#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>
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)))
{
}
}
}
-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");
}
}
-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*>();
+ return std::vector<const UnfoldingEvent*>();
}
- std::stack<UnfoldingEvent*> event_stack;
- std::vector<UnfoldingEvent*> topological_ordering;
+ std::stack<const UnfoldingEvent*> event_stack;
+ std::vector<const UnfoldingEvent*> topological_ordering;
EventSet unknown_events = events_;
EventSet temporarily_marked_events;
EventSet permanently_marked_events;
event_stack.push(*unknown_events.begin());
while (not event_stack.empty()) {
- UnfoldingEvent* evt = event_stack.top();
+ const UnfoldingEvent* evt = event_stack.top();
discovered_events.insert(evt);
if (not temporarily_marked_events.contains(evt)) {
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);
topological_ordering.push_back(evt);
// Only now do we remove the event, i.e. once
- // we've processed the same event again
+ // we've processed the same event twice
event_stack.pop();
}
}
return 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
+ // The implementation 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.
return topological_events;
}
-std::unique_ptr<CompatibilityGraph>
-Configuration::make_compatibility_graph_filtered_on(std::function<bool(const UnfoldingEvent*)> pred) const
+EventSet Configuration::get_minimally_reproducible_events() const
{
- auto G = std::make_unique<CompatibilityGraph>();
-
- struct UnfoldingEventSearchData {
- int immediate_children_count = 0;
- CompatibilityGraphNode* potential_placement = nullptr;
- std::unordered_set<CompatibilityGraphNode*> conflicts = std::unordered_set<CompatibilityGraphNode*>();
- };
- std::unordered_map<UnfoldingEvent*, UnfoldingEventSearchData> 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<CompatibilityGraphNode>(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);
- }
- }
-
- // 2. Update the children of `e`
-
- const EventSet& e_immediate_causes = e->get_immediate_causes();
-
- // 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`).
- //
- // 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;
- }
- }
-
- // 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);
+ // 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;
}
- 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);
- }
- }
-
- // 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);
}
-
- return G;
-}
-
-std::unique_ptr<CompatibilityGraph> Configuration::make_compatibility_graph() const
-{
- return make_compatibility_graph_filtered_on([=](const UnfoldingEvent*) { return true; });
+ return minimally_reproducible_events;
}
} // namespace simgrid::mc::udpor
