X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/49e85177c669d793e84242983a1b1f430e47184e..73d1f79133c1e0e086ce5e2414aa04d180cba08a:/src/surf/maxmin.cpp

diff --git a/src/surf/maxmin.cpp b/src/surf/maxmin.cpp
index cb6085876a..40e186f60d 100644
--- a/src/surf/maxmin.cpp
+++ b/src/surf/maxmin.cpp
@@ -1,18 +1,20 @@
-/* Copyright (c) 2004-2014. The SimGrid Team.
+/* Copyright (c) 2004-2015. The SimGrid Team.
  * All rights reserved.                                                     */
 
 /* This program is free software; you can redistribute it and/or modify it
  * under the terms of the license (GNU LGPL) which comes with this package. */
 
+/* \file callbacks.h */
+
 #include "xbt/sysdep.h"
 #include "xbt/log.h"
+#include "xbt/strbuff.h"
 #include "xbt/mallocator.h"
 #include "maxmin_private.hpp"
 #include <stdlib.h>
 #include <stdio.h>              /* sprintf */
 #include <math.h>
-XBT_LOG_NEW_DEFAULT_SUBCATEGORY(surf_maxmin, surf,
-                                "Logging specific to SURF (maxmin)");
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(surf_maxmin, surf, "Logging specific to SURF (maxmin)");
 
 typedef struct s_dyn_light {
   int *data;
@@ -20,24 +22,61 @@ typedef struct s_dyn_light {
   int size;
 } s_dyn_light_t, *dyn_light_t;
 
-XBT_EXPORT_NO_IMPORT(double) sg_maxmin_precision = 0.00001;
+double sg_maxmin_precision = 0.00001;
+double sg_surf_precision   = 0.00001;
+int    sg_concurrency_limit= 100;
 
-static void *lmm_variable_mallocator_new_f(void);
+static void *lmm_variable_mallocator_new_f();
 static void lmm_variable_mallocator_free_f(void *var);
-#define lmm_variable_mallocator_reset_f ((void_f_pvoid_t)NULL)
-static void lmm_update_modified_set(lmm_system_t sys,
-                                    lmm_constraint_t cnst);
+#define lmm_variable_mallocator_reset_f ((void_f_pvoid_t)nullptr)
+static void lmm_update_modified_set(lmm_system_t sys, lmm_constraint_t cnst);
 static void lmm_remove_all_modified_set(lmm_system_t sys);
 static int Global_debug_id = 1;
 static int Global_const_debug_id = 1;
 
 static void lmm_var_free(lmm_system_t sys, lmm_variable_t var);
-static XBT_INLINE void lmm_cnst_free(lmm_system_t sys,
-                                     lmm_constraint_t cnst);
+static inline void lmm_cnst_free(lmm_system_t sys, lmm_constraint_t cnst);
+
+static void lmm_on_disabled_var(lmm_system_t sys, lmm_constraint_t cnstr);
+static void lmm_enable_var(lmm_system_t sys, lmm_variable_t var);
+static int lmm_can_enable_var(lmm_variable_t var);
+static void lmm_disable_var(lmm_system_t sys, lmm_variable_t var);
+static int lmm_concurrency_slack(lmm_constraint_t cnstr);
+static int lmm_cnstrs_min_concurrency_slack(lmm_variable_t var);
+
+static void lmm_check_concurrency(lmm_system_t sys);
+
+inline int lmm_element_concurrency(lmm_element_t elem) {
+  //Ignore element with weight less than one (e.g. cross-traffic)
+  return (elem->value>=1)?1:0;
+  //There are other alternatives, but they will change the behaviour of the model..
+  //So do not use it unless you want to make a new model.
+  //If you do, remember to change the variables concurrency share to reflect it.
+  //Potential examples are:
+  //return (elem->weight>0)?1:0;//Include element as soon  as weight is non-zero
+  //return (int)ceil(elem->weight);//Include element as the rounded-up integer value of the element weight
+}
+
+inline void lmm_decrease_concurrency(lmm_element_t elem) {
+  xbt_assert(elem->constraint->concurrency_current>=lmm_element_concurrency(elem));
+  elem->constraint->concurrency_current-=lmm_element_concurrency(elem);
+}
+
+inline void lmm_increase_concurrency(lmm_element_t elem) {
+  elem->constraint->concurrency_current+= lmm_element_concurrency(elem);
+
+  lmm_constraint_t cnstr=elem->constraint;
+
+  if(cnstr->concurrency_current > cnstr->concurrency_maximum)
+    cnstr->concurrency_maximum= cnstr->concurrency_current;
+
+  xbt_assert(cnstr->concurrency_limit<0 || cnstr->concurrency_current<=cnstr->concurrency_limit,
+             "Concurrency limit overflow!");
+}
 
 lmm_system_t lmm_system_new(int selective_update)
 {
-  lmm_system_t l = NULL;
+  lmm_system_t l = nullptr;
   s_lmm_variable_t var;
   s_lmm_constraint_t cnst;
 
@@ -47,23 +86,16 @@ lmm_system_t lmm_system_new(int selective_update)
   l->selective_update_active = selective_update;
   l->visited_counter = 1;
 
-  XBT_DEBUG("Setting selective_update_active flag to %d\n",
-         l->selective_update_active);
+  XBT_DEBUG("Setting selective_update_active flag to %d", l->selective_update_active);
 
-  xbt_swag_init(&(l->variable_set),
-                xbt_swag_offset(var, variable_set_hookup));
-  xbt_swag_init(&(l->constraint_set),
-                xbt_swag_offset(cnst, constraint_set_hookup));
+  xbt_swag_init(&(l->variable_set), xbt_swag_offset(var, variable_set_hookup));
+  xbt_swag_init(&(l->constraint_set), xbt_swag_offset(cnst, constraint_set_hookup));
 
-  xbt_swag_init(&(l->active_constraint_set),
-                xbt_swag_offset(cnst, active_constraint_set_hookup));
+  xbt_swag_init(&(l->active_constraint_set), xbt_swag_offset(cnst, active_constraint_set_hookup));
 
-  xbt_swag_init(&(l->modified_constraint_set),
-                xbt_swag_offset(cnst, modified_constraint_set_hookup));
-  xbt_swag_init(&(l->saturated_variable_set),
-                xbt_swag_offset(var, saturated_variable_set_hookup));
-  xbt_swag_init(&(l->saturated_constraint_set),
-                xbt_swag_offset(cnst, saturated_constraint_set_hookup));
+  xbt_swag_init(&(l->modified_constraint_set), xbt_swag_offset(cnst, modified_constraint_set_hookup));
+  xbt_swag_init(&(l->saturated_variable_set), xbt_swag_offset(var, saturated_variable_set_hookup));
+  xbt_swag_init(&(l->saturated_constraint_set), xbt_swag_offset(cnst, saturated_constraint_set_hookup));
 
   l->variable_mallocator = xbt_mallocator_new(65536,
                                               lmm_variable_mallocator_new_f,
@@ -75,16 +107,16 @@ lmm_system_t lmm_system_new(int selective_update)
 
 void lmm_system_free(lmm_system_t sys)
 {
-  lmm_variable_t var = NULL;
-  lmm_constraint_t cnst = NULL;
+  lmm_variable_t var = nullptr;
+  lmm_constraint_t cnst = nullptr;
+
+  if (!sys)
+    return;
 
   while ((var = (lmm_variable_t) extract_variable(sys))) {
-    XBT_WARN
-        ("Variable %p (%d) still in LMM system when freing it: this may be a bug",
-         var, var->id_int);
+    XBT_WARN("Variable %d still in system when freing it: this may be a bug", var->id_int);
     lmm_var_free(sys, var);
   }
-
   while ((cnst = (lmm_constraint_t) extract_constraint(sys)))
     lmm_cnst_free(sys, cnst);
 
@@ -92,97 +124,140 @@ void lmm_system_free(lmm_system_t sys)
   free(sys);
 }
 
-static XBT_INLINE void lmm_variable_disable(lmm_system_t sys, lmm_variable_t var)
+static inline void lmm_variable_remove(lmm_system_t sys, lmm_variable_t var)
 {
   int i;
-  int n;
+  int nelements;
 
-  lmm_element_t elem = NULL;
+  lmm_element_t elem = nullptr;
 
   XBT_IN("(sys=%p, var=%p)", sys, var);
   sys->modified = 1;
 
-  n = 0;
+  //TODOLATER Can do better than that by leaving only the variable in only one enabled_element_set, call
+  //lmm_update_modified_set, and then remove it..
+  if(var->cnsts_number)
+    lmm_update_modified_set(sys, var->cnsts[0].constraint);
+
   for (i = 0; i < var->cnsts_number; i++) {
     elem = &var->cnsts[i];
-    xbt_swag_remove(elem, &(elem->constraint->element_set));
+    if(var->weight>0)
+    lmm_decrease_concurrency(elem);
+    xbt_swag_remove(elem, &(elem->constraint->enabled_element_set));
+    xbt_swag_remove(elem, &(elem->constraint->disabled_element_set));
     xbt_swag_remove(elem, &(elem->constraint->active_element_set));
-    if (!xbt_swag_size(&(elem->constraint->element_set)))
+    nelements=xbt_swag_size(&(elem->constraint->enabled_element_set)) +
+              xbt_swag_size(&(elem->constraint->disabled_element_set));
+    if (!nelements)
       make_constraint_inactive(sys, elem->constraint);
-    else {
-      if (n < i)
-        var->cnsts[n].constraint = elem->constraint;
-      n++;
-    }
+    else
+      lmm_on_disabled_var(sys,elem->constraint);
   }
-  if (n) {
-    var->cnsts_number = n;
-    lmm_update_modified_set(sys, var->cnsts[0].constraint);
+
+  //Check if we can enable new variables going through the constraints where var was.
+  //Do it after removing all elements, so he first disabled variables get priority over those with smaller requirement
+  for (i = 0; i < var->cnsts_number; i++) {
+    elem = &var->cnsts[i];
+    if(xbt_swag_size(&(elem->constraint->disabled_element_set)))
+      lmm_on_disabled_var(sys,elem->constraint);
   }
 
   var->cnsts_number = 0;
+
+  lmm_check_concurrency(sys);
+
   XBT_OUT();
 }
 
 static void lmm_var_free(lmm_system_t sys, lmm_variable_t var)
 {
-
-  lmm_variable_disable(sys, var);
+  lmm_variable_remove(sys, var);
   xbt_mallocator_release(sys->variable_mallocator, var);
 }
 
-static XBT_INLINE void lmm_cnst_free(lmm_system_t sys,
-                                     lmm_constraint_t cnst)
+static inline void lmm_cnst_free(lmm_system_t sys, lmm_constraint_t cnst)
 {
-/*   xbt_assert(xbt_swag_size(&(cnst->element_set)), */
-/*         "This list should be empty!"); */
   make_constraint_inactive(sys, cnst);
   free(cnst);
 }
 
-lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id,
-                                    double bound_value)
+lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id, double bound_value)
 {
-  lmm_constraint_t cnst = NULL;
+  lmm_constraint_t cnst = nullptr;
   s_lmm_element_t elem;
 
   cnst = xbt_new0(s_lmm_constraint_t, 1);
   cnst->id = id;
   cnst->id_int = Global_const_debug_id++;
-  xbt_swag_init(&(cnst->element_set),
-                xbt_swag_offset(elem, element_set_hookup));
-  xbt_swag_init(&(cnst->active_element_set),
-                xbt_swag_offset(elem, active_element_set_hookup));
+  xbt_swag_init(&(cnst->enabled_element_set), xbt_swag_offset(elem, enabled_element_set_hookup));
+  xbt_swag_init(&(cnst->disabled_element_set), xbt_swag_offset(elem, disabled_element_set_hookup));
+  xbt_swag_init(&(cnst->active_element_set), xbt_swag_offset(elem, active_element_set_hookup));
 
   cnst->bound = bound_value;
+  cnst->concurrency_maximum=0;
+  cnst->concurrency_current=0;
+  cnst->concurrency_limit=sg_concurrency_limit;
   cnst->usage = 0;
-  cnst->shared = 1;
+  cnst->sharing_policy = 1; /* FIXME: don't hardcode the value */
   insert_constraint(sys, cnst);
 
   return cnst;
 }
 
+int lmm_constraint_concurrency_limit_get(lmm_constraint_t cnst)
+{
+ return cnst->concurrency_limit;
+}
+
+void lmm_constraint_concurrency_limit_set(lmm_constraint_t cnst, int concurrency_limit)
+{
+  xbt_assert(concurrency_limit<0 || cnst->concurrency_maximum<=concurrency_limit,
+             "New concurrency limit should be larger than observed concurrency maximum. Maybe you want to call"
+             " lmm_constraint_concurrency_maximum_reset() to reset the maximum?");
+  cnst->concurrency_limit = concurrency_limit;
+}
+
+void lmm_constraint_concurrency_maximum_reset(lmm_constraint_t cnst)
+{
+  cnst->concurrency_maximum = 0;
+}
+
+int lmm_constraint_concurrency_maximum_get(lmm_constraint_t cnst)
+{
+ xbt_assert(cnst->concurrency_limit<0 || cnst->concurrency_maximum<=cnst->concurrency_limit,
+            "Very bad: maximum observed concurrency is higher than limit. This is a bug of SURF, please report it.");
+  return cnst->concurrency_maximum;
+}
+
 void lmm_constraint_shared(lmm_constraint_t cnst)
 {
-  cnst->shared = 0;
+  cnst->sharing_policy = 0;
 }
 
-int lmm_constraint_is_shared(lmm_constraint_t cnst)
+/** Return true if the constraint is shared, and false if it's FATPIPE */
+int lmm_constraint_sharing_policy(lmm_constraint_t cnst)
 {
-  return (cnst->shared);
+  return (cnst->sharing_policy);
 }
 
-XBT_INLINE void lmm_constraint_free(lmm_system_t sys,
-                                    lmm_constraint_t cnst)
+/* @brief Remove a constraint 
+ * Currently this is dead code, but it is exposed in maxmin.h
+ * Apparently, this call was designed assuming that constraint would no more have elements in it. 
+ * If not the case, assertion will fail, and you need to add calls e.g. to lmm_shrink before effectively removing it.
+ */
+inline void lmm_constraint_free(lmm_system_t sys,lmm_constraint_t cnst)
 {
+  xbt_assert(!xbt_swag_size(&(cnst->active_element_set)),"Removing constraint but it still has active elements");
+  xbt_assert(!xbt_swag_size(&(cnst->enabled_element_set)),"Removing constraint but it still has enabled elements");
+  xbt_assert(!xbt_swag_size(&(cnst->disabled_element_set)),"Removing constraint but it still has disabled elements");
   remove_constraint(sys, cnst);
   lmm_cnst_free(sys, cnst);
 }
 
-static void *lmm_variable_mallocator_new_f(void)
+static void *lmm_variable_mallocator_new_f()
 {
   lmm_variable_t var = xbt_new(s_lmm_variable_t, 1);
-  var->cnsts = NULL; /* will be created by realloc */
+  var->cnsts = nullptr; /* will be created by realloc */
   return var;
 }
 
@@ -192,33 +267,34 @@ static void lmm_variable_mallocator_free_f(void *var)
   xbt_free(var);
 }
 
-lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id,
-                                double weight,
-                                double bound, int number_of_constraints)
+lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id, double weight, double bound, int number_of_constraints)
 {
-  lmm_variable_t var = NULL;
+  lmm_variable_t var = nullptr;
   int i;
 
-  XBT_IN("(sys=%p, id=%p, weight=%f, bound=%f, num_cons =%d)",
-          sys, id, weight, bound, number_of_constraints);
+  XBT_IN("(sys=%p, id=%p, weight=%f, bound=%f, num_cons =%d)", sys, id, weight, bound, number_of_constraints);
 
   var = (lmm_variable_t) xbt_mallocator_get(sys->variable_mallocator);
   var->id = id;
   var->id_int = Global_debug_id++;
   var->cnsts = (s_lmm_element_t *) xbt_realloc(var->cnsts, number_of_constraints * sizeof(s_lmm_element_t));
   for (i = 0; i < number_of_constraints; i++) {
-    var->cnsts[i].element_set_hookup.next = NULL;
-    var->cnsts[i].element_set_hookup.prev = NULL;
-    var->cnsts[i].active_element_set_hookup.next = NULL;
-    var->cnsts[i].active_element_set_hookup.prev = NULL;
-    var->cnsts[i].constraint = NULL;
-    var->cnsts[i].variable = NULL;
+    var->cnsts[i].enabled_element_set_hookup.next = nullptr;
+    var->cnsts[i].enabled_element_set_hookup.prev = nullptr;
+    var->cnsts[i].disabled_element_set_hookup.next = nullptr;
+    var->cnsts[i].disabled_element_set_hookup.prev = nullptr;
+    var->cnsts[i].active_element_set_hookup.next = nullptr;
+    var->cnsts[i].active_element_set_hookup.prev = nullptr;
+    var->cnsts[i].constraint = nullptr;
+    var->cnsts[i].variable = nullptr;
     var->cnsts[i].value = 0.0;
   }
   var->cnsts_size = number_of_constraints;
   var->cnsts_number = 0;
   var->weight = weight;
+  var->staged_weight = 0.0;
   var->bound = bound;
+  var->concurrency_share = 1;
   var->value = 0.0;
   var->visited = sys->visited_counter - 1;
   var->mu = 0.0;
@@ -227,10 +303,10 @@ lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id,
   var->func_fp = func_fp_def;
   var->func_fpi = func_fpi_def;
 
-  var->variable_set_hookup.next = NULL;
-  var->variable_set_hookup.prev = NULL;
-  var->saturated_variable_set_hookup.next = NULL;
-  var->saturated_variable_set_hookup.prev = NULL;
+  var->variable_set_hookup.next = nullptr;
+  var->variable_set_hookup.prev = nullptr;
+  var->saturated_variable_set_hookup.next = nullptr;
+  var->saturated_variable_set_hookup.prev = nullptr;
 
   if (weight)
     xbt_swag_insert_at_head(var, &(sys->variable_set));
@@ -252,42 +328,19 @@ double lmm_variable_getvalue(lmm_variable_t var)
   return (var->value);
 }
 
-double lmm_variable_getbound(lmm_variable_t var)
+void lmm_variable_concurrency_share_set(lmm_variable_t var, short int concurrency_share)
 {
-  return (var->bound);
+  var->concurrency_share=concurrency_share;
 }
 
-/* Replace the content of elem_a with elem_b. The content of elem_b is cleared. */
-static void renew_elem_entry(lmm_element_t elem_a, lmm_element_t elem_b)
+double lmm_variable_getbound(lmm_variable_t var)
 {
-    elem_a->constraint = elem_b->constraint;
-    elem_a->variable   = elem_b->variable;
-    elem_a->value      = elem_b->value;
-
-    /* If elem_b is in the element_set swag, register the new element to the swag. */
-    if (xbt_swag_remove(elem_b, &(elem_b->constraint->element_set))) {
-      if (elem_a->variable->weight)
-        xbt_swag_insert_at_head(elem_a, &(elem_a->constraint->element_set));
-      else
-        xbt_swag_insert_at_tail(elem_a, &(elem_a->constraint->element_set));
-    }
-
-    if (xbt_swag_remove(elem_b, &(elem_b->constraint->active_element_set))) {
-      if (elem_a->variable->weight)
-        xbt_swag_insert_at_head(elem_a, &(elem_a->constraint->active_element_set));
-      else
-        xbt_swag_insert_at_tail(elem_a, &(elem_a->constraint->active_element_set));
-    }
-
-    elem_b->constraint = NULL;
-    elem_b->variable   = NULL;
-    elem_b->value      = 0;
+  return (var->bound);
 }
 
-void lmm_shrink(lmm_system_t sys, lmm_constraint_t cnst,
-                lmm_variable_t var)
+void lmm_shrink(lmm_system_t sys, lmm_constraint_t cnst, lmm_variable_t var)
 {
-  lmm_element_t elem = NULL;
+  lmm_element_t elem = nullptr;
   int found = 0;
 
   int i;
@@ -306,48 +359,68 @@ void lmm_shrink(lmm_system_t sys, lmm_constraint_t cnst,
 
   sys->modified = 1;
 
-  XBT_DEBUG("remove elem(value %f, cnst %p, var %p) in var %p",
-      elem->value, elem->constraint, elem->variable, var);
-
-
+  XBT_DEBUG("remove elem(value %f, cnst %p, var %p) in var %p", elem->value, elem->constraint, elem->variable, var);
 
   /* We are going to change the constraint object and the variable object.
-   * Propagate this change to other objects. Calling here (not after
-   * modification) is correct? */
+   * Propagate this change to other objects. Calling here before removing variable from not active elements
+   * (inactive elements are not visited)
+   */
   lmm_update_modified_set(sys, cnst);
-  lmm_update_modified_set(sys, var->cnsts[0].constraint); // will look up element_set of this constraint, and then each var in the element_set, and each var->cnsts[i].
-
-
+  //Useful in case var was already removed from the constraint
+  lmm_update_modified_set(sys, var->cnsts[0].constraint); // will look up enabled_element_set of this constraint, and
+                                                     //then each var in the enabled_element_set, and each var->cnsts[i].
 
-  /* now var->cnsts[i] is not necessary any more */
+  if(xbt_swag_remove(elem, &(elem->constraint->enabled_element_set)))
+    lmm_decrease_concurrency(elem);
 
-  xbt_swag_remove(elem, &(elem->constraint->element_set));
   xbt_swag_remove(elem, &(elem->constraint->active_element_set));
-  elem->constraint = NULL;
-  elem->variable = NULL;
+  elem->constraint = nullptr;
+  elem->variable = nullptr;
   elem->value = 0;
 
-
-
-  /* We do not want to have an empty element entry before the last entry. So,
-   * plug up the hole with the last one. */
-  if (i < var->cnsts_number - 1)
-    renew_elem_entry(&var->cnsts[i], &var->cnsts[var->cnsts_number - 1]);
-
   var->cnsts_number -= 1;
 
-
-  if (xbt_swag_size(&(cnst->element_set)) == 0)
+  //No variable in this constraint -> make it inactive
+  if (xbt_swag_size(&(cnst->enabled_element_set))+xbt_swag_size(&(cnst->disabled_element_set)) == 0)
     make_constraint_inactive(sys, cnst);
+  else {
+    //Check maxconcurrency to see if we can enable new variables
+    lmm_on_disabled_var(sys,elem->constraint);       
+  }
+
+  lmm_check_concurrency(sys);
 }
 
-void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
-                lmm_variable_t var, double value)
+void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst, lmm_variable_t var, double value)
 {
-  lmm_element_t elem = NULL;
+  lmm_element_t elem = nullptr;
+  double weight;
+  int i,current_share;
 
   sys->modified = 1;
 
+  //Check if this variable already has an active element in this constraint
+  //If it does, substract it from the required slack
+  current_share=0;
+  if(var->concurrency_share>1){
+    for( i=0; i<var->cnsts_number;i++){
+      if(var->cnsts[i].constraint==cnst &&
+         xbt_swag_belongs(&var->cnsts[i],&(var->cnsts[i].constraint->enabled_element_set)))
+         current_share+=lmm_element_concurrency(&(var->cnsts[i]));
+    }
+  }
+
+  //Check if we need to disable the variable 
+  if(var->weight>0 && var->concurrency_share-current_share>lmm_concurrency_slack(cnst)) {
+    weight=var->weight;
+    lmm_disable_var(sys,var);
+    for (i = 0; i < var->cnsts_number; i++)
+      lmm_on_disabled_var(sys,var->cnsts[i].constraint);
+    value=0;
+    var->staged_weight=weight;
+    xbt_assert(!var->weight);
+  }
+
   xbt_assert(var->cnsts_number < var->cnsts_size, "Too much constraints");
 
   elem = &(var->cnsts[var->cnsts_number++]);
@@ -356,53 +429,75 @@ void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
   elem->constraint = cnst;
   elem->variable = var;
 
-  if (var->weight)
-    xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
-  else
-    xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
+  if (var->weight){
+    xbt_swag_insert_at_head(elem, &(elem->constraint->enabled_element_set));
+    lmm_increase_concurrency(elem);
+  } else
+    xbt_swag_insert_at_tail(elem, &(elem->constraint->disabled_element_set));
+
   if(!sys->selective_update_active) {
     make_constraint_active(sys, cnst);
   } else if(elem->value>0 || var->weight >0) {
     make_constraint_active(sys, cnst);
     lmm_update_modified_set(sys, cnst);
+    //TODOLATER: Why do we need this second call?
     if (var->cnsts_number > 1)
       lmm_update_modified_set(sys, var->cnsts[0].constraint);
   }
+
+  lmm_check_concurrency(sys);
 }
 
-void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
-                    lmm_variable_t var, double value)
+void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst, lmm_variable_t var, double value)
 {
-  int i;
+  int i,j;
+  double weight;
   sys->modified = 1;
 
+  lmm_check_concurrency(sys);
+
+  //BEWARE: In case you have multiple elements in one constraint, this will always add value to the first element.
   for (i = 0; i < var->cnsts_number; i++)
     if (var->cnsts[i].constraint == cnst)
       break;
 
   if (i < var->cnsts_number) {
-    if (cnst->shared)
+    if (var->weight)
+      lmm_decrease_concurrency(&var->cnsts[i]);
+
+    if (cnst->sharing_policy)
       var->cnsts[i].value += value;
     else
       var->cnsts[i].value = MAX(var->cnsts[i].value, value);
+
+    //We need to check that increasing value of the element does not cross the concurrency limit
+    if (var->weight){
+      if(lmm_concurrency_slack(cnst)<lmm_element_concurrency(&var->cnsts[i])){
+        weight=var->weight;
+        lmm_disable_var(sys,var);
+        for (j = 0; j < var->cnsts_number; j++)
+          lmm_on_disabled_var(sys,var->cnsts[j].constraint);
+        var->staged_weight=weight;
+        xbt_assert(!var->weight);
+      }
+      lmm_increase_concurrency(&var->cnsts[i]);
+    }
     lmm_update_modified_set(sys, cnst);
   } else
     lmm_expand(sys, cnst, var, value);
+
+  lmm_check_concurrency(sys);
 }
 
-lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t /*sys*/,
-                                                  lmm_variable_t var,
-                                                  int num)
+lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t /*sys*/, lmm_variable_t var, int num)
 {
   if (num < var->cnsts_number)
     return (var->cnsts[num].constraint);
   else
-    return NULL;
+    return nullptr;
 }
 
-double lmm_get_cnst_weight_from_var(lmm_system_t /*sys*/,
-                                                         lmm_variable_t var,
-                                                         int num)
+double lmm_get_cnst_weight_from_var(lmm_system_t /*sys*/, lmm_variable_t var, int num)
 {
   if (num < var->cnsts_number)
     return (var->cnsts[num].value);
@@ -410,24 +505,66 @@ double lmm_get_cnst_weight_from_var(lmm_system_t /*sys*/,
     return 0.0;
 }
 
-int lmm_get_number_of_cnst_from_var(lmm_system_t /*sys*/,
-                                               lmm_variable_t var)
+int lmm_get_number_of_cnst_from_var(lmm_system_t /*sys*/, lmm_variable_t var)
 {
   return (var->cnsts_number);
 }
 
-lmm_variable_t lmm_get_var_from_cnst(lmm_system_t /*sys*/,
-                                     lmm_constraint_t cnst,
-                                     lmm_element_t * elem)
+lmm_variable_t lmm_get_var_from_cnst(lmm_system_t /*sys*/, lmm_constraint_t cnst, lmm_element_t * elem)
 {
-  if (!(*elem))
-    *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->element_set));
-  else
-    *elem = (lmm_element_t) xbt_swag_getNext(*elem, cnst->element_set.offset);
+  if (!(*elem)) {
+    // That is the first call, pick the first element among enabled_element_set (or disabled_element_set if
+    // enabled_element_set is empty)
+    *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->enabled_element_set));
+    if (!(*elem))
+      *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->disabled_element_set));
+  } else {
+    //elem is not null, so we carry on
+    if(xbt_swag_belongs(*elem,&(cnst->enabled_element_set))){
+      //Look at enabled_element_set, and jump to disabled_element_set when finished
+      *elem = (lmm_element_t) xbt_swag_getNext(*elem, cnst->enabled_element_set.offset);
+      if (!(*elem))
+        *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->disabled_element_set));
+    } else {
+      *elem = (lmm_element_t) xbt_swag_getNext(*elem, cnst->disabled_element_set.offset);      
+    }
+  }
   if (*elem)
     return (*elem)->variable;
   else
-    return NULL;
+    return nullptr;
+}
+
+//if we modify the swag between calls, normal version may loop forever
+//this safe version ensures that we browse the swag elements only once
+lmm_variable_t lmm_get_var_from_cnst_safe(lmm_system_t /*sys*/, lmm_constraint_t cnst, lmm_element_t * elem,
+                                          lmm_element_t * nextelem, int * numelem)
+{
+  if (!(*elem)){
+    *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->enabled_element_set));
+    *numelem = xbt_swag_size(&(cnst->enabled_element_set))+xbt_swag_size(&(cnst->disabled_element_set))-1;
+    if (!(*elem))
+      *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->disabled_element_set));
+  }else{
+    *elem = *nextelem;
+    if(*numelem>0){
+     (*numelem) --;
+    }else
+      return nullptr;
+  }
+  if (*elem){
+    //elem is not null, so we carry on
+    if(xbt_swag_belongs(*elem,&(cnst->enabled_element_set))){
+      //Look at enabled_element_set, and jump to disabled_element_set when finished
+      *nextelem = (lmm_element_t) xbt_swag_getNext(*elem, cnst->enabled_element_set.offset);
+      if (!(*nextelem))
+        *nextelem = (lmm_element_t) xbt_swag_getFirst(&(cnst->disabled_element_set));
+    } else {
+      *nextelem = (lmm_element_t) xbt_swag_getNext(*elem, cnst->disabled_element_set.offset);      
+    }
+    return (*elem)->variable;
+  }else
+    return nullptr;
 }
 
 void *lmm_constraint_id(lmm_constraint_t cnst)
@@ -440,45 +577,43 @@ void *lmm_variable_id(lmm_variable_t var)
   return var->id;
 }
 
-static XBT_INLINE void saturated_constraint_set_update(double usage,
-                                                      int cnst_light_num,
-                                                      dyn_light_t saturated_constraint_set,
-                                                      double *min_usage)
+static inline void saturated_constraint_set_update(double usage, int cnst_light_num,
+                                                   dyn_light_t saturated_constraint_set, double *min_usage)
 {
   xbt_assert(usage > 0,"Impossible");
 
   if (*min_usage < 0 || *min_usage > usage) {
     *min_usage = usage;
-    // XBT_HERE(" min_usage=%f (cnst->remaining / cnst->usage =%f)", *min_usage, usage);
+    XBT_HERE(" min_usage=%f (cnst->remaining / cnst->usage =%f)", *min_usage, usage);
     saturated_constraint_set->data[0] = cnst_light_num;
     saturated_constraint_set->pos = 1;
   } else if (*min_usage == usage) {
     if(saturated_constraint_set->pos == saturated_constraint_set->size) { // realloc the size
       saturated_constraint_set->size *= 2;
-      saturated_constraint_set->data = (int*) xbt_realloc(saturated_constraint_set->data, (saturated_constraint_set->size) * sizeof(int));
+      saturated_constraint_set->data =
+        (int*) xbt_realloc(saturated_constraint_set->data, (saturated_constraint_set->size) * sizeof(int));
     }
     saturated_constraint_set->data[saturated_constraint_set->pos] = cnst_light_num;
     saturated_constraint_set->pos++;
   }
 }
 
-static XBT_INLINE void saturated_variable_set_update(
-    s_lmm_constraint_light_t *cnst_light_tab,
-    dyn_light_t saturated_constraint_set,
-    lmm_system_t sys)
+static inline void saturated_variable_set_update(s_lmm_constraint_light_t *cnst_light_tab,
+                                                 dyn_light_t saturated_constraint_set, lmm_system_t sys)
 {
-  lmm_constraint_light_t cnst = NULL;
+  /* Add active variables (i.e. variables that need to be set) from the set of constraints to saturate (cnst_light_tab)*/ 
+  lmm_constraint_light_t cnst = nullptr;
   void *_elem;
-  lmm_element_t elem = NULL;
-  xbt_swag_t elem_list = NULL;
+  lmm_element_t elem = nullptr;
+  xbt_swag_t elem_list = nullptr;
   int i;
   for(i = 0; i< saturated_constraint_set->pos; i++){
     cnst = &cnst_light_tab[saturated_constraint_set->data[i]];
     elem_list = &(cnst->cnst->active_element_set);
     xbt_swag_foreach(_elem, elem_list) {
       elem = (lmm_element_t)_elem;
-      if (elem->variable->weight <= 0)
-        break;
+      //Visiting active_element_set, so, by construction, should never get a zero weight, correct?
+      xbt_assert(elem->variable->weight > 0);
       if ((elem->value > 0))
         xbt_swag_insert(elem->variable, &(sys->saturated_variable_set));
     }
@@ -488,111 +623,95 @@ static XBT_INLINE void saturated_variable_set_update(
 void lmm_print(lmm_system_t sys)
 {
   void *_cnst, *_elem, *_var;
-  lmm_constraint_t cnst = NULL;
-  lmm_element_t elem = NULL;
-  lmm_variable_t var = NULL;
-  xbt_swag_t cnst_list = NULL;
-  xbt_swag_t var_list = NULL;
-  xbt_swag_t elem_list = NULL;
-  char print_buf[1024];
-  char *trace_buf = (char*) xbt_malloc0(sizeof(char));
+  lmm_constraint_t cnst = nullptr;
+  lmm_element_t elem = nullptr;
+  lmm_variable_t var = nullptr;
+  xbt_swag_t cnst_list = nullptr;
+  xbt_swag_t var_list = nullptr;
+  xbt_swag_t elem_list = nullptr;
+  xbt_strbuff_t buf = xbt_strbuff_new();
   double sum = 0.0;
 
   /* Printing Objective */
   var_list = &(sys->variable_set);
-  sprintf(print_buf, "MAX-MIN ( ");
-  trace_buf = (char*)
-      xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
-  strcat(trace_buf, print_buf);
+  xbt_strbuff_append(buf, "MAX-MIN ( ");
   xbt_swag_foreach(_var, var_list) {
-	var = (lmm_variable_t)_var;
-    sprintf(print_buf, "'%d'(%f) ", var->id_int, var->weight);
-    trace_buf = (char*)
-        xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
-    strcat(trace_buf, print_buf);
+    var = (lmm_variable_t)_var;
+    xbt_strbuff_printf(buf, "'%d'(%f) ", var->id_int, var->weight);
   }
-  sprintf(print_buf, ")");
-  trace_buf = (char*)
-      xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
-  strcat(trace_buf, print_buf);
-  XBT_DEBUG("%20s", trace_buf);
-  trace_buf[0] = '\000';
+  xbt_strbuff_append(buf, ")");
+  XBT_DEBUG("%20s", buf->data);
+  xbt_strbuff_clear(buf);
 
   XBT_DEBUG("Constraints");
   /* Printing Constraints */
   cnst_list = &(sys->active_constraint_set);
   xbt_swag_foreach(_cnst, cnst_list) {
-	cnst = (lmm_constraint_t)_cnst;
+  cnst = (lmm_constraint_t)_cnst;
     sum = 0.0;
-    elem_list = &(cnst->element_set);
-    sprintf(print_buf, "\t");
-    trace_buf = (char*)
-        xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
-    strcat(trace_buf, print_buf);
-    sprintf(print_buf, "%s(",(cnst->shared)?"":"max");
-    trace_buf = (char*)
-      xbt_realloc(trace_buf,
-      strlen(trace_buf) + strlen(print_buf) + 1);
-    strcat(trace_buf, print_buf);      
+    //Show  the enabled variables
+    elem_list = &(cnst->enabled_element_set);
+    xbt_strbuff_append(buf, "\t");
+    xbt_strbuff_printf(buf, "%s(", (cnst->sharing_policy)?"":"max");
     xbt_swag_foreach(_elem, elem_list) {
       elem = (lmm_element_t)_elem;
-      sprintf(print_buf, "%f.'%d'(%f) %s ", elem->value,
-              elem->variable->id_int, elem->variable->value,(cnst->shared)?"+":",");
-      trace_buf = (char*)
-          xbt_realloc(trace_buf,
-                      strlen(trace_buf) + strlen(print_buf) + 1);
-      strcat(trace_buf, print_buf);
-      if(cnst->shared) 
-  sum += elem->value * elem->variable->value;
+      xbt_strbuff_printf(buf, "%f.'%d'(%f) %s ", elem->value,
+              elem->variable->id_int, elem->variable->value,(cnst->sharing_policy)?"+":",");
+      if(cnst->sharing_policy)
+        sum += elem->value * elem->variable->value;
       else 
-  sum = MAX(sum,elem->value * elem->variable->value);
+        sum = MAX(sum,elem->value * elem->variable->value);
     }
-    sprintf(print_buf, "0) <= %f ('%d')", cnst->bound, cnst->id_int);
-    trace_buf = (char*)
-        xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
-    strcat(trace_buf, print_buf);
-
-    if (!cnst->shared) {
-      sprintf(print_buf, " [MAX-Constraint]");
-      trace_buf = (char*)
-          xbt_realloc(trace_buf,
-                      strlen(trace_buf) + strlen(print_buf) + 1);
-      strcat(trace_buf, print_buf);
+    //TODO: Adding disabled elements only for test compatibility, but do we really want them to be printed?
+    elem_list = &(cnst->disabled_element_set);
+    xbt_swag_foreach(_elem, elem_list) {
+      elem = (lmm_element_t)_elem;
+      xbt_strbuff_printf(buf, "%f.'%d'(%f) %s ", elem->value,
+              elem->variable->id_int, elem->variable->value,(cnst->sharing_policy)?"+":",");
+      if(cnst->sharing_policy)
+        sum += elem->value * elem->variable->value;
+      else 
+        sum = MAX(sum,elem->value * elem->variable->value);
     }
-    XBT_DEBUG("%s", trace_buf);
-    trace_buf[0] = '\000';
-    xbt_assert(!double_positive(sum - cnst->bound),
-                "Incorrect value (%f is not smaller than %f): %g",
-                sum, cnst->bound, sum - cnst->bound);
+
+    xbt_strbuff_printf(buf, "0) <= %f ('%d')", cnst->bound, cnst->id_int);
+
+    if (!cnst->sharing_policy) {
+      xbt_strbuff_printf(buf, " [MAX-Constraint]");
+    }
+    XBT_DEBUG("%s", buf->data);
+    xbt_strbuff_clear(buf);
+    xbt_assert(!double_positive(sum - cnst->bound, cnst->bound*sg_maxmin_precision),
+        "Incorrect value (%f is not smaller than %f): %g", sum, cnst->bound, sum - cnst->bound);
+       //if(double_positive(sum - cnst->bound, cnst->bound*sg_maxmin_precision))
+       //XBT_ERROR("Incorrect value (%f is not smaller than %f): %g",sum, cnst->bound, sum - cnst->bound);
   }
 
   XBT_DEBUG("Variables");
   /* Printing Result */
   xbt_swag_foreach(_var, var_list) {
-	var = (lmm_variable_t)_var;
+  var = (lmm_variable_t)_var;
     if (var->bound > 0) {
-      XBT_DEBUG("'%d'(%f) : %f (<=%f)", var->id_int, var->weight, var->value,
-             var->bound);
-      xbt_assert(!double_positive(var->value - var->bound),
-                  "Incorrect value (%f is not smaller than %f",
-                  var->value, var->bound);
+      XBT_DEBUG("'%d'(%f) : %f (<=%f)", var->id_int, var->weight, var->value, var->bound);
+      xbt_assert(!double_positive(var->value - var->bound, var->bound*sg_maxmin_precision),
+                  "Incorrect value (%f is not smaller than %f", var->value, var->bound);
     } else {
       XBT_DEBUG("'%d'(%f) : %f", var->id_int, var->weight, var->value);
     }
   }
 
-  free(trace_buf);
+  xbt_strbuff_free(buf);
 }
 
 void lmm_solve(lmm_system_t sys)
 {
   void *_var, *_cnst, *_cnst_next, *_elem;
-  lmm_variable_t var = NULL;
-  lmm_constraint_t cnst = NULL;
-  lmm_element_t elem = NULL;
-  xbt_swag_t cnst_list = NULL;
-  xbt_swag_t var_list = NULL;
-  xbt_swag_t elem_list = NULL;
+  lmm_variable_t var = nullptr;
+  lmm_constraint_t cnst = nullptr;
+  lmm_element_t elem = nullptr;
+  xbt_swag_t cnst_list = nullptr;
+  xbt_swag_t var_list = nullptr;
+  xbt_swag_t elem_list = nullptr;
   double min_usage = -1;
   double min_bound = -1;
 
@@ -601,60 +720,57 @@ void lmm_solve(lmm_system_t sys)
 
   XBT_IN("(sys=%p)", sys);
 
-  /*
-   * Compute Usage and store the variables that reach the maximum.
+  /* Compute Usage and store the variables that reach the maximum. If selective_update_active is true, only constraints
+   * that changed are considered. Otherwise all constraints with active actions are considered.
    */
-  cnst_list =
-      sys->
-      selective_update_active ? &(sys->modified_constraint_set) :
-      &(sys->active_constraint_set);
+  cnst_list = sys->selective_update_active ? &(sys->modified_constraint_set) : &(sys->active_constraint_set);
 
   XBT_DEBUG("Active constraints : %d", xbt_swag_size(cnst_list));
-  /* Init: Only modified code portions */
+  /* Init: Only modified code portions: reset the value of active variables */
   xbt_swag_foreach(_cnst, cnst_list) {
-	cnst = (lmm_constraint_t)_cnst;
-    elem_list = &(cnst->element_set);
+  cnst = (lmm_constraint_t)_cnst;
+    elem_list = &(cnst->enabled_element_set);
     //XBT_DEBUG("Variable set : %d", xbt_swag_size(elem_list));
     xbt_swag_foreach(_elem, elem_list) {
       var = ((lmm_element_t)_elem)->variable;
-      if (var->weight <= 0.0)
-        break;
+      xbt_assert(var->weight > 0.0);
       var->value = 0.0;
     }
   }
 
-  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));
+  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));
   int cnst_light_num = 0;
   dyn_light_t saturated_constraint_set = xbt_new0(s_dyn_light_t,1);
   saturated_constraint_set->size = 5;
   saturated_constraint_set->data = xbt_new0(int, saturated_constraint_set->size);
 
   xbt_swag_foreach_safe(_cnst, _cnst_next, cnst_list) {
-	cnst = (lmm_constraint_t)_cnst;
-    /* INIT */
+  cnst = (lmm_constraint_t)_cnst;
+    /* INIT: Collect constraints that actually need to be saturated (i.e remaining  and usage are strictly positive)
+     * into cnst_light_tab. */
     cnst->remaining = cnst->bound;
-    if (cnst->remaining == 0)
+    if (!double_positive(cnst->remaining, cnst->bound*sg_maxmin_precision))
       continue;
     cnst->usage = 0;
-    elem_list = &(cnst->element_set);
+    elem_list = &(cnst->enabled_element_set);
     xbt_swag_foreach(_elem, elem_list) {
       elem = (lmm_element_t)_elem;
-      /* 0-weighted elements (ie, sleep actions) are at the end of the swag and we don't want to consider them */
-      if (elem->variable->weight <= 0)
-        break;
+      xbt_assert(elem->variable->weight > 0);
       if ((elem->value > 0)) {
-        if (cnst->shared)
+        if (cnst->sharing_policy)
           cnst->usage += elem->value / elem->variable->weight;
         else if (cnst->usage < elem->value / elem->variable->weight)
           cnst->usage = elem->value / elem->variable->weight;
 
         make_elem_active(elem);
-        ActionPtr action = static_cast<ActionPtr>(elem->variable->id);
+        simgrid::surf::Action *action = static_cast<simgrid::surf::Action*>(elem->variable->id);
         if (sys->keep_track && !action->is_linked())
           sys->keep_track->push_back(*action);
       }
     }
-    XBT_DEBUG("Constraint Usage '%d' : %f", cnst->id_int, cnst->usage);
+    XBT_DEBUG("Constraint '%d' usage: %f remaining: %f concurrency: %i<=%i<=%i", cnst->id_int, cnst->usage,
+              cnst->remaining,cnst->concurrency_current,cnst->concurrency_maximum,cnst->concurrency_limit);
     /* Saturated constraints update */
 
     if(cnst->usage > 0) {
@@ -663,16 +779,14 @@ void lmm_solve(lmm_system_t sys)
       cnst_light_tab[cnst_light_num].remaining_over_usage = cnst->remaining / cnst->usage;
       saturated_constraint_set_update(cnst_light_tab[cnst_light_num].remaining_over_usage,
         cnst_light_num, saturated_constraint_set, &min_usage);
+      xbt_assert(cnst->active_element_set.count>0, "There is no sense adding a constraint that has no active element!");
       cnst_light_num++;
     }
   }
 
-  saturated_variable_set_update(  cnst_light_tab,
-                                  saturated_constraint_set,
-                                  sys);
+  saturated_variable_set_update(  cnst_light_tab, saturated_constraint_set, sys);
 
   /* Saturated variables update */
-
   do {
     /* Fix the variables that have to be */
     var_list = &(sys->saturated_variable_set);
@@ -681,84 +795,99 @@ void lmm_solve(lmm_system_t sys)
       var = (lmm_variable_t)_var;
       if (var->weight <= 0.0)
         DIE_IMPOSSIBLE;
-      /* First check if some of these variables have reach their upper
-         bound and update min_usage accordingly. */
+      /* First check if some of these variables could reach their upper bound and update min_bound accordingly. */
       XBT_DEBUG
           ("var=%d, var->bound=%f, var->weight=%f, min_usage=%f, var->bound*var->weight=%f",
-           var->id_int, var->bound, var->weight, min_usage,
-           var->bound * var->weight);
+           var->id_int, var->bound, var->weight, min_usage, var->bound * var->weight);
       if ((var->bound > 0) && (var->bound * var->weight < min_usage)) {
         if (min_bound < 0)
-          min_bound = var->bound;
+          min_bound = var->bound*var->weight;
         else
-          min_bound = MIN(min_bound, var->bound);
+          min_bound = MIN(min_bound, (var->bound*var->weight));
         XBT_DEBUG("Updated min_bound=%f", min_bound);
       }
     }
 
-
     while ((var = (lmm_variable_t)xbt_swag_getFirst(var_list))) {
       int i;
 
       if (min_bound < 0) {
+        //If no variable could reach its bound, deal iteratively the constraints usage ( at worst one constraint is
+        // saturated at each cycle)
         var->value = min_usage / var->weight;
+        // XBT_DEBUG("Setting %p (%d) value to %f\n", var, var->id_int, var->value);
+        XBT_DEBUG("Setting var (%d) value to %f\n", var->id_int, var->value);
       } else {
-        if (min_bound == var->bound)
-          var->value = var->bound;
-        else {
-          xbt_swag_remove(var, var_list);
-          continue;
-        }
+         //If there exist a variable that can reach its bound, only update it (and other with the same bound) for now.
+         if (double_equals(min_bound, var->bound*var->weight, sg_maxmin_precision)){
+            var->value = var->bound;
+            XBT_DEBUG("Setting %p (%d) value to %f\n", var, var->id_int, var->value);
+         } else {
+           // Variables which bound is different are not considered for this cycle, but they will be afterwards.
+           XBT_DEBUG("Do not consider %p (%d) \n", var, var->id_int);
+           xbt_swag_remove(var, var_list);
+           continue;
+         }
       }
       XBT_DEBUG("Min usage: %f, Var(%d)->weight: %f, Var(%d)->value: %f ",
-             min_usage, var->id_int, var->weight, var->id_int, var->value);
-
-
-      /* Update usage */
+                min_usage, var->id_int, var->weight, var->id_int, var->value);
 
+      /* Update the usage of contraints where this variable is involved */
       for (i = 0; i < var->cnsts_number; i++) {
         elem = &var->cnsts[i];
         cnst = elem->constraint;
-        if (cnst->shared) {
-          double_update(&(cnst->remaining), elem->value * var->value);
-          double_update(&(cnst->usage), elem->value / var->weight);
-          if(cnst->usage<=0 || cnst->remaining<=0) {
+        if (cnst->sharing_policy) {
+          //Remember: shared constraints require that sum(elem->value * var->value) < cnst->bound
+          double_update(&(cnst->remaining),  elem->value * var->value, cnst->bound*sg_maxmin_precision);
+          double_update(&(cnst->usage), elem->value / var->weight, sg_maxmin_precision);
+          //If the constraint is saturated, remove it from the set of active constraints (light_tab)
+          if(!double_positive(cnst->usage,sg_maxmin_precision) ||
+             !double_positive(cnst->remaining,cnst->bound*sg_maxmin_precision)) {
             if (cnst->cnst_light) {
               int index = (cnst->cnst_light-cnst_light_tab);
-              XBT_DEBUG("index: %d \t cnst_light_num: %d \t || \t cnst: %p \t cnst->cnst_light: %p \t cnst_light_tab: %p ",
-                  index,cnst_light_num, cnst, cnst->cnst_light, cnst_light_tab);
+              XBT_DEBUG("index: %d \t cnst_light_num: %d \t || usage: %f remaining: %f bound: %f  ",
+                         index,cnst_light_num, cnst->usage, cnst->remaining, cnst->bound);
+              //XBT_DEBUG("index: %d \t cnst_light_num: %d \t || \t cnst: %p \t cnst->cnst_light: %p "
+              //          "\t cnst_light_tab: %p usage: %f remaining: %f bound: %f  ", index,cnst_light_num,
+              //          cnst, cnst->cnst_light, cnst_light_tab, cnst->usage, cnst->remaining, cnst->bound);
               cnst_light_tab[index]=cnst_light_tab[cnst_light_num-1];
               cnst_light_tab[index].cnst->cnst_light = &cnst_light_tab[index];
               cnst_light_num--;
-              cnst->cnst_light = NULL;
+              cnst->cnst_light = nullptr;
             }
           } else {
             cnst->cnst_light->remaining_over_usage = cnst->remaining / cnst->usage;
           }
           make_elem_inactive(elem);
         } else {
+          //Remember: non-shared constraints only require that max(elem->value * var->value) < cnst->bound
           cnst->usage = 0.0;
           make_elem_inactive(elem);
-          elem_list = &(cnst->element_set);
+          elem_list = &(cnst->enabled_element_set);
           xbt_swag_foreach(_elem, elem_list) {
-        	elem = (lmm_element_t)_elem;
-            if (elem->variable->weight <= 0 || elem->variable->value > 0)
-              break;
+            elem = (lmm_element_t)_elem;
+            xbt_assert(elem->variable->weight > 0);
+            if (elem->variable->value > 0) continue;
             if (elem->value > 0)
               cnst->usage = MAX(cnst->usage, elem->value / elem->variable->weight);
           }
-          if (cnst->usage<=0 || cnst->remaining<=0) {
+          //If the constraint is saturated, remove it from the set of active constraints (light_tab)
+          if(!double_positive(cnst->usage,sg_maxmin_precision) ||
+             !double_positive(cnst->remaining,cnst->bound*sg_maxmin_precision)) {
             if(cnst->cnst_light) {
               int index = (cnst->cnst_light-cnst_light_tab);
-              XBT_DEBUG("index: %d \t cnst_light_num: %d \t || \t cnst: %p \t cnst->cnst_light: %p \t cnst_light_tab: %p ",
-                  index,cnst_light_num, cnst, cnst->cnst_light, cnst_light_tab);
+              XBT_DEBUG("index: %d \t cnst_light_num: %d \t || \t cnst: %p \t cnst->cnst_light: %p "
+                        "\t cnst_light_tab: %p usage: %f remaining: %f bound: %f  ", index,cnst_light_num, cnst,
+                        cnst->cnst_light, cnst_light_tab, cnst->usage, cnst->remaining, cnst->bound);
               cnst_light_tab[index]=cnst_light_tab[cnst_light_num-1];
               cnst_light_tab[index].cnst->cnst_light = &cnst_light_tab[index];
               cnst_light_num--;
-              cnst->cnst_light = NULL;
+              cnst->cnst_light = nullptr;
             }
           } else {
             cnst->cnst_light->remaining_over_usage = cnst->remaining / cnst->usage;
+            xbt_assert(cnst->active_element_set.count>0, "Should not keep a maximum constraint that has no active"
+                       " element! You want to check the maxmin precision and possible rounding effects." );
           }
         }
       }
@@ -770,16 +899,17 @@ void lmm_solve(lmm_system_t sys)
     min_bound = -1;
     saturated_constraint_set->pos = 0;
     int pos;
-    for(pos=0; pos<cnst_light_num; pos++)
-      saturated_constraint_set_update(
-          cnst_light_tab[pos].remaining_over_usage,
-          pos,
-          saturated_constraint_set,
-          &min_usage);
+    for(pos=0; pos<cnst_light_num; pos++){
+      xbt_assert(cnst_light_tab[pos].cnst->active_element_set.count>0, "Cannot saturate more a constraint that has"
+                 " no active element! You may want to change the maxmin precision (--cfg=maxmin/precision:<new_value>)"
+                 " because of possible rounding effects.\n\tFor the record, the usage of this constraint is %g while "
+                 "the maxmin precision to which it is compared is %g.\n\tThe usage of the previous constraint is %g.",
+                 cnst_light_tab[pos].cnst->usage, sg_maxmin_precision, cnst_light_tab[pos-1].cnst->usage);
+      saturated_constraint_set_update(cnst_light_tab[pos].remaining_over_usage, pos, saturated_constraint_set,
+                                      &min_usage);
+    }
 
-    saturated_variable_set_update(  cnst_light_tab,
-                                    saturated_constraint_set,
-                                    sys);
+    saturated_variable_set_update(cnst_light_tab, saturated_constraint_set, sys);
 
   } while (cnst_light_num > 0);
 
@@ -791,42 +921,24 @@ void lmm_solve(lmm_system_t sys)
     lmm_print(sys);
   }
 
+  lmm_check_concurrency(sys);
+
   xbt_free(saturated_constraint_set->data);
   xbt_free(saturated_constraint_set);
   xbt_free(cnst_light_tab);
   XBT_OUT();
 }
 
-/* Not a O(1) function */
-
-void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
-                lmm_variable_t var, double value)
-{
-  int i;
-
-  for (i = 0; i < var->cnsts_number; i++)
-    if (var->cnsts[i].constraint == cnst) {
-      var->cnsts[i].value = value;
-      sys->modified = 1;
-      lmm_update_modified_set(sys, cnst);
-      return;
-    }
-}
-
 /** \brief Attribute the value bound to var->bound.
  * 
  *  \param sys the lmm_system_t
  *  \param var the lmm_variable_t
  *  \param bound the new bound to associate with var
  * 
- *  Makes var->bound equal to bound. Whenever this function is called 
- *  a change is  signed in the system. To
- *  avoid false system changing detection it is a good idea to test 
- *  (bound != 0) before calling it.
- *
+ *  Makes var->bound equal to bound. Whenever this function is called a change is  signed in the system. To
+ *  avoid false system changing detection it is a good idea to test (bound != 0) before calling it.
  */
-void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
-                               double bound)
+void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var, double bound)
 {
   sys->modified = 1;
   var->bound = bound;
@@ -835,39 +947,191 @@ void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
     lmm_update_modified_set(sys, var->cnsts[0].constraint);
 }
 
+int lmm_concurrency_slack(lmm_constraint_t cnstr){
+  //FIXME MARTIN: Replace by infinite value std::numeric_limits<int>::(max)(), or something better within Simgrid?
+  if(cnstr->concurrency_limit<0)
+    return 666;
 
-void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
-                                double weight)
-{
+  return  cnstr->concurrency_limit - cnstr->concurrency_current;  
+}
+
+/** \brief Measure the minimum concurrency slack across all constraints where the given var is involved */
+int lmm_cnstrs_min_concurrency_slack(lmm_variable_t var){
+  int i;
+  //FIXME MARTIN: Replace by infinite value std::numeric_limits<int>::(max)(), or something better within Simgrid?
+  int slack,minslack=666;
+  for (i = 0; i < var->cnsts_number; i++) {
+    slack=lmm_concurrency_slack(var->cnsts[i].constraint);
+
+    //This is only an optimization, to avoid looking at more constraints when slack is already zero
+    //Disable it when debugging to let lmm_concurrency_slack catch nasty things
+    if(!slack   && !XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug))
+      return 0;
+
+    if(minslack>slack)
+      minslack=slack;
+  }
+
+  return minslack;
+}
+
+/* /Check if a variable can be enabled
+ *
+ * Make sure to set staged_weight before, if your intent is only to check concurrency 
+ */
+int lmm_can_enable_var(lmm_variable_t var){
+  return var->staged_weight>0 && lmm_cnstrs_min_concurrency_slack(var)>=var->concurrency_share;
+}
+
+//Small remark: In this implementation of lmm_enable_var and lmm_disable_var, we will meet multiple times with var when
+// running lmm_update_modified_set.
+//A priori not a big performance issue, but we might do better by calling lmm_update_modified_set within the for loops
+// (after doing the first for enabling==1, and before doing the last for disabling==1)
+void lmm_enable_var(lmm_system_t sys, lmm_variable_t var){
   int i;
   lmm_element_t elem;
 
-  if (weight == var->weight)
-    return;
-  XBT_IN("(sys=%p, var=%p, weight=%f)", sys, var, weight);
-  sys->modified = 1;
-  var->weight = weight;
+  xbt_assert(lmm_can_enable_var(var));
+
+  var->weight = var->staged_weight;
+  var->staged_weight = 0;
+
+  //Enabling the variable, move to var to list head. Subtility is: here, we need to call lmm_update_modified_set AFTER
+  // moving at least one element of var.
+
   xbt_swag_remove(var, &(sys->variable_set));
-  if (weight)
-    xbt_swag_insert_at_head(var, &(sys->variable_set));
-  else
-    xbt_swag_insert_at_tail(var, &(sys->variable_set));
+  xbt_swag_insert_at_head(var, &(sys->variable_set));
+  for (i = 0; i < var->cnsts_number; i++) {
+    elem = &var->cnsts[i];
+    xbt_swag_remove(elem, &(elem->constraint->disabled_element_set));
+    xbt_swag_insert_at_head(elem, &(elem->constraint->enabled_element_set));
+    lmm_increase_concurrency(elem);
+  }
+  if (var->cnsts_number)
+    lmm_update_modified_set(sys, var->cnsts[0].constraint);
 
+  //When used within lmm_on_disabled_var, we would get an assertion fail, because transiently there can be variables
+  // that are staged and could be activated.
+  //Anyway, caller functions all call lmm_check_concurrency() in the end. 
+  //  lmm_check_concurrency(sys);
+}
+
+void lmm_disable_var(lmm_system_t sys, lmm_variable_t var){
+  int i;
+  lmm_element_t elem;
+
+  xbt_assert(!var->staged_weight,"Staged weight should have been cleared");
+  //Disabling the variable, move to var to list tail. Subtility is: here, we need to call lmm_update_modified_set BEFORE
+  //moving the last element of var.
+  xbt_swag_remove(var, &(sys->variable_set));
+  xbt_swag_insert_at_tail(var, &(sys->variable_set));
+  if (var->cnsts_number)
+    lmm_update_modified_set(sys, var->cnsts[0].constraint);
   for (i = 0; i < var->cnsts_number; i++) {
     elem = &var->cnsts[i];
-    xbt_swag_remove(elem, &(elem->constraint->element_set));
-    if (weight)
-      xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
-    else
-      xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
+    xbt_swag_remove(elem, &(elem->constraint->enabled_element_set));
+    xbt_swag_insert_at_tail(elem, &(elem->constraint->disabled_element_set));
+
+    xbt_swag_remove(elem, &(elem->constraint->active_element_set));
 
-    if (i == 0)
-      lmm_update_modified_set(sys, elem->constraint);
+    lmm_decrease_concurrency(elem);
   }
-  if (!weight)
-    var->value = 0.0;
+
+  var->weight=0.0;
+  var->staged_weight=0.0;
+  var->value = 0.0;
+  lmm_check_concurrency(sys);
+}
+ 
+/* /brief Find variables that can be enabled and enable them.
+ * 
+ * Assuming that the variable has already been removed from non-zero weights
+ * Can we find a staged variable to add?
+ * If yes, check that none of the constraints that this variable is involved in is at the limit of its concurrency
+ * And then add it to enabled variables
+ */
+void lmm_on_disabled_var(lmm_system_t sys, lmm_constraint_t cnstr){
+  lmm_element_t elem;
+  lmm_element_t nextelem;
+  int numelem;
+
+  if(cnstr->concurrency_limit<0)
+    return;
+
+  numelem=xbt_swag_size(&(cnstr->disabled_element_set));
+  if(!numelem)
+    return;
+
+  elem= (lmm_element_t) xbt_swag_getFirst(&(cnstr->disabled_element_set));
+
+  //Cannot use xbt_swag_foreach, because lmm_enable_var will modify disabled_element_set.. within the loop
+  while(numelem-- && elem ){
+
+    nextelem = (lmm_element_t) xbt_swag_getNext(elem, cnstr->disabled_element_set.offset);      
+
+    if (elem->variable->staged_weight>0 ){
+      //Found a staged variable
+      //TODOLATER: Add random timing function to model reservation protocol fuzziness? Then how to make sure that
+      //staged variables will eventually be called?
+      if(lmm_can_enable_var(elem->variable)){
+        lmm_enable_var(sys,elem->variable);
+      }
+    }
+
+    xbt_assert(cnstr->concurrency_current<=cnstr->concurrency_limit,"Concurrency overflow!");
+    if(cnstr->concurrency_current==cnstr->concurrency_limit)
+      break;
+
+    elem = nextelem;
+  }
+
+  //We could get an assertion fail, because transiently there can be variables that are staged and could be activated.
+  //And we need to go through all constraints of the disabled var before getting back a coherent state.
+  //Anyway, caller functions all call lmm_check_concurrency() in the end. 
+  //  lmm_check_concurrency(sys);
+}
+
+/* \brief update the weight of a variable, and enable/disable it.
+ * @return Returns whether a change was made
+ */
+void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var, double weight)
+{
+  int minslack;
+
+  xbt_assert(weight>=0,"Variable weight should not be negative!");
+
+  if (weight == var->weight)
+    return;
+
+  int enabling_var=  (weight>0 && var->weight<=0);
+  int disabling_var= (weight<=0 && var->weight>0);
+
+  XBT_IN("(sys=%p, var=%p, weight=%f)", sys, var, weight);
+
+  sys->modified = 1;
+
+  //Are we enabling this variable?
+  if (enabling_var){
+    var->staged_weight = weight;
+    minslack=lmm_cnstrs_min_concurrency_slack(var);
+    if(minslack<var->concurrency_share){      
+      XBT_DEBUG("Staging var (instead of enabling) because min concurrency slack %i, with weight %f and concurrency"
+                " share %i", minslack, weight, var->concurrency_share);
+      return;
+    }
+    XBT_DEBUG("Enabling var with min concurrency slack %i", minslack);
+    lmm_enable_var(sys,var);
+  } else if (disabling_var){
+    //Are we disabling this variable?
+    lmm_disable_var(sys,var);
+  } else {
+    var->weight=weight;
+  }
+
+  lmm_check_concurrency(sys);
 
   XBT_OUT();
+  return;
 }
 
 double lmm_get_variable_weight(lmm_variable_t var)
@@ -875,9 +1139,7 @@ double lmm_get_variable_weight(lmm_variable_t var)
   return var->weight;
 }
 
-void lmm_update_constraint_bound(lmm_system_t sys,
-                                            lmm_constraint_t cnst,
-                                            double bound)
+void lmm_update_constraint_bound(lmm_system_t sys, lmm_constraint_t cnst, double bound)
 {
   sys->modified = 1;
   lmm_update_modified_set(sys, cnst);
@@ -889,66 +1151,49 @@ int lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst)
   return xbt_swag_belongs(cnst, &(sys->active_constraint_set));
 }
 
-XBT_INLINE lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t
-                                                            sys)
+inline lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t sys)
 {
   return (lmm_constraint_t)xbt_swag_getFirst(&(sys->active_constraint_set));
 }
 
-XBT_INLINE lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t
-                                                           sys,
-                                                           lmm_constraint_t
-                                                           cnst)
+inline lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t sys, lmm_constraint_t cnst)
 {
   return (lmm_constraint_t)xbt_swag_getNext(cnst, (sys->active_constraint_set).offset);
 }
 
-#ifdef HAVE_LATENCY_BOUND_TRACKING
-XBT_INLINE int lmm_is_variable_limited_by_latency(lmm_variable_t var)
-{
-  return (double_equals(var->bound, var->value));
-}
-#endif
-
-
 /** \brief Update the constraint set propagating recursively to
  *  other constraints so the system should not be entirely computed.
  *
  *  \param sys the lmm_system_t
  *  \param cnst the lmm_constraint_t affected by the change
  *
- *  A recursive algorithm to optimize the system recalculation selecting only
- *  constraints that have changed. Each constraint change is propagated
- *  to the list of constraints for each variable.
+ *  A recursive algorithm to optimize the system recalculation selecting only constraints that have changed. Each
+ *  constraint change is propagated to the list of constraints for each variable.
  */
-static void lmm_update_modified_set_rec(lmm_system_t sys,
-                                        lmm_constraint_t cnst)
+static void lmm_update_modified_set_rec(lmm_system_t sys, lmm_constraint_t cnst)
 {
   void* _elem;
 
-  xbt_swag_foreach(_elem, &cnst->element_set) {
+  //TODOLATER: Why lmm_modified_set has been changed in git version 2392B5157...? Looks equivalent logically and less obvious..
+  xbt_swag_foreach(_elem, &cnst->enabled_element_set) {
     lmm_variable_t var = ((lmm_element_t)_elem)->variable;
     s_lmm_element_t *cnsts = var->cnsts;
     int i;
-    for (i = 0; var->visited != sys->visited_counter
-             && i < var->cnsts_number ; i++) {
-      if (cnsts[i].constraint != cnst
-          && !xbt_swag_belongs(cnsts[i].constraint,
-                               &sys->modified_constraint_set)) {
+    for (i = 0; var->visited != sys->visited_counter && i < var->cnsts_number ; i++) {
+      if (cnsts[i].constraint != cnst && !xbt_swag_belongs(cnsts[i].constraint, &sys->modified_constraint_set)) {
         xbt_swag_insert(cnsts[i].constraint, &sys->modified_constraint_set);
         lmm_update_modified_set_rec(sys, cnsts[i].constraint);
       }
     }
+    //var will be ignored in later visits as long as sys->visited_counter does not move 
     var->visited = sys->visited_counter;
   }
 }
 
-static void lmm_update_modified_set(lmm_system_t sys,
-                                    lmm_constraint_t cnst)
+static void lmm_update_modified_set(lmm_system_t sys, lmm_constraint_t cnst)
 {
   /* nothing to do if selective update isn't active */
-  if (sys->selective_update_active
-      && !xbt_swag_belongs(cnst, &sys->modified_constraint_set)) {
+  if (sys->selective_update_active && !xbt_swag_belongs(cnst, &sys->modified_constraint_set)) {
     xbt_swag_insert(cnst, &sys->modified_constraint_set);
     lmm_update_modified_set_rec(sys, cnst);
   }
@@ -960,40 +1205,102 @@ static void lmm_update_modified_set(lmm_system_t sys,
  */
 static void lmm_remove_all_modified_set(lmm_system_t sys)
 {
+  //We cleverly un-flag all variables just by incrementing sys->visited_counter
+  //In effect, the var->visited value will no more be equal to sys->visited counter
+  //To be clean, when visited counter has wrapped around, we force these var->visited values so that variables that
+  //were in the modified a long (long long) time ago are not wrongly skipped here, which would lead to very nasty bugs
+  //(i.e. not readibily reproducible, and requiring a lot of run time before happening).
   if (++sys->visited_counter == 1) {
     /* the counter wrapped around, reset each variable->visited */
-	void *_var;
+  void *_var;
     xbt_swag_foreach(_var, &sys->variable_set)
       ((lmm_variable_t)_var)->visited = 0;
-  }
+  } 
   xbt_swag_reset(&sys->modified_constraint_set);
 }
 
 /**
- *  Returns total resource load
+ *  Returns resource load (in flop per second, or byte per second, or similar)
  *
- *  \param cnst the lmm_constraint_t associated to the resource
+ *  If the resource is shared (the default case), the load is sum of
+ *  resource usage made by every variables located on this resource.
  *
+ * If the resource is not shared (ie in FATPIPE mode), then the the
+ * load is the max (not the sum) of all resource usages located on this resource.
+ * .
+ * \param cnst the lmm_constraint_t associated to the resource
  */
 double lmm_constraint_get_usage(lmm_constraint_t cnst) {
    double usage = 0.0;
-   xbt_swag_t elem_list = &(cnst->element_set);
+   xbt_swag_t elem_list = &(cnst->enabled_element_set);
    void *_elem;
-   lmm_element_t elem = NULL;
 
    xbt_swag_foreach(_elem, elem_list) {
-	 elem = (lmm_element_t)_elem;
-     /* 0-weighted elements (ie, sleep actions) are at the end of the swag and we don't want to consider them */
-     if (elem->variable->weight <= 0)
-       break;
-     if ((elem->value > 0)) {
-       if (cnst->shared)
+     lmm_element_t elem = (lmm_element_t)_elem;
+     if (elem->value > 0) {
+       if (cnst->sharing_policy)
          usage += elem->value * elem->variable->value;
        else if (usage < elem->value * elem->variable->value)
-         usage = elem->value * elem->variable->value;
+         usage = max(usage, elem->value * elem->variable->value);
      }
    }
   return usage;
 }
 
+void lmm_check_concurrency(lmm_system_t sys){
+  void* _cnst;
+  void* _elem;
+  void* _var;
+  lmm_element_t elem;
+  lmm_constraint_t cnst;
+  lmm_variable_t var;
+  int concurrency;
+  int i,belong_to_enabled,belong_to_disabled,belong_to_active;
+
+  //These checks are very expensive, so do them only if we want to debug SURF LMM
+  if (XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug)) {
+    xbt_swag_foreach(_cnst, &(sys->constraint_set)) {
+      cnst = (lmm_constraint_t) _cnst;
+      concurrency=0;
+      xbt_swag_foreach(_elem, &(cnst->enabled_element_set)) {
+        elem = (lmm_element_t)_elem;
+        xbt_assert(elem->variable->weight > 0);
+        concurrency+=lmm_element_concurrency(elem);
+      }
+
+      xbt_swag_foreach(_elem, &(cnst->disabled_element_set)) {
+        elem = (lmm_element_t)_elem;
+        //We should have staged variables only if concurrency is reached in some constraint
+        xbt_assert(cnst->concurrency_limit<0 || elem->variable->staged_weight==0 ||
+                   lmm_cnstrs_min_concurrency_slack(elem->variable) < elem->variable->concurrency_share,
+                   "should not have staged variable!");
+      }
+
+      xbt_assert(cnst->concurrency_limit<0 || cnst->concurrency_limit >= concurrency,"concurrency check failed!");
+      xbt_assert(cnst->concurrency_current == concurrency, "concurrency_current is out-of-date!");
+    }
+
+    //Check that for each variable, all corresponding elements are in the same state (i.e. same element sets)
+    xbt_swag_foreach(_var, &(sys->variable_set)) {
+      var= (lmm_variable_t) _var;
+
+      if(!var->cnsts_number)
+        continue;
 
+      elem = &var->cnsts[0];
+      belong_to_enabled=xbt_swag_belongs(elem,&(elem->constraint->enabled_element_set));
+      belong_to_disabled=xbt_swag_belongs(elem,&(elem->constraint->disabled_element_set));
+      belong_to_active=xbt_swag_belongs(elem,&(elem->constraint->active_element_set));
+
+      for (i = 1; i < var->cnsts_number; i++) {
+        elem = &var->cnsts[i];
+        xbt_assert(belong_to_enabled==xbt_swag_belongs(elem,&(elem->constraint->enabled_element_set)),
+                   "Variable inconsistency (1): enabled_element_set");
+        xbt_assert(belong_to_disabled==xbt_swag_belongs(elem,&(elem->constraint->disabled_element_set)),
+                   "Variable inconsistency (2): disabled_element_set");
+        xbt_assert(belong_to_active==xbt_swag_belongs(elem,&(elem->constraint->active_element_set)),
+                   "Variable inconsistency (3): active_element_set");
+      }
+    }
+  }
+}