-/* 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
#ifndef SIMGRID_MC_UDPOR_CHECKER_HPP
#define SIMGRID_MC_UDPOR_CHECKER_HPP
+#include "src/mc/api/State.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 <list>
+#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;
-};
+ std::unique_ptr<State> get_current_state() { return std::make_unique<State>(get_remote_app()); }
+
+private:
+ Unfolding unfolding = Unfolding();
+
+ // The current sequence of states that the checker has
+ // visited in order to reach the current configuration
+ std::list<std::unique_ptr<State>> state_stack;
+
+ /**
+ * @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
+ *
+ * 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, EventSet prev_exC);
-} // namespace simgrid::mc
+ /**
+ * @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
+ */
+ 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 akin to 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);
+ EventSet compute_enC(const Configuration& C, const EventSet& exC) const;
+
+ /**
+ *
+ */
+ void move_to_stateCe(State* stateC, UnfoldingEvent* e);
+
+ /**
+ * @brief Creates a new snapshot of the state of the application
+ * as it currently looks
+ */
+ std::unique_ptr<State> record_current_state();
+
+ /**
+ * @brief Move the application side into the state at the top of the
+ * state stack provided
+ *
+ * As UDPOR performs its search, it moves the application-side along with
+ * it so that the application is always providing the checker with
+ * the correct information about what each actor is running (and whether
+ * those actors are enabled) at the state reached by the configuration it
+ * decides to search.
+ *
+ * When UDPOR decides to "backtrack" (e.g. after reaching a configuration
+ * whose en(C) is empty), before it attempts to continue the search by taking
+ * a different path from a configuration it visited in the past, it must ensure
+ * that the application-side has moved back into `state(C)`.
+ *
+ * The search may have moved the application arbitrarily deep into its execution,
+ * and the search may backtrack arbitrarily closer to the beginning of the execution.
+ * The UDPOR implementation in SimGrid ensures that the stack is updated appropriately,
+ * but the process must still be regenerated.
+ */
+ void restore_program_state_with_current_stack();
+
+ /**
+ * @brief Perform the functionality of the `Remove(e, C, D)` function in [1]
+ */
+ void clean_up_explore(const UnfoldingEvent* e, const Configuration& C, const EventSet& D);
+};
+} // namespace simgrid::mc::udpor
#endif
