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[simgrid.git] / src / mc / mc_dpor.c
index 267e610..a97440a 100644 (file)
-/* Copyright (c) 2008 Martin Quinson, Cristian Rosa.
-   All rights reserved.                                          */
+/* Copyright (c) 2008-2013. Da 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. */
 
-#include "private.h"
+#include "mc_private.h"
 
 XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_dpor, mc,
                                 "Logging specific to MC DPOR exploration");
 
+xbt_dynar_t visited_states;
+xbt_dict_t first_enabled_state;
+
+static void visited_state_free(mc_visited_state_t state){
+  if(state){
+    MC_free_snapshot(state->system_state);
+    xbt_free(state);
+  }
+}
+
+static void visited_state_free_voidp(void *s){
+  visited_state_free((mc_visited_state_t) * (void **) s);
+}
+
+static mc_visited_state_t visited_state_new(){
+
+  mc_visited_state_t new_state = NULL;
+  new_state = xbt_new0(s_mc_visited_state_t, 1);
+  new_state->heap_bytes_used = mmalloc_get_bytes_used(std_heap);
+  new_state->nb_processes = xbt_swag_size(simix_global->process_list);
+  new_state->system_state = MC_take_snapshot();
+  new_state->num = mc_stats->expanded_states - 1;
+
+  return new_state;
+  
+}
+
+/* Dichotomic search in visited_states dynar. 
+ * States are ordered by the number of processes then the number of bytes used in std_heap */
+
+static int is_visited_state(){
+
+  if(_sg_mc_visited == 0)
+    return -1;
+
+  int raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
+
+  MC_SET_RAW_MEM;
+  mc_visited_state_t new_state = visited_state_new();
+  MC_UNSET_RAW_MEM;
+  
+  if(xbt_dynar_is_empty(visited_states)){
+
+    MC_SET_RAW_MEM;
+    xbt_dynar_push(visited_states, &new_state); 
+    MC_UNSET_RAW_MEM;
+
+    if(raw_mem_set)
+      MC_SET_RAW_MEM;
+
+    return -1;
+
+  }else{
+
+    MC_SET_RAW_MEM;
+    
+    size_t current_bytes_used = new_state->heap_bytes_used;
+    int current_nb_processes = new_state->nb_processes;
+
+    unsigned int cursor = 0;
+    int previous_cursor = 0, next_cursor = 0;
+    int start = 0;
+    int end = xbt_dynar_length(visited_states) - 1;
+
+    mc_visited_state_t state_test = NULL;
+    size_t bytes_used_test;
+    int nb_processes_test;
+    int same_processes_and_bytes_not_found = 1;
+
+    while(start <= end && same_processes_and_bytes_not_found){
+      cursor = (start + end) / 2;
+      state_test = (mc_visited_state_t)xbt_dynar_get_as(visited_states, cursor, mc_visited_state_t);
+      bytes_used_test = state_test->heap_bytes_used;
+      nb_processes_test = state_test->nb_processes;
+      if(nb_processes_test < current_nb_processes)
+        start = cursor + 1;
+      if(nb_processes_test > current_nb_processes)
+        end = cursor - 1; 
+      if(nb_processes_test == current_nb_processes){
+        if(bytes_used_test < current_bytes_used)
+          start = cursor + 1;
+        if(bytes_used_test > current_bytes_used)
+          end = cursor - 1;
+        if(bytes_used_test == current_bytes_used){
+          same_processes_and_bytes_not_found = 0;
+          if(snapshot_compare(new_state->system_state, state_test->system_state) == 0){
+            xbt_dynar_remove_at(visited_states, cursor, NULL);
+            xbt_dynar_insert_at(visited_states, cursor, &new_state);
+            XBT_DEBUG("State %d already visited ! (equal to state %d)", new_state->num, state_test->num);
+            if(raw_mem_set)
+              MC_SET_RAW_MEM;
+            else
+              MC_UNSET_RAW_MEM;
+            return state_test->num;
+          }else{
+            /* Search another state with same number of bytes used in std_heap */
+            previous_cursor = cursor - 1;
+            while(previous_cursor >= 0){
+              state_test = (mc_visited_state_t)xbt_dynar_get_as(visited_states, previous_cursor, mc_visited_state_t);
+              bytes_used_test = state_test->system_state->heap_bytes_used;
+              if(bytes_used_test != current_bytes_used)
+                break;
+              if(snapshot_compare(new_state->system_state, state_test->system_state) == 0){
+                xbt_dynar_remove_at(visited_states, previous_cursor, NULL);
+                xbt_dynar_insert_at(visited_states, previous_cursor, &new_state);
+                XBT_DEBUG("State %d already visited ! (equal to state %d)", new_state->num, state_test->num);
+                if(raw_mem_set)
+                  MC_SET_RAW_MEM;
+                else
+                  MC_UNSET_RAW_MEM;
+                return state_test->num;
+              }
+              previous_cursor--;
+            }
+            next_cursor = cursor + 1;
+            while(next_cursor < xbt_dynar_length(visited_states)){
+              state_test = (mc_visited_state_t)xbt_dynar_get_as(visited_states, next_cursor, mc_visited_state_t);
+              bytes_used_test = state_test->system_state->heap_bytes_used;
+              if(bytes_used_test != current_bytes_used)
+                break;
+              if(snapshot_compare(new_state->system_state, state_test->system_state) == 0){
+                xbt_dynar_remove_at(visited_states, next_cursor, NULL);
+                xbt_dynar_insert_at(visited_states, next_cursor, &new_state);
+                XBT_DEBUG("State %d already visited ! (equal to state %d)", new_state->num, state_test->num);
+                if(raw_mem_set)
+                  MC_SET_RAW_MEM;
+                else
+                  MC_UNSET_RAW_MEM;
+                return state_test->num;
+              }
+              next_cursor++;
+            }
+          }   
+        }
+      }
+    }
+
+    state_test = (mc_visited_state_t)xbt_dynar_get_as(visited_states, cursor, mc_visited_state_t);
+    bytes_used_test = state_test->heap_bytes_used;
+
+    if(bytes_used_test < current_bytes_used)
+      xbt_dynar_insert_at(visited_states, cursor + 1, &new_state);
+    else
+      xbt_dynar_insert_at(visited_states, cursor, &new_state);
+
+    if(xbt_dynar_length(visited_states) > _sg_mc_visited){
+      int min = mc_stats->expanded_states;
+      unsigned int cursor2 = 0;
+      unsigned int index = 0;
+      xbt_dynar_foreach(visited_states, cursor2, state_test){
+        if(state_test->num < min){
+          index = cursor2;
+          min = state_test->num;
+        }
+      }
+      xbt_dynar_remove_at(visited_states, index, NULL);
+    }
+    
+    MC_UNSET_RAW_MEM;
+
+    if(raw_mem_set)
+      MC_SET_RAW_MEM;
+    
+    return -1;
+    
+  }
+}
+
 /**
  *  \brief Initialize the DPOR exploration algorithm
  */
 void MC_dpor_init()
 {
+  
+  int raw_mem_set = (mmalloc_get_current_heap() == raw_heap);
+
   mc_state_t initial_state = NULL;
   smx_process_t process;
   
   /* Create the initial state and push it into the exploration stack */
   MC_SET_RAW_MEM;
+
   initial_state = MC_state_new();
-  xbt_fifo_unshift(mc_stack, initial_state);
+  visited_states = xbt_dynar_new(sizeof(mc_visited_state_t), visited_state_free_voidp);
+
+  first_enabled_state = xbt_dict_new_homogeneous(&xbt_free_f);
+
   MC_UNSET_RAW_MEM;
 
   XBT_DEBUG("**************************************************");
@@ -30,51 +204,75 @@ void MC_dpor_init()
   MC_wait_for_requests();
 
   MC_SET_RAW_MEM;
   /* Get an enabled process and insert it in the interleave set of the initial state */
   xbt_swag_foreach(process, simix_global->process_list){
     if(MC_process_is_enabled(process)){
       MC_state_interleave_process(initial_state, process);
-      break;
+      if(mc_reduce_kind != e_mc_reduce_none)
+        break;
     }
   }
+
+  xbt_fifo_unshift(mc_stack_safety, initial_state);
+
+  /* To ensure the soundness of DPOR, we have to keep a list of 
+     processes which are still enabled at each step of the exploration. 
+     If max depth is reached, we interleave them in the state in which they have 
+     been enabled for the first time. */
+  xbt_swag_foreach(process, simix_global->process_list){
+    if(MC_process_is_enabled(process)){
+      char *key = bprintf("%lu", process->pid);
+      char *data = bprintf("%d", xbt_fifo_size(mc_stack_safety));
+      xbt_dict_set(first_enabled_state, key, data, NULL);
+      xbt_free(key);
+    }
+  }
+
   MC_UNSET_RAW_MEM;
-    
-  /* FIXME: Update Statistics 
-  mc_stats->state_size +=
-      xbt_setset_set_size(initial_state->enabled_transitions); */
+
+  if(raw_mem_set)
+    MC_SET_RAW_MEM;
+  else
+    MC_UNSET_RAW_MEM;
+  
 }
 
 
 /**
- *     \brief Perform the model-checking operation using a depth-first search exploration
+ *   \brief Perform the model-checking operation using a depth-first search exploration
  *         with Dynamic Partial Order Reductions
  */
 void MC_dpor(void)
 {
+
   char *req_str;
-  int value;
-  smx_req_t req = NULL, prev_req = NULL;
-  mc_state_t state = NULL, prev_state = NULL, next_state = NULL;
+  int value, value2;
+  smx_simcall_t req = NULL, prev_req = NULL, req2 = NULL;
+  s_smx_simcall_t req3;
+  mc_state_t state = NULL, prev_state = NULL, next_state = NULL, restore_state=NULL;
   smx_process_t process = NULL;
   xbt_fifo_item_t item = NULL;
+  int pos;
+  int visited_state;
 
-  while (xbt_fifo_size(mc_stack) > 0) {
+  while (xbt_fifo_size(mc_stack_safety) > 0) {
 
     /* Get current state */
     state = (mc_state_t) 
-      xbt_fifo_get_item_content(xbt_fifo_get_first_item(mc_stack));
+      xbt_fifo_get_item_content(xbt_fifo_get_first_item(mc_stack_safety));
 
     XBT_DEBUG("**************************************************");
     XBT_DEBUG("Exploration depth=%d (state=%p)(%u interleave)",
-           xbt_fifo_size(mc_stack), state,
-           MC_state_interleave_size(state));
+              xbt_fifo_size(mc_stack_safety), state,
+              MC_state_interleave_size(state));
 
     /* Update statistics */
     mc_stats->visited_states++;
 
     /* If there are processes to interleave and the maximum depth has not been reached
        then perform one step of the exploration algorithm */
-    if (xbt_fifo_size(mc_stack) < MAX_DEPTH &&
+    if (xbt_fifo_size(mc_stack_safety) <= _sg_mc_max_depth &&
         (req = MC_state_get_request(state, &value))) {
 
       /* Debug information */
@@ -83,455 +281,88 @@ void MC_dpor(void)
         XBT_DEBUG("Execute: %s", req_str);
         xbt_free(req_str);
       }
+        
+      req_str = MC_request_get_dot_output(req, value);
 
       MC_state_set_executed_request(state, req, value);
       mc_stats->executed_transitions++;
 
-      /* Answer the request */
-      SIMIX_request_pre(req, value); /* After this call req is no longer usefull */
-
-      /* Wait for requests (schedules processes) */
-      MC_wait_for_requests();
-
-      /* Create the new expanded state */
       MC_SET_RAW_MEM;
-      next_state = MC_state_new();
-      xbt_fifo_unshift(mc_stack, next_state);
-
-      /* Get an enabled process and insert it in the interleave set of the next state */
-      xbt_swag_foreach(process, simix_global->process_list){
-        if(MC_process_is_enabled(process)){
-          MC_state_interleave_process(next_state, process);
-          break;
-        }
-      }
-      MC_UNSET_RAW_MEM;
-
-      /* FIXME: Update Statistics
-      mc_stats->state_size +=
-          xbt_setset_set_size(next_state->enabled_transitions);*/
-
-      /* Let's loop again */
-
-      /* The interleave set is empty or the maximum depth is reached, let's back-track */
-    } else {
-      XBT_DEBUG("There are no more processes to interleave.");
-
-      /* Trash the current state, no longer needed */
-      MC_SET_RAW_MEM;
-      xbt_fifo_shift(mc_stack);
-      MC_state_delete(state);
-      MC_UNSET_RAW_MEM;
-
-      /* Check for deadlocks */
-      if(MC_deadlock_check()){
-        MC_show_deadlock(NULL);
-        return;
-      }
-
-      MC_SET_RAW_MEM;
-      /* Traverse the stack backwards until a state with a non empty interleave
-         set is found, deleting all the states that have it empty in the way.
-         For each deleted state, check if the request that has generated it 
-         (from it's predecesor state), depends on any other previous request 
-         executed before it. If it does then add it to the interleave set of the
-         state that executed that previous request. */
-      while ((state = xbt_fifo_shift(mc_stack)) != NULL) {
-        req = MC_state_get_internal_request(state);
-        xbt_fifo_foreach(mc_stack, item, prev_state, mc_state_t) {
-          if(MC_request_depend(req, MC_state_get_internal_request(prev_state))){
-            if(XBT_LOG_ISENABLED(mc_dpor, xbt_log_priority_debug)){
-              XBT_DEBUG("Dependent Transitions:");
-              prev_req = MC_state_get_executed_request(prev_state, &value);
-              req_str = MC_request_to_string(prev_req, value);
-              XBT_DEBUG("%s (state=%p)", req_str, prev_state);
-              xbt_free(req_str);
-              prev_req = MC_state_get_executed_request(state, &value);
-              req_str = MC_request_to_string(prev_req, value);
-              XBT_DEBUG("%s (state=%p)", req_str, state);
-              xbt_free(req_str);              
-            }
-
-            if(!MC_state_process_is_done(prev_state, req->issuer))
-              MC_state_interleave_process(prev_state, req->issuer);
-            else
-              XBT_DEBUG("Process %p is in done set", req->issuer);
-
-            break;
-          }
-        }
-        if (MC_state_interleave_size(state)) {
-          /* We found a back-tracking point, let's loop */
-          xbt_fifo_unshift(mc_stack, state);
-          XBT_DEBUG("Back-tracking to depth %d", xbt_fifo_size(mc_stack));
-          MC_UNSET_RAW_MEM;
-          MC_replay(mc_stack);
-          break;
-        } else {
-          MC_state_delete(state);
-        }
-      }
+      char *key = bprintf("%lu", req->issuer->pid);
+      xbt_dict_remove(first_enabled_state, key); 
+      xbt_free(key);
       MC_UNSET_RAW_MEM;
-    }
-  }
-  MC_UNSET_RAW_MEM;
-  return;
-}
-
-
-/********************* DPOR without replay *********************/
-
-mc_state_ws_t new_state_ws(mc_snapshot_t s, mc_state_t gs){
-  mc_state_ws_t sws = NULL;
-  sws = xbt_new0(s_mc_state_ws_t, 1);
-  sws->system_state = s;
-  sws->graph_state = gs;
-  return sws;
-}
-
-void MC_dpor_with_restore_snapshot_init(){
-
-  XBT_DEBUG("**************************************************");
-  XBT_DEBUG("DPOR (with restore snapshot) init");
-  XBT_DEBUG("**************************************************");
-
-  mc_state_t initial_graph_state;
-  smx_process_t process; 
-  mc_snapshot_t initial_system_snapshot;
-  mc_state_ws_t initial_state ;
-  
-  MC_wait_for_requests();
-
-  MC_SET_RAW_MEM;
-
-  initial_system_snapshot = xbt_new0(s_mc_snapshot_t, 1);
-
-  initial_graph_state = MC_state_new();
-  xbt_swag_foreach(process, simix_global->process_list){
-    if(MC_process_is_enabled(process)){
-      MC_state_interleave_process(initial_graph_state, process);
-      break;
-    }
-  }
-
-  MC_take_snapshot(initial_system_snapshot);
-
-  initial_state = new_state_ws(initial_system_snapshot, initial_graph_state);
-  xbt_fifo_unshift(mc_snapshot_stack, initial_state);
-
-  MC_UNSET_RAW_MEM;
-         
-  MC_dpor_with_restore_snapshot();
-
-}
-
-void MC_dpor_with_restore_snapshot(){
-
-  smx_process_t process = NULL;
-  
-  if(xbt_fifo_size(mc_snapshot_stack) == 0)
-    return;
-
-  int value;
-  mc_state_t next_graph_state = NULL;
-  smx_req_t req = NULL, prev_req = NULL;
-  char *req_str;
-  xbt_fifo_item_t item = NULL;
-
-  mc_snapshot_t next_snapshot;
-  mc_state_ws_t current_state;
-  mc_state_ws_t prev_state;
-  mc_state_ws_t next_state;
-  while(xbt_fifo_size(mc_snapshot_stack) > 0){
-
-    current_state = (mc_state_ws_t)xbt_fifo_get_item_content(xbt_fifo_get_first_item(mc_snapshot_stack));
-
-    
-    XBT_DEBUG("**************************************************");
-    XBT_DEBUG("Depth : %d, State : %p , %u interleave", xbt_fifo_size(mc_snapshot_stack),current_state, MC_state_interleave_size(current_state->graph_state));
-    
-
-    if((xbt_fifo_size(mc_snapshot_stack) < MAX_DEPTH) && (req = MC_state_get_request(current_state->graph_state, &value))){
-
-      /* Debug information */
-      if(XBT_LOG_ISENABLED(mc_dpor, xbt_log_priority_debug)){
-       req_str = MC_request_to_string(req, value);
-       XBT_DEBUG("Execute: %s", req_str);
-       xbt_free(req_str);
-      }
 
-      MC_state_set_executed_request(current_state->graph_state, req, value);
+      MC_state_set_executed_request(state, req, value);
 
       /* Answer the request */
-      SIMIX_request_pre(req, value);
-      
+      SIMIX_simcall_pre(req, value); /* After this call req is no longer usefull */
+
       /* Wait for requests (schedules processes) */
       MC_wait_for_requests();
-      
-      /* Create the new expanded graph_state */
-      MC_SET_RAW_MEM;
-      
-      next_graph_state = MC_state_new();
-      
-      /* Get an enabled process and insert it in the interleave set of the next graph_state */
-      xbt_swag_foreach(process, simix_global->process_list){
-       if(MC_process_is_enabled(process)){
-         MC_state_interleave_process(next_graph_state, process);
-         break;
-       }
-      }
-
-      next_snapshot = xbt_new0(s_mc_snapshot_t, 1);
-      MC_take_snapshot(next_snapshot);
 
-      next_state = new_state_ws(next_snapshot, next_graph_state);
-      xbt_fifo_unshift(mc_snapshot_stack, next_state);
-      
-      MC_UNSET_RAW_MEM;
-
-    }else{
-      XBT_DEBUG("There are no more processes to interleave.");
-      
-      /* Trash the current state, no longer needed */
+      /* Create the new expanded state */
       MC_SET_RAW_MEM;
-      xbt_fifo_shift(mc_snapshot_stack);
-      MC_UNSET_RAW_MEM;
-
-      while((current_state = xbt_fifo_shift(mc_snapshot_stack)) != NULL){
-       req = MC_state_get_internal_request(current_state->graph_state);
-       xbt_fifo_foreach(mc_snapshot_stack, item, prev_state, mc_state_ws_t) {
-          if(MC_request_depend(req, MC_state_get_internal_request(prev_state->graph_state))){
-            if(XBT_LOG_ISENABLED(mc_dpor, xbt_log_priority_debug)){
-              XBT_DEBUG("Dependent Transitions:");
-              prev_req = MC_state_get_executed_request(prev_state->graph_state, &value);
-              req_str = MC_request_to_string(prev_req, value);
-              XBT_DEBUG("%s (state=%p)", req_str, prev_state->graph_state);
-              xbt_free(req_str);
-              prev_req = MC_state_get_executed_request(current_state->graph_state, &value);
-              req_str = MC_request_to_string(prev_req, value);
-              XBT_DEBUG("%s (state=%p)", req_str, current_state->graph_state);
-              xbt_free(req_str);              
-            }
 
-            if(!MC_state_process_is_done(prev_state->graph_state, req->issuer)){
-              MC_state_interleave_process(prev_state->graph_state, req->issuer);
-             
-           } else {
-              XBT_DEBUG("Process %p is in done set", req->issuer);
-           }
+      next_state = MC_state_new();
 
-            break;
+      if((visited_state = is_visited_state()) == -1){
+     
+        /* Get an enabled process and insert it in the interleave set of the next state */
+        xbt_swag_foreach(process, simix_global->process_list){
+          if(MC_process_is_enabled(process)){
+            MC_state_interleave_process(next_state, process);
+            if(mc_reduce_kind != e_mc_reduce_none)
+              break;
           }
         }
 
-       if(MC_state_interleave_size(current_state->graph_state)){
-         MC_restore_snapshot(current_state->system_state);
-         xbt_fifo_unshift(mc_snapshot_stack, current_state);
-         XBT_DEBUG("Back-tracking to depth %d", xbt_fifo_size(mc_snapshot_stack));
-         MC_UNSET_RAW_MEM;
-         break;
-       }
-      }
-
-      MC_UNSET_RAW_MEM;
-
-    } 
-  }
-  MC_UNSET_RAW_MEM;
-  return;
-}
-
-
-
-/************ DPOR 2 (invisible and independant transitions) ************/
-
-
-void MC_dpor2_init(xbt_automaton_t a)
-{
-  mc_pair_t initial_pair = NULL;
-  mc_state_t initial_graph_state = NULL;
-  mc_snapshot_t initial_system_state = NULL;
-  xbt_state_t initial_automaton_state = NULL;
-  smx_process_t process;
-  
-
-  MC_SET_RAW_MEM;
-  initial_graph_state = MC_state_new();
-  MC_UNSET_RAW_MEM;
-
-  /* Wait for requests (schedules processes) */
-  MC_wait_for_requests();
-
-  MC_SET_RAW_MEM;
-  xbt_swag_foreach(process, simix_global->process_list){
-    if(MC_process_is_enabled(process)){
-      MC_state_interleave_process(initial_graph_state, process);
-      break;
-    }
-  }
-  MC_UNSET_RAW_MEM;
-
-  unsigned int cursor = 0;
-  unsigned int cursor2 = 0;
-  xbt_state_t automaton_state = NULL;
-  int res;
-  xbt_transition_t transition_succ;
-
-  xbt_dynar_foreach(a->states, cursor, automaton_state){
-    if(automaton_state->type == -1){
-      xbt_dynar_foreach(automaton_state->out, cursor2, transition_succ){
-       res = MC_automaton_evaluate_label(a, transition_succ->label);
-       if((res == 1) || (res == 2)){
-         initial_automaton_state = transition_succ->dst;
-         break;
-       }
-      }
-    }
-
-    if(xbt_fifo_size(mc_snapshot_stack) > 0)
-      break;
-  }
-
-  if(xbt_fifo_size(mc_snapshot_stack) == 0){
-    cursor = 0;
-    xbt_dynar_foreach(a->states, cursor, automaton_state){
-      if(automaton_state->type == -1){
-       initial_automaton_state = automaton_state;
-       break;
-      }
-    }
-  }
-
-  MC_SET_RAW_MEM;
-  initial_system_state = xbt_new0(s_mc_snapshot_t, 1);
-  MC_take_snapshot(initial_system_state);
-  initial_pair = new_pair(initial_system_state, initial_graph_state, initial_automaton_state);
-  xbt_fifo_unshift(mc_snapshot_stack, initial_pair);
-  MC_UNSET_RAW_MEM;
-
-  XBT_DEBUG("**************************************************");
-  XBT_DEBUG("Initial pair");
-
-  MC_dpor2(a, 0);
-    
-}
-
-
-void MC_dpor2(xbt_automaton_t a, int search_cycle)
-{
-  char *req_str;
-  int value;
-  smx_req_t req = NULL, prev_req = NULL;
-  mc_state_t next_graph_state = NULL;
-  mc_snapshot_t next_system_state = NULL;
-  xbt_state_t next_automaton_state = NULL;
-  xbt_transition_t transition_succ;
-  unsigned int cursor;
-  int res;
-  mc_pair_t pair = NULL, next_pair = NULL, prev_pair = NULL;
-  smx_process_t process = NULL;
-  xbt_fifo_item_t item = NULL;
-
-  while (xbt_fifo_size(mc_snapshot_stack) > 0) {
-
-    /* Get current pair */
-    pair = (mc_pair_t) 
-      xbt_fifo_get_item_content(xbt_fifo_get_first_item(mc_snapshot_stack));
-
-    XBT_DEBUG("**************************************************");
-    XBT_DEBUG("Exploration depth=%d (pair=%p)(%u interleave)",
-           xbt_fifo_size(mc_snapshot_stack), pair,
-           MC_state_interleave_size(pair->graph_state));
-
-    /* Update statistics */
-    mc_stats_pair->visited_pairs++;
+        if(_sg_mc_checkpoint && ((xbt_fifo_size(mc_stack_safety) + 1) % _sg_mc_checkpoint == 0)){
+          next_state->system_state = MC_take_snapshot();
+        }
 
-    /* Test acceptance pair and acceptance cycle*/
+        if(dot_output != NULL)
+          fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num, next_state->num, req_str);
 
-    if(pair->automaton_state->type == 1){
-      if(search_cycle == 0){
-       set_pair_reached(pair);
-       XBT_DEBUG("Acceptance pair : graph=%p, automaton=%p(%s)", pair->graph_state, pair->automaton_state, pair->automaton_state->id);
       }else{
-       if(reached(pair) == 1){
-         XBT_INFO("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
-         XBT_INFO("|             ACCEPTANCE CYCLE            |");
-         XBT_INFO("*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*");
-         XBT_INFO("Counter-example that violates formula :");
-         MC_show_snapshot_stack(mc_snapshot_stack);
-         MC_dump_snapshot_stack(mc_snapshot_stack);
-         MC_print_statistics_pairs(mc_stats_pair);
-         exit(0);
-       }
-      }
-    }
 
-    /* If there are processes to interleave and the maximum depth has not been reached
-       then perform one step of the exploration algorithm */
-    if (xbt_fifo_size(mc_snapshot_stack) < MAX_DEPTH &&
-        (req = MC_state_get_request(pair->graph_state, &value))) {
+        if(dot_output != NULL)
+          fprintf(dot_output, "\"%d\" -> \"%d\" [%s];\n", state->num, visited_state, req_str);
 
-      /* Debug information */
-      if(XBT_LOG_ISENABLED(mc_dpor, xbt_log_priority_debug)){
-        req_str = MC_request_to_string(req, value);
-        XBT_DEBUG("Execute: %s", req_str);
-        xbt_free(req_str);
       }
 
-      MC_state_set_executed_request(pair->graph_state, req, value);
-      //mc_stats_pairs->executed_transitions++;
-
-      /* Answer the request */
-      SIMIX_request_pre(req, value); /* After this call req is no longer usefull */
-
-      /* Wait for requests (schedules processes) */
-      MC_wait_for_requests();
-
-      /* Create the new expanded state */
-      MC_SET_RAW_MEM;
-      next_graph_state = MC_state_new();
+      xbt_fifo_unshift(mc_stack_safety, next_state);
 
-      /* Get an enabled process and insert it in the interleave set of the next state */
+      /* Insert in dict all enabled processes, if not included yet */
       xbt_swag_foreach(process, simix_global->process_list){
         if(MC_process_is_enabled(process)){
-          MC_state_interleave_process(next_graph_state, process);
-          break;
+          char *key = bprintf("%lu", process->pid);
+          if(xbt_dict_get_or_null(first_enabled_state, key) == NULL){
+            char *data = bprintf("%d", xbt_fifo_size(mc_stack_safety));
+            xbt_dict_set(first_enabled_state, key, data, NULL); 
+          }
+          xbt_free(key);
         }
       }
 
-      next_system_state = xbt_new0(s_mc_snapshot_t, 1);
-      MC_take_snapshot(next_system_state);
       MC_UNSET_RAW_MEM;
 
-      cursor = 0;
-      xbt_dynar_foreach(pair->automaton_state->out, cursor, transition_succ){
-       res = MC_automaton_evaluate_label(a, transition_succ->label);   
-       if((res == 1) || (res == 2)){ // enabled transition in automaton
-         next_automaton_state = transition_succ->dst;
-         break;
-       }
-      }
-
-      if(next_automaton_state == NULL){
-       next_automaton_state = pair->automaton_state;
-      }
-      
-      MC_SET_RAW_MEM;
-      next_pair = new_pair(next_system_state, next_graph_state, next_automaton_state);
-      xbt_fifo_unshift(mc_snapshot_stack, next_pair);
-      MC_UNSET_RAW_MEM;
+      xbt_free(req_str);
 
       /* Let's loop again */
 
       /* The interleave set is empty or the maximum depth is reached, let's back-track */
     } else {
-      XBT_DEBUG("There are no more processes to interleave.");
+
+      if(xbt_fifo_size(mc_stack_safety) == _sg_mc_max_depth)  
+        XBT_WARN("/!\\ Max depth reached ! /!\\ ");
+      else
+        XBT_DEBUG("There are no more processes to interleave.");
 
       /* Trash the current state, no longer needed */
       MC_SET_RAW_MEM;
-      xbt_fifo_shift(mc_snapshot_stack);
-      //MC_state_delete(state);
+      xbt_fifo_shift(mc_stack_safety);
+      MC_state_delete(state);
       MC_UNSET_RAW_MEM;
 
       /* Check for deadlocks */
@@ -547,44 +378,110 @@ void MC_dpor2(xbt_automaton_t a, int search_cycle)
          (from it's predecesor state), depends on any other previous request 
          executed before it. If it does then add it to the interleave set of the
          state that executed that previous request. */
-      while ((pair = xbt_fifo_shift(mc_snapshot_stack)) != NULL) {
-        req = MC_state_get_internal_request(pair->graph_state);
-        xbt_fifo_foreach(mc_snapshot_stack, item, prev_pair, mc_pair_t) {
-          if(MC_request_depend(req, MC_state_get_internal_request(prev_pair->graph_state))){
-            if(XBT_LOG_ISENABLED(mc_dpor, xbt_log_priority_debug)){
-              XBT_DEBUG("Dependent Transitions:");
-              prev_req = MC_state_get_executed_request(prev_pair->graph_state, &value);
-              req_str = MC_request_to_string(prev_req, value);
-              XBT_DEBUG("%s (pair=%p)", req_str, prev_pair);
-              xbt_free(req_str);
-              prev_req = MC_state_get_executed_request(pair->graph_state, &value);
-              req_str = MC_request_to_string(prev_req, value);
-              XBT_DEBUG("%s (pair=%p)", req_str, pair);
-              xbt_free(req_str);              
+      
+      while ((state = xbt_fifo_shift(mc_stack_safety)) != NULL) {
+        if(mc_reduce_kind != e_mc_reduce_none){
+          req = MC_state_get_internal_request(state);
+          /* If max_depth reached, check only for the last state if the request that has generated
+             it, depends on any other processes still enabled when max_depth reached */
+          if(xbt_fifo_size(mc_stack_safety) == _sg_mc_max_depth - 1){
+            req3 = *req;
+            xbt_swag_foreach(process, simix_global->process_list){
+              if(MC_process_is_enabled(process) && !MC_state_process_is_done(state, process)){
+                MC_state_interleave_process(state, process);
+                req2 = MC_state_get_request(state, &value2);
+                MC_state_set_executed_request(state, req2, value2);
+                req2 = MC_state_get_internal_request(state);
+                if(MC_request_depend(&req3, req2)){
+                  if(XBT_LOG_ISENABLED(mc_dpor, xbt_log_priority_debug)){
+                    XBT_DEBUG("Dependent Transitions:");
+                    req_str = MC_request_to_string(&req3, value);
+                    XBT_DEBUG("%s (state=%p)", req_str, state);
+                    xbt_free(req_str);
+                    req_str = MC_request_to_string(req2, value);
+                    XBT_DEBUG("%s (state=%p)", req_str, state);
+                    xbt_free(req_str);              
+                  } 
+                  MC_state_interleave_process(state, process);
+                  break;
+                }
+              }
             }
+          }
+          xbt_fifo_foreach(mc_stack_safety, item, prev_state, mc_state_t) {
+            if(MC_request_depend(req, MC_state_get_internal_request(prev_state))){
+              if(XBT_LOG_ISENABLED(mc_dpor, xbt_log_priority_debug)){
+                XBT_DEBUG("Dependent Transitions:");
+                prev_req = MC_state_get_executed_request(prev_state, &value);
+                req_str = MC_request_to_string(prev_req, value);
+                XBT_DEBUG("%s (state=%p)", req_str, prev_state);
+                xbt_free(req_str);
+                prev_req = MC_state_get_executed_request(state, &value);
+                req_str = MC_request_to_string(prev_req, value);
+                XBT_DEBUG("%s (state=%p)", req_str, state);
+                xbt_free(req_str);              
+              }
+
+              if(!MC_state_process_is_done(prev_state, req->issuer))
+                MC_state_interleave_process(prev_state, req->issuer);
+              else
+                XBT_DEBUG("Process %p is in done set", req->issuer);
+
+              break;
+
+            }else if(req->issuer == MC_state_get_internal_request(prev_state)->issuer){
+
+              XBT_DEBUG("Simcall %d and %d with same issuer", req->call, MC_state_get_internal_request(prev_state)->call);
+              break;
 
-            if(!MC_state_process_is_done(prev_pair->graph_state, req->issuer))
-              MC_state_interleave_process(prev_pair->graph_state, req->issuer);
-            else
-              XBT_DEBUG("Process %p is in done set", req->issuer);
-
-            break;
+            }
           }
         }
-        if (MC_state_interleave_size(pair->graph_state)) {
+             
+        if (MC_state_interleave_size(state)) {
           /* We found a back-tracking point, let's loop */
-         MC_restore_snapshot(pair->system_state);
-          xbt_fifo_unshift(mc_snapshot_stack, pair);
-          XBT_DEBUG("Back-tracking to depth %d", xbt_fifo_size(mc_snapshot_stack));
-          MC_UNSET_RAW_MEM;
+          if(_sg_mc_checkpoint){
+            if(state->system_state != NULL){
+              MC_restore_snapshot(state->system_state);
+              xbt_fifo_unshift(mc_stack_safety, state);
+              MC_UNSET_RAW_MEM;
+            }else{
+              pos = xbt_fifo_size(mc_stack_safety);
+              item = xbt_fifo_get_first_item(mc_stack_safety);
+              while(pos>0){
+                restore_state = (mc_state_t) xbt_fifo_get_item_content(item);
+                if(restore_state->system_state != NULL){
+                  break;
+                }else{
+                  item = xbt_fifo_get_next_item(item);
+                  pos--;
+                }
+              }
+              MC_restore_snapshot(restore_state->system_state);
+              xbt_fifo_unshift(mc_stack_safety, state);
+              MC_UNSET_RAW_MEM;
+              MC_replay(mc_stack_safety, pos);
+            }
+          }else{
+            xbt_fifo_unshift(mc_stack_safety, state);
+            MC_UNSET_RAW_MEM;
+            MC_replay(mc_stack_safety, -1);
+          }
+          XBT_DEBUG("Back-tracking to depth %d", xbt_fifo_size(mc_stack_safety));
           break;
         } else {
-          //MC_state_delete(state);
+          MC_state_delete(state);
         }
       }
       MC_UNSET_RAW_MEM;
     }
   }
-  MC_UNSET_RAW_MEM;
+  MC_print_statistics(mc_stats);
+  MC_UNSET_RAW_MEM;  
+
   return;
 }
+
+
+
+