swag_foreach(var, var_list) {
 463     int nb=0;
 464     int i;
 465     if(var->weight<=0.0) break;
 466     var->value = 0.0;
 467     for (i = 0; i < var->cnsts_number; i++) {
 468       if(var->cnsts[i].value==0.0) nb++;
 469     }
 470     if((nb==var->cnsts_number) && (var->weight>0.0))
 471       var->value = 1.0;
 472   }
 473
 474   /*
 475    * Compute Usage and store the variables that reach the maximum.
 476    */
 477   cnst_list = &(sys->active_constraint_set);
 478   DEBUG1("Active constraints : %d", xbt_swag_size(cnst_list));
 479   xbt_swag_foreach(cnst, cnst_list) {
 480     /* INIT */
 481     cnst->remaining = cnst->bound;
 482     cnst->usage = 0;
 483     elem_list = &(cnst->element_set);
 484     cnst->usage = 0.0;
 485     xbt_swag_foreach(elem, elem_list) {
 486       if (elem->variable->weight <= 0)
 487         break;
 488       if ((elem->value > 0)) {
 489         if (cnst->shared)
 490           cnst->usage += elem->value / elem->variable->weight;
 491         else if (cnst->usage < elem->value / elem->variable->weight)
 492           cnst->usage = elem->value / elem->variable->weight;
 493         DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
 494         make_elem_active(elem);
 495       }
 496     }
 497     /* Saturated constraints update */
 498     saturated_constraint_set_update(sys, cnst, &min_usage);
 499   }
 500   saturated_variable_set_update(sys);
 501
 502   /* Saturated variables update */
 503
 504   do {
 505     /* Fix the variables that have to be */
 506     var_list = &(sys->saturated_variable_set);
 507
 508     xbt_swag_foreach(var, var_list) {
 509       if(var->weight<=0.0) DIE_IMPOSSIBLE;
 510       /* First check if some of these variables have reach their upper
 511          bound and update min_usage accordingly. */
 512       DEBUG5
 513           ("var=%p, var->bound=%f, var->weight=%f, min_usage=%f, var->bound*var->weight=%f",
 514            var, var->bound, var->weight, min_usage,
 515            var->bound * var->weight);
 516       if ((var->bound > 0) && (var->bound * var->weight < min_usage)) {
 517         min_usage = var->bound * var->weight;
 518         DEBUG1("Updated min_usage=%f", min_usage);
 519       }
 520     }
 521
 522
 523     while ((var = xbt_swag_getFirst(var_list))) {
 524       int i;
 525
 526       var->value = min_usage / var->weight;
 527       DEBUG5("Min usage: %f, Var(%p)->weight: %f, Var(%p)->value: %f ",
 528              min_usage, var, var->weight, var, var->value);
 529
 530
 531       /* Update usage */
 532
 533       for (i = 0; i < var->cnsts_number; i++) {
 534         elem = &var->cnsts[i];
 535         cnst = elem->constraint;
 536         if (cnst->shared) {
 537           double_update(&(cnst->remaining), elem->value * var->value);
 538           double_update(&(cnst->usage), elem->value / var->weight);
 539           make_elem_inactive(elem);
 540         } else {                /* FIXME one day: We recompute usage.... :( */
 541           cnst->usage = 0.0;
 542           make_elem_inactive(elem);
 543           xbt_swag_foreach(elem, elem_list) {
 544             if (elem->variable->weight <= 0)
 545               break;
 546             if (elem->variable->value > 0)
 547               break;
 548             if ((elem->value > 0)) {
 549               if (cnst->usage < elem->value / elem->variable->weight)
 550                 cnst->usage = elem->value / elem->variable->weight;
 551               DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
 552               make_elem_active(elem);
 553             }
 554           }
 555         }
 556       }
 557       xbt_swag_remove(var, var_list);
 558     }
 559
 560     /* Find out which variables reach the maximum */
 561     cnst_list = &(sys->active_constraint_set);
 562     min_usage = -1;
 563     xbt_swag_foreach(cnst, cnst_list) {
 564       saturated_constraint_set_update(sys, cnst, &min_usage);
 565     }
 566     saturated_variable_set_update(sys);
 567
 568   } while (xbt_swag_size(&(sys->saturated_variable_set)));
 569
 570   sys->modified = 0;
 571   if (XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug)) {
 572     lmm_print(sys);
 573   }
 574 }
 575
 576 /* Not a O(1) function */
 577
 578 void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
 579                 lmm_variable_t var, double value)
 580 {
 581   int i;
 582
 583   sys->modified = 1;
 584   for (i = 0; i < var->cnsts_number; i++)
 585     if (var->cnsts[i].constraint == cnst) {
 586       var->cnsts[i].value = value;
 587       return;
 588     }
 589 }
 590
 591 /** \brief Attribute the value bound to var->bound.
 592  *
 593  *  \param sys the lmm_system_t
 594  *  \param var the lmm_variable_t
 595  *  \param bound the new bound to associate with var
 596  *
 597  *  Makes var->bound equal to bound. Whenever this function is called
 598  *  a change is  signed in the system. To
 599  *  avoid false system changing detection it is a good idea to test
 600  *  (bound != 0) before calling it.
 601  *
 602  */
 603 void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
 604                                double bound)
 605 {
 606   sys->modified = 1;
 607   var->bound = bound;
 608 }
 609
 610 /** \brief Add the value delta to var->df (the sum of latencies).
 611  *
 612  *  \param sys the lmm_system_t associated
 613  *  \param var the lmm_variable_t which need to updated
 614  *  \param delta the variation of the latency
 615  *
 616  *  Add the value delta to var->df (the sum of latencys associated to the
 617  *  flow). Whenever this function is called a change is  signed in the system. To
 618  *  avoid false system changing detection it is a good idea to test
 619  *  (delta != 0) before calling it.
 620  *
 621  */
 622 void lmm_update_variable_latency(lmm_system_t sys, lmm_variable_t var,
 623                                  double delta)
 624 {
 625   sys->modified = 1;
 626   var->df += delta;
 627 }
 628
 629 void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
 630                                 double weight)
 631 {
 632   int i;
 633   lmm_element_t elem;
 634
 635   if(weight==var->weight) 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 }