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/explo/udpor/Configuration.hpp"
12 #include "src/mc/explo/udpor/EventSet.hpp"
13 #include "src/mc/explo/udpor/StateManager.hpp"
14 #include "src/mc/explo/udpor/Unfolding.hpp"
15 #include "src/mc/explo/udpor/UnfoldingEvent.hpp"
16 #include "src/mc/mc_record.hpp"
20 namespace simgrid::mc::udpor {
23 * @brief Performs exploration of a concurrent system via the
26 * The `UdporChecker` implementation is based primarily off three papers,
27 * herein referred to as [1], [2], and [3] respectively, as well as the
28 * current implementation of `tiny_simgrid`:
30 * 1. "Unfolding-based Partial Order Reduction" by Rodriguez et al.
31 * 2. Quasi-Optimal Partial Order Reduction by Nguyen et al.
32 * 3. The Anh Pham's Thesis "Exploration efficace de l'espace ..."
34 class XBT_PRIVATE UdporChecker : public Exploration {
36 explicit UdporChecker(const std::vector<char*>& args);
39 RecordTrace get_record_trace() override;
40 std::vector<std::string> get_textual_trace() override;
42 inline std::unique_ptr<State> get_current_state() { return std::make_unique<State>(get_remote_app()); }
46 * The total number of events created whilst exploring the unfolding
48 uint32_t nb_events = 0;
49 uint32_t nb_traces = 0;
52 * @brief The "relevant" portions of the unfolding that must be kept around to ensure that
53 * UDPOR properly searches the state space
55 * The set `U` is a global variable which is maintained by UDPOR
56 * to keep track of "just enough" information about the unfolding
57 * to compute *alternatives* (see the paper for more details).
59 * @invariant: When a new event is created by UDPOR, it is inserted into
60 * this set. All new events that are created by UDPOR have causes that
61 * also exist in U and are valid for the duration of the search.
63 * If an event is discarded instead of moved from set `U` to set `G`,
64 * the event and its contents will be discarded.
69 * @brief The "irrelevant" portions of the unfolding that do not need to be kept
70 * around to ensure that UDPOR functions correctly
72 * The set `G` is another global variable maintained by the UDPOR algorithm which
73 * is used to keep track of all events which used to be important to UDPOR
78 * Maintains the mapping between handles referenced by events in
79 * the current state of the unfolding
81 StateManager state_manager_;
84 * @brief UDPOR's current "view" of the program it is exploring
86 Unfolding unfolding = Unfolding();
90 * @brief Explores the unfolding of the concurrent system
91 * represented by the ModelChecker instance "mcmodel_checker"
93 * This function performs the actual search following the
94 * UDPOR algorithm according to [1].
96 * @param C the current configuration from which UDPOR will be used
97 * to explore expansions of the concurrent system being modeled
98 * @param D the set of events that should not be considered by UDPOR
99 * while performing its searches, in order to avoid sleep-set blocked
100 * executions. See [1] for more details
101 * @param A the set of events to "guide" UDPOR in the correct direction
102 * when it returns back to a node in the unfolding and must decide among
103 * events to select from `ex(C)`. See [1] for more details
104 * @param stateC the state of the program after having executed `C`,
105 * viz. `state(C)` using the notation of [1]
107 * TODO: Add the optimization where we can check if e == e_prior
108 * to prevent repeated work when computing ex(C)
110 void explore(Configuration C, EventSet D, EventSet A, std::unique_ptr<State> stateC, EventSet prev_exC);
113 * @brief Identifies the next event from the unfolding of the concurrent system
114 * that should next be explored as an extension of a configuration with
115 * enabled events `enC`
117 * @param A The set of events `A` maintained by the UDPOR algorithm to help
118 * determine how events should be selected. See the original paper [1] for more details
120 * @param enC The set `enC` of enabled events from the extension set `exC` used
121 * by the UDPOR algorithm to select new events to search. See the original
122 * paper [1] for more details
124 UnfoldingEvent* select_next_unfolding_event(const EventSet& A, const EventSet& enC);
127 * @brief Computes the sets `ex(C)` and `en(C)` of the given configuration
128 * `C` as an incremental computation from the the previous computation of `ex(C)`
130 * A central component to UDPOR is the computation of the set `ex(C)`. The
131 * extension set `ex(C)` of a configuration `C` is defined as the set of events
132 * outside of `C` whose full dependency chain is contained in `C` (see [1]
135 * In general, computing `ex(C)` is very expensive. In paper [3], The Anh Pham
136 * shows a method of incremental computation of the set `ex(C)` under the
137 * conclusions afforded under the computation model in consideration, of which
138 * SimGrid is apart, which allow for `ex(C)` to be computed much more efficiently.
139 * Intuitively, the idea is to take advantage of the fact that you can avoid a lot
140 * of repeated computation by exploiting the aforementioned properties (in [3]) in
141 * what is effectively a dynamic programming optimization. See [3] for more details
143 * @param C the configuration based on which the two sets `ex(C)` and `en(C)` are
145 * @param prev_exC the previous value of `ex(C)`, viz. that which was computed for
146 * the configuration `C' := C - {e}`
147 * @returns a tuple containing the pair of sets `ex(C)` and `en(C)` respectively
149 std::tuple<EventSet, EventSet> compute_extension(const Configuration& C, const EventSet& prev_exC) const;
154 EventSet compute_partial_alternative(const EventSet& D, const Configuration& C, const unsigned k) const;
159 void move_to_stateCe(State& stateC, const UnfoldingEvent& e);
162 * @brief Creates a new snapshot of the state of the progam undergoing
165 * @returns the handle used to uniquely identify this state later in the
166 * exploration of the unfolding. You provide this handle to an event in the
167 * unfolding to regenerate past states
169 std::unique_ptr<State> record_current_state();
174 void restore_program_state_to(const State& stateC);
179 void clean_up_explore(const UnfoldingEvent* e, const Configuration& C, const EventSet& D);
181 } // namespace simgrid::mc::udpor