1 /* Copyright (c) 2010-2022. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 /***************** Centralized Mutual Exclusion Algorithm *********************/
7 /* This example implements a centralized mutual exclusion algorithm. */
8 /* There is no bug on it, it is just provided to test the state space */
9 /* reduction of DPOR. */
10 /******************************************************************************/
12 #include "simgrid/s4u.hpp"
14 constexpr int AMOUNT_OF_CLIENTS = 4;
15 constexpr int CS_PER_PROCESS = 2;
17 XBT_LOG_NEW_DEFAULT_CATEGORY(centralized, "my log messages");
21 enum class Kind { GRANT, REQUEST, RELEASE };
22 Kind kind = Kind::GRANT;
23 simgrid::s4u::Mailbox* return_mailbox = nullptr;
24 explicit Message(Message::Kind kind, simgrid::s4u::Mailbox* mbox) : kind(kind), return_mailbox(mbox) {}
27 static void coordinator()
29 std::queue<simgrid::s4u::Mailbox*> requests;
30 simgrid::s4u::Mailbox* mbox = simgrid::s4u::Mailbox::by_name("coordinator");
32 bool CS_used = false; // initially the CS is idle
33 int todo = AMOUNT_OF_CLIENTS * CS_PER_PROCESS; // amount of releases we are expecting
36 auto m = mbox->get_unique<Message>();
37 if (m->kind == Message::Kind::REQUEST) {
38 if (CS_used) { // need to push the request in the vector
39 XBT_INFO("CS already used. Queue the request");
40 requests.push(m->return_mailbox);
41 } else { // can serve it immediately
42 XBT_INFO("CS idle. Grant immediately");
43 m->return_mailbox->put(new Message(Message::Kind::GRANT, mbox), 1000);
46 } else { // that's a release. Check if someone was waiting for the lock
47 if (not requests.empty()) {
48 XBT_INFO("CS release. Grant to queued requests (queue size: %zu)", requests.size());
49 simgrid::s4u::Mailbox* req = requests.front();
51 req->put(new Message(Message::Kind::GRANT, mbox), 1000);
53 } else { // nobody wants it
54 XBT_INFO("CS release. resource now idle");
60 XBT_INFO("Received all releases, quit now");
65 aid_t my_pid = simgrid::s4u::this_actor::get_pid();
67 simgrid::s4u::Mailbox* my_mailbox = simgrid::s4u::Mailbox::by_name(std::to_string(my_pid));
69 // request the CS 3 times, sleeping a bit in between
70 for (int i = 0; i < CS_PER_PROCESS; i++) {
71 XBT_INFO("Ask the request");
72 simgrid::s4u::Mailbox::by_name("coordinator")->put(new Message(Message::Kind::REQUEST, my_mailbox), 1000);
73 // wait for the answer
74 auto grant = my_mailbox->get_unique<Message>();
75 XBT_INFO("got the answer. Sleep a bit and release it");
76 simgrid::s4u::this_actor::sleep_for(1);
78 simgrid::s4u::Mailbox::by_name("coordinator")->put(new Message(Message::Kind::RELEASE, my_mailbox), 1000);
79 simgrid::s4u::this_actor::sleep_for(static_cast<double>(my_pid));
81 XBT_INFO("Got all the CS I wanted, quit now");
84 int main(int argc, char* argv[])
86 simgrid::s4u::Engine e(&argc, argv);
88 e.load_platform(argv[1]);
90 simgrid::s4u::Actor::create("coordinator", e.host_by_name("Tremblay"), coordinator);
91 simgrid::s4u::Actor::create("client", e.host_by_name("Fafard"), client);
92 simgrid::s4u::Actor::create("client", e.host_by_name("Boivin"), client);
93 simgrid::s4u::Actor::create("client", e.host_by_name("Jacquelin"), client);
94 simgrid::s4u::Actor::create("client", e.host_by_name("Ginette"), client);