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 "maxmin_private.h"
  12 #include <stdlib.h>
  13 #include <stdio.h>              /* sprintf */
  14 #include <math.h>
  15 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(surf_maxmin, surf,
  16                                 "Logging specific to SURF (maxmin)");
  17
  18 double sg_maxmin_precision = 0.00001;
  19
  20 static void *lmm_variable_mallocator_new_f(void);
  21 static void lmm_variable_mallocator_free_f(void *var);
  22 #define lmm_variable_mallocator_reset_f ((void_f_pvoid_t)NULL)
  23 static void lmm_update_modified_set(lmm_system_t sys,
  24                                     lmm_constraint_t cnst);
  25 static void lmm_remove_all_modified_set(lmm_system_t sys);
  26 static int Global_debug_id = 1;
  27 static int Global_const_debug_id = 1;
  28
  29 lmm_system_t lmm_system_new(int selective_update)
  30 {
  31   lmm_system_t l = NULL;
  32   s_lmm_variable_t var;
  33   s_lmm_constraint_t cnst;
  34
  35   l = xbt_new0(s_lmm_system_t, 1);
  36
  37   l->modified = 0;
  38   l->selective_update_active = selective_update;
  39   l->visited_counter = 1;
  40
  41   XBT_DEBUG("Setting selective_update_active flag to %d\n",
  42          l->selective_update_active);
  43
  44   xbt_swag_init(&(l->variable_set),
  45                 xbt_swag_offset(var, variable_set_hookup));
  46   xbt_swag_init(&(l->constraint_set),
  47                 xbt_swag_offset(cnst, constraint_set_hookup));
  48
  49   xbt_swag_init(&(l->active_constraint_set),
  50                 xbt_swag_offset(cnst, active_constraint_set_hookup));
  51
  52   xbt_swag_init(&(l->modified_constraint_set),
  53                 xbt_swag_offset(cnst, modified_constraint_set_hookup));
  54   xbt_swag_init(&(l->saturated_variable_set),
  55                 xbt_swag_offset(var, saturated_variable_set_hookup));
  56   xbt_swag_init(&(l->saturated_constraint_set),
  57                 xbt_swag_offset(cnst, saturated_constraint_set_hookup));
  58
  59   l->variable_mallocator = xbt_mallocator_new(65536,
  60                                               lmm_variable_mallocator_new_f,
  61                                               lmm_variable_mallocator_free_f,
  62                                               lmm_variable_mallocator_reset_f);
  63
  64   return l;
  65 }
  66
  67 void lmm_system_free(lmm_system_t sys)
  68 {
  69   lmm_variable_t var = NULL;
  70   lmm_constraint_t cnst = NULL;
  71
  72   while ((var = extract_variable(sys))) {
  73     XBT_WARN
  74         ("Variable %p (%d) still in LMM system when freing it: this may be a bug",
  75          var, var->id_int);
  76     lmm_var_free(sys, var);
  77   }
  78
  79   while ((cnst = extract_constraint(sys)))
  80     lmm_cnst_free(sys, cnst);
  81
  82   xbt_mallocator_free(sys->variable_mallocator);
  83   free(sys);
  84 }
  85
  86 XBT_INLINE void lmm_variable_disable(lmm_system_t sys, lmm_variable_t var)
  87 {
  88   int i;
  89   int n;
  90
  91   lmm_element_t elem = NULL;
  92
  93   XBT_IN("(sys=%p, var=%p)", sys, var);
  94   sys->modified = 1;
  95
  96   n = 0;
  97   for (i = 0; i < var->cnsts_number; i++) {
  98     elem = &var->cnsts[i];
  99     xbt_swag_remove(elem, &(elem->constraint->element_set));
 100     xbt_swag_remove(elem, &(elem->constraint->active_element_set));
 101     if (!xbt_swag_size(&(elem->constraint->element_set)))
 102       make_constraint_inactive(sys, elem->constraint);
 103     else {
 104       if (n < i)
 105         var->cnsts[n].constraint = elem->constraint;
 106       n++;
 107     }
 108   }
 109   if (n) {
 110     var->cnsts_number = n;
 111     lmm_update_modified_set(sys, var->cnsts[0].constraint);
 112   }
 113
 114   var->cnsts_number = 0;
 115   XBT_OUT();
 116 }
 117
 118 static void lmm_var_free(lmm_system_t sys, lmm_variable_t var)
 119 {
 120
 121   lmm_variable_disable(sys, var);
 122   xbt_mallocator_release(sys->variable_mallocator, var);
 123 }
 124
 125 static XBT_INLINE void lmm_cnst_free(lmm_system_t sys,
 126                                      lmm_constraint_t cnst)
 127 {
 128 /*   xbt_assert(xbt_swag_size(&(cnst->element_set)), */
 129 /*            "This list should be empty!"); */
 130   make_constraint_inactive(sys, cnst);
 131   free(cnst);
 132 }
 133
 134 lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id,
 135                                     double bound_value)
 136 {
 137   lmm_constraint_t cnst = NULL;
 138   s_lmm_element_t elem;
 139
 140   cnst = xbt_new0(s_lmm_constraint_t, 1);
 141   cnst->id = id;
 142   cnst->id_int = Global_const_debug_id++;
 143   xbt_swag_init(&(cnst->element_set),
 144                 xbt_swag_offset(elem, element_set_hookup));
 145   xbt_swag_init(&(cnst->active_element_set),
 146                 xbt_swag_offset(elem, active_element_set_hookup));
 147
 148   cnst->bound = bound_value;
 149   cnst->usage = 0;
 150   cnst->shared = 1;
 151   insert_constraint(sys, cnst);
 152
 153   return cnst;
 154 }
 155
 156 XBT_INLINE void lmm_constraint_shared(lmm_constraint_t cnst)
 157 {
 158   cnst->shared = 0;
 159 }
 160
 161 XBT_INLINE int lmm_constraint_is_shared(lmm_constraint_t cnst)
 162 {
 163   return (cnst->shared);
 164 }
 165
 166 XBT_INLINE void lmm_constraint_free(lmm_system_t sys,
 167                                     lmm_constraint_t cnst)
 168 {
 169   remove_constraint(sys, cnst);
 170   lmm_cnst_free(sys, cnst);
 171 }
 172
 173 static void *lmm_variable_mallocator_new_f(void)
 174 {
 175   lmm_variable_t var = xbt_new(s_lmm_variable_t, 1);
 176   var->cnsts = NULL; /* will be created by realloc */
 177   return var;
 178 }
 179
 180 static void lmm_variable_mallocator_free_f(void *var)
 181 {
 182   xbt_free(((lmm_variable_t) var)->cnsts);
 183   xbt_free(var);
 184 }
 185
 186 lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id,
 187                                 double weight,
 188                                 double bound, int number_of_constraints)
 189 {
 190   lmm_variable_t var = NULL;
 191   int i;
 192
 193   XBT_IN("(sys=%p, id=%p, weight=%f, bound=%f, num_cons =%d)",
 194           sys, id, weight, bound, number_of_constraints);
 195
 196   var = xbt_mallocator_get(sys->variable_mallocator);
 197   var->id = id;
 198   var->id_int = Global_debug_id++;
 199   var->cnsts = xbt_realloc(var->cnsts, number_of_constraints * sizeof(s_lmm_element_t));
 200   for (i = 0; i < number_of_constraints; i++) {
 201     var->cnsts[i].element_set_hookup.next = NULL;
 202     var->cnsts[i].element_set_hookup.prev = NULL;
 203     var->cnsts[i].active_element_set_hookup.next = NULL;
 204     var->cnsts[i].active_element_set_hookup.prev = NULL;
 205     var->cnsts[i].constraint = NULL;
 206     var->cnsts[i].variable = NULL;
 207     var->cnsts[i].value = 0.0;
 208   }
 209   var->cnsts_size = number_of_constraints;
 210   var->cnsts_number = 0;
 211   var->weight = weight;
 212   var->bound = bound;
 213   var->value = 0.0;
 214   var->visited = sys->visited_counter - 1;
 215   var->mu = 0.0;
 216   var->new_mu = 0.0;
 217   var->func_f = func_f_def;
 218   var->func_fp = func_fp_def;
 219   var->func_fpi = func_fpi_def;
 220
 221   var->variable_set_hookup.next = NULL;
 222   var->variable_set_hookup.prev = NULL;
 223   var->saturated_variable_set_hookup.next = NULL;
 224   var->saturated_variable_set_hookup.prev = NULL;
 225
 226   if (weight)
 227     xbt_swag_insert_at_head(var, &(sys->variable_set));
 228   else
 229     xbt_swag_insert_at_tail(var, &(sys->variable_set));
 230
 231   XBT_OUT(" returns %p", var);
 232   return var;
 233 }
 234
 235 void lmm_variable_free(lmm_system_t sys, lmm_variable_t var)
 236 {
 237   remove_variable(sys, var);
 238   lmm_var_free(sys, var);
 239 }
 240
 241 XBT_INLINE double lmm_variable_getvalue(lmm_variable_t var)
 242 {
 243   return (var->value);
 244 }
 245
 246 XBT_INLINE double lmm_variable_getbound(lmm_variable_t var)
 247 {
 248   return (var->bound);
 249 }
 250
 251 void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
 252                 lmm_variable_t var, double value)
 253 {
 254   lmm_element_t elem = NULL;
 255
 256   sys->modified = 1;
 257
 258   xbt_assert(var->cnsts_number < var->cnsts_size, "Too much constraints");
 259
 260   elem = &(var->cnsts[var->cnsts_number++]);
 261
 262   elem->value = value;
 263   elem->constraint = cnst;
 264   elem->variable = var;
 265
 266   if (var->weight)
 267     xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 268   else
 269     xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 270
 271   make_constraint_active(sys, cnst);
 272   lmm_update_modified_set(sys, cnst);
 273   if (var->cnsts_number > 1)
 274     lmm_update_modified_set(sys, var->cnsts[0].constraint);
 275 }
 276
 277 void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
 278                     lmm_variable_t var, double value)
 279 {
 280   int i;
 281   sys->modified = 1;
 282
 283   for (i = 0; i < var->cnsts_number; i++)
 284     if (var->cnsts[i].constraint == cnst)
 285       break;
 286
 287   if (i < var->cnsts_number) {
 288     if (cnst->shared)
 289       var->cnsts[i].value += value;
 290     else
 291       var->cnsts[i].value = MAX(var->cnsts[i].value, value);
 292     lmm_update_modified_set(sys, cnst);
 293   } else
 294     lmm_expand(sys, cnst, var, value);
 295 }
 296
 297 void lmm_elem_set_value(lmm_system_t sys, lmm_constraint_t cnst,
 298                         lmm_variable_t var, double value)
 299 {
 300   int i;
 301
 302   for (i = 0; i < var->cnsts_number; i++)
 303     if (var->cnsts[i].constraint == cnst)
 304       break;
 305
 306   if (i < var->cnsts_number) {
 307     var->cnsts[i].value = value;
 308     sys->modified = 1;
 309     lmm_update_modified_set(sys, cnst);
 310   } else
 311     DIE_IMPOSSIBLE;
 312 }
 313
 314 XBT_INLINE lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t sys,
 315                                                   lmm_variable_t var,
 316                                                   int num)
 317 {
 318   if (num < var->cnsts_number)
 319     return (var->cnsts[num].constraint);
 320   else
 321     return NULL;
 322 }
 323
 324 XBT_INLINE double lmm_get_cnst_weight_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].value);
 330   else
 331     return 0.0;
 332 }
 333
 334 XBT_INLINE int lmm_get_number_of_cnst_from_var(lmm_system_t sys,
 335                                                lmm_variable_t var)
 336 {
 337   return (var->cnsts_number);
 338 }
 339
 340 lmm_variable_t lmm_get_var_from_cnst(lmm_system_t sys,
 341                                      lmm_constraint_t cnst,
 342                                      lmm_element_t * elem)
 343 {
 344   if (!(*elem))
 345     *elem = xbt_swag_getFirst(&(cnst->element_set));
 346   else
 347     *elem = xbt_swag_getNext(*elem, cnst->element_set.offset);
 348   if (*elem)
 349     return (*elem)->variable;
 350   else
 351     return NULL;
 352 }
 353
 354 XBT_INLINE void *lmm_constraint_id(lmm_constraint_t cnst)
 355 {
 356   return cnst->id;
 357 }
 358
 359 XBT_INLINE void *lmm_variable_id(lmm_variable_t var)
 360 {
 361   return var->id;
 362 }
 363
 364 static XBT_INLINE int saturated_constraint_set_update(lmm_system_t sys,
 365                                                       lmm_constraint_t
 366                                                       cnst,
 367                                                       double *min_usage)
 368 {
 369   XBT_IN("sys=%p, cnst=%p, min_usage=%f", sys, cnst, *min_usage);
 370   if (cnst->usage <= 0) {
 371     XBT_OUT();
 372     return 1;
 373   }
 374   if (cnst->remaining <= 0) {
 375     XBT_OUT();
 376     return 1;
 377   }
 378   if ((*min_usage < 0) || (*min_usage > cnst->remaining / cnst->usage)) {
 379     *min_usage = cnst->remaining / cnst->usage;
 380     XBT_HERE(" min_usage=%f (cnst->remaining=%f, cnst->usage=%f)",
 381              *min_usage, cnst->remaining, cnst->usage);
 382     xbt_swag_reset(&sys->saturated_constraint_set);
 383     xbt_swag_insert(cnst, &sys->saturated_constraint_set);
 384   } else if (*min_usage == cnst->remaining / cnst->usage) {
 385     xbt_swag_insert(cnst, &sys->saturated_constraint_set);
 386   }
 387   XBT_OUT();
 388   return 0;
 389 }
 390
 391 static XBT_INLINE void saturated_variable_set_update(lmm_system_t sys)
 392 {
 393   lmm_constraint_t cnst = NULL;
 394   xbt_swag_t cnst_list = NULL;
 395   lmm_element_t elem = NULL;
 396   xbt_swag_t elem_list = NULL;
 397
 398   cnst_list = &(sys->saturated_constraint_set);
 399   while ((cnst = xbt_swag_getFirst(cnst_list))) {
 400     elem_list = &(cnst->active_element_set);
 401     xbt_swag_foreach(elem, elem_list) {
 402       if (elem->variable->weight <= 0)
 403         break;
 404       if ((elem->value > 0))
 405         xbt_swag_insert(elem->variable, &(sys->saturated_variable_set));
 406     }
 407     xbt_swag_remove(cnst, cnst_list);
 408   }
 409 }
 410
 411 void lmm_print(lmm_system_t sys)
 412 {
 413   lmm_constraint_t cnst = NULL;
 414   lmm_element_t elem = NULL;
 415   lmm_variable_t var = NULL;
 416   xbt_swag_t cnst_list = NULL;
 417   xbt_swag_t var_list = NULL;
 418   xbt_swag_t elem_list = NULL;
 419   char print_buf[1024];
 420   char *trace_buf = xbt_malloc0(sizeof(char));
 421   double sum = 0.0;
 422
 423   /* Printing Objective */
 424   var_list = &(sys->variable_set);
 425   sprintf(print_buf, "MAX-MIN ( ");
 426   trace_buf =
 427       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 428   strcat(trace_buf, print_buf);
 429   xbt_swag_foreach(var, var_list) {
 430     sprintf(print_buf, "'%d'(%f) ", var->id_int, var->weight);
 431     trace_buf =
 432         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 433     strcat(trace_buf, print_buf);
 434   }
 435   sprintf(print_buf, ")");
 436   trace_buf =
 437       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 438   strcat(trace_buf, print_buf);
 439   XBT_DEBUG("%20s", trace_buf);
 440   trace_buf[0] = '\000';
 441
 442   XBT_DEBUG("Constraints");
 443   /* Printing Constraints */
 444   cnst_list = &(sys->active_constraint_set);
 445   xbt_swag_foreach(cnst, cnst_list) {
 446     sum = 0.0;
 447     elem_list = &(cnst->element_set);
 448     sprintf(print_buf, "\t");
 449     trace_buf =
 450         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 451     strcat(trace_buf, print_buf);
 452     sprintf(print_buf, "%s(",(cnst->shared)?"":"max");
 453     trace_buf =
 454       xbt_realloc(trace_buf,
 455                   strlen(trace_buf) + strlen(print_buf) + 1);
 456     strcat(trace_buf, print_buf);
 457     xbt_swag_foreach(elem, elem_list) {
 458       sprintf(print_buf, "%f.'%d'(%f) %s ", elem->value,
 459               elem->variable->id_int, elem->variable->value,(cnst->shared)?"+":",");
 460       trace_buf =
 461           xbt_realloc(trace_buf,
 462                       strlen(trace_buf) + strlen(print_buf) + 1);
 463       strcat(trace_buf, print_buf);
 464       if(cnst->shared)
 465         sum += elem->value * elem->variable->value;
 466       else
 467         sum = MAX(sum,elem->value * elem->variable->value);
 468     }
 469     sprintf(print_buf, "0) <= %f ('%d')", cnst->bound, cnst->id_int);
 470     trace_buf =
 471         xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
 472     strcat(trace_buf, print_buf);
 473
 474     if (!cnst->shared) {
 475       sprintf(print_buf, " [MAX-Constraint]");
 476       trace_buf =
 477           xbt_realloc(trace_buf,
 478                       strlen(trace_buf) + strlen(print_buf) + 1);
 479       strcat(trace_buf, print_buf);
 480     }
 481     XBT_DEBUG("%s", trace_buf);
 482     trace_buf[0] = '\000';
 483     xbt_assert(!double_positive(sum - cnst->bound),
 484                 "Incorrect value (%f is not smaller than %f): %g",
 485                 sum, cnst->bound, sum - cnst->bound);
 486   }
 487
 488   XBT_DEBUG("Variables");
 489   /* Printing Result */
 490   xbt_swag_foreach(var, var_list) {
 491     if (var->bound > 0) {
 492       XBT_DEBUG("'%d'(%f) : %f (<=%f)", var->id_int, var->weight, var->value,
 493              var->bound);
 494       xbt_assert(!double_positive(var->value - var->bound),
 495                   "Incorrect value (%f is not smaller than %f",
 496                   var->value, var->bound);
 497     } else {
 498       XBT_DEBUG("'%d'(%f) : %f", var->id_int, var->weight, var->value);
 499     }
 500   }
 501
 502   free(trace_buf);
 503 }
 504
 505 void lmm_solve(lmm_system_t sys)
 506 {
 507   lmm_variable_t var = NULL;
 508   lmm_constraint_t cnst = NULL;
 509   lmm_constraint_t cnst_next = NULL;
 510   lmm_element_t elem = NULL;
 511   xbt_swag_t cnst_list = NULL;
 512   xbt_swag_t var_list = NULL;
 513   xbt_swag_t elem_list = NULL;
 514   double min_usage = -1;
 515   double min_bound = -1;
 516
 517   if (!(sys->modified))
 518     return;
 519
 520   XBT_IN("(sys=%p)", sys);
 521
 522   /*
 523    * Compute Usage and store the variables that reach the maximum.
 524    */
 525   cnst_list =
 526       sys->
 527       selective_update_active ? &(sys->modified_constraint_set) :
 528       &(sys->active_constraint_set);
 529
 530   XBT_DEBUG("Active constraints : %d", xbt_swag_size(cnst_list));
 531   /* Init: Only modified code portions */
 532   xbt_swag_foreach(cnst, cnst_list) {
 533     elem_list = &(cnst->element_set);
 534     //XBT_DEBUG("Variable set : %d", xbt_swag_size(elem_list));
 535     xbt_swag_foreach(elem, elem_list) {
 536       var = elem->variable;
 537       if (var->weight <= 0.0)
 538         break;
 539       var->value = 0.0;
 540     }
 541   }
 542
 543   xbt_swag_foreach_safe(cnst, cnst_next, cnst_list) {
 544     /* INIT */
 545     cnst->remaining = cnst->bound;
 546     if (cnst->remaining == 0)
 547       continue;
 548     cnst->usage = 0;
 549     elem_list = &(cnst->element_set);
 550     xbt_swag_foreach(elem, elem_list) {
 551       /* 0-weighted elements (ie, sleep actions) are at the end of the swag and we don't want to consider them */
 552       if (elem->variable->weight <= 0)
 553         break;
 554       if ((elem->value > 0)) {
 555         if (cnst->shared)
 556           cnst->usage += elem->value / elem->variable->weight;
 557         else if (cnst->usage < elem->value / elem->variable->weight)
 558           cnst->usage = elem->value / elem->variable->weight;
 559
 560         make_elem_active(elem);
 561         if (sys->keep_track)
 562           xbt_swag_insert(elem->variable->id, sys->keep_track);
 563       }
 564     }
 565     XBT_DEBUG("Constraint Usage '%d' : %f", cnst->id_int, cnst->usage);
 566     /* Saturated constraints update */
 567     if(cnst->usage>0) {
 568       xbt_swag_remove(cnst, cnst_list);
 569       xbt_swag_insert_at_head(cnst, cnst_list);
 570     }
 571     saturated_constraint_set_update(sys, cnst, &min_usage);
 572   }
 573   saturated_variable_set_update(sys);
 574
 575   /* Saturated variables update */
 576
 577   do {
 578     /* Fix the variables that have to be */
 579     var_list = &(sys->saturated_variable_set);
 580
 581     xbt_swag_foreach(var, var_list) {
 582       if (var->weight <= 0.0)
 583         DIE_IMPOSSIBLE;
 584       /* First check if some of these variables have reach their upper
 585          bound and update min_usage accordingly. */
 586       XBT_DEBUG
 587           ("var=%d, var->bound=%f, var->weight=%f, min_usage=%f, var->bound*var->weight=%f",
 588            var->id_int, var->bound, var->weight, min_usage,
 589            var->bound * var->weight);
 590       if ((var->bound > 0) && (var->bound * var->weight < min_usage)) {
 591         if (min_bound < 0)
 592           min_bound = var->bound;
 593         else
 594           min_bound = MIN(min_bound, var->bound);
 595         XBT_DEBUG("Updated min_bound=%f", min_bound);
 596       }
 597     }
 598
 599
 600     while ((var = xbt_swag_getFirst(var_list))) {
 601       int i;
 602
 603       if (min_bound < 0) {
 604         var->value = min_usage / var->weight;
 605       } else {
 606         if (min_bound == var->bound)
 607           var->value = var->bound;
 608         else {
 609           xbt_swag_remove(var, var_list);
 610           continue;
 611         }
 612       }
 613       XBT_DEBUG("Min usage: %f, Var(%d)->weight: %f, Var(%d)->value: %f ",
 614              min_usage, var->id_int, var->weight, var->id_int, var->value);
 615
 616
 617       /* Update usage */
 618
 619       for (i = 0; i < var->cnsts_number; i++) {
 620         elem = &var->cnsts[i];
 621         cnst = elem->constraint;
 622         if (cnst->shared) {
 623           double_update(&(cnst->remaining), elem->value * var->value);
 624           double_update(&(cnst->usage), elem->value / var->weight);
 625           if(cnst->usage<=0 || cnst->remaining<=0) {
 626             xbt_swag_remove(cnst, cnst_list);
 627             xbt_swag_insert_at_tail(cnst, cnst_list);
 628           }
 629           make_elem_inactive(elem);
 630         } else {                /* FIXME one day: We recompute usage.... :( */
 631           cnst->usage = 0.0;
 632           make_elem_inactive(elem);
 633           elem_list = &(cnst->element_set);
 634           xbt_swag_foreach(elem, elem_list) {
 635             if (elem->variable->weight <= 0)
 636               break;
 637             if (elem->variable->value > 0)
 638               break;
 639             if ((elem->value > 0)) {
 640               cnst->usage =
 641                   MAX(cnst->usage, elem->value / elem->variable->weight);
 642               XBT_DEBUG("Constraint Usage %d : %f", cnst->id_int,
 643                      cnst->usage);
 644               make_elem_active(elem);
 645             }
 646           }
 647         }
 648       }
 649       xbt_swag_remove(var, var_list);
 650     }
 651
 652     /* Find out which variables reach the maximum */
 653     min_usage = -1;
 654     min_bound = -1;
 655
 656     xbt_swag_foreach(cnst, cnst_list) {
 657       if(saturated_constraint_set_update(sys, cnst, &min_usage)) break;
 658     }
 659     saturated_variable_set_update(sys);
 660
 661   } while (xbt_swag_size(&(sys->saturated_variable_set)));
 662
 663   sys->modified = 0;
 664   if (sys->selective_update_active)
 665     lmm_remove_all_modified_set(sys);
 666
 667   if (XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug)) {
 668     lmm_print(sys);
 669   }
 670   XBT_OUT();
 671 }
 672
 673 /* Not a O(1) function */
 674
 675 void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
 676                 lmm_variable_t var, double value)
 677 {
 678   int i;
 679
 680   for (i = 0; i < var->cnsts_number; i++)
 681     if (var->cnsts[i].constraint == cnst) {
 682       var->cnsts[i].value = value;
 683       sys->modified = 1;
 684       lmm_update_modified_set(sys, cnst);
 685       return;
 686     }
 687 }
 688
 689 /** \brief Attribute the value bound to var->bound.
 690  *
 691  *  \param sys the lmm_system_t
 692  *  \param var the lmm_variable_t
 693  *  \param bound the new bound to associate with var
 694  *
 695  *  Makes var->bound equal to bound. Whenever this function is called
 696  *  a change is  signed in the system. To
 697  *  avoid false system changing detection it is a good idea to test
 698  *  (bound != 0) before calling it.
 699  *
 700  */
 701 void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
 702                                double bound)
 703 {
 704   sys->modified = 1;
 705   var->bound = bound;
 706
 707   if (var->cnsts_number)
 708     lmm_update_modified_set(sys, var->cnsts[0].constraint);
 709 }
 710
 711
 712 void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
 713                                 double weight)
 714 {
 715   int i;
 716   lmm_element_t elem;
 717
 718   if (weight == var->weight)
 719     return;
 720   XBT_IN("(sys=%p, var=%p, weight=%f)", sys, var, weight);
 721   sys->modified = 1;
 722   var->weight = weight;
 723   xbt_swag_remove(var, &(sys->variable_set));
 724   if (weight)
 725     xbt_swag_insert_at_head(var, &(sys->variable_set));
 726   else
 727     xbt_swag_insert_at_tail(var, &(sys->variable_set));
 728
 729   for (i = 0; i < var->cnsts_number; i++) {
 730     elem = &var->cnsts[i];
 731     xbt_swag_remove(elem, &(elem->constraint->element_set));
 732     if (weight)
 733       xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
 734     else
 735       xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 736
 737     if (i == 0)
 738       lmm_update_modified_set(sys, elem->constraint);
 739   }
 740   if (!weight)
 741     var->value = 0.0;
 742
 743   XBT_OUT();
 744 }
 745
 746 XBT_INLINE double lmm_get_variable_weight(lmm_variable_t var)
 747 {
 748   return var->weight;
 749 }
 750
 751 XBT_INLINE void lmm_update_constraint_bound(lmm_system_t sys,
 752                                             lmm_constraint_t cnst,
 753                                             double bound)
 754 {
 755   sys->modified = 1;
 756   lmm_update_modified_set(sys, cnst);
 757   cnst->bound = bound;
 758 }
 759
 760 XBT_INLINE int lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst)
 761 {
 762   return xbt_swag_belongs(cnst, &(sys->active_constraint_set));
 763 }
 764
 765 XBT_INLINE lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t
 766                                                             sys)
 767 {
 768   return xbt_swag_getFirst(&(sys->active_constraint_set));
 769 }
 770
 771 XBT_INLINE lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t
 772                                                            sys,
 773                                                            lmm_constraint_t
 774                                                            cnst)
 775 {
 776   return xbt_swag_getNext(cnst, (sys->active_constraint_set).offset);
 777 }
 778
 779 #ifdef HAVE_LATENCY_BOUND_TRACKING
 780 XBT_INLINE int lmm_is_variable_limited_by_latency(lmm_variable_t var)
 781 {
 782   return (double_equals(var->bound, var->value));
 783 }
 784 #endif
 785
 786
 787 /** \brief Update the constraint set propagating recursively to
 788  *  other constraints so the system should not be entirely computed.
 789  *
 790  *  \param sys the lmm_system_t
 791  *  \param cnst the lmm_constraint_t affected by the change
 792  *
 793  *  A recursive algorithm to optimize the system recalculation selecting only
 794  *  constraints that have changed. Each constraint change is propagated
 795  *  to the list of constraints for each variable.
 796  */
 797 static void lmm_update_modified_set_rec(lmm_system_t sys,
 798                                         lmm_constraint_t cnst)
 799 {
 800   lmm_element_t elem;
 801
 802   xbt_swag_foreach(elem, &cnst->element_set) {
 803     lmm_variable_t var = elem->variable;
 804     s_lmm_element_t *cnsts = var->cnsts;
 805     int i;
 806     for (i = 0; var->visited != sys->visited_counter
 807              && i < var->cnsts_number ; i++) {
 808       if (cnsts[i].constraint != cnst
 809           && !xbt_swag_belongs(cnsts[i].constraint,
 810                                &sys->modified_constraint_set)) {
 811         xbt_swag_insert(cnsts[i].constraint, &sys->modified_constraint_set);
 812         lmm_update_modified_set_rec(sys, cnsts[i].constraint);
 813       }
 814     }
 815     var->visited = sys->visited_counter;
 816   }
 817 }
 818
 819 static void lmm_update_modified_set(lmm_system_t sys,
 820                                     lmm_constraint_t cnst)
 821 {
 822   /* nothing to do if selective update isn't active */
 823   if (sys->selective_update_active
 824       && !xbt_swag_belongs(cnst, &sys->modified_constraint_set)) {
 825     xbt_swag_insert(cnst, &sys->modified_constraint_set);
 826     lmm_update_modified_set_rec(sys, cnst);
 827   }
 828 }
 829
 830 /** \brief Remove all constraints of the modified_constraint_set.
 831  *
 832  *  \param sys the lmm_system_t
 833  */
 834 static void lmm_remove_all_modified_set(lmm_system_t sys)
 835 {
 836   if (++sys->visited_counter == 1) {
 837     /* the counter wrapped around, reset each variable->visited */
 838     lmm_variable_t var;
 839     xbt_swag_foreach(var, &sys->variable_set)
 840       var->visited = 0;
 841   }
 842   xbt_swag_reset(&sys->modified_constraint_set);
 843 }