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/api/State.hpp"
11 #include "src/mc/explo/Exploration.hpp"
12 #include "src/mc/explo/udpor/Configuration.hpp"
13 #include "src/mc/explo/udpor/EventSet.hpp"
14 #include "src/mc/explo/udpor/Unfolding.hpp"
15 #include "src/mc/explo/udpor/UnfoldingEvent.hpp"
16 #include "src/mc/mc_record.hpp"
22 namespace simgrid::mc::udpor {
25 * @brief Performs exploration of a concurrent system via the
28 * The `UdporChecker` implementation is based primarily off three papers,
29 * herein referred to as [1], [2], and [3] respectively, as well as the
30 * current implementation of `tiny_simgrid`:
32 * 1. "Unfolding-based Partial Order Reduction" by Rodriguez et al.
33 * 2. "Quasi-Optimal Partial Order Reduction" by Nguyen et al.
34 * 3. The Anh Pham's Thesis "Exploration efficace de l'espace ..."
36 class XBT_PRIVATE UdporChecker : public Exploration {
38 explicit UdporChecker(const std::vector<char*>& args);
41 RecordTrace get_record_trace() override;
42 std::unique_ptr<State> get_current_state() { return std::make_unique<State>(get_remote_app()); }
45 Unfolding unfolding = Unfolding();
47 // The current sequence of states that the checker has
48 // visited in order to reach the current configuration
49 std::list<std::unique_ptr<State>> state_stack;
52 * @brief Explores the unfolding of the concurrent system
53 * represented by the ModelChecker instance "mcmodel_checker"
55 * This function performs the actual search following the
56 * UDPOR algorithm according to [1].
58 * @param C the current configuration from which UDPOR will be used
59 * to explore expansions of the concurrent system being modeled
60 * @param D the set of events that should not be considered by UDPOR
61 * while performing its searches, in order to avoid sleep-set blocked
62 * executions. See [1] for more details
63 * @param A the set of events to "guide" UDPOR in the correct direction
64 * when it returns back to a node in the unfolding and must decide among
65 * events to select from `ex(C)`. See [1] for more details
67 * TODO: Add the optimization where we can check if e == e_prior
68 * to prevent repeated work when computing ex(C)
70 void explore(const Configuration& C, EventSet D, EventSet A, EventSet prev_exC);
73 * @brief Identifies the next event from the unfolding of the concurrent system
74 * that should next be explored as an extension of a configuration with
75 * enabled events `enC`
77 * @param A The set of events `A` maintained by the UDPOR algorithm to help
78 * determine how events should be selected. See the original paper [1] for more details
80 * @param enC The set `enC` of enabled events from the extension set `exC` used
81 * by the UDPOR algorithm to select new events to search. See the original
82 * paper [1] for more details
84 UnfoldingEvent* select_next_unfolding_event(const EventSet& A, const EventSet& enC);
87 * @brief Computes the sets `ex(C)` and `en(C)` of the given configuration
88 * `C` as an incremental computation from the the previous computation of `ex(C)`
90 * A central component to UDPOR is the computation of the set `ex(C)`. The
91 * extension set `ex(C)` of a configuration `C` is defined as the set of events
92 * outside of `C` whose full dependency chain is contained in `C` (see [1]
95 * In general, computing `ex(C)` is very expensive. In paper [3], The Anh Pham
96 * shows a method of incremental computation of the set `ex(C)` under the
97 * conclusions afforded under the computation model in consideration, of which
98 * SimGrid is apart, which allow for `ex(C)` to be computed much more efficiently.
99 * Intuitively, the idea is to take advantage of the fact that you can avoid a lot
100 * of repeated computation by exploiting the aforementioned properties (in [3]) in
101 * what is akin to a dynamic programming optimization. See [3] for more details
103 * @param C the configuration based on which the two sets `ex(C)` and `en(C)` are
105 * @param stateC the state of the program after having executed C (viz. `state(C)`)
106 * @param prev_exC the previous value of `ex(C)`, viz. that which was computed for
107 * the configuration `C' := C - {e}`
108 * @returns the extension set `ex(C)` of `C`
110 EventSet compute_exC(const Configuration& C, const State& stateC, const EventSet& prev_exC);
111 EventSet compute_enC(const Configuration& C, const EventSet& exC) const;
116 void move_to_stateCe(State* stateC, UnfoldingEvent* e);
119 * @brief Creates a new snapshot of the state of the application
120 * as it currently looks
122 std::unique_ptr<State> record_current_state();
125 * @brief Move the application side into the state at the top of the
126 * state stack provided
128 * As UDPOR performs its search, it moves the application-side along with
129 * it so that the application is always providing the checker with
130 * the correct information about what each actor is running (and whether
131 * those actors are enabled) at the state reached by the configuration it
134 * When UDPOR decides to "backtrack" (e.g. after reaching a configuration
135 * whose en(C) is empty), before it attempts to continue the search by taking
136 * a different path from a configuration it visited in the past, it must ensure
137 * that the application-side has moved back into `state(C)`.
139 * The search may have moved the application arbitrarily deep into its execution,
140 * and the search may backtrack arbitrarily closer to the beginning of the execution.
141 * The UDPOR implementation in SimGrid ensures that the stack is updated appropriately,
142 * but the process must still be regenerated.
144 void restore_program_state_with_current_stack();
147 * @brief Perform the functionality of the `Remove(e, C, D)` function in [1]
149 void clean_up_explore(const UnfoldingEvent* e, const Configuration& C, const EventSet& D);
151 } // namespace simgrid::mc::udpor