#include "src/mc/explo/udpor/Configuration.hpp"
#include "src/mc/explo/udpor/History.hpp"
#include "src/mc/explo/udpor/UnfoldingEvent.hpp"
+#include "src/mc/explo/udpor/maximal_subsets_iterator.hpp"
#include "xbt/asserts.h"
#include <algorithm>
-#include <stack>
#include <stdexcept>
namespace simgrid::mc::udpor {
-Configuration::Configuration(std::initializer_list<UnfoldingEvent*> events) : Configuration(EventSet(std::move(events)))
+Configuration::Configuration(std::initializer_list<const UnfoldingEvent*> events)
+ : Configuration(EventSet(std::move(events)))
{
}
-Configuration::Configuration(EventSet events) : events_(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");
}
}
-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");
return;
}
+ // Preserves the property that the configuration is conflict-free
+ if (e->conflicts_with(*this)) {
+ 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;
- // 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<UnfoldingEvent*> Configuration::get_topologically_sorted_events() const
+std::vector<const UnfoldingEvent*> Configuration::get_topologically_sorted_events() const
{
- if (events_.empty()) {
- return std::vector<UnfoldingEvent*>();
- }
-
- std::stack<UnfoldingEvent*> event_stack;
- std::vector<UnfoldingEvent*> topological_ordering;
- EventSet unknown_events = events_, temporarily_marked_events, 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();
- }
- }
- }
- return topological_ordering;
+ return this->events_.get_topological_ordering();
}
-std::vector<UnfoldingEvent*> Configuration::get_topologically_sorted_events_of_reverse_graph() const
+std::vector<const UnfoldingEvent*> Configuration::get_topologically_sorted_events_of_reverse_graph() 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_of_reverse_graph();
}
-std::unique_ptr<CompatibilityGraph>
-Configuration::make_compatibility_graph_filtered_on(std::function<bool(UnfoldingEvent*)> pred) const
+EventSet Configuration::get_minimally_reproducible_events() const
{
- auto G = std::make_unique<CompatibilityGraph>();
-
- std::unordered_map<UnfoldingEvent*, std::unordered_set<CompatibilityGraphNode*>> discovered_conflicts;
- std::unordered_map<UnfoldingEvent*, CompatibilityGraphNode*> potential_placements;
- std::unordered_map<UnfoldingEvent*, int> direct_children_count;
-
- 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 known_conflicts = discovered_conflicts.find(e);
- const auto potential_placement = potential_placements.find(e);
- const auto potential_child_count = direct_children_count.find(e);
-
- const bool no_known_conflicts = known_conflicts == discovered_conflicts.end();
- const bool no_known_placement = potential_placement == potential_placements.end();
- const bool no_known_child_count = potential_child_count == direct_children_count.end();
-
- const auto e_conflicts =
- no_known_conflicts ? std::unordered_set<CompatibilityGraphNode*>() : std::move(known_conflicts->second);
- const auto e_child_count = no_known_child_count ? 0 : potential_child_count->second;
-
- CompatibilityGraphNode* e_placement = nullptr;
-
- // The justification is as follows:
- //
- // no_known_placement:
- // If nobody told us about a placement, we must either be a leaf event
- // OR be the cause of an event that itself has more than one cause.
- //
- // child_count >= 2:
- // If there are two or more events that this event causes,
- // then we certainly must be part of a different compatibility
- // graph node since
- const bool new_placement_required = no_known_placement || e_child_count >= 2;
-
- if (new_placement_required) {
- auto new_graph_node = std::make_unique<CompatibilityGraphNode>(e_conflicts, EventSet({e}));
- e_placement = new_graph_node.get();
- G->insert(std::move(new_graph_node));
+ // 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<Configuration>(*this)) {
+ if (maximal_set.size() > minimally_reproducible_events.size()) {
+ minimally_reproducible_events = maximal_set;
} 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 precense");
- // A child event told us this node can be in the
- // same compatibility node in the graph G. Add ourselves now
- e_placement = potential_placement->second;
- e_placement->add_event(e);
+ // 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;
}
-
- // 2. Update the children of `e`
-
- const EventSet& e_immediate_causes = e->get_immediate_causes();
- if (e_immediate_causes.size() == 1) {
- // 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`)
- UnfoldingEvent* only_ancestor = *e_immediate_causes.begin();
- potential_placements[only_ancestor] = e_placement;
- }
-
- // Our ancestors conflict with everyone `e` does else PLUS `e` itself
- auto parent_conflicts = std::move(e_conflicts);
- parent_conflicts.insert(e_placement);
- for (auto* cause : e_immediate_causes) {
- direct_children_count[cause] += 1;
- discovered_conflicts[cause] = parent_conflicts;
- }
-
- // This event will only ever be seen once in the
- // topological ordering. Hence, its resources do not
- // need to be kept around
- discovered_conflicts.erase(e);
- direct_children_count.erase(e);
- potential_placements.erase(e);
}
-
- return G;
+ return minimally_reproducible_events;
}
} // namespace simgrid::mc::udpor