X-Git-Url: http://info.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/e1b1f93df3f76ae35629926c2f7014f301bfceeb..362b4dbfe18e585af36789119acafa5d5350fa20:/examples/msg/chord/chord.c

diff --git a/examples/msg/chord/chord.c b/examples/msg/chord/chord.c
index 606a649704..de95ba8c02 100644
--- a/examples/msg/chord/chord.c
+++ b/examples/msg/chord/chord.c
@@ -1,3 +1,4 @@
+
 /* Copyright (c) 2010. The SimGrid Team.
  * All rights reserved.                                                     */
 
@@ -5,359 +6,923 @@
  * under the terms of the license (GNU LGPL) which comes with this package. */
 
 #include <stdio.h>
-#include <math.h>
-#include "msg/msg.h"            /* Yeah! If you want to use msg, you need to include msg/msg.h */
-#include "xbt/sysdep.h"         /* calloc, printf */
-
-/* Create a log channel to have nice outputs. */
+#include "msg/msg.h"
 #include "xbt/log.h"
 #include "xbt/asserts.h"
-XBT_LOG_NEW_DEFAULT_CATEGORY(msg_test,
+#include "simgrid/modelchecker.h"
+#include "xbt/xbt_os_time.h"
+
+XBT_LOG_NEW_DEFAULT_CATEGORY(msg_chord,
                              "Messages specific for this msg example");
-#define KEY_BITS  6
-#define CHORD_NB_KEYS 64
-/*
-* Finger Element
-*/
-typedef struct{
-	int id;
-	const char *host_name;
-	const char *mailbox;
-}finger_elem;
 
-/*
- * Node Data
+#define COMM_SIZE 10
+#define COMP_SIZE 0
+#define MAILBOX_NAME_SIZE 10
+
+static int nb_bits = 24;
+static int nb_keys = 0;
+static int timeout = 50;
+static int max_simulation_time = 1000;
+static int periodic_stabilize_delay = 20;
+static int periodic_fix_fingers_delay = 120;
+static int periodic_check_predecessor_delay = 120;
+static int periodic_lookup_delay = 10;
+
+extern long int smx_total_comms;
+
+/**
+ * Finger element.
+ */
+typedef struct finger {
+  int id;
+  char mailbox[MAILBOX_NAME_SIZE]; // string representation of the id
+} s_finger_t, *finger_t;
+
+/**
+ * Node data.
+ */
+typedef struct node {
+  int id;                                 // my id
+  char mailbox[MAILBOX_NAME_SIZE];        // my mailbox name (string representation of the id)
+  s_finger_t *fingers;                    // finger table, of size nb_bits (fingers[0] is my successor)
+  int pred_id;                            // predecessor id
+  char pred_mailbox[MAILBOX_NAME_SIZE];   // predecessor's mailbox name
+  int next_finger_to_fix;                 // index of the next finger to fix in fix_fingers()
+  msg_comm_t comm_receive;                // current communication to receive
+  double last_change_date;                // last time I changed a finger or my predecessor
+} s_node_t, *node_t;
+
+/**
+ * Types of tasks exchanged between nodes.
+ */
+typedef enum {
+  TASK_FIND_SUCCESSOR,
+  TASK_FIND_SUCCESSOR_ANSWER,
+  TASK_GET_PREDECESSOR,
+  TASK_GET_PREDECESSOR_ANSWER,
+  TASK_NOTIFY,
+  TASK_SUCCESSOR_LEAVING,
+  TASK_PREDECESSOR_LEAVING
+} e_task_type_t;
+
+/**
+ * Data attached with the tasks sent and received
  */
-typedef struct{
-	int id; // my id
-	const char *host_name; //my host name
-	const char* mailbox; //my mailbox
-	int fingers_nb; // size of finger list
-	finger_elem* fingers; // finger list  [ fingers[0] >> Successor
-	int next; //next finger to fix
-	int pred_id; // predecessor id
-	const char* pred_host_name; // predecessor host name
-	const char* pred_mailbox; // predecessor mailbox
-}data_node;
-
-//global;
-
-int get_node_from_key(int key);
-int node(int argc, char *argv[]);
-int sender(int argc,char *argv[]);
-void find_successor_node(data_node *my_data, m_task_t join_task);
-finger_elem find_finger_elem(data_node* my_data, int id);
-const char* find_closest_preceding(data_node* n_node, int id); //return a mailbox
-int get_successor_id(m_host_t);
-//need by qsort function
-int compare (const void * a, const void * b)
+typedef struct task_data {
+  e_task_type_t type;                     // type of task
+  int request_id;                         // id paramater (used by some types of tasks)
+  int request_finger;                     // finger parameter (used by some types of tasks)
+  int answer_id;                          // answer (used by some types of tasks)
+  char answer_to[MAILBOX_NAME_SIZE];      // mailbox to send an answer to (if any)
+  const char* issuer_host_name;           // used for logging
+} s_task_data_t, *task_data_t;
+
+static int *powers2;
+
+// utility functions
+static void chord_initialize(void);
+static void chord_exit(void);
+static int normalize(int id);
+static int is_in_interval(int id, int start, int end);
+static void get_mailbox(int host_id, char* mailbox);
+static void task_free(void* task);
+static void print_finger_table(node_t node);
+static void set_finger(node_t node, int finger_index, int id);
+static void set_predecessor(node_t node, int predecessor_id);
+
+// process functions
+static int node(int argc, char *argv[]);
+static void handle_task(node_t node, m_task_t task);
+
+// Chord core
+static void create(node_t node);
+static int join(node_t node, int known_id);
+static void leave(node_t node);
+static int find_successor(node_t node, int id);
+static int remote_find_successor(node_t node, int ask_to_id, int id);
+static int remote_get_predecessor(node_t node, int ask_to_id);
+static int closest_preceding_node(node_t node, int id);
+static void stabilize(node_t node);
+static void notify(node_t node, int predecessor_candidate_id);
+static void remote_notify(node_t node, int notify_to, int predecessor_candidate_id);
+static void fix_fingers(node_t node);
+static void check_predecessor(node_t node);
+static void random_lookup(node_t);
+static void quit_notify(node_t node, int to);
+
+/**
+ * \brief Global initialization of the Chord simulation.
+ */
+static void chord_initialize(void)
 {
-  return ( *(int*)a - *(int*)b );
+  // compute the powers of 2 once for all
+  powers2 = xbt_new(int, nb_bits);
+  int pow = 1;
+  int i;
+  for (i = 0; i < nb_bits; i++) {
+    powers2[i] = pow;
+    pow = pow << 1;
+  }
+  nb_keys = pow;
+  XBT_DEBUG("Sets nb_keys to %d", nb_keys);
 }
 
-MSG_error_t test_all(const char *platform_file,
-                     const char *application_file);
+static void chord_exit(void)
+{
+  xbt_free(powers2);
+}
 
-static int is_in_interval(unsigned int id, unsigned int start, unsigned int end) {
+/**
+ * \brief Turns an id into an equivalent id in [0, nb_keys).
+ * \param id an id
+ * \return the corresponding normalized id
+ */
+static int normalize(int id)
+{
+  // like id % nb_keys, but works with negatives numbers (and faster)
+  return id & (nb_keys - 1);
+}
 
-id = id % CHORD_NB_KEYS;
-start = start % CHORD_NB_KEYS;
-end = end % CHORD_NB_KEYS;
+/**
+ * \brief Returns whether an id belongs to the interval [start, end].
+ *
+ * The parameters are noramlized to make sure they are between 0 and nb_keys - 1).
+ * 1 belongs to [62, 3]
+ * 1 does not belong to [3, 62]
+ * 63 belongs to [62, 3]
+ * 63 does not belong to [3, 62]
+ * 24 belongs to [21, 29]
+ * 24 does not belong to [29, 21]
+ *
+ * \param id id to check
+ * \param start lower bound
+ * \param end upper bound
+ * \return a non-zero value if id in in [start, end]
+ */
+static int is_in_interval(int id, int start, int end)
+{
+  id = normalize(id);
+  start = normalize(start);
+  end = normalize(end);
+
+  // make sure end >= start and id >= start
+  if (end < start) {
+    end += nb_keys;
+  }
+
+  if (id < start) {
+    id += nb_keys;
+  }
 
-/* make sure end >= start and id >= start */
-if (end < start) {
-end += CHORD_NB_KEYS;
+  return id <= end;
 }
 
-if (id < start) {
-id += CHORD_NB_KEYS;
+/**
+ * \brief Gets the mailbox name of a host given its chord id.
+ * \param node_id id of a node
+ * \param mailbox pointer to where the mailbox name should be written
+ * (there must be enough space)
+ */
+static void get_mailbox(int node_id, char* mailbox)
+{
+  snprintf(mailbox, MAILBOX_NAME_SIZE - 1, "%d", node_id);
+}
+
+/**
+ * \brief Frees the memory used by a task.
+ * \param task the MSG task to destroy
+ */
+static void task_free(void* task)
+{
+  // TODO add a parameter data_free_function to MSG_task_create?
+  xbt_free(MSG_task_get_data(task));
+  MSG_task_destroy(task);
 }
 
-return id < end;
+/**
+ * \brief Displays the finger table of a node.
+ * \param node a node
+ */
+static void print_finger_table(node_t node)
+{
+  if (XBT_LOG_ISENABLED(msg_chord, xbt_log_priority_verbose)) {
+    int i;
+    XBT_VERB("My finger table:");
+    XBT_VERB("Start | Succ ");
+    for (i = 0; i < nb_bits; i++) {
+      XBT_VERB(" %3d  | %3d ", (node->id + powers2[i]) % nb_keys, node->fingers[i].id);
+    }
+    XBT_VERB("Predecessor: %d", node->pred_id);
+  }
 }
 
+/**
+ * \brief Sets a finger of the current node.
+ * \param node the current node
+ * \param finger_index index of the finger to set (0 to nb_bits - 1)
+ * \param id the id to set for this finger
+ */
+static void set_finger(node_t node, int finger_index, int id)
+{
+  if (id != node->fingers[finger_index].id) {
+    node->fingers[finger_index].id = id;
+    get_mailbox(id, node->fingers[finger_index].mailbox);
+    node->last_change_date = MSG_get_clock();
+    XBT_DEBUG("My new finger #%d is %d", finger_index, id);
+  }
+}
 
-/*
- * Node Function
+/**
+ * \brief Sets the predecessor of the current node.
+ * \param node the current node
+ * \param id the id to predecessor, or -1 to unset the predecessor
  */
+static void set_predecessor(node_t node, int predecessor_id)
+{
+  if (predecessor_id != node->pred_id) {
+    node->pred_id = predecessor_id;
+
+    if (predecessor_id != -1) {
+      get_mailbox(predecessor_id, node->pred_mailbox);
+    }
+    node->last_change_date = MSG_get_clock();
+
+    XBT_DEBUG("My new predecessor is %d", predecessor_id);
+  }
+}
 
-/*<process host="host_name" function="node">
-   <argument value="id"/> <!-- my id -->
-   <argument value="mailbox"/> <!-- mailbox -->
-   <!-- optional -->
-   <argument value="known_host_name" />
-   <argument value="knwon_host_mailbox" />
-   >argument value="time_to_sleep"/>
-  </process>
-*/
-static int cpt = 0;
+/**
+ * \brief Node Function
+ * Arguments:
+ * - my id
+ * - the id of a guy I know in the system (except for the first node)
+ * - the time to sleep before I join (except for the first node)
+ */
 int node(int argc, char *argv[])
 {
-	m_task_t recv_request = NULL;
-	int first = 1;
-	int joined = 0;
-	int res,create = 0;
-	if ( argc == 3)   // if no known host are declared >>> first node >>> create chord ring
-	{
-		create = 1;
+  /* Reduce the run size for the MC */
+  if(MC_IS_ENABLED){
+    periodic_stabilize_delay = 8;
+    periodic_fix_fingers_delay = 8;
+    periodic_check_predecessor_delay = 8;
+  }
+
+  double init_time = MSG_get_clock();
+  m_task_t task_received = NULL;
+  int i;
+  int join_success = 0;
+  double deadline;
+  double next_stabilize_date = init_time + periodic_stabilize_delay;
+  double next_fix_fingers_date = init_time + periodic_fix_fingers_delay;
+  double next_check_predecessor_date = init_time + periodic_check_predecessor_delay;
+  double next_lookup_date = init_time + periodic_lookup_delay;
+
+  xbt_assert(argc == 3 || argc == 5, "Wrong number of arguments for this node");
+
+  // initialize my node
+  s_node_t node = {0};
+  node.id = atoi(argv[1]);
+  get_mailbox(node.id, node.mailbox);
+  node.next_finger_to_fix = 0;
+  node.fingers = xbt_new0(s_finger_t, nb_bits);
+  node.last_change_date = init_time;
+
+  for (i = 0; i < nb_bits; i++) {
+    node.fingers[i].id = -1;
+    set_finger(&node, i, node.id);
+  }
+
+  if (argc == 3) { // first ring
+    deadline = atof(argv[2]);
+    create(&node);
+    join_success = 1;
+  }
+  else {
+    int known_id = atoi(argv[2]);
+    //double sleep_time = atof(argv[3]);
+    deadline = atof(argv[4]);
+
+    /*
+    // sleep before starting
+    XBT_DEBUG("Let's sleep during %f", sleep_time);
+    MSG_process_sleep(sleep_time);
+    */
+    XBT_DEBUG("Hey! Let's join the system.");
+
+    join_success = join(&node, known_id);
+  }
+
+  if (join_success) {
+    while (MSG_get_clock() < init_time + deadline
+//	&& MSG_get_clock() < node.last_change_date + 1000
+	&& MSG_get_clock() < max_simulation_time) {
+
+      if (node.comm_receive == NULL) {
+        task_received = NULL;
+        node.comm_receive = MSG_task_irecv(&task_received, node.mailbox);
+        // FIXME: do not make MSG_task_irecv() calls from several functions
+      }
+
+      if (!MSG_comm_test(node.comm_receive)) {
+
+        // no task was received: make some periodic calls
+        if (MSG_get_clock() >= next_stabilize_date) {
+          stabilize(&node);
+          next_stabilize_date = MSG_get_clock() + periodic_stabilize_delay;
+        }
+        else if (MSG_get_clock() >= next_fix_fingers_date) {
+          fix_fingers(&node);
+          next_fix_fingers_date = MSG_get_clock() + periodic_fix_fingers_delay;
+        }
+        else if (MSG_get_clock() >= next_check_predecessor_date) {
+          check_predecessor(&node);
+          next_check_predecessor_date = MSG_get_clock() + periodic_check_predecessor_delay;
+        }
+	else if (MSG_get_clock() >= next_lookup_date) {
+	  random_lookup(&node);
+	  next_lookup_date = MSG_get_clock() + periodic_lookup_delay;
 	}
+        else {
+          // nothing to do: sleep for a while
+          MSG_process_sleep(5);
+        }
+      }
+
+      if (node.comm_receive && MSG_comm_test(node.comm_receive)) {
+
+        // a transfer has occured
+
+        MSG_error_t status = MSG_comm_get_status(node.comm_receive);
+
+        if (status != MSG_OK) {
+          XBT_DEBUG("Failed to receive a task. Nevermind.");
+          MSG_comm_destroy(node.comm_receive);
+          node.comm_receive = NULL;
+        }
+        else {
+          // the task was successfully received
+          MSG_comm_destroy(node.comm_receive);
+          node.comm_receive = NULL;
+          handle_task(&node, task_received);
+        }
+      }
+    }
+
+    if (node.comm_receive) {
+      MSG_comm_destroy(node.comm_receive);
+      node.comm_receive = NULL;
+    }
+
+    // leave the ring
+    leave(&node);
+  }
 
-	int id = atoi(argv[1]);
-	int mailbox = atoi(argv[2]);
-	// init data node
-	data_node *data = xbt_new(data_node,1);
-	data->host_name = MSG_host_get_name(MSG_host_self());
-	data->id =  atoi(argv[1]);
-	data->mailbox = argv[2];
-	data->fingers_nb = 1;
-	data->fingers = xbt_new(finger_elem,KEY_BITS);
-	data->fingers[0].host_name = data->host_name;
-	data->fingers[0].id = data->id;
-	data->fingers[0].mailbox = data->mailbox;
-	data->next = 0;
-	data->pred_host_name = NULL;
-	data->pred_id = -1;
-	data->pred_mailbox = NULL;
+  // stop the simulation
+  xbt_free(node.fingers);
+  return 0;
+}
 
-/*
- * Ring Point Entry Node
+/**
+ * \brief This function is called when the current node receives a task.
+ * \param node the current node
+ * \param task the task to handle (don't touch it then:
+ * it will be destroyed, reused or forwarded)
  */
-	if (create) // first ring
-	{
-		INFO0("Create new Chord Ring...");
-		joined = 1;
-		cpt++;
-		//sucessor = n
-		data->fingers[0].host_name = data->host_name;
-		data->fingers[0].id = data->id;
-		data->fingers[0].mailbox = data->mailbox;
-		while(cpt < MSG_get_host_number()-1)  //make condition!!!
-		{
-			recv_request = NULL;
-			res = MSG_task_receive(&(recv_request),data->mailbox);
-			xbt_assert0(res == MSG_OK, "MSG_receiev failed");
-			if (!strcmp(MSG_task_get_name(recv_request), "Join Call"))
-			{
-				if(MSG_task_get_data(recv_request)==NULL)
-				{
-					WARN0("Receiving an Empty Data");
-				}
-				data_node *recv_data = (data_node*)MSG_task_get_data(recv_request);
-				INFO1("Receiving a Join Call from %s",recv_data->host_name);
-				if (first)
-				{
-					// predecessor(recv_data) >>>> data
-					recv_data->pred_host_name = data->host_name;
-					recv_data->pred_id = data->id;
-					recv_data->pred_mailbox = data->mailbox;
-					data->fingers_nb = 1;
-					// successor(recv_data) >>> data
-					recv_data->fingers[0].id = data->id;
-					recv_data->fingers[0].host_name = data->host_name;
-					recv_data->fingers[0].mailbox = data->mailbox;
-					//successor(data) >>>> recv_data
-					data->fingers[data->fingers_nb - 1].host_name = recv_data->host_name;
-					data->fingers[data->fingers_nb - 1].id = recv_data->id;
-					data->fingers[data->fingers_nb - 1].mailbox = recv_data->mailbox;
-					INFO1("Sending back a Join Request to %s",recv_data->host_name);
-					MSG_task_set_name(recv_request,"Join Response");
-					MSG_task_send(recv_request,recv_data->mailbox);
-					first = 0;
-				}
-				else{
-					find_successor_node(data,recv_request);
-				}
-
-			}
-		}
-	}
-/*
- * Joining Node
+static void handle_task(node_t node, m_task_t task) {
+
+  XBT_DEBUG("Handling task %p", task);
+  char mailbox[MAILBOX_NAME_SIZE];
+  task_data_t task_data = (task_data_t) MSG_task_get_data(task);
+  e_task_type_t type = task_data->type;
+
+  switch (type) {
+
+    case TASK_FIND_SUCCESSOR:
+      XBT_DEBUG("Receiving a 'Find Successor' request from %s for id %d",
+          task_data->issuer_host_name, task_data->request_id);
+      // is my successor the successor?
+      if (is_in_interval(task_data->request_id, node->id + 1, node->fingers[0].id)) {
+        task_data->type = TASK_FIND_SUCCESSOR_ANSWER;
+        task_data->answer_id = node->fingers[0].id;
+        XBT_DEBUG("Sending back a 'Find Successor Answer' to %s (mailbox %s): the successor of %d is %d",
+            task_data->issuer_host_name,
+	    task_data->answer_to,
+            task_data->request_id, task_data->answer_id);
+        MSG_task_dsend(task, task_data->answer_to, task_free);
+      }
+      else {
+        // otherwise, forward the request to the closest preceding finger in my table
+        int closest = closest_preceding_node(node, task_data->request_id);
+        XBT_DEBUG("Forwarding the 'Find Successor' request for id %d to my closest preceding finger %d",
+            task_data->request_id, closest);
+        get_mailbox(closest, mailbox);
+        MSG_task_dsend(task, mailbox, task_free);
+      }
+      break;
+
+    case TASK_GET_PREDECESSOR:
+      XBT_DEBUG("Receiving a 'Get Predecessor' request from %s", task_data->issuer_host_name);
+      task_data->type = TASK_GET_PREDECESSOR_ANSWER;
+      task_data->answer_id = node->pred_id;
+      XBT_DEBUG("Sending back a 'Get Predecessor Answer' to %s via mailbox '%s': my predecessor is %d",
+          task_data->issuer_host_name,
+          task_data->answer_to, task_data->answer_id);
+      MSG_task_dsend(task, task_data->answer_to, task_free);
+      break;
+
+    case TASK_NOTIFY:
+      // someone is telling me that he may be my new predecessor
+      XBT_DEBUG("Receiving a 'Notify' request from %s", task_data->issuer_host_name);
+      notify(node, task_data->request_id);
+      task_free(task);
+      break;
+
+    case TASK_PREDECESSOR_LEAVING:
+      // my predecessor is about to quit
+      XBT_DEBUG("Receiving a 'Predecessor Leaving' message from %s", task_data->issuer_host_name);
+      // modify my predecessor
+      set_predecessor(node, task_data->request_id);
+      task_free(task);
+      /*TODO :
+      >> notify my new predecessor
+      >> send a notify_predecessors !!
+       */
+      break;
+
+    case TASK_SUCCESSOR_LEAVING:
+      // my successor is about to quit
+      XBT_DEBUG("Receiving a 'Successor Leaving' message from %s", task_data->issuer_host_name);
+      // modify my successor FIXME : this should be implicit ?
+      set_finger(node, 0, task_data->request_id);
+      task_free(task);
+      /* TODO
+      >> notify my new successor
+      >> update my table & predecessors table */
+      break;
+
+    case TASK_FIND_SUCCESSOR_ANSWER:
+    case TASK_GET_PREDECESSOR_ANSWER:
+      XBT_DEBUG("Ignoring unexpected task of type %d (%p)", type, task);
+      task_free(task);
+      break;
+  }
+}
+
+/**
+ * \brief Initializes the current node as the first one of the system.
+ * \param node the current node
  */
-	else if(!create)
-	{
-		//Sleep Before Starting
-		INFO1("Let's Sleep >>%i",atoi(argv[6]));
-		MSG_process_sleep(atoi(argv[5]));
-		INFO0("Hey! Let's Send a Join Request");
-		//send a join task to the known host via its(known host) mailbox
-		const char* known_host_name = argv[3];
-		const char* known_mailbox = argv[4];
-		int known_id = atoi(argv[5]);
-		m_task_t join_request = MSG_task_create("Join Call",10000,2000,data);   // define comp size and comm size (#define ...)
-		INFO2("Sending a join request to %s via mailbox %s",known_host_name,known_mailbox);
-		MSG_task_send(join_request,known_mailbox);
-		//wait for answer on my mailbox
-		while(cpt < MSG_get_host_number()-1)
-		{
-			recv_request = NULL;
-			int res = MSG_task_receive(&(recv_request),data->mailbox);
-			//check if it's the response for my request
-			xbt_assert0(res == MSG_OK, "MSG_receiev failed");
-			// get data
-			data_node *recv_data = (data_node*)MSG_task_get_data(recv_request);
-			// Join Call Message
-			if(!strcmp(MSG_task_get_name(recv_request), "Join Call"))
-			{
-
-				INFO1("Receiving Join Call From %s",recv_data->host_name);
-				if(!joined)
-				{
-					INFO1("Sorry %s... I'm not yet joined",recv_data->host_name);
-					//No Treatment
-					MSG_task_set_name(recv_request,"Join Failed");
-					MSG_task_send(recv_request,recv_data->mailbox);
-						}
-					else
-					{
-						find_successor_node(data,recv_request);
-					}
-
-			}
-			// Join Response
-			else if(!strcmp(MSG_task_get_name(recv_request), "Join Response"))
-			{
-				INFO0("Receiving Join Response!!!");
-				INFO1("My successor is : %s",data->fingers[0].host_name);
-				INFO1("My Predecessor is : %s",data->pred_host_name);
-				cpt++;
-				joined = 1;
-				INFO1("My finger table size : %i",data->fingers_nb);
-				INFO0("***********************************************************************");
-
-				/*
-				MSG_task_set_name(recv_request,"Fix Fingers");
-
-				MSG_task_send(recv_request,data->pred_mailbox);
-				MSG_task_send(recv_request,data->fingers[0].mailbox);
-				*/
-				//init_finger_table(data,known_id);
-
-				//treatment
-			}
-			// Join Failure Message
-			else if(!strcmp(MSG_task_get_name(recv_request), "Join Failed"))
-			{
-				INFO0("My Join call has failed... let's Try Again");
-				// send back
-				//MSG_task_send(join_request,known_mailbox);
-				// !!!!!!!!! YVes Jaques Always...???§§§§**************************
-
-			}
-			else if(!strcmp(MSG_task_get_name(recv_request), "Fix Fingers"))
-			{
-				int i;
-				for(i = KEY_BITS -1 ; i>= 0;i--)
-				{
-					data->fingers[i] = find_finger_elem(data,(data->id)+pow(2,i-1));
-				}
-			}
-		}
-	}
+static void create(node_t node)
+{
+  XBT_DEBUG("Create a new Chord ring...");
+  set_predecessor(node, -1); // -1 means that I have no predecessor
+  print_finger_table(node);
+}
+
+/**
+ * \brief Makes the current node join the ring, knowing the id of a node
+ * already in the ring
+ * \param node the current node
+ * \param known_id id of a node already in the ring
+ * \return 1 if the join operation succeeded, 0 otherwise
+ */
+static int join(node_t node, int known_id)
+{
+  XBT_INFO("Joining the ring with id %d, knowing node %d", node->id, known_id);
+  set_predecessor(node, -1); // no predecessor (yet)
+
+  /*
+  int i;
+  for (i = 0; i < nb_bits; i++) {
+    set_finger(node, i, known_id);
+  }
+  */
+
+  int successor_id = remote_find_successor(node, known_id, node->id);
+  if (successor_id == -1) {
+    XBT_INFO("Cannot join the ring.");
+  }
+  else {
+    set_finger(node, 0, successor_id);
+    print_finger_table(node);
+  }
+
+  return successor_id != -1;
+}
+
+/**
+ * \brief Makes the current node quit the system
+ * \param node the current node
+ */
+static void leave(node_t node)
+{
+  XBT_DEBUG("Well Guys! I Think it's time for me to quit ;)");
+  quit_notify(node, 1);  // notify to my successor ( >>> 1 );
+  quit_notify(node, -1); // notify my predecessor  ( >>> -1);
+  // TODO ...
 }
 
 /*
- *
+ * \brief Notifies the successor or the predecessor of the current node
+ * of the departure
+ * \param node the current node
+ * \param to 1 to notify the successor, -1 to notify the predecessor
+ * FIXME: notify both nodes with only one call
  */
-void find_successor_node(data_node* n_data,m_task_t join_task)  //use all data
+static void quit_notify(node_t node, int to)
 {
-	//get recv data
-	data_node *recv_data = (data_node*)MSG_task_get_data(join_task);
-	INFO3("recv_data->id : %i , n_data->id :%i , successor->id :%i",recv_data->id,n_data->id,n_data->fingers[0].id);
-	//if ((recv_data->id >= n_data->id) && (recv_data->id <= n_data->fingers[0].id))
-	if (is_in_interval(recv_data->id,n_data->id,n_data->fingers[0].id))
-	{
-		INFO1("Successor Is %s",n_data->fingers[0].host_name);
-		//predecessor(recv_data) >>>> n_data
-		recv_data->pred_host_name = n_data->host_name;
-		recv_data->pred_id = n_data->id;
-		recv_data->pred_mailbox = n_data->pred_mailbox;
-		// successor(recv_data) >>>> n_data.finger[0]
-		recv_data->fingers_nb = 1;
-		recv_data->fingers[0].host_name = n_data->fingers[0].host_name;
-		recv_data->fingers[0].id = n_data->fingers[0].id;
-		recv_data->fingers[0].mailbox = n_data->fingers[0].mailbox;
-		// successor(n_data) >>>> recv_sucessor
-		n_data->fingers[0].id = recv_data->id;
-		n_data->fingers[0].host_name = recv_data->host_name;
-		n_data->fingers[0].mailbox = recv_data->mailbox;
-		// Logs
-		INFO1("Sending back a Join Request to %s",recv_data->host_name);
-		MSG_task_set_name(join_task,"Join Response");
-		MSG_task_send(join_task,recv_data->mailbox);
-	}
+  /* TODO
+  task_data_t req_data = xbt_new0(s_task_data_t, 1);
+  req_data->request_id = node->id;
+  req_data->successor_id = node->fingers[0].id;
+  req_data->pred_id = node->pred_id;
+  req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+  req_data->answer_to = NULL;
+  const char* task_name = NULL;
+  const char* to_mailbox = NULL;
+  if (to == 1) {    // notify my successor
+    to_mailbox = node->fingers[0].mailbox;
+    XBT_INFO("Telling my Successor %d about my departure via mailbox %s",
+	  node->fingers[0].id, to_mailbox);
+    req_data->type = TASK_PREDECESSOR_LEAVING;
+  }
+  else if (to == -1) {    // notify my predecessor
 
-	else
-	{
-		const char* closest_preceding_mailbox = find_closest_preceding(n_data,recv_data->id);
-		INFO1("Forwarding Join Call to mailbox %s",closest_preceding_mailbox);
-		MSG_task_send(join_task,closest_preceding_mailbox);
-	}
+    if (node->pred_id == -1) {
+      return;
+    }
+
+    to_mailbox = node->pred_mailbox;
+    XBT_INFO("Telling my Predecessor %d about my departure via mailbox %s",
+	  node->pred_id, to_mailbox);
+    req_data->type = TASK_SUCCESSOR_LEAVING;
+  }
+  m_task_t task = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+  //char* mailbox = get_mailbox(to_mailbox);
+  msg_comm_t comm = MSG_task_isend(task, to_mailbox);
+  xbt_dynar_push(node->comms, &comm);
+  */
 }
 
-const char* find_closest_preceding(data_node* n_node,int id)
+/**
+ * \brief Makes the current node find the successor node of an id.
+ * \param node the current node
+ * \param id the id to find
+ * \return the id of the successor node, or -1 if the request failed
+ */
+static int find_successor(node_t node, int id)
 {
-	int i;
-	for(i = n_node->fingers_nb-1; i >= 0 ; i--)
-	{
-			if (n_node->fingers[i].id <= id)
-				return n_node->fingers[i].mailbox;
+  // is my successor the successor?
+  if (is_in_interval(id, node->id + 1, node->fingers[0].id)) {
+    return node->fingers[0].id;
+  }
+
+  // otherwise, ask the closest preceding finger in my table
+  int closest = closest_preceding_node(node, id);
+  return remote_find_successor(node, closest, id);
+}
+
+/**
+ * \brief Asks another node the successor node of an id.
+ * \param node the current node
+ * \param ask_to the node to ask to
+ * \param id the id to find
+ * \return the id of the successor node, or -1 if the request failed
+ */
+static int remote_find_successor(node_t node, int ask_to, int id)
+{
+  int successor = -1;
+  int stop = 0;
+  char mailbox[MAILBOX_NAME_SIZE];
+  get_mailbox(ask_to, mailbox);
+  task_data_t req_data = xbt_new0(s_task_data_t, 1);
+  req_data->type = TASK_FIND_SUCCESSOR;
+  req_data->request_id = id;
+  get_mailbox(node->id, req_data->answer_to);
+  req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+  // send a "Find Successor" request to ask_to_id
+  m_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+  XBT_DEBUG("Sending a 'Find Successor' request (task %p) to %d for id %d", task_sent, ask_to, id);
+  MSG_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
+
+  if (res != MSG_OK) {
+    XBT_DEBUG("Failed to send the 'Find Successor' request (task %p) to %d for id %d",
+        task_sent, ask_to, id);
+    task_free(task_sent);
+  }
+  else {
+
+    // receive the answer
+    XBT_DEBUG("Sent a 'Find Successor' request (task %p) to %d for key %d, waiting for the answer",
+        task_sent, ask_to, id);
+
+    do {
+      if (node->comm_receive == NULL) {
+        m_task_t task_received = NULL;
+        node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
+      }
+
+      res = MSG_comm_wait(node->comm_receive, timeout);
+
+      if (res != MSG_OK) {
+        XBT_DEBUG("Failed to receive the answer to my 'Find Successor' request (task %p): %d",
+            task_sent, res);
+        stop = 1;
+	MSG_comm_destroy(node->comm_receive);
+	node->comm_receive = NULL;
+      }
+      else {
+        m_task_t task_received = MSG_comm_get_task(node->comm_receive);
+        XBT_DEBUG("Received a task (%p)", task_received);
+        task_data_t ans_data = MSG_task_get_data(task_received);
+
+	if (MC_IS_ENABLED) {
+	  MC_assert(task_received == task_sent);
 	}
 
-	return n_node->mailbox; // !!!!!!!!!!!!!!
+        if (task_received != task_sent) {
+          // this is not the expected answer
+	  MSG_comm_destroy(node->comm_receive);
+	  node->comm_receive = NULL;
+          handle_task(node, task_received);
+        }
+        else {
+          // this is our answer
+          XBT_DEBUG("Received the answer to my 'Find Successor' request for id %d (task %p): the successor of key %d is %d",
+              ans_data->request_id, task_received, id, ans_data->answer_id);
+          successor = ans_data->answer_id;
+          stop = 1;
+	  MSG_comm_destroy(node->comm_receive);
+	  node->comm_receive = NULL;
+          task_free(task_received);
+        }
+      }
+    } while (!stop);
+  }
+
+  return successor;
 }
-/*
- * Fin successor id : used to fix finger list
+
+/**
+ * \brief Asks another node its predecessor.
+ * \param node the current node
+ * \param ask_to the node to ask to
+ * \return the id of its predecessor node, or -1 if the request failed
+ * (or if the node does not know its predecessor)
  */
-finger_elem find_finger_elem(data_node* n_data, int id)
+static int remote_get_predecessor(node_t node, int ask_to)
 {
-	//if(id >= n_data->id && id <= n_data->fingers[0].id)
-	if (is_in_interval(id,n_data->id,n_data->fingers[0].id))
-		return n_data->fingers[0];
-	//else
-		//return find_finger_elem(...,id);
+  int predecessor_id = -1;
+  int stop = 0;
+  char mailbox[MAILBOX_NAME_SIZE];
+  get_mailbox(ask_to, mailbox);
+  task_data_t req_data = xbt_new0(s_task_data_t, 1);
+  req_data->type = TASK_GET_PREDECESSOR;
+  get_mailbox(node->id, req_data->answer_to);
+  req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+  // send a "Get Predecessor" request to ask_to_id
+  XBT_DEBUG("Sending a 'Get Predecessor' request to %d", ask_to);
+  m_task_t task_sent = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+  MSG_error_t res = MSG_task_send_with_timeout(task_sent, mailbox, timeout);
+
+  if (res != MSG_OK) {
+    XBT_DEBUG("Failed to send the 'Get Predecessor' request (task %p) to %d",
+        task_sent, ask_to);
+    task_free(task_sent);
+  }
+  else {
+
+    // receive the answer
+    XBT_DEBUG("Sent 'Get Predecessor' request (task %p) to %d, waiting for the answer on my mailbox '%s'",
+        task_sent, ask_to, req_data->answer_to);
+
+    do {
+      if (node->comm_receive == NULL) { // FIXME simplify this
+        m_task_t task_received = NULL;
+        node->comm_receive = MSG_task_irecv(&task_received, node->mailbox);
+      }
+
+      res = MSG_comm_wait(node->comm_receive, timeout);
+
+      if (res != MSG_OK) {
+        XBT_DEBUG("Failed to receive the answer to my 'Get Predecessor' request (task %p): %d",
+            task_sent, res);
+        stop = 1;
+	MSG_comm_destroy(node->comm_receive);
+	node->comm_receive = NULL;
+      }
+      else {
+        m_task_t task_received = MSG_comm_get_task(node->comm_receive);
+        task_data_t ans_data = MSG_task_get_data(task_received);
+
+	if (MC_IS_ENABLED) {
+	  MC_assert(task_received == task_sent);
+	}
+
+        if (task_received != task_sent) {
+	  MSG_comm_destroy(node->comm_receive);
+	  node->comm_receive = NULL;
+          handle_task(node, task_received);
+        }
+        else {
+          XBT_DEBUG("Received the answer to my 'Get Predecessor' request (task %p): the predecessor of node %d is %d",
+              task_received, ask_to, ans_data->answer_id);
+          predecessor_id = ans_data->answer_id;
+          stop = 1;
+	  MSG_comm_destroy(node->comm_receive);
+	  node->comm_receive = NULL;
+          task_free(task_received);
+        }
+      }
+    } while (!stop);
+  }
 
+  return predecessor_id;
 }
 
+/**
+ * \brief Returns the closest preceding finger of an id
+ * with respect to the finger table of the current node.
+ * \param node the current node
+ * \param id the id to find
+ * \return the closest preceding finger of that id
+ */
+int closest_preceding_node(node_t node, int id)
+{
+  int i;
+  for (i = nb_bits - 1; i >= 0; i--) {
+    if (is_in_interval(node->fingers[i].id, node->id + 1, id - 1)) {
+      return node->fingers[i].id;
+    }
+  }
+  return node->id;
+}
 
-/** Test function */
-MSG_error_t test_all(const char *platform_file,
-                     const char *application_file)
+/**
+ * \brief This function is called periodically. It checks the immediate
+ * successor of the current node.
+ * \param node the current node
+ */
+static void stabilize(node_t node)
 {
-  MSG_error_t res = MSG_OK;
+  XBT_DEBUG("Stabilizing node");
 
-  /* MSG_config("workstation/model","KCCFLN05"); */
-  {                             /*  Simulation setting */
-    MSG_set_channel_number(0);
-    MSG_create_environment(platform_file);
+  // get the predecessor of my immediate successor
+  int candidate_id;
+  int successor_id = node->fingers[0].id;
+  if (successor_id != node->id) {
+    candidate_id = remote_get_predecessor(node, successor_id);
+  }
+  else {
+    candidate_id = node->pred_id;
+  }
 
+  // this node is a candidate to become my new successor
+  if (candidate_id != -1
+      && is_in_interval(candidate_id, node->id + 1, successor_id - 1)) {
+    set_finger(node, 0, candidate_id);
   }
-  {                             /*   Application deployment */
-	MSG_function_register("node",node);
-    MSG_launch_application(application_file);
+  if (successor_id != node->id) {
+    remote_notify(node, successor_id, node->id);
   }
-  res = MSG_main();
-  INFO1("Simulation time %g", MSG_get_clock());
+}
 
-  return res;
-}                               /* end_of_test_all */
+/**
+ * \brief Notifies the current node that its predecessor may have changed.
+ * \param node the current node
+ * \param candidate_id the possible new predecessor
+ */
+static void notify(node_t node, int predecessor_candidate_id) {
 
-/** Main function */
-int main(int argc, char *argv[])
+  if (node->pred_id == -1
+    || is_in_interval(predecessor_candidate_id, node->pred_id + 1, node->id - 1)) {
+
+    set_predecessor(node, predecessor_candidate_id);
+    print_finger_table(node);
+  }
+  else {
+    XBT_DEBUG("I don't have to change my predecessor to %d", predecessor_candidate_id);
+  }
+}
+
+/**
+ * \brief Notifies a remote node that its predecessor may have changed.
+ * \param node the current node
+ * \param notify_id id of the node to notify
+ * \param candidate_id the possible new predecessor
+ */
+static void remote_notify(node_t node, int notify_id, int predecessor_candidate_id) {
+
+  task_data_t req_data = xbt_new0(s_task_data_t, 1);
+  req_data->type = TASK_NOTIFY;
+  req_data->request_id = predecessor_candidate_id;
+  req_data->issuer_host_name = MSG_host_get_name(MSG_host_self());
+
+  // send a "Notify" request to notify_id
+  m_task_t task = MSG_task_create(NULL, COMP_SIZE, COMM_SIZE, req_data);
+  XBT_DEBUG("Sending a 'Notify' request (task %p) to %d", task, notify_id);
+  char mailbox[MAILBOX_NAME_SIZE];
+  get_mailbox(notify_id, mailbox);
+  MSG_task_dsend(task, mailbox, task_free);
+}
+
+/**
+ * \brief This function is called periodically.
+ * It refreshes the finger table of the current node.
+ * \param node the current node
+ */
+static void fix_fingers(node_t node) {
+
+  XBT_DEBUG("Fixing fingers");
+  int i = node->next_finger_to_fix;
+  int id = find_successor(node, node->id + powers2[i]);
+  if (id != -1) {
+
+    if (id != node->fingers[i].id) {
+      set_finger(node, i, id);
+      print_finger_table(node);
+    }
+    node->next_finger_to_fix = (i + 1) % nb_bits;
+  }
+}
+
+/**
+ * \brief This function is called periodically.
+ * It checks whether the predecessor has failed
+ * \param node the current node
+ */
+static void check_predecessor(node_t node)
 {
-  MSG_error_t res = MSG_OK;
+  XBT_DEBUG("Checking whether my predecessor is alive");
+  // TODO
+}
+
+/**
+ * \brief Performs a find successor request to a random id.
+ * \param node the current node
+ */
+static void random_lookup(node_t node)
+{
+  int id = 1337; // TODO pick a pseudorandom id
+  XBT_DEBUG("Making a lookup request for id %d", id);
+  find_successor(node, id);
+}
 
+/**
+ * \brief Main function.
+ */
+int main(int argc, char *argv[])
+{
   MSG_global_init(&argc, argv);
   if (argc < 3) {
-    printf("Usage: %s platform_file deployment_file\n", argv[0]);
-    printf("example: %s msg_platform.xml msg_deployment.xml\n", argv[0]);
+    printf("Usage: %s [-nb_bits=n] [-timeout=t] platform_file deployment_file\n", argv[0]);
+    printf("example: %s ../msg_platform.xml chord.xml\n", argv[0]);
     exit(1);
   }
-  res = test_all(argv[1], argv[2]);
+
+  char **options = &argv[1];
+  while (!strncmp(options[0], "-", 1)) {
+
+    int length = strlen("-nb_bits=");
+    if (!strncmp(options[0], "-nb_bits=", length) && strlen(options[0]) > length) {
+      nb_bits = atoi(options[0] + length);
+      XBT_DEBUG("Set nb_bits to %d", nb_bits);
+    }
+    else {
+
+      length = strlen("-timeout=");
+      if (!strncmp(options[0], "-timeout=", length) && strlen(options[0]) > length) {
+	timeout = atoi(options[0] + length);
+	XBT_DEBUG("Set timeout to %d", timeout);
+      }
+      else {
+	xbt_die("Invalid chord option '%s'", options[0]);
+      }
+    }
+    options++;
+  }
+
+  const char* platform_file = options[0];
+  const char* application_file = options[1];
+
+  chord_initialize();
+
+  MSG_create_environment(platform_file);
+
+  MSG_function_register("node", node);
+  MSG_launch_application(application_file);
+
+  MSG_error_t res = MSG_main();
+  XBT_CRITICAL("Messages created: %ld", smx_total_comms);
+  XBT_INFO("Simulated time: %g", MSG_get_clock());
+
   MSG_clean();
+  chord_exit();
 
   if (res == MSG_OK)
     return 0;
   else
     return 1;
-}                               /* end_of_main */
+}