src/surf/maxmin.c

   1 /* Copyright (c) 2004-2011. The SimGrid Team.
   2  * All rights reserved.                                                     */
   3
   4 /* This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the license (GNU LGPL) which comes with this package. */
   6
   7
   8 #include "xbt/sysdep.h"
   9 #include "xbt/log.h"
  10 #include "xbt/mallocator.h"
  11 #include "xbt/dynar.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 typedef struct s_dyn_light {
  20   int *data;
  21   int pos;
  22   int size;
  23 } s_dyn_light_t, *dyn_light_t;
  24
  25 double sg_maxmin_precision = 0.00001;
  26
  27 static void *lmm_variable_mallocator_new_f(void);
  28 static void lmm_variable_mallocator_free_f(void *var);
  29 #define lmm_variable_mallocator_reset_f ((void_f_pvoid_t)NULL)
  30 static void lmm_update_modified_set(lmm_system_t sys,
  31                                     lmm_constraint_t cnst);
  32 static void lmm_remove_all_modified_set(lmm_system_t sys);
  33 static int Global_debug_id = 1;
  34 static int Global_const_debug_id = 1;
  35
  36 lmm_system_t lmm_system_new(int selective_update)
  37 {
  38   lmm_system_t l = NULL;
  39   s_lmm_variable_t var;
  40   s_lmm_constraint_t cnst;
  41
  42   l = xbt_new0(s_lmm_system_t, 1);
  43
  44   l->modified = 0;
  45   l->selective_update_active = selective_update;
  46   l->visited_counter = 1;
  47
  48   XBT_DEBUG("Setting selective_update_active flag to %d\n",
  49          l->selective_update_active);
  50
  51   xbt_swag_init(&(l->variable_set),
  52                 xbt_swag_offset(var, variable_set_hookup));
  53   xbt_swag_init(&(l->constraint_set),
  54                 xbt_swag_offset(cnst, constraint_set_hookup));
  55
  56   xbt_swag_init(&(l->active_constraint_set),
  57                 xbt_swag_offset(cnst, active_constraint_set_hookup));
  58
  59   xbt_swag_init(&(l->modified_constraint_set),
  60                 xbt_swag_offset(cnst, modified_constraint_set_hookup));
  61   xbt_swag_init(&(l->saturated_variable_set),
  62                 xbt_swag_offset(var, saturated_variable_set_hookup));
  63   xbt_swag_init(&(l->saturated_constraint_set),
  64                 xbt_swag_offset(cnst, saturated_constraint_set_hookup));
  65
  66   l->variable_mallocator = xbt_mallocator_new(65536,
  67                                               lmm_variable_mallocator_new_f,
  68                                               lmm_variable_mallocator_free_f,
  69                                               lmm_variable_mallocator_reset_f);
  70
  71   return l;
  72 }
  73
  74 void lmm_system_free(lmm_system_t sys)
  75 {
  76   lmm_variable_t var = NULL;
  77   lmm_constraint_t cnst = NULL;
  78
  79   while ((var = extract_variable(sys))) {
  80     XBT_WARN
  81         ("Variable %p (%d) still in LMM system when freing it: this may be a bug",
  82          var, var->id_int);
  83     lmm_var_free(sys, var);
  84   }
  85
  86   while ((cnst = extract_constraint(sys)))
  87     lmm_cnst_free(sys, cnst);
  88
  89   xbt_mallocator_free(sys->variable_mallocator);
  90   free(sys);
  91 }
  92
  93 XBT_INLINE void lmm_variable_disable(lmm_system_t sys, lmm_variable_t var)
  94 {
  95   int i;
  96   int n;
  97
  98   lmm_element_t elem = NULL;
  99
 100   XBT_IN("(sys=%p, var=%p)", sys, var);
 101   sys->modified = 1;
 102
 103   n = 0;
 104   for (i = 0; i < var->cnsts_number; i++) {
 105     elem = &var->cnsts[i];
 106     xbt_swag_remove(elem, &(elem->constraint->element_set));
 107     xbt_swag_remove(elem, &(elem->constraint->active_element_set));
 108     if (!xbt_swag_size(&(elem->constraint->element_set)))
 109       make_constraint_inactive(sys, elem->constraint);
 110     else {
 111       if (n < i)
 112         var->cnsts[n].constraint = elem->constraint;
 113       n++;
 114     }
 115   }
 116   if (n) {
 117     var->cnsts_number = n;
 118     lmm_update_modified_set(sys, var->cnsts[0].constraint);
 119   }
 120
 121   var->cnsts_number = 0;
 122   XBT_OUT();
 123 }
 124
 125 static void lmm_var_free(lmm_system_t sys, lmm_variable_t var)
 126 {
 127
 128   lmm_variable_disable(sys, var);
 129   xbt_mallocator_release(sys->variable_mallocator, var);
 130 }
 131
 132 static XBT_INLINE void lmm_cnst_free(lmm_system_t sys,
 133                                      lmm_constraint_t cnst)
 134 {
 135 /*   xbt_assert(xbt_swag_size(&(cnst->element_set)), */
 136 /*         "This list should be empty!"); */
 137   make_constraint_inactive(sys, cnst);
 138   free(cnst);
 139 }
 140
 141 lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id,
 142                                     double bound_value)
 143 {
 144   lmm_constraint_t cnst = NULL;
 145   s_lmm_element_t elem;
 146
 147   cnst = xbt_new0(s_lmm_constraint_t, 1);
 148   cnst->id = id;
 149   cnst->id_int = Global_const_debug_id++;
 150   xbt_swag_init(&(cnst->element_set),
 151                 xbt_swag_offset(elem, element_set_hookup));
 152   xbt_swag_init(&(cnst->active_element_set),
 153                 xbt_swag_offset(elem, active_element_set_hookup));
 154
 155   cnst->bound = bound_value;
 156   cnst->usage = 0;
 157   cnst->shared = 1;
 158   insert_constraint(sys, cnst);
 159
 160   return cnst;
 161 }
 162
 163 XBT_INLINE void lmm_constraint_shared(lmm_constraint_t cnst)
 164 {
 165   cnst->shared = 0;
 166 }
 167
 168 XBT_INLINE int lmm_constraint_is_shared(lmm_constraint_t cnst)
 169 {
 170   return (cnst->shared);
 171 }
 172
 173 XBT_INLINE void lmm_constraint_free(lmm_system_t sys,
 174                                     lmm_constraint_t cnst)
 175 {
 176   remove_constraint(sys, cnst);
 177   lmm_cnst_free(sys, cnst);
 178 }
 179
 180 static void *lmm_variable_mallocator_new_f(void)
 181 {
 182   lmm_variable_t var = xbt_new(s_lmm_variable_t, 1);
 183   var->cnsts = NULL; /* will be created by realloc */
 184   return var;
 185 }
 186
 187 static void lmm_variable_mallocator_free_f(void *var)
 188 {
 189   xbt_free(((lmm_variable_t) var)->cnsts);
 190   xbt_free(var);
 191 }
 192
 193 lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id,
 194                                 double weight,
 195                                 double bound, int number_of_constraints)
 196 {
 197   lmm_variable_t var = NULL;
 198   int i;
 199
 200   XBT_IN("(sys=%p, id=%p, weight=%f, bound=%f, num_cons =%d)",
 201           sys, id, weight, bound, number_of_constraints);
 202
 203   var = xbt_mallocator_get(sys->variable_mallocator);
 204   var->id = id;
 205   var->id_int = Global_debug_id++;
 206   var->cnsts = xbt_realloc(var->cnsts, number_of_constraints * sizeof(s_lmm_element_t));
 207   for (i = 0; i < number_of_constraints; i++) {
 208     var->cnsts[i].element_set_hookup.next = NULL;
 209     var->cnsts[i].element_set_hookup.prev = NULL;
 210     var->cnsts[i].active_element_set_hookup.next = NULL;
 211     var->cnsts[i].active_element_set_hookup.prev = NULL;
 212     var->cnsts[i].constraint = NULL;
 213     var->cnsts[i].variable = NULL;
 214     var->cnsts[i].value = 0.0;
 215   }
 216   var->cnsts_size = number_of_constraints;
 217   var->cnsts_number = 0;
 218   var->weight = weight;
 219   var->bound = bound;
 220   var->value = 0.0;
 221   var->visited = sys->visited_counter - 1;
 222   var->mu = 0.0;
 223   var->new_mu = 0.0;
 224   var->func_f = func_f_def;
 225   var->func_fp = func_fp_def;
 226   var->func_fpi = func_fpi_def;
 227
 228   var->variable_set_hookup.next = NULL;
 229   var->variable_set_hookup.prev = NULL;
 230   var->saturated_variable_set_hookup.next = NULL;
 231   var->saturated_variable_set_hookup.prev = NULL;
 232
 233   if (weight)
 234     xbt_swag_insert_at_head(var, &(sys->variable_set));
 235   else
 236     xbt_swag_insert_at_tail(var, &(sys->variable_set));
 237
 238   XBT_OUT(" returns %p", var);
 239   return var;
 240 }
 241
 242 void lmm_variable_free(lmm_system_t sys, lmm_variable_t var)
 243 {
 244   remove_variable(sys, var);
 245   lmm_var_free(sys, var);
 246 }
 247
 248 XBT_INLINE double lmm_variable_getvalue(lmm_variable_t var)
 249 {
 250   return (var->value);
 251 }
 252
 253 XBT_INLINE double lmm_variable_getbound(lmm_variable_t var)
 254 {
 255   return (var->bound);
 256 }
 257
 258 void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
 259                 lmm_variable_t var, double value)
 260 {
 261   lmm_element_t elem = NULL;
 262
 263   sys->modified = 1;
 264
 265   xbt_assert(var->cnsts_number < var->cnsts_size, "Too much constraints");
 266
 267   elem = &(var->cnsts[var->cnsts_number++]);
 268
 269   elem->value = value;
 270   elem->constraint = cnst;
 271   elem->variable = var;
 272
 273   if (var->weight)
 274     xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 275   else
 276     xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 277   if(!sys->selective_update_active) {
 278     make_constraint_active(sys, cnst);
 279   } else if(elem->value>0 || var->weight >0) {
 280     make_constraint_active(sys, cnst);
 281     lmm_update_modified_set(sys, cnst);
 282     if (var->cnsts_number > 1)
 283       lmm_update_modified_set(sys, var->cnsts[0].constraint);
 284   }
 285 }
 286
 287 void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
 288                     lmm_variable_t var, double value)
 289 {
 290   int i;
 291   sys->modified = 1;
 292
 293   for (i = 0; i < var->cnsts_number; i++)
 294     if (var->cnsts[i].constraint == cnst)
 295       break;
 296
 297   if (i < var->cnsts_number) {
 298     if (cnst->shared)
 299       var->cnsts[i].value += value;
 300     else
 301       var->cnsts[i].value = MAX(var->cnsts[i].value, value);
 302     lmm_update_modified_set(sys, cnst);
 303   } else
 304     lmm_expand(sys, cnst, var, value);
 305 }
 306
 307 void lmm_elem_set_value(lmm_system_t sys, lmm_constraint_t cnst,
 308                         lmm_variable_t var, double value)
 309 {
 310   int i;
 311
 312   for (i = 0; i < var->cnsts_number; i++)
 313     if (var->cnsts[i].constraint == cnst)
 314       break;
 315
 316   if (i < var->cnsts_number) {
 317     var->cnsts[i].value = value;
 318     sys->modified = 1;
 319     lmm_update_modified_set(sys, cnst);
 320   } else
 321     DIE_IMPOSSIBLE;
 322 }
 323
 324 XBT_INLINE lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t sys,
 325                                                   lmm_variable_t var,
 326                                                   int num)
 327 {
 328   if (num < var->cnsts_number)
 329     return (var->cnsts[num].constraint);
 330   else
 331     return NULL;
 332 }
 333
 334 XBT_INLINE double lmm_get_cnst_weight_from_var(lmm_system_t sys,
 335                                                          lmm_variable_t var,
 336                                                          int num)
 337 {
 338   if (num < var->cnsts_number)
 339     return (var->cnsts[num].value);
 340   else
 341     return 0.0;
 342 }
 343
 344 XBT_INLINE int lmm_get_number_of_cnst_from_var(lmm_system_t sys,
 345                                                lmm_variable_t var)
 346 {
 347   return (var->cnsts_number);
 348 }
 349
 350 lmm_variable_t lmm_get_var_from_cnst(lmm_system_t sys,
 351                                      lmm_constraint_t cnst,
 352                                      lmm_element_t * elem)
 353 {
 354   if (!(*elem))
 355     *elem = xbt_swag_getFirst(&(cnst->element_set));
 356   else
 357     *elem = xbt_swag_getNext(*elem, cnst->element_set.offset);
 358   if (*elem)
 359     return (*elem)->variable;
 360   else
 361     return NULL;
 362 }
 363
 364 XBT_INLINE void *lmm_constraint_id(lmm_constraint_t cnst)
 365 {
 366   return cnst->id;
 367 }
 368
 369 XBT_INLINE void *lmm_variable_id(lmm_variable_t var)
 370 {
 371   return var->id;
 372 }
 373
 374 static XBT_INLINE void saturated_constraint_set_update(double usage,
 375                                                       int cnst_light_num,
 376                                                       dyn_light_t saturated_constraint_set,
 377                                                       double *min_usage)
 378 {
 379   xbt_assert(usage > 0,"Impossible");
 380
 381   if (*min_usage < 0 || *min_usage > usage) {
 382     *min_usage = usage;
 383     // XBT_HERE(" min_usage=%f (cnst->remaining / cnst->usage =%f)", *min_usage, usage);
 384     saturated_constraint_set->data[0] = cnst_light_num;
 385     saturated_constraint_set->pos = 1;
 386   } else if (*min_usage == usage) {
 387     if(saturated_constraint_set->pos == saturated_constraint_set->size) { // realloc the size
 388       saturated_constraint_set->size *= 2;
 389       saturated_constraint_set->data = realloc(saturated_constraint_set->data, (saturated_constraint_set->size) * sizeof(int));
 390     }
 391     saturated_constraint_set->data[saturated_constraint_set->pos] = cnst_light_num;
 392     saturated_constraint_set->pos++;
 393   }
 394 }
 395
 396 static XBT_INLINE void saturated_variable_set_update(
 397     s_lmm_constraint_light_t *cnst_light_tab,
 398     dyn_light_t saturated_constraint_set,
 399     lmm_system_t sys)
 400 {
 401   lmm_constraint_light_t cnst = NULL;
 402   lmm_element_t elem = NULL;
 403   xbt_swag_t elem_list = NULL;
 404   int i;
 405   for(i = 0; i< saturated_constraint_set->pos; i++){
 406     cnst = &cnst_light_tab[saturated_constraint_set->data[i]];
 407     elem_list = &(cnst->cnst->active_element_set);
 408     xbt_swag_foreach(elem, elem_list) {
 409       if (elem->variable->weight <= 0)
 410         break;
 411       if ((elem->value > 0))
 412         xbt_swag_insert(elem->variable, &(sys->saturated_variable_set));
 413     }
 414   }
 415 }
 416
 417 void lmm_print(lmm_system_t sys)
 418 {
 419   lmm_constraint_t cnst = NULL;
 420   lmm_element_t elem = NULL;
 421   lmm_variable_t var = NULL;
 422   xbt_swag_t cnst_list = NULL;
 423   xbt_swag_t var_list = NULL;
 424   xbt_swag_t elem_list = NULL;
 425   char print_buf[1024];
 426   char *trace_buf = xbt_malloc0(sizeof(char));
 427   double sum = 0.0;
 428
 429   /* Printing Objective */
 430   var_list = &(sys->variable_set);
 431   sprintf(print_buf, "MAX-MIN ( ");
 432   trace_buf =
 433       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 434   strcat(trace_buf, print_buf);
 435   xbt_swag_foreach(var, var_list) {
 436     sprintf(print_buf, "'%d'(%f) ", var->id_int, var->weight);
 437     trace_buf =
 438         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 439     strcat(trace_buf, print_buf);
 440   }
 441   sprintf(print_buf, ")");
 442   trace_buf =
 443       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 444   strcat(trace_buf, print_buf);
 445   XBT_DEBUG("%20s", trace_buf);
 446   trace_buf[0] = '\000';
 447
 448   XBT_DEBUG("Constraints");
 449   /* Printing Constraints */
 450   cnst_list = &(sys->active_constraint_set);
 451   xbt_swag_foreach(cnst, cnst_list) {
 452     sum = 0.0;
 453     elem_list = &(cnst->element_set);
 454     sprintf(print_buf, "\t");
 455     trace_buf =
 456         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 457     strcat(trace_buf, print_buf);
 458     sprintf(print_buf, "%s(",(cnst->shared)?"":"max");
 459     trace_buf =
 460       xbt_realloc(trace_buf,
 461       strlen(trace_buf) + strlen(print_buf) + 1);
 462     strcat(trace_buf, print_buf);
 463     xbt_swag_foreach(elem, elem_list) {
 464       sprintf(print_buf, "%f.'%d'(%f) %s ", elem->value,
 465               elem->variable->id_int, elem->variable->value,(cnst->shared)?"+":",");
 466       trace_buf =
 467           xbt_realloc(trace_buf,
 468                       strlen(trace_buf) + strlen(print_buf) + 1);
 469       strcat(trace_buf, print_buf);
 470       if(cnst->shared)
 471   sum += elem->value * elem->variable->value;
 472       else
 473   sum = MAX(sum,elem->value * elem->variable->value);
 474     }
 475     sprintf(print_buf, "0) <= %f ('%d')", cnst->bound, cnst->id_int);
 476     trace_buf =
 477         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 478     strcat(trace_buf, print_buf);
 479
 480     if (!cnst->shared) {
 481       sprintf(print_buf, " [MAX-Constraint]");
 482       trace_buf =
 483           xbt_realloc(trace_buf,
 484                       strlen(trace_buf) + strlen(print_buf) + 1);
 485       strcat(trace_buf, print_buf);
 486     }
 487     XBT_DEBUG("%s", trace_buf);
 488     trace_buf[0] = '\000';
 489     xbt_assert(!double_positive(sum - cnst->bound),
 490                 "Incorrect value (%f is not smaller than %f): %g",
 491                 sum, cnst->bound, sum - cnst->bound);
 492   }
 493
 494   XBT_DEBUG("Variables");
 495   /* Printing Result */
 496   xbt_swag_foreach(var, var_list) {
 497     if (var->bound > 0) {
 498       XBT_DEBUG("'%d'(%f) : %f (<=%f)", var->id_int, var->weight, var->value,
 499              var->bound);
 500       xbt_assert(!double_positive(var->value - var->bound),
 501                   "Incorrect value (%f is not smaller than %f",
 502                   var->value, var->bound);
 503     } else {
 504       XBT_DEBUG("'%d'(%f) : %f", var->id_int, var->weight, var->value);
 505     }
 506   }
 507
 508   free(trace_buf);
 509 }
 510
 511 void lmm_solve(lmm_system_t sys)
 512 {
 513   lmm_variable_t var = NULL;
 514   lmm_constraint_t cnst = NULL;
 515   lmm_constraint_t cnst_next = NULL;
 516   lmm_element_t elem = NULL;
 517   xbt_swag_t cnst_list = NULL;
 518   xbt_swag_t var_list = NULL;
 519   xbt_swag_t elem_list = NULL;
 520   double min_usage = -1;
 521   double min_bound = -1;
 522
 523   if (!(sys->modified))
 524     return;
 525
 526   XBT_IN("(sys=%p)", sys);
 527
 528   /*
 529    * Compute Usage and store the variables that reach the maximum.
 530    */
 531   cnst_list =
 532       sys->
 533       selective_update_active ? &(sys->modified_constraint_set) :
 534       &(sys->active_constraint_set);
 535
 536   XBT_DEBUG("Active constraints : %d", xbt_swag_size(cnst_list));
 537   /* Init: Only modified code portions */
 538   xbt_swag_foreach(cnst, cnst_list) {
 539     elem_list = &(cnst->element_set);
 540     //XBT_DEBUG("Variable set : %d", xbt_swag_size(elem_list));
 541     xbt_swag_foreach(elem, elem_list) {
 542       var = elem->variable;
 543       if (var->weight <= 0.0)
 544         break;
 545       var->value = 0.0;
 546     }
 547   }
 548
 549   s_lmm_constraint_light_t *cnst_light_tab = (s_lmm_constraint_light_t *)xbt_malloc0(xbt_swag_size(cnst_list)*sizeof(s_lmm_constraint_light_t));
 550   int cnst_light_num = 0;
 551   dyn_light_t saturated_constraint_set = xbt_new0(s_dyn_light_t,1);
 552   saturated_constraint_set->size = 5;
 553   saturated_constraint_set->data = xbt_new0(int, saturated_constraint_set->size);
 554
 555   xbt_swag_foreach_safe(cnst, cnst_next, cnst_list) {
 556     /* INIT */
 557     cnst->remaining = cnst->bound;
 558     if (cnst->remaining == 0)
 559       continue;
 560     cnst->usage = 0;
 561     elem_list = &(cnst->element_set);
 562     xbt_swag_foreach(elem, elem_list) {
 563       /* 0-weighted elements (ie, sleep actions) are at the end of the swag and we don't want to consider them */
 564       if (elem->variable->weight <= 0)
 565         break;
 566       if ((elem->value > 0)) {
 567         if (cnst->shared)
 568           cnst->usage += elem->value / elem->variable->weight;
 569         else if (cnst->usage < elem->value / elem->variable->weight)
 570           cnst->usage = elem->value / elem->variable->weight;
 571
 572         make_elem_active(elem);
 573         if (sys->keep_track)
 574           xbt_swag_insert(elem->variable->id, sys->keep_track);
 575       }
 576     }
 577     XBT_DEBUG("Constraint Usage '%d' : %f", cnst->id_int, cnst->usage);
 578     /* Saturated constraints update */
 579
 580     if(cnst->usage > 0) {
 581       cnst_light_tab[cnst_light_num].cnst = cnst;
 582       cnst->cnst_light = &(cnst_light_tab[cnst_light_num]);
 583       cnst_light_tab[cnst_light_num].remaining_over_usage = cnst->remaining / cnst->usage;
 584       saturated_constraint_set_update(cnst_light_tab[cnst_light_num].remaining_over_usage,
 585         cnst_light_num, saturated_constraint_set, &min_usage);
 586       cnst_light_num++;
 587     }
 588   }
 589
 590   saturated_variable_set_update(  cnst_light_tab,
 591                                   saturated_constraint_set,
 592                                   sys);
 593
 594   /* Saturated variables update */
 595
 596   do {
 597     /* Fix the variables that have to be */
 598     var_list = &(sys->saturated_variable_set);
 599
 600     xbt_swag_foreach(var, var_list) {
 601       if (var->weight <= 0.0)
 602         DIE_IMPOSSIBLE;
 603       /* First check if some of these variables have reach their upper
 604          bound and update min_usage accordingly. */
 605       XBT_DEBUG
 606           ("var=%d, var->bound=%f, var->weight=%f, min_usage=%f, var->bound*var->weight=%f",
 607            var->id_int, var->bound, var->weight, min_usage,
 608            var->bound * var->weight);
 609       if ((var->bound > 0) && (var->bound * var->weight < min_usage)) {
 610         if (min_bound < 0)
 611           min_bound = var->bound;
 612         else
 613           min_bound = MIN(min_bound, var->bound);
 614         XBT_DEBUG("Updated min_bound=%f", min_bound);
 615       }
 616     }
 617
 618
 619     while ((var = xbt_swag_getFirst(var_list))) {
 620       int i;
 621
 622       if (min_bound < 0) {
 623         var->value = min_usage / var->weight;
 624       } else {
 625         if (min_bound == var->bound)
 626           var->value = var->bound;
 627         else {
 628           xbt_swag_remove(var, var_list);
 629           continue;
 630         }
 631       }
 632       XBT_DEBUG("Min usage: %f, Var(%d)->weight: %f, Var(%d)->value: %f ",
 633              min_usage, var->id_int, var->weight, var->id_int, var->value);
 634
 635
 636       /* Update usage */
 637
 638       for (i = 0; i < var->cnsts_number; i++) {
 639         elem = &var->cnsts[i];
 640         cnst = elem->constraint;
 641         if (cnst->shared) {
 642           double_update(&(cnst->remaining), elem->value * var->value);
 643           double_update(&(cnst->usage), elem->value / var->weight);
 644           cnst->cnst_light->remaining_over_usage = cnst->remaining /  cnst->usage;
 645           if(cnst->usage<=0 || cnst->remaining<=0) {
 646             xbt_swag_remove(cnst, cnst_list);
 647             xbt_swag_insert_at_tail(cnst, cnst_list);
 648           }
 649           make_elem_inactive(elem);
 650         } else {                /* FIXME one day: We recompute usage.... :( */
 651           cnst->usage = 0.0;
 652           make_elem_inactive(elem);
 653           elem_list = &(cnst->element_set);
 654           xbt_swag_foreach(elem, elem_list) {
 655             if (elem->variable->weight <= 0)
 656               break;
 657             if (elem->variable->value > 0)
 658               break;
 659             if ((elem->value > 0)) {
 660               cnst->usage =
 661                   MAX(cnst->usage, elem->value / elem->variable->weight);
 662               cnst->cnst_light->remaining_over_usage = cnst->remaining /  cnst->usage;
 663               XBT_DEBUG("Constraint Usage %d : %f", cnst->id_int,
 664                      cnst->usage);
 665               make_elem_active(elem);
 666             }
 667           }
 668         }
 669       }
 670       xbt_swag_remove(var, var_list);
 671     }
 672
 673     /* Find out which variables reach the maximum */
 674     min_usage = -1;
 675     min_bound = -1;
 676     saturated_constraint_set->pos = 0;
 677     int pos;
 678     for(pos=0; pos<cnst_light_num; pos++){
 679       if(cnst_light_tab[pos].remaining_over_usage > 0)
 680         saturated_constraint_set_update(
 681           cnst_light_tab[pos].remaining_over_usage,
 682           pos,
 683           saturated_constraint_set,
 684           &min_usage);
 685     }
 686     saturated_variable_set_update(  cnst_light_tab,
 687                                     saturated_constraint_set,
 688                                     sys);
 689
 690   } while (xbt_swag_size(&(sys->saturated_variable_set)));
 691
 692   sys->modified = 0;
 693   if (sys->selective_update_active)
 694     lmm_remove_all_modified_set(sys);
 695
 696   if (XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug)) {
 697     lmm_print(sys);
 698   }
 699
 700   xbt_free(saturated_constraint_set->data);
 701   xbt_free(saturated_constraint_set);
 702   xbt_free(cnst_light_tab);
 703   XBT_OUT();
 704 }
 705
 706 /* Not a O(1) function */
 707
 708 void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
 709                 lmm_variable_t var, double value)
 710 {
 711   int i;
 712
 713   for (i = 0; i < var->cnsts_number; i++)
 714     if (var->cnsts[i].constraint == cnst) {
 715       var->cnsts[i].value = value;
 716       sys->modified = 1;
 717       lmm_update_modified_set(sys, cnst);
 718       return;
 719     }
 720 }
 721
 722 /** \brief Attribute the value bound to var->bound.
 723  *
 724  *  \param sys the lmm_system_t
 725  *  \param var the lmm_variable_t
 726  *  \param bound the new bound to associate with var
 727  *
 728  *  Makes var->bound equal to bound. Whenever this function is called
 729  *  a change is  signed in the system. To
 730  *  avoid false system changing detection it is a good idea to test
 731  *  (bound != 0) before calling it.
 732  *
 733  */
 734 void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
 735                                double bound)
 736 {
 737   sys->modified = 1;
 738   var->bound = bound;
 739
 740   if (var->cnsts_number)
 741     lmm_update_modified_set(sys, var->cnsts[0].constraint);
 742 }
 743
 744
 745 void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
 746                                 double weight)
 747 {
 748   int i;
 749   lmm_element_t elem;
 750
 751   if (weight == var->weight)
 752     return;
 753   XBT_IN("(sys=%p, var=%p, weight=%f)", sys, var, weight);
 754   sys->modified = 1;
 755   var->weight = weight;
 756   xbt_swag_remove(var, &(sys->variable_set));
 757   if (weight)
 758     xbt_swag_insert_at_head(var, &(sys->variable_set));
 759   else
 760     xbt_swag_insert_at_tail(var, &(sys->variable_set));
 761
 762   for (i = 0; i < var->cnsts_number; i++) {
 763     elem = &var->cnsts[i];
 764     xbt_swag_remove(elem, &(elem->constraint->element_set));
 765     if (weight)
 766       xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 767     else
 768       xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 769
 770     if (i == 0)
 771       lmm_update_modified_set(sys, elem->constraint);
 772   }
 773   if (!weight)
 774     var->value = 0.0;
 775
 776   XBT_OUT();
 777 }
 778
 779 XBT_INLINE double lmm_get_variable_weight(lmm_variable_t var)
 780 {
 781   return var->weight;
 782 }
 783
 784 XBT_INLINE void lmm_update_constraint_bound(lmm_system_t sys,
 785                                             lmm_constraint_t cnst,
 786                                             double bound)
 787 {
 788   sys->modified = 1;
 789   lmm_update_modified_set(sys, cnst);
 790   cnst->bound = bound;
 791 }
 792
 793 XBT_INLINE int lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst)
 794 {
 795   return xbt_swag_belongs(cnst, &(sys->active_constraint_set));
 796 }
 797
 798 XBT_INLINE lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t
 799                                                             sys)
 800 {
 801   return xbt_swag_getFirst(&(sys->active_constraint_set));
 802 }
 803
 804 XBT_INLINE lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t
 805                                                            sys,
 806                                                            lmm_constraint_t
 807                                                            cnst)
 808 {
 809   return xbt_swag_getNext(cnst, (sys->active_constraint_set).offset);
 810 }
 811
 812 #ifdef HAVE_LATENCY_BOUND_TRACKING
 813 XBT_INLINE int lmm_is_variable_limited_by_latency(lmm_variable_t var)
 814 {
 815   return (double_equals(var->bound, var->value));
 816 }
 817 #endif
 818
 819
 820 /** \brief Update the constraint set propagating recursively to
 821  *  other constraints so the system should not be entirely computed.
 822  *
 823  *  \param sys the lmm_system_t
 824  *  \param cnst the lmm_constraint_t affected by the change
 825  *
 826  *  A recursive algorithm to optimize the system recalculation selecting only
 827  *  constraints that have changed. Each constraint change is propagated
 828  *  to the list of constraints for each variable.
 829  */
 830 static void lmm_update_modified_set_rec(lmm_system_t sys,
 831                                         lmm_constraint_t cnst)
 832 {
 833   lmm_element_t elem;
 834
 835   xbt_swag_foreach(elem, &cnst->element_set) {
 836     lmm_variable_t var = elem->variable;
 837     s_lmm_element_t *cnsts = var->cnsts;
 838     int i;
 839     for (i = 0; var->visited != sys->visited_counter
 840              && i < var->cnsts_number ; i++) {
 841       if (cnsts[i].constraint != cnst
 842           && !xbt_swag_belongs(cnsts[i].constraint,
 843                                &sys->modified_constraint_set)) {
 844         xbt_swag_insert(cnsts[i].constraint, &sys->modified_constraint_set);
 845         lmm_update_modified_set_rec(sys, cnsts[i].constraint);
 846       }
 847     }
 848     var->visited = sys->visited_counter;
 849   }
 850 }
 851
 852 static void lmm_update_modified_set(lmm_system_t sys,
 853                                     lmm_constraint_t cnst)
 854 {
 855   /* nothing to do if selective update isn't active */
 856   if (sys->selective_update_active
 857       && !xbt_swag_belongs(cnst, &sys->modified_constraint_set)) {
 858     xbt_swag_insert(cnst, &sys->modified_constraint_set);
 859     lmm_update_modified_set_rec(sys, cnst);
 860   }
 861 }
 862
 863 /** \brief Remove all constraints of the modified_constraint_set.
 864  *
 865  *  \param sys the lmm_system_t
 866  */
 867 static void lmm_remove_all_modified_set(lmm_system_t sys)
 868 {
 869   if (++sys->visited_counter == 1) {
 870     /* the counter wrapped around, reset each variable->visited */
 871     lmm_variable_t var;
 872     xbt_swag_foreach(var, &sys->variable_set)
 873       var->visited = 0;
 874   }
 875   xbt_swag_reset(&sys->modified_constraint_set);
 876 }