-/* Copyright (c) 2007-2022. The SimGrid Team.
+/* Copyright (c) 2007-2023. The SimGrid Team.
* All rights reserved. */
/* This program is free software; you can redistribute it and/or modify it
#define SIMGRID_MC_UDPOR_CHECKER_HPP
#include "src/mc/explo/Exploration.hpp"
+#include "src/mc/explo/udpor/Configuration.hpp"
+#include "src/mc/explo/udpor/EventSet.hpp"
+#include "src/mc/explo/udpor/Unfolding.hpp"
+#include "src/mc/explo/udpor/UnfoldingEvent.hpp"
#include "src/mc/mc_record.hpp"
-namespace simgrid::mc {
+#include <functional>
+#include <optional>
+namespace simgrid::mc::udpor {
+
+/**
+ * @brief Performs exploration of a concurrent system via the
+ * UDPOR algorithm
+ *
+ * The `UdporChecker` implementation is based primarily off three papers,
+ * herein referred to as [1], [2], and [3] respectively, as well as the
+ * current implementation of `tiny_simgrid`:
+ *
+ * 1. "Unfolding-based Partial Order Reduction" by Rodriguez et al.
+ * 2. Quasi-Optimal Partial Order Reduction by Nguyen et al.
+ * 3. The Anh Pham's Thesis "Exploration efficace de l'espace ..."
+ */
class XBT_PRIVATE UdporChecker : public Exploration {
public:
- explicit UdporChecker(RemoteApp& remote_app);
+ explicit UdporChecker(const std::vector<char*>& args);
+
void run() override;
RecordTrace get_record_trace() override;
std::vector<std::string> get_textual_trace() override;
- void log_state() override;
-};
-} // namespace simgrid::mc
+ inline std::unique_ptr<State> get_current_state() { return std::make_unique<State>(get_remote_app()); }
+
+private:
+ /**
+ * @brief The "relevant" portions of the unfolding that must be kept around to ensure that
+ * UDPOR properly searches the state space
+ *
+ * The set `U` is a global variable which is maintained by UDPOR
+ * to keep track of "just enough" information about the unfolding
+ * to compute *alternatives* (see the paper for more details).
+ *
+ * @invariant: When a new event is created by UDPOR, it is inserted into
+ * this set. All new events that are created by UDPOR have causes that
+ * also exist in U and are valid for the duration of the search.
+ *
+ * If an event is discarded instead of moved from set `U` to set `G`,
+ * the event and its contents will be discarded.
+ */
+ EventSet U;
+
+ /**
+ * @brief The "irrelevant" portions of the unfolding that do not need to be kept
+ * around to ensure that UDPOR functions correctly
+ *
+ * The set `G` is another global variable maintained by the UDPOR algorithm which
+ * is used to keep track of all events which used to be important to UDPOR
+ */
+ EventSet G;
+
+ /// @brief UDPOR's current "view" of the program it is exploring
+ Unfolding unfolding = Unfolding();
+
+ /**
+ * @brief A collection of specialized functions which can incrementally
+ * compute the extension of a configuration based on the action taken
+ */
+ using ExtensionFunction = std::function<EventSet(const Configuration&, const std::shared_ptr<Transition>)>;
+ std::unordered_map<Transition::Type, ExtensionFunction> incremental_extension_functions =
+ std::unordered_map<Transition::Type, ExtensionFunction>();
+
+ /**
+ * @brief Explores the unfolding of the concurrent system
+ * represented by the ModelChecker instance "mcmodel_checker"
+ *
+ * This function performs the actual search following the
+ * UDPOR algorithm according to [1].
+ *
+ * @param C the current configuration from which UDPOR will be used
+ * to explore expansions of the concurrent system being modeled
+ * @param D the set of events that should not be considered by UDPOR
+ * while performing its searches, in order to avoid sleep-set blocked
+ * executions. See [1] for more details
+ * @param A the set of events to "guide" UDPOR in the correct direction
+ * when it returns back to a node in the unfolding and must decide among
+ * events to select from `ex(C)`. See [1] for more details
+ * @param stateC the state of the program after having executed `C`,
+ * viz. `state(C)` using the notation of [1]
+ *
+ * TODO: Add the optimization where we can check if e == e_prior
+ * to prevent repeated work when computing ex(C)
+ */
+ void explore(const Configuration& C, EventSet D, EventSet A, std::unique_ptr<State> stateC, EventSet prev_exC);
+
+ /**
+ * @brief Identifies the next event from the unfolding of the concurrent system
+ * that should next be explored as an extension of a configuration with
+ * enabled events `enC`
+ *
+ * @param A The set of events `A` maintained by the UDPOR algorithm to help
+ * determine how events should be selected. See the original paper [1] for more details
+ *
+ * @param enC The set `enC` of enabled events from the extension set `exC` used
+ * by the UDPOR algorithm to select new events to search. See the original
+ * paper [1] for more details
+ */
+ const UnfoldingEvent* select_next_unfolding_event(const EventSet& A, const EventSet& enC);
+
+ /**
+ * @brief Computes the sets `ex(C)` and `en(C)` of the given configuration
+ * `C` as an incremental computation from the the previous computation of `ex(C)`
+ *
+ * A central component to UDPOR is the computation of the set `ex(C)`. The
+ * extension set `ex(C)` of a configuration `C` is defined as the set of events
+ * outside of `C` whose full dependency chain is contained in `C` (see [1]
+ * for more details).
+ *
+ * In general, computing `ex(C)` is very expensive. In paper [3], The Anh Pham
+ * shows a method of incremental computation of the set `ex(C)` under the
+ * conclusions afforded under the computation model in consideration, of which
+ * SimGrid is apart, which allow for `ex(C)` to be computed much more efficiently.
+ * Intuitively, the idea is to take advantage of the fact that you can avoid a lot
+ * of repeated computation by exploiting the aforementioned properties (in [3]) in
+ * what is effectively a dynamic programming optimization. See [3] for more details
+ *
+ * @param C the configuration based on which the two sets `ex(C)` and `en(C)` are
+ * computed
+ * @param stateC the state of the program after having executed C (viz. `state(C)`)
+ * @param prev_exC the previous value of `ex(C)`, viz. that which was computed for
+ * the configuration `C' := C - {e}`
+ * @returns the extension set `ex(C)` of `C`
+ */
+ EventSet compute_exC(const Configuration& C, const State& stateC, const EventSet& prev_exC);
+
+ /**
+ * @brief Computes a portion of the extension set of a configuration given
+ * some action `action`
+ */
+ EventSet compute_exC_by_enumeration(const Configuration& C, const std::shared_ptr<Transition> action);
+
+ EventSet compute_enC(const Configuration& C, const EventSet& exC) const;
+
+ /**
+ *
+ */
+ EventSet compute_partial_alternative(const EventSet& D, const Configuration& C, const unsigned k) const;
+
+ /**
+ *
+ */
+ void move_to_stateCe(State& stateC, const UnfoldingEvent& e);
+
+ /**
+ * @brief Creates a new snapshot of the state of the progam undergoing
+ * model checking
+ *
+ * @returns the handle used to uniquely identify this state later in the
+ * exploration of the unfolding. You provide this handle to an event in the
+ * unfolding to regenerate past states
+ */
+ std::unique_ptr<State> record_current_state();
+
+ /**
+ *
+ */
+ void restore_program_state_to(const State& stateC);
+
+ /**
+ *
+ */
+ void clean_up_explore(const UnfoldingEvent* e, const Configuration& C, const EventSet& D);
+};
+} // namespace simgrid::mc::udpor
#endif
