X-Git-Url: http://bilbo.iut-bm.univ-fcomte.fr/pub/gitweb/simgrid.git/blobdiff_plain/b54403a768353ed64e0b4f4b5afcc89933f585f4..45c3a73f3553c8d365f61eaa8445f038db9bdb8f:/src/mc/explo/udpor/Configuration.cpp diff --git a/src/mc/explo/udpor/Configuration.cpp b/src/mc/explo/udpor/Configuration.cpp index 1923345630..44ec27005f 100644 --- a/src/mc/explo/udpor/Configuration.cpp +++ b/src/mc/explo/udpor/Configuration.cpp @@ -4,240 +4,244 @@ * under the terms of the license (GNU LGPL) which comes with this package. */ #include "src/mc/explo/udpor/Configuration.hpp" +#include "src/mc/explo/udpor/Comb.hpp" #include "src/mc/explo/udpor/History.hpp" +#include "src/mc/explo/udpor/Unfolding.hpp" #include "src/mc/explo/udpor/UnfoldingEvent.hpp" +#include "src/mc/explo/udpor/maximal_subsets_iterator.hpp" +#include "src/xbt/utils/iter/variable_for_loop.hpp" #include "xbt/asserts.h" #include -#include #include namespace simgrid::mc::udpor { -Configuration::Configuration(std::initializer_list events) : Configuration(EventSet(std::move(events))) +Configuration::Configuration(std::initializer_list events) + : Configuration(EventSet(std::move(events))) { } +Configuration::Configuration(const UnfoldingEvent* e) : Configuration(e->get_local_config()) +{ + // The local configuration should always be a valid configuration. We + // check the invariant regardless as a sanity check +} + +Configuration::Configuration(const History& history) : Configuration(history.get_all_events()) {} + Configuration::Configuration(const EventSet& events) : events_(events) { if (!events_.is_valid_configuration()) { throw std::invalid_argument("The events do not form a valid configuration"); } + + // Since we add in topological order under `<`, we know that the "most-recent" + // transition executed by each actor will appear last + for (const UnfoldingEvent* e : get_topologically_sorted_events()) { + this->latest_event_mapping[e->get_actor()] = e; + } } -void Configuration::add_event(UnfoldingEvent* e) +void Configuration::add_event(const UnfoldingEvent* e) { if (e == nullptr) { throw std::invalid_argument("Expected a nonnull `UnfoldingEvent*` but received NULL instead"); } + // The event is already a member of the configuration: there's + // nothing to do in this case if (this->events_.contains(e)) { return; } + // Preserves the property that the configuration is conflict-free + if (e->conflicts_with_any(this->events_)) { + throw std::invalid_argument("The newly added event conflicts with the events already " + "contained in the configuration. Adding this event violates " + "the property that a configuration is conflict-free"); + } + this->events_.insert(e); - this->newest_event = e; + this->newest_event = e; + this->latest_event_mapping[e->get_actor()] = e; - // Preserves the property that the configuration is valid - History history(e); - if (!this->events_.contains(history)) { + // Preserves the property that the configuration is causally closed + if (auto history = History(e); !this->events_.contains(history)) { throw std::invalid_argument("The newly added event has dependencies " "which are missing from this configuration"); } } -std::vector Configuration::get_topologically_sorted_events() const +bool Configuration::is_compatible_with(const UnfoldingEvent* e) const { - if (events_.empty()) { - return std::vector(); - } + // 1. `e`'s history must be contained in the configuration; + // otherwise adding the event would violate the invariant + // that a configuration is causally-closed + // + // 2. `e` itself must not conflict with any events of + // the configuration; otherwise adding the event would + // violate the invariant that a configuration is conflict-free + return contains(e->get_history()) and (not e->conflicts_with_any(this->events_)); +} - std::stack event_stack; - std::vector topological_ordering; - EventSet unknown_events = events_; - EventSet temporarily_marked_events; - EventSet permanently_marked_events; - - while (not unknown_events.empty()) { - EventSet discovered_events; - event_stack.push(*unknown_events.begin()); - - while (not event_stack.empty()) { - UnfoldingEvent* evt = event_stack.top(); - discovered_events.insert(evt); - - if (not temporarily_marked_events.contains(evt)) { - // If this event hasn't yet been marked, do - // so now so that if we see it again in a child we can - // detect a cycle and if we see it again here - // we can detect that the node is re-processed - temporarily_marked_events.insert(evt); - - EventSet immediate_causes = evt->get_immediate_causes(); - if (!immediate_causes.empty() && immediate_causes.is_subset_of(temporarily_marked_events)) { - throw std::invalid_argument("Attempted to perform a topological sort on a configuration " - "whose contents contain a cycle. The configuration (and the graph " - "connecting all of the events) is an invalid event structure"); - } - immediate_causes.subtract(discovered_events); - immediate_causes.subtract(permanently_marked_events); - const EventSet undiscovered_causes = std::move(immediate_causes); - - for (const auto cause : undiscovered_causes) { - event_stack.push(cause); - } - } else { - // Mark this event as: - // 1. discovered across all DFSs performed - // 2. permanently marked - // 3. part of the topological search - unknown_events.remove(evt); - temporarily_marked_events.remove(evt); - permanently_marked_events.insert(evt); - - // In moving this event to the end of the list, - // we are saying this events "happens before" other - // events that are added later. - topological_ordering.push_back(evt); - - // Only now do we remove the event, i.e. once - // we've processed the same event again - event_stack.pop(); - } - } +bool Configuration::is_compatible_with(const History& history) const +{ + // Note: We don't need to check if the `C` will be causally-closed + // after adding `history` to it since a) `C` itself is already + // causally-closed and b) the history is already causally closed + const auto event_diff = history.get_event_diff_with(*this); + + // The events that are contained outside of the configuration + // must themselves be free of conflicts. + if (not event_diff.is_conflict_free()) { + return false; } - return topological_ordering; + + // Now we need only ensure that there are no conflicts + // between events of the configuration and the events + // that lie outside of the configuration. There is no + // need to check if there are conflicts in `C`: we already + // know that it's conflict free + const auto begin = simgrid::xbt::variable_for_loop{{event_diff}, {this->events_}}; + const auto end = simgrid::xbt::variable_for_loop(); + return std::none_of(begin, end, [=](const auto event_pair) { + const UnfoldingEvent* e1 = *event_pair[0]; + const UnfoldingEvent* e2 = *event_pair[1]; + return e1->conflicts_with(e2); + }); } -std::vector Configuration::get_topologically_sorted_events_of_reverse_graph() const +std::vector Configuration::get_topologically_sorted_events() const { - // The method exploits the property that - // a topological sorting S^R of the reverse graph G^R - // of some graph G is simply the reverse of any - // topological sorting S of G. - auto topological_events = get_topologically_sorted_events(); - std::reverse(topological_events.begin(), topological_events.end()); - return topological_events; + return this->events_.get_topological_ordering(); } -std::unique_ptr -Configuration::make_compatibility_graph_filtered_on(std::function pred) const +std::vector Configuration::get_topologically_sorted_events_of_reverse_graph() const { - auto G = std::make_unique(); + return this->events_.get_topological_ordering_of_reverse_graph(); +} - struct UnfoldingEventSearchData { - int immediate_children_count = 0; - CompatibilityGraphNode* potential_placement = nullptr; - std::unordered_set conflicts = std::unordered_set(); - }; - std::unordered_map search_data; - - for (auto* e : get_topologically_sorted_events_of_reverse_graph()) { - - // 1. Figure out where to place `e` in `G` - - // Determine which nodes in the graph are in conflict - // with this event. These nodes would have been added by child - // events while iterating over the topological ordering of the reverse graph - - const auto e_search_data_loc = search_data.find(e); - const bool e_has_no_search_data = e_search_data_loc == search_data.end(); - const auto e_search_data = e_has_no_search_data ? UnfoldingEventSearchData() : std::move(e_search_data_loc->second); - - const auto& e_conflicts = e_search_data.conflicts; - const auto& e_potential_placement = e_search_data.potential_placement; - const auto e_child_count = e_search_data.immediate_children_count; - - const bool e_should_appear = pred(e); - CompatibilityGraphNode* e_placement = nullptr; - - if (e_should_appear) { - // The justification is as follows: - // - // e_has_no_search_data: - // The event `e` is a leaf node, so there are no prior - // nodes in `G` to join - // - // child_count >= 2: - // If there are two or more events that this event causes, - // then we certainly must be part of a compatibility - // graph node that conflicts with each of our children - // - // e_potential_placement == nullptr: - // If nobody told us about a placement and yet still have search - // data, this means means that our child `C` had more than one child itself, - // so it we could not have moved into `C`'s _potential_ placement. - const bool new_placement_required = - e_has_no_search_data || e_child_count >= 2 || e_potential_placement == nullptr; - - if (new_placement_required) { - auto new_graph_node = std::make_unique(e_conflicts, EventSet({e})); - e_placement = new_graph_node.get(); - G->insert(std::move(new_graph_node)); - } else { - xbt_assert(e_child_count == 1, "An event was informed by an immediate child of placement in " - "the same compatibility graph node, yet the child did not inform " - "the parent about its presence"); - // A child event told us this node can be in the - // same compatibility node in the graph G. Add ourselves now - e_placement = e_potential_placement; - e_placement->add_event(e); - } +EventSet Configuration::get_minimally_reproducible_events() const +{ + // The implementation exploits the following observations: + // + // To select the smallest reproducible set of events, we want + // to pick events that "knock out" a lot of others. Furthermore, + // we need to ensure that the events furthest down in the + // causality graph are also selected. If you combine these ideas, + // you're basically left with traversing the set of maximal + // subsets of C! And we have an iterator for that already! + // + // The next observation is that the moment we don't increase in size + // the current maximal set (or decrease the number of events), + // we know that the prior set `S` covered the entire history of C and + // was maximal. Subsequent sets will miss events earlier in the + // topological ordering that appear in `S` + EventSet minimally_reproducible_events = EventSet(); + + for (const auto& maximal_set : maximal_subsets_iterator_wrapper(*this)) { + if (maximal_set.size() > minimally_reproducible_events.size()) { + minimally_reproducible_events = maximal_set; + } else { + // The moment we see the iterator generate a set of size + // that is not monotonically increasing, we can stop: + // the set prior was the minimally-reproducible one + return minimally_reproducible_events; } + } + return minimally_reproducible_events; +} - // 2. Update the children of `e` - - const EventSet& e_immediate_causes = e->get_immediate_causes(); +std::optional Configuration::compute_alternative_to(const EventSet& D, const Unfolding& U) const +{ + // A full alternative can be computed by checking against everything in D + return compute_k_partial_alternative_to(D, U, D.size()); +} - // If there is only a single ancestor, then it MAY BE in - // the same "chain" of events as us. Note that the ancestor must - // also have only a single child (see the note on `new_placement_required`). +std::optional Configuration::compute_k_partial_alternative_to(const EventSet& D, const Unfolding& U, + size_t k) const +{ + // 1. Select k (of |D|, whichever is smaller) arbitrary events e_1, ..., e_k from D + const size_t k_alt_size = std::min(k, D.size()); + const auto D_hat = [&k_alt_size, &D]() { + std::vector D_hat(k_alt_size); + // TODO: Since any subset suffices for computing `k`-partial alternatives, + // potentially select intelligently here (e.g. perhaps pick events + // with transitions that we know are totally independent). This may be + // especially important if the enumeration is the slowest part of + // UDPOR // - // If there is more than one child, then each child is in conflict with `e` - // so we don't potentially place it - if (e_immediate_causes.size() == 1) { - UnfoldingEvent* only_ancestor = *e_immediate_causes.begin(); - - // If `e` is included in the graph, forward its placement on to - // the sole child. Otherwise attempt to forward `e`'s _potential_ - // (potential is stressed) placement. We can only forward `e`'s - // potential placement iff `e` has only a single child; for if - // `e` had more children, then our sole ancestor would conflict with - // each one of `e`'s children and thus couldn't be in the same group - // as any of them - if (e_should_appear) { - search_data[only_ancestor].potential_placement = e_placement; - } else { - search_data[only_ancestor].potential_placement = e_child_count == 1 ? e_potential_placement : nullptr; + // For now, simply pick the first `k` events + std::copy_n(D.begin(), k_alt_size, D_hat.begin()); + return D_hat; + }(); + + // 2. Build a U-comb of size k, where spike `s_i` contains + // all events in conflict with `e_i` + // + // 3. EXCEPT those events e' for which [e'] + C is not a configuration or + // [e'] intersects D + // + // NOTE: This is an expensive operation as we must traverse the entire unfolding + // and compute `C.is_compatible_with(History)` for every event in the structure :/. + // A later performance improvement would be to incorporate the work of Nguyen et al. + // into SimGrid which associated additonal data structures with each unfolding event. + // Since that is a rather complicated addition, we defer it to a later time... + Comb comb(k); + + for (const auto* e : U) { + for (size_t i = 0; i < k_alt_size; i++) { + const UnfoldingEvent* e_i = D_hat[i]; + if (const auto e_local_config = History(e); + e_i->conflicts_with(e) and (not D.intersects(e_local_config)) and is_compatible_with(e_local_config)) { + comb[i].push_back(e); } } + } - // Our ancestors conflict with everyone `e` does else PLUS `e` itself - // ONLY IF e actually was placed - auto parent_conflicts = std::move(e_conflicts); - if (e_should_appear) { - parent_conflicts.insert(e_placement); - } - for (auto* cause : e_immediate_causes) { - search_data[cause].immediate_children_count += 1; - - for (auto parent_conflict : parent_conflicts) { - search_data[cause].conflicts.insert(parent_conflict); - } + // 4. Find any such combination in comb satisfying + // ~(e_i' # e_j') for i != j + // + // NOTE: This is a VERY expensive operation: it enumerates all possible + // ways to select an element from each spike. Unfortunately there's no + // way around the enumeration, as computing a full alternative in general is + // NP-complete (although computing the k-partial alternative is polynomial in + // the number of events) + const auto map_events = [](const std::vector& spikes) { + std::vector events; + for (const auto& event_in_spike : spikes) { + events.push_back(*event_in_spike); } + return EventSet(std::move(events)); + }; + const auto alternative = + std::find_if(comb.combinations_begin(), comb.combinations_end(), + [&map_events](const auto& vector) { return map_events(vector).is_conflict_free(); }); - // This event will only ever be seen once in the - // topological ordering. Hence, its resources do not - // need to be kept around - search_data.erase(e); + // No such alternative exists + if (alternative == comb.combinations_end()) { + return std::nullopt; } - return G; + // 5. J := [e_1] + [e_2] + ... + [e_k] is a k-partial alternative + return Configuration(History(map_events(*alternative))); +} + +std::optional Configuration::get_latest_event_of(aid_t aid) const +{ + if (const auto latest_event = latest_event_mapping.find(aid); latest_event != latest_event_mapping.end()) { + return std::optional{latest_event->second}; + } + return std::nullopt; } -std::unique_ptr Configuration::make_compatibility_graph() const +std::optional Configuration::get_latest_action_of(aid_t aid) const { - return make_compatibility_graph_filtered_on([=](const UnfoldingEvent*) { return true; }); + if (const auto latest_event = get_latest_event_of(aid); latest_event.has_value()) { + return std::optional{latest_event.value()->get_transition()}; + } + return std::nullopt; } } // namespace simgrid::mc::udpor