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 * @param C the current configuration from which UDPOR will be used
88 * to explore expansions of the concurrent system being modeled
89 * @param D the set of events that should not be considered by UDPOR
90 * while performing its searches, in order to avoid sleep-set blocked
91 * executions. See [1] for more details
92 * @param A the set of events to "guide" UDPOR in the correct direction
93 * when it returns back to a node in the unfolding and must decide among
94 * events to select from `ex(C)`. See [1] for more details
95 * @param max_evt_history
97 * @param e the event where UDPOR currently "rests", viz. the event UDPOR
98 * is now currently considering. This event is contained in the set `C`
99 * and is the last event that was added to C
102 * TODO: Add the optimization where we can check if e == e_prior
103 * to prevent repeated work when computing ex(C)
105 void explore(Configuration C, EventSet D, EventSet A, std::list<EventSet> max_evt_history, UnfoldingEvent* e_cur,
109 * @brief Computes the sets `ex(C)` and `en(C)` of the given configuration
110 * `C` as an incremental computation from the the previous computation of `ex(C)`
112 * A central component to UDPOR is the computation of the set `ex(C)`. The
113 * extension set `ex(C)` of a configuration `C` is defined as the set of events
114 * outside of `C` whose full dependency chain is contained in `C` (see [1]
117 * In general, computing `ex(C)` is very expensive. In paper [3], The Anh Pham
118 * shows a method of incremental computation of the set `ex(C)` under the
119 * conclusions afforded under the computation model in consideration, of which
120 * SimGrid is apart, which allow for `ex(C)` to be computed much more efficiently.
121 * Intuitively, the idea is to take advantage of the fact that you can avoid a lot
122 * of repeated computation by exploiting the aforementioned properties (in [3]) in
123 * what is effectively a dynamic programming optimization. See [3] for more details
125 * @param C the configuration based on which the two sets `ex(C)` and `en(C)` are
127 * @param e the event where UDPOR currently "rests", viz. the event UDPOR
128 * is now currently considering
129 * @param prev_exC the previous value of `ex(C)`, viz. that which was computed for
130 * the configuration `C' := C - {e}`
131 * @returns a tuple containing the pair of sets `ex(C)` and `en(C)` respectively
133 std::tuple<EventSet, EventSet> compute_extension(const Configuration& C, const std::list<EventSet>& max_evt_history,
134 UnfoldingEvent* e, const EventSet& prev_exC) const;
139 StateHandle observe_unfolding_event(const UnfoldingEvent& event);
142 * @brief Resolves the state handle maintained by an event
143 * into a concrete reference to a state
145 State& get_state_referenced_by(const UnfoldingEvent& event);
148 * @brief Creates a new snapshot of the state of the progam undergoing
151 * @returns the handle used to uniquely identify this state later in the
152 * exploration of the unfolding. You provide this handle to an event in the
153 * unfolding to regenerate past states
155 StateHandle record_current_state();
158 * @brief Identifies the next event from the unfolding of the concurrent system
159 * that should next be explored as an extension of a configuration with
160 * enabled events `enC`
162 * @param A The set of events `A` maintained by the UDPOR algorithm to help
163 * determine how events should be selected. See the original paper [1] for more details
165 * @param enC The set `enC` of enabled events from the extension set `exC` used
166 * by the UDPOR algorithm to select new events to search. See the original
167 * paper [1] for more details
169 UnfoldingEvent* select_next_unfolding_event(const EventSet& A, const EventSet& enC);
174 EventSet compute_partial_alternative(const EventSet& D, const Configuration& C, const unsigned k) const;
179 void clean_up_explore(const UnfoldingEvent* e, const Configuration& C, const EventSet& D);
181 } // namespace simgrid::mc::udpor