1 /* Copyright (c) 2007-2023. The SimGrid Team.
2 * All rights reserved. */
4 /* This program is free software; you can redistribute it and/or modify it
5 * under the terms of the license (GNU LGPL) which comes with this package. */
7 #ifndef SIMGRID_MC_UDPOR_CHECKER_HPP
8 #define SIMGRID_MC_UDPOR_CHECKER_HPP
10 #include "src/mc/explo/Exploration.hpp"
11 #include "src/mc/mc_record.hpp"
12 #include "src/mc/udpor_global.hpp"
16 namespace simgrid::mc::udpor {
19 * @brief Performs exploration of a concurrent system via the
22 * The `UdporChecker` implementation is based primarily off three papers,
23 * herein referred to as [1], [2], and [3] respectively, as well as the
24 * current implementation of `tiny_simgrid`:
26 * 1. "Unfolding-based Partial Order Reduction" by Rodriguez et al.
27 * 2. Quasi-Optimal Partial Order Reduction by Nguyen et al.
28 * 3. The Anh Pham's Thesis "Exploration efficace de l'espace ..."
30 class XBT_PRIVATE UdporChecker : public Exploration {
32 explicit UdporChecker(const std::vector<char*>& args);
35 RecordTrace get_record_trace() override;
36 std::vector<std::string> get_textual_trace() override;
38 inline std::unique_ptr<State> get_current_state() { return std::make_unique<State>(get_remote_app()); }
42 * The total number of events created whilst exploring the unfolding
44 uint32_t nb_events = 0;
45 uint32_t nb_traces = 0;
48 * @brief The "relevant" portions of the unfolding that must be kept around to ensure that
49 * UDPOR properly searches the state space
51 * The set `U` is a global variable which is maintained by UDPOR
52 * to keep track of "just enough" information about the unfolding
53 * to compute *alternatives* (see the paper for more details).
55 * @invariant: When a new event is created by UDPOR, it is inserted into
56 * this set. All new events that are created by UDPOR have causes that
57 * also exist in U and are valid for the duration of the search.
59 * If an event is discarded instead of moved from set `U` to set `G`,
60 * the event and its contents will be discarded.
65 * @brief The "irrelevant" portions of the unfolding that do not need to be kept
66 * around to ensure that UDPOR functions correctly
68 * The set `G` is another global variable maintained by the UDPOR algorithm which
69 * is used to keep track of all events which used to be important to UDPOR
74 * Maintains the mapping between handles referenced by events in
75 * the current state of the unfolding
77 StateManager state_manager_;
81 * @brief Explores the unfolding of the concurrent system
82 * represented by the ModelChecker instance "mcmodel_checker"
84 * This function performs the actual search following the
85 * UDPOR algorithm according to [1].
87 void explore(Configuration C, EventSet D, EventSet A, std::list<EventSet> max_evt_history, UnfoldingEvent* cur_event,
91 * @brief Computes the sets `ex(C)` and `en(C)` of the given configuration
92 * `C` as an incremental computation from the the previous computation of `ex(C)`
94 * A central component to UDPOR is the computation of the set `ex(C)`. The
95 * extension set `ex(C)` of a configuration `C` is defined as the set of events
96 * outside of `C` whose full dependency chain is contained in `C` (see [1]
99 * In general, computing `ex(C)` is very expensive. In paper [3], The Anh Pham
100 * shows a method of incremental computation of the set `ex(C)` under the
101 * conclusions afforded under the computation model in consideration, of which
102 * SimGrid is apart, which allow for `ex(C)` to be computed much more efficiently.
103 * Intuitively, the idea is to take advantage of the fact that you can avoid a lot
104 * of repeated computation by exploiting the aforementioned properties (in [3]) in
105 * what is effectively a dynamic programming optimization. See [3] for more details
107 * @param C the configuration based on which the two sets `ex(C)` and `en(C)` are
109 * @param cur_event the event where UDPOR currently "rests", viz. the event UDPOR
110 * is now currently considering
111 * @param prev_exC the previous value of `ex(C)`, viz. that which was computed for
112 * the configuration `C' := C - {cur_event}`
113 * @returns a tuple containing the pair of sets `ex(C)` and `en(C)` respectively
115 std::tuple<EventSet, EventSet> compute_extension(const Configuration& C, const std::list<EventSet>& max_evt_history,
116 const UnfoldingEvent& cur_event, const EventSet& prev_exC) const;
121 void observe_unfolding_event(const UnfoldingEvent& event);
122 State& get_state_referenced_by(const UnfoldingEvent& event);
123 StateHandle record_newly_visited_state();
126 * @brief Identifies the next event from the unfolding of the concurrent system
127 * that should next be explored as an extension of a configuration with
128 * enabled events `enC`
130 * @param A The set of events `A` maintained by the UDPOR algorithm to help
131 * determine how events should be selected. See the original paper [1] for more details
133 * @param enC The set `enC` of enabled events from the extension set `exC` used
134 * by the UDPOR algorithm to select new events to search. See the original
135 * paper [1] for more details
137 UnfoldingEvent* select_next_unfolding_event(const EventSet& A, const EventSet& enC);
142 EventSet compute_partial_alternative(const EventSet& D, const Configuration& C, const unsigned k) const;
147 void clean_up_explore(const UnfoldingEvent* e, const Configuration& C, const EventSet& D);
149 } // namespace simgrid::mc::udpor