X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/8c354c48ec90c997cc7213ce96ca97d882934166..90efa0c7c4d4c88517e6c638b4478cc2573954ad:/src/surf/maxmin.c

diff --git a/src/surf/maxmin.c b/src/surf/maxmin.c
index 513ad7a0c1..250e3e7b28 100644
--- a/src/surf/maxmin.c
+++ b/src/surf/maxmin.c
@@ -7,9 +7,18 @@
 
 
 #include "xbt/sysdep.h"
-#include "xbt/error.h"
+#include "xbt/log.h"
+#include "xbt/mallocator.h"
 #include "maxmin_private.h"
 #include <stdlib.h>
+#include <stdio.h> /* sprintf */
+#include <math.h>
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(surf_maxmin, surf,
+				"Logging specific to SURF (maxmin)");
+
+static void *lmm_variable_mallocator_new_f(void);
+static void lmm_variable_mallocator_free_f(void *var);
+static void lmm_variable_mallocator_reset_f(void *var);
 
 lmm_system_t lmm_system_new(void)
 {
@@ -33,6 +42,11 @@ lmm_system_t lmm_system_new(void)
   xbt_swag_init(&(l->saturated_constraint_set),
 		xbt_swag_offset(cnst, saturated_constraint_set_hookup));
 
+  l->variable_mallocator = xbt_mallocator_new(64,
+					      lmm_variable_mallocator_new_f,
+					      lmm_variable_mallocator_free_f,
+					      lmm_variable_mallocator_reset_f);
+
   return l;
 }
 
@@ -47,7 +61,8 @@ void lmm_system_free(lmm_system_t sys)
   while ((cnst = extract_constraint(sys)))
     lmm_cnst_free(sys, cnst);
 
-  xbt_free(sys);
+  xbt_mallocator_free(sys->variable_mallocator);
+  free(sys);
 }
 
 void lmm_variable_disable(lmm_system_t sys, lmm_variable_t var)
@@ -55,36 +70,38 @@ void lmm_variable_disable(lmm_system_t sys, lmm_variable_t var)
   int i;
   lmm_element_t elem = NULL;
 
+  XBT_IN2("(sys=%p, var=%p)", sys, var);
   sys->modified = 1;
 
   for (i = 0; i < var->cnsts_number; i++) {
     elem = &var->cnsts[i];
     xbt_swag_remove(elem, &(elem->constraint->element_set));
-    if (xbt_swag_size(&(elem->constraint->element_set)))
+    xbt_swag_remove(elem, &(elem->constraint->active_element_set));
+    if (!xbt_swag_size(&(elem->constraint->element_set)))
       make_constraint_inactive(sys, elem->constraint);
   }
   var->cnsts_number = 0;
+  XBT_OUT;
 }
 
 static void lmm_var_free(lmm_system_t sys, lmm_variable_t var)
 {
 
   lmm_variable_disable(sys, var);
-
-  xbt_free(var->cnsts);
-  xbt_free(var);
+  free(var->cnsts);
+  xbt_mallocator_release(sys->variable_mallocator, var);
 }
 
 static void lmm_cnst_free(lmm_system_t sys, lmm_constraint_t cnst)
 {
-/*   xbt_assert0(xbt_fifo_size(&(cnst->row)), */
-/* 		 "This list should be empty!"); */
+/*   xbt_assert0(xbt_swag_size(&(cnst->element_set)), */
+/* 	      "This list should be empty!"); */
   remove_active_constraint(sys, cnst);
-  xbt_free(cnst);
+  free(cnst);
 }
 
 lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id,
-				    xbt_maxmin_float_t bound_value)
+				    double bound_value)
 {
   lmm_constraint_t cnst = NULL;
   s_lmm_element_t elem;
@@ -98,34 +115,85 @@ lmm_constraint_t lmm_constraint_new(lmm_system_t sys, void *id,
 
   cnst->bound = bound_value;
   cnst->usage = 0;
+  cnst->shared = 1;
   insert_constraint(sys, cnst);
 
   return cnst;
 }
 
+void lmm_constraint_shared(lmm_constraint_t cnst)
+{
+  cnst->shared = 0;
+}
+
+int lmm_constraint_is_shared(lmm_constraint_t cnst)
+{
+  return (cnst->shared);
+}
+
 void lmm_constraint_free(lmm_system_t sys, lmm_constraint_t cnst)
 {
   remove_constraint(sys, cnst);
   lmm_cnst_free(sys, cnst);
 }
 
+static void *lmm_variable_mallocator_new_f(void)
+{
+  return xbt_new(s_lmm_variable_t, 1);
+}
+
+static void lmm_variable_mallocator_free_f(void *var)
+{
+  xbt_free(var);
+}
+
+static void lmm_variable_mallocator_reset_f(void *var)
+{
+  /* memset to zero like calloc */
+  memset(var, 0, sizeof(s_lmm_variable_t));
+}
+
 lmm_variable_t lmm_variable_new(lmm_system_t sys, void *id,
-				xbt_maxmin_float_t weight,
-				xbt_maxmin_float_t bound,
-				int number_of_constraints)
+				double weight,
+				double bound, int number_of_constraints)
 {
   lmm_variable_t var = NULL;
+  int i;
 
-  var = xbt_new0(s_lmm_variable_t, 1);
+  XBT_IN5("(sys=%p, id=%p, weight=%f, bound=%f, num_cons =%d)",
+	  sys, id, weight, bound, number_of_constraints);
+
+  var = xbt_mallocator_get(sys->variable_mallocator);
   var->id = id;
   var->cnsts = xbt_new0(s_lmm_element_t, number_of_constraints);
+  for (i = 0; i < number_of_constraints; i++) {
+    /* Should be useless because of the 
+       calloc but it seems to help valgrind... */
+    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].value = 0.0;
+  }
   var->cnsts_size = number_of_constraints;
-  /* var->cnsts_number = 0; *//* Useless because of the calloc  */
+  var->cnsts_number = 0;	/* Should be useless because of the 
+				   calloc but it seems to help valgrind... */
   var->weight = weight;
   var->bound = bound;
-  var->value = -1;
-  insert_variable(sys, var);
-
+  var->value = 0.0;
+  var->df = 0.0;
+
+  var->func_f = func_f_def;
+  var->func_fp = func_fp_def;
+  var->func_fpi = func_fpi_def;
+
+  if (weight)
+    xbt_swag_insert_at_head(var, &(sys->variable_set));
+  else
+    xbt_swag_insert_at_tail(var, &(sys->variable_set));
+  XBT_OUT;
   return var;
 }
 
@@ -135,20 +203,24 @@ void lmm_variable_free(lmm_system_t sys, lmm_variable_t var)
   lmm_var_free(sys, var);
 }
 
-xbt_maxmin_float_t lmm_variable_getvalue(lmm_variable_t var)
+double lmm_variable_getvalue(lmm_variable_t var)
 {
   return (var->value);
 }
 
+double lmm_variable_getbound(lmm_variable_t var)
+{
+  return (var->bound);
+}
+
 void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
-		lmm_variable_t var, xbt_maxmin_float_t value)
+		lmm_variable_t var, double value)
 {
   lmm_element_t elem = NULL;
 
   sys->modified = 1;
 
-  if (var->cnsts_number >= var->cnsts_size)
-    abort();
+  xbt_assert0(var->cnsts_number < var->cnsts_size, "Too much constraints");
 
   elem = &(var->cnsts[var->cnsts_number++]);
 
@@ -156,28 +228,73 @@ void lmm_expand(lmm_system_t sys, lmm_constraint_t cnst,
   elem->constraint = cnst;
   elem->variable = var;
 
-  insert_elem_in_constraint(elem);
+  if (var->weight)
+    xbt_swag_insert_at_head(elem, &(elem->constraint->element_set));
+  else
+    xbt_swag_insert_at_tail(elem, &(elem->constraint->element_set));
 
   make_constraint_active(sys, cnst);
 }
 
-lmm_constraint_t lmm_get_cnst_from_var(lmm_system_t sys, lmm_variable_t var, int num)
+void lmm_expand_add(lmm_system_t sys, lmm_constraint_t cnst,
+		    lmm_variable_t var, double value)
 {
-  if(num<var->cnsts_number) return(var->cnsts[num].constraint);
-  else return NULL;
+  int i;
+  sys->modified = 1;
+
+  for (i = 0; i < var->cnsts_number; i++)
+    if (var->cnsts[i].constraint == cnst)
+      break;
+
+  if (i < var->cnsts_number) {
+    if(cnst->shared) var->cnsts[i].value += value;
+    else var->cnsts[i].value = MAX(var->cnsts[i].value,value);
+  }  else
+    lmm_expand(sys, cnst, var, value);
+}
+
+void lmm_elem_set_value(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)
+      break;
+
+  if (i < var->cnsts_number) {
+    var->cnsts[i].value = value;
+    sys->modified = 1;
+  } else
+    DIE_IMPOSSIBLE;
+}
+
+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;
 }
 
 int lmm_get_number_of_cnst_from_var(lmm_system_t sys, lmm_variable_t var)
 {
-  return(var->cnsts_number);
+  return (var->cnsts_number);
 }
 
-lmm_variable_t lmm_get_var_from_cnst(lmm_system_t sys, lmm_constraint_t cnst, 
-				     lmm_variable_t *var)
+lmm_variable_t lmm_get_var_from_cnst(lmm_system_t sys,
+				     lmm_constraint_t cnst,
+				     lmm_element_t * elem)
 {
-  if(!(*var)) xbt_swag_getFirst(&(cnst->element_set));
-  else *var=xbt_swag_getNext(*var,cnst->element_set.offset);
-  return *var;
+  if (!(*elem))
+    *elem = xbt_swag_getFirst(&(cnst->element_set));
+  else
+    *elem = xbt_swag_getNext(*elem, cnst->element_set.offset);
+  if(*elem)
+    return (*elem)->variable;
+  else 
+    return NULL;
 }
 
 void *lmm_constraint_id(lmm_constraint_t cnst)
@@ -190,46 +307,140 @@ void *lmm_variable_id(lmm_variable_t var)
   return var->id;
 }
 
-static void saturated_constraints_update(lmm_system_t sys,
-					 lmm_constraint_t cnst,
-					 xbt_maxmin_float_t * min_usage)
+static void saturated_constraint_set_update(lmm_system_t sys,
+					    lmm_constraint_t cnst,
+					    double *min_usage)
 {
   lmm_constraint_t useless_cnst = NULL;
 
-  sys->modified = 1;
-
-  if (cnst->remaining <= 0)
+  XBT_IN3("sys=%p, cnst=%p, min_usage=%f", sys, cnst, *min_usage);
+  if (cnst->usage <= 0) {
+    XBT_OUT;
+    return;
+  }
+  if (cnst->remaining <= 0) {
+    XBT_OUT;
     return;
+  }
   if ((*min_usage < 0) || (*min_usage > cnst->remaining / cnst->usage)) {
     *min_usage = cnst->remaining / cnst->usage;
-
-    while ((useless_cnst = xbt_swag_getFirst(&(sys->saturated_constraint_set))))
+    LOG3(xbt_log_priority_trace,
+	 "min_usage=%f (cnst->remaining=%f, cnst->usage=%f)", *min_usage,
+	 cnst->remaining, cnst->usage);
+    while ((useless_cnst =
+	    xbt_swag_getFirst(&(sys->saturated_constraint_set))))
       xbt_swag_remove(useless_cnst, &(sys->saturated_constraint_set));
 
     xbt_swag_insert(cnst, &(sys->saturated_constraint_set));
   } else if (*min_usage == cnst->remaining / cnst->usage) {
     xbt_swag_insert(cnst, &(sys->saturated_constraint_set));
   }
+  XBT_OUT;
 }
 
-static void saturated_variables_update(lmm_system_t sys)
+static void saturated_variable_set_update(lmm_system_t sys)
 {
   lmm_constraint_t cnst = NULL;
   xbt_swag_t cnst_list = NULL;
   lmm_element_t elem = NULL;
   xbt_swag_t elem_list = NULL;
 
-  sys->modified = 1;
-
   cnst_list = &(sys->saturated_constraint_set);
   while ((cnst = xbt_swag_getFirst(cnst_list))) {
-/*   xbt_swag_foreach(cnst, cnst_list) { */
     elem_list = &(cnst->active_element_set);
-    xbt_swag_foreach(elem, elem_list)
+    xbt_swag_foreach(elem, elem_list) {
+      if (elem->variable->weight <= 0)
+	break;
+      if ((elem->value > 0))
 	xbt_swag_insert(elem->variable, &(sys->saturated_variable_set));
+    }
     xbt_swag_remove(cnst, cnst_list);
   }
+}
+
+void lmm_print(lmm_system_t sys)
+{
+  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 = xbt_malloc0(sizeof(char));
+  double sum = 0.0;
+
+  /* Printing Objective */
+  var_list = &(sys->variable_set);
+  sprintf(print_buf, "MAX-MIN ( ");
+  trace_buf =
+      xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
+  strcat(trace_buf, print_buf);
+  xbt_swag_foreach(var, var_list) {
+    sprintf(print_buf, "'%p'(%f) ", var, var->weight);
+    trace_buf =
+	xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
+    strcat(trace_buf, print_buf);
+  }
+  sprintf(print_buf, ")");
+  trace_buf =
+      xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
+  strcat(trace_buf, print_buf);
+  DEBUG1("%s", trace_buf);
+  trace_buf[0] = '\000';
+
+  DEBUG0("Constraints");
+  /* Printing Constraints */
+  cnst_list = &(sys->active_constraint_set);
+  xbt_swag_foreach(cnst, cnst_list) {
+    sum = 0.0;
+    elem_list = &(cnst->element_set);
+    sprintf(print_buf, "\t");
+    trace_buf =
+	xbt_realloc(trace_buf, strlen(trace_buf) + strlen(print_buf) + 1);
+    strcat(trace_buf, print_buf);
+    xbt_swag_foreach(elem, elem_list) {
+      sprintf(print_buf, "%f.'%p'(%f) + ", elem->value,
+	      elem->variable, elem->variable->value);
+      trace_buf =
+	  xbt_realloc(trace_buf,
+		      strlen(trace_buf) + strlen(print_buf) + 1);
+      strcat(trace_buf, print_buf);
+      sum += elem->value * elem->variable->value;
+    }
+    sprintf(print_buf, "0 <= %f ('%p')", cnst->bound, cnst);
+    trace_buf =
+	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 =
+	  xbt_realloc(trace_buf,
+		      strlen(trace_buf) + strlen(print_buf) + 1);
+      strcat(trace_buf, print_buf);
+    }
+    DEBUG1("%s", trace_buf);
+    trace_buf[0] = '\000';
+    xbt_assert3(!double_positive(sum - cnst->bound),
+		"Incorrect value (%f is not smaller than %f): %g",
+		sum, cnst->bound, sum - cnst->bound);    
+  }
 
+  DEBUG0("Variables");
+  /* Printing Result */
+  xbt_swag_foreach(var, var_list) {
+    if (var->bound > 0) {
+      DEBUG4("'%p'(%f) : %f (<=%f)", var, var->weight, var->value,
+	     var->bound);
+      xbt_assert2(!double_positive(var->value - var->bound),
+		  "Incorrect value (%f is not smaller than %f",
+		  var->value, var->bound);
+    } else
+      DEBUG3("'%p'(%f) : %f", var, var->weight, var->value);
+  }
+
+  free(trace_buf);
 }
 
 void lmm_solve(lmm_system_t sys)
@@ -240,35 +451,53 @@ void lmm_solve(lmm_system_t sys)
   xbt_swag_t cnst_list = NULL;
   xbt_swag_t var_list = NULL;
   xbt_swag_t elem_list = NULL;
-  xbt_maxmin_float_t min_usage = -1;
+  double min_usage = -1;
 
-  if(!(sys->modified)) return;
+  if (!(sys->modified))
+    return;
 
   /* Init */
   var_list = &(sys->variable_set);
+  DEBUG1("Variable set : %d", xbt_swag_size(var_list));
   xbt_swag_foreach(var, var_list) {
-    var->value = -1;
+    int nb=0;
+    int i;
+    if(var->weight<=0.0) break;
+    var->value = 0.0;
+    for (i = 0; i < var->cnsts_number; i++) {
+      if(var->cnsts[i].value==0.0) nb++;
+    }
+    if((nb==var->cnsts_number) && (var->weight>0.0))
+      var->value = 1.0;
   }
 
-
-  /* Compute Usage and store the variables that reach the maximum */
-
+  /* 
+   * Compute Usage and store the variables that reach the maximum.
+   */
   cnst_list = &(sys->active_constraint_set);
+  DEBUG1("Active constraints : %d", xbt_swag_size(cnst_list));
   xbt_swag_foreach(cnst, cnst_list) {
     /* INIT */
-    elem_list = &(cnst->element_set);
     cnst->remaining = cnst->bound;
     cnst->usage = 0;
+    elem_list = &(cnst->element_set);
+    cnst->usage = 0.0;
     xbt_swag_foreach(elem, elem_list) {
-      cnst->usage += elem->value / elem->variable->weight;
-      insert_active_elem_in_constraint(elem);
+      if (elem->variable->weight <= 0)
+	break;
+      if ((elem->value > 0)) {
+	if (cnst->shared)
+	  cnst->usage += elem->value / elem->variable->weight;
+	else if (cnst->usage < elem->value / elem->variable->weight)
+	  cnst->usage = elem->value / elem->variable->weight;
+	DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
+	make_elem_active(elem);
+      }
     }
-
     /* Saturated constraints update */
-    saturated_constraints_update(sys, cnst, &min_usage);
+    saturated_constraint_set_update(sys, cnst, &min_usage);
   }
-
-  saturated_variables_update(sys);
+  saturated_variable_set_update(sys);
 
   /* Saturated variables update */
 
@@ -276,12 +505,17 @@ void lmm_solve(lmm_system_t sys)
     /* Fix the variables that have to be */
     var_list = &(sys->saturated_variable_set);
 
-
     xbt_swag_foreach(var, var_list) {
+      if(var->weight<=0.0) DIE_IMPOSSIBLE;
       /* First check if some of these variables have reach their upper
          bound and update min_usage accordingly. */
-      if ((var->bound > 0) && (var->bound / var->weight < min_usage)) {
-	min_usage = var->bound / var->weight;
+      DEBUG5
+	  ("var=%p, var->bound=%f, var->weight=%f, min_usage=%f, var->bound*var->weight=%f",
+	   var, var->bound, var->weight, min_usage,
+	   var->bound * var->weight);
+      if ((var->bound > 0) && (var->bound * var->weight < min_usage)) {
+	min_usage = var->bound * var->weight;
+	DEBUG1("Updated min_usage=%f", min_usage);
       }
     }
 
@@ -290,15 +524,35 @@ void lmm_solve(lmm_system_t sys)
       int i;
 
       var->value = min_usage / var->weight;
+      DEBUG5("Min usage: %f, Var(%p)->weight: %f, Var(%p)->value: %f ",
+	     min_usage, var, var->weight, var, var->value);
+
 
       /* Update usage */
 
       for (i = 0; i < var->cnsts_number; i++) {
 	elem = &var->cnsts[i];
 	cnst = elem->constraint;
-	cnst->remaining -= elem->value * var->value;
-	cnst->usage -= elem->value / var->weight;
-	remove_active_elem_in_constraint(elem);
+	if (cnst->shared) {
+	  double_update(&(cnst->remaining), elem->value * var->value);
+	  double_update(&(cnst->usage), elem->value / var->weight);
+	  make_elem_inactive(elem);
+	} else {		/* FIXME one day: We recompute usage.... :( */
+	  cnst->usage = 0.0;
+	  make_elem_inactive(elem);
+	  xbt_swag_foreach(elem, elem_list) {
+	    if (elem->variable->weight <= 0)
+	      break;
+	    if (elem->variable->value > 0)
+	      break;
+	    if ((elem->value > 0)) {
+	      if (cnst->usage < elem->value / elem->variable->weight)
+		cnst->usage = elem->value / elem->variable->weight;
+	      DEBUG2("Constraint Usage %p : %f", cnst, cnst->usage);
+	      make_elem_active(elem);
+	    }
+	  }
+	}
       }
       xbt_swag_remove(var, var_list);
     }
@@ -307,47 +561,108 @@ void lmm_solve(lmm_system_t sys)
     cnst_list = &(sys->active_constraint_set);
     min_usage = -1;
     xbt_swag_foreach(cnst, cnst_list) {
-      saturated_constraints_update(sys, cnst, &min_usage);
+      saturated_constraint_set_update(sys, cnst, &min_usage);
     }
-    saturated_variables_update(sys);
+    saturated_variable_set_update(sys);
 
   } while (xbt_swag_size(&(sys->saturated_variable_set)));
 
   sys->modified = 0;
+  if (XBT_LOG_ISENABLED(surf_maxmin, xbt_log_priority_debug)) {
+    lmm_print(sys);
+  }
 }
 
 /* Not a O(1) function */
 
 void lmm_update(lmm_system_t sys, lmm_constraint_t cnst,
-		lmm_variable_t var, xbt_maxmin_float_t value)
+		lmm_variable_t var, double value)
 {
   int i;
-  lmm_element_t elem = NULL;
 
   sys->modified = 1;
   for (i = 0; i < var->cnsts_number; i++)
     if (var->cnsts[i].constraint == cnst) {
-      elem->value = value;
+      var->cnsts[i].value = value;
       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.
+ *
+ */
 void lmm_update_variable_bound(lmm_system_t sys, lmm_variable_t var,
-			       xbt_maxmin_float_t bound)
+			       double bound)
 {
   sys->modified = 1;
   var->bound = bound;
 }
 
+/** \brief Add the value delta to var->df (the sum of latencies).
+ * 
+ *  \param sys the lmm_system_t associated
+ *  \param var the lmm_variable_t which need to updated
+ *  \param delta the variation of the latency
+ * 
+ *  Add the value delta to var->df (the sum of latencys associated to the
+ *  flow). 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 
+ *  (delta != 0) before calling it.
+ *
+ */
+void lmm_update_variable_latency(lmm_system_t sys, lmm_variable_t var,
+				 double delta)
+{
+  sys->modified = 1;
+  var->df += delta;
+}
+
 void lmm_update_variable_weight(lmm_system_t sys, lmm_variable_t var,
-				xbt_maxmin_float_t weight)
+				double weight)
 {
+  int i;
+  lmm_element_t elem;
+
+  if(weight==var->weight) return;
+  XBT_IN3("(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));
+
+  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));
+  }
+  if(!weight)
+    var->value = 0.0;
+
+  XBT_OUT;
+}
+
+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,
-				 xbt_maxmin_float_t bound)
+				 double bound)
 {
   sys->modified = 1;
   cnst->bound = bound;
@@ -355,22 +670,16 @@ void lmm_update_constraint_bound(lmm_system_t sys, lmm_constraint_t cnst,
 
 int lmm_constraint_used(lmm_system_t sys, lmm_constraint_t cnst)
 {
-  return xbt_swag_belongs(cnst,&(sys->active_constraint_set));
+  return xbt_swag_belongs(cnst, &(sys->active_constraint_set));
 }
 
+lmm_constraint_t lmm_get_first_active_constraint(lmm_system_t sys)
+{
+  return xbt_swag_getFirst(&(sys->active_constraint_set));
+}
 
-/* void lmm_print(lmm_system_t sys) */
-/* { */
-/*   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; */
-
-/*   var_list = &(sys->variable_set); */
-/*   xbt_swag_foreach(var, var_list) { */
-/*     printf("%s : {\n",var->id); */
-/*     printf("\t %s : {\n",var->id); */
-/*   } */
-/* } */
+lmm_constraint_t lmm_get_next_active_constraint(lmm_system_t sys,
+						lmm_constraint_t cnst)
+{
+  return xbt_swag_getNext(cnst, (sys->active_constraint_set).offset);
+}