X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/be168aff446047bcd2ac666608920a2ba9def0cd..16bbb8a8212497d9c44c81333ed2c0e689e0c5af:/src/surf/maxmin.cpp

diff --git a/src/surf/maxmin.cpp b/src/surf/maxmin.cpp
index a060d6b7f2..5e7441057e 100644
--- a/src/surf/maxmin.cpp
+++ b/src/surf/maxmin.cpp
@@ -4,6 +4,8 @@
 /* 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/mallocator.h"
@@ -36,6 +38,26 @@ 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 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 void lmm_decrease_concurrency(lmm_constraint_t cnstr){
+  xbt_assert(cnstr->concurrency_current>0);
+  cnstr->concurrency_current--;
+}
+
+inline void lmm_increase_concurrency(lmm_constraint_t cnstr){
+  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;
@@ -79,9 +101,10 @@ void lmm_system_free(lmm_system_t sys)
   lmm_variable_t var = NULL;
   lmm_constraint_t cnst = NULL;
 
+  
   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",
+        ("Variable %p (%d) still in  system when freing it: this may be a bug",
          var, var->id_int);
     lmm_var_free(sys, var);
   }
@@ -93,32 +116,34 @@ 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 XBT_INLINE void lmm_variable_remove(lmm_system_t sys, lmm_variable_t var)
 {
   int i;
-  int n;
-
+  int nelements;
+  
   lmm_element_t elem = NULL;
-
+  
   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->constraint);
+    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++;
-    }
-  }
-  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.
+    else
+      lmm_on_disabled_var(sys,elem->constraint);
   }
 
   var->cnsts_number = 0;
@@ -128,15 +153,13 @@ static XBT_INLINE void lmm_variable_disable(lmm_system_t sys, lmm_variable_t var
 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)
 {
-/*   xbt_assert(xbt_swag_size(&(cnst->element_set)), */
-/*         "This list should be empty!"); */
   make_constraint_inactive(sys, cnst);
   free(cnst);
 }
@@ -150,32 +173,62 @@ lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id,
   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->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;
+  //TODO MARTIN Maybe a configuration item for the default cap concurrency? 
+  cnst->concurrency_limit=100;
   cnst->usage = 0;
-  cnst->shared = 1;
+  cnst->sharing_policy = 1; /* FIXME: don't hardcode the value */
   insert_constraint(sys, cnst);
 
   return cnst;
 }
 
+void lmm_constraint_concurrency_limit_set(lmm_constraint_t cnst, int concurrency_limit)
+{
+  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)
+{
+  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);
 }
 
+/* @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 this is not the case, assertion will fail, and you need to add calls e.g. to lmm_shrink before effectively removing it.
+ */
 XBT_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);
 }
@@ -208,8 +261,10 @@ lmm_variable_t lmm_variable_new(lmm_system_t sys, void *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].enabled_element_set_hookup.next = NULL;
+    var->cnsts[i].enabled_element_set_hookup.prev = NULL;
+    var->cnsts[i].disabled_element_set_hookup.next = NULL;
+    var->cnsts[i].disabled_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;
@@ -219,7 +274,9 @@ lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id,
   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;
@@ -253,36 +310,15 @@ 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,
@@ -310,45 +346,53 @@ void lmm_shrink(lmm_system_t sys, lmm_constraint_t cnst,
   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].
 
+  if(xbt_swag_remove(elem, &(elem->constraint->enabled_element_set)))
+    lmm_decrease_concurrency(elem->constraint);
 
-  /* now var->cnsts[i] is not necessary any more */
-
-  xbt_swag_remove(elem, &(elem->constraint->element_set));
   xbt_swag_remove(elem, &(elem->constraint->active_element_set));
   elem->constraint = NULL;
   elem->variable = NULL;
   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)
 {
   lmm_element_t elem = NULL;
-
+  double weight;
+  int i;
+  
   sys->modified = 1;
 
+  if(var->weight>0 && lmm_concurrency_slack(cnst)==0){
+    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++]);
@@ -357,18 +401,25 @@ 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));
+  
+  if (var->weight){
+    xbt_swag_insert_at_head(elem, &(elem->constraint->enabled_element_set));
+    lmm_increase_concurrency(elem->constraint);
+  }
   else
-    xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
+    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,
@@ -377,18 +428,22 @@ void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
   int i;
   sys->modified = 1;
 
+  lmm_check_concurrency(sys);
+
   for (i = 0; i < var->cnsts_number; i++)
     if (var->cnsts[i].constraint == cnst)
       break;
 
   if (i < var->cnsts_number) {
-    if (cnst->shared)
+    if (cnst->sharing_policy)
       var->cnsts[i].value += value;
     else
       var->cnsts[i].value = MAX(var->cnsts[i].value, value);
     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*/,
@@ -421,10 +476,23 @@ 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
@@ -440,8 +508,10 @@ lmm_variable_t lmm_get_var_from_cnst_safe(lmm_system_t /*sys*/,
                                      int * numelem)
 {
   if (!(*elem)){
-    *elem = (lmm_element_t) xbt_swag_getFirst(&(cnst->element_set));
-    *numelem = xbt_swag_size(&(cnst->element_set))-1;
+    *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){
@@ -450,7 +520,15 @@ lmm_variable_t lmm_get_var_from_cnst_safe(lmm_system_t /*sys*/,
       return NULL;
   }
   if (*elem){
-    *nextelem = (lmm_element_t) xbt_swag_getNext(*elem, cnst->element_set.offset);
+    //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 NULL;
@@ -475,7 +553,7 @@ static XBT_INLINE void saturated_constraint_set_update(double usage,
 
   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) {
@@ -504,8 +582,8 @@ static XBT_INLINE void saturated_variable_set_update(
     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));
     }
@@ -532,7 +610,7 @@ void lmm_print(lmm_system_t sys)
       xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
   strcat(trace_buf, print_buf);
   xbt_swag_foreach(_var, var_list) {
-	var = (lmm_variable_t)_var;
+  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);
@@ -549,14 +627,15 @@ void lmm_print(lmm_system_t sys)
   /* 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);
+    //Show  the enabled variables
+    elem_list = &(cnst->enabled_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");
+    sprintf(print_buf, "%s(",(cnst->sharing_policy)?"":"max");
     trace_buf = (char*)
       xbt_realloc(trace_buf,
       strlen(trace_buf) + strlen(print_buf) + 1);
@@ -564,22 +643,38 @@ void lmm_print(lmm_system_t sys)
     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)?"+":",");
+              elem->variable->id_int, elem->variable->value,(cnst->sharing_policy)?"+":",");
       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;
+      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);
     }
+    //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;
+      sprintf(print_buf, "%f.'%d'(%f) %s ", elem->value,
+              elem->variable->id_int, elem->variable->value,(cnst->sharing_policy)?"+":",");
+      trace_buf = (char*)
+          xbt_realloc(trace_buf,
+                      strlen(trace_buf) + strlen(print_buf) + 1);
+      strcat(trace_buf, print_buf);
+      if(cnst->sharing_policy)
+        sum += elem->value * elem->variable->value;
+      else 
+        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) {
+    if (!cnst->sharing_policy) {
       sprintf(print_buf, " [MAX-Constraint]");
       trace_buf = (char*)
           xbt_realloc(trace_buf,
@@ -596,7 +691,7 @@ void lmm_print(lmm_system_t sys)
   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);
@@ -639,13 +734,12 @@ void lmm_solve(lmm_system_t sys)
   XBT_DEBUG("Active constraints : %d", xbt_swag_size(cnst_list));
   /* 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;
     }
   }
@@ -657,26 +751,24 @@ void lmm_solve(lmm_system_t sys)
   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;
+  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 (!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);
-        Action *action = static_cast<Action*>(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);
       }
@@ -729,17 +821,17 @@ void lmm_solve(lmm_system_t sys)
       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) 
+  //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);
       } else {
-	//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)){
+  //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.  
+    // 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;
@@ -753,16 +845,16 @@ void lmm_solve(lmm_system_t sys)
       for (i = 0; i < var->cnsts_number; i++) {
         elem = &var->cnsts[i];
         cnst = elem->constraint;
-        if (cnst->shared) {
-	  //Remember: shared constraints require that sum(elem->value * var->value) < cnst->bound
+        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 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 usage: %f remaining: %f bound: %f  ",
-			index,cnst_light_num, cnst, cnst->cnst_light, cnst_light_tab, cnst->usage, cnst->remaining, cnst->bound);
+      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--;
@@ -773,23 +865,23 @@ void lmm_solve(lmm_system_t sys)
           }
           make_elem_inactive(elem);
         } else {
-	  //Remember: non-shared constraints only require that max(elem->value * var->value) < cnst->bound
+    //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) break; //Found an inactive variable -> no more active variables
-            if (elem->variable->value > 0) continue;
-            if (elem->value > 0)
-              cnst->usage = MAX(cnst->usage, elem->value / elem->variable->weight);
+      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 the constraint is saturated, remove it from the set of active constraints (light_tab)
+    //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 usage: %f remaining: %f bound: %f  ",
-			index,cnst_light_num, cnst, cnst->cnst_light, cnst_light_tab, cnst->usage, cnst->remaining, cnst->bound);
+      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--;
@@ -816,7 +908,7 @@ void lmm_solve(lmm_system_t sys)
           pos,
           saturated_constraint_set,
           &min_usage);
-	}
+  }
 
     saturated_variable_set_update(  cnst_light_tab,
                                     saturated_constraint_set,
@@ -838,21 +930,6 @@ void lmm_solve(lmm_system_t sys)
   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.
  * 
@@ -865,9 +942,9 @@ void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
  *  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)
+    double bound)
 {
   sys->modified = 1;
   var->bound = bound;
@@ -877,38 +954,182 @@ void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
 }
 
 
-void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
-                                double weight)
-{
+
+int lmm_concurrency_slack(lmm_constraint_t cnstr){
+
+  xbt_assert(xbt_swag_size(&(cnstr->enabled_element_set))==cnstr->concurrency_current,"concurrency_current is not up to date!");
+
+  //FIXME MARTIN: Replace by infinite value std::numeric_limits<int>::(max)(), or something better within Simgrid?
+  if(cnstr->concurrency_limit<0)
+    return 666;
+
+  return  cnstr->concurrency_limit - cnstr->concurrency_current;  
+}
+
+/** \brief Measure the minimum concurrency slack across all constraints where var is involved
+ *
+ * \param The variable to check for
+ *
+ */
+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;
+  
+  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.
 
-  if (weight == var->weight)
-    return;
-  XBT_IN("(sys=%p, var=%p, weight=%f)", sys, var, weight);
-  sys->modified = 1;
-  var->weight = weight;
   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->constraint);
+  }
+  if (var->cnsts_number)
+    lmm_update_modified_set(sys, var->cnsts[0].constraint);
 
+  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));
+
+    lmm_decrease_concurrency(elem->constraint);
+  }
+
+  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;
+  if(cnstr->concurrency_limit<0)
+    return;
+  
+  int concurrency=cnstr->concurrency_current;
+  xbt_swag_foreach(elem, &(cnstr->disabled_element_set)) {
+
+    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);
+    concurrency++;
+  }        
+      }
 
-    if (i == 0)
-      lmm_update_modified_set(sys, elem->constraint);
+    xbt_assert(concurrency<=cnstr->concurrency_limit,"Concurrency overflow!");
+    if(concurrency==cnstr->concurrency_limit)
+      break;
   }
-  if (!weight)
-    var->value = 0.0;
 
+  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==0){      
+      XBT_DEBUG("Staging var (instead of enabling) because min concurrency slack %i, with weight %f", minslack, weight);
+      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)
@@ -945,7 +1166,7 @@ XBT_INLINE lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t
 }
 
 #ifdef HAVE_LATENCY_BOUND_TRACKING
-XBT_INLINE int lmm_is_variable_limited_by_latency(lmm_variable_t var)
+XBT_PUBLIC(int) lmm_is_variable_limited_by_latency(lmm_variable_t var)
 {
   return (double_equals(var->bound, var->value, var->bound*sg_maxmin_precision));
 }
@@ -967,7 +1188,9 @@ static void lmm_update_modified_set_rec(lmm_system_t sys,
 {
   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;
@@ -980,6 +1203,7 @@ static void lmm_update_modified_set_rec(lmm_system_t sys,
         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;
   }
 }
@@ -998,12 +1222,17 @@ static void lmm_update_modified_set(lmm_system_t sys,
 /** \brief Remove all constraints of the modified_constraint_set.
  *
  *  \param sys the lmm_system_t
+ *
  */
 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;
   }
@@ -1013,22 +1242,21 @@ static void lmm_remove_all_modified_set(lmm_system_t sys)
 /**
  *  Returns total resource load
  *
- *  \param cnst the lmm_constraint_t associated to the resource
+ * \param cnst the lmm_constraint_t associated to the resource
  *
+ *
+ * This is dead code, but we may use it later for debug/trace.
  */
 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;
+   elem = (lmm_element_t)_elem;
      if ((elem->value > 0)) {
-       if (cnst->shared)
+       if (cnst->sharing_policy)
          usage += elem->value * elem->variable->value;
        else if (usage < elem->value * elem->variable->value)
          usage = elem->value * elem->variable->value;
@@ -1037,4 +1265,37 @@ double lmm_constraint_get_usage(lmm_constraint_t cnst) {
   return usage;
 }
 
+void lmm_check_concurrency(lmm_system_t sys){
+  void* _cnst;
+  void* _elem;
+  lmm_element_t elem;
+  lmm_constraint_t cnst;
+  int concurrency;
+
+  //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++;
+      }
+
+      xbt_swag_foreach(_elem, &(cnst->disabled_element_set)) {
+  elem = (lmm_element_t)_elem;
+  //We should have staged variables only if conccurency 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!");
+      xbt_assert(cnst->concurrency_current == xbt_swag_size(&(cnst->enabled_element_set)), "concurrency_current is out-of-date (2) !");
+
+    }
 
+  }
+}