* under the terms of the license (GNU LGPL) which comes with this package. */
#include "src/mc/explo/odpor/Execution.hpp"
-#include <exception>
+#include "src/mc/api/State.hpp"
+#include "src/mc/explo/odpor/ReversibleRaceCalculator.hpp"
+#include "xbt/asserts.h"
+#include "xbt/string.hpp"
+#include <algorithm>
#include <limits>
+#include <vector>
+
+XBT_LOG_NEW_DEFAULT_SUBCATEGORY(mc_odpor_execution, mc_dfs, "ODPOR exploration algorithm of the model-checker");
namespace simgrid::mc::odpor {
+std::vector<std::string> get_textual_trace(const PartialExecution& w)
+{
+ std::vector<std::string> trace;
+ for (const auto& t : w) {
+ auto a = xbt::string_printf("Actor %ld: %s", t->aid_, t->to_string(true).c_str());
+ trace.emplace_back(std::move(a));
+ }
+ return trace;
+}
+
+Execution::Execution(const PartialExecution& w)
+{
+ push_partial_execution(w);
+}
+
+void Execution::push_transition(std::shared_ptr<Transition> t)
+{
+ if (t == nullptr) {
+ throw std::invalid_argument("Unexpectedly received `nullptr`");
+ }
+ ClockVector max_clock_vector;
+ for (const Event& e : this->contents_) {
+ if (e.get_transition()->depends(t.get())) {
+ max_clock_vector = ClockVector::max(max_clock_vector, e.get_clock_vector());
+ }
+ }
+ max_clock_vector[t->aid_] = this->size();
+ contents_.push_back(Event({std::move(t), max_clock_vector}));
+}
+
+void Execution::push_partial_execution(const PartialExecution& w)
+{
+ for (const auto& t : w) {
+ push_transition(t);
+ }
+}
+
+std::vector<std::string> Execution::get_textual_trace() const
+{
+ std::vector<std::string> trace;
+ for (const auto& t : this->contents_) {
+ auto a = xbt::string_printf("Actor %ld: %s", t.get_transition()->aid_, t.get_transition()->to_string(true).c_str());
+ trace.emplace_back(std::move(a));
+ }
+ return trace;
+}
+
std::unordered_set<Execution::EventHandle> Execution::get_racing_events_of(Execution::EventHandle target) const
{
std::unordered_set<Execution::EventHandle> racing_events;
+ // This keep tracks of events that happens-before the target
std::unordered_set<Execution::EventHandle> disqualified_events;
// For each event of the execution
- for (auto e_i = target; e_i > 0 && e_i != std::numeric_limits<Execution::EventHandle>::max(); e_i--) {
+ for (auto e_i = target; e_i != std::numeric_limits<Execution::EventHandle>::max(); e_i--) {
// We need `e_i -->_E target` as a necessary condition
if (not happens_before(e_i, target)) {
+ XBT_DEBUG("ODPOR_RACING_EVENTS with `%u` : `%u` discarded because `%u` --\\-->_E `%u`", target, e_i, e_i, target);
continue;
}
// Further, `proc(e_i) != proc(target)`
if (get_actor_with_handle(e_i) == get_actor_with_handle(target)) {
disqualified_events.insert(e_i);
+ XBT_DEBUG("ODPOR_RACING_EVENTS with `%u` : `%u` disqualified because proc(`%u`)=proc(`%u`)", target, e_i, e_i,
+ target);
continue;
}
// 2. disqualified_events.count(e_j) > 0
// then e_i --->_E target indirectly (either through
// e_j directly, or transitively through e_j)
- if (happens_before(e_i, e_j) and disqualified_events.count(e_j) > 0) {
+ if (disqualified_events.count(e_j) > 0 && happens_before(e_i, e_j)) {
+ XBT_DEBUG("ODPOR_RACING_EVENTS with `%u` : `%u` disqualified because `%u` happens-between `%u`-->`%u`-->`%u`)",
+ target, e_i, e_j, e_i, e_j, target);
disqualified_events.insert(e_i);
break;
}
// it (since this would transitively make it the event
// which "happens-between" `target` and `e`)
if (disqualified_events.count(e_i) == 0) {
+ XBT_DEBUG("ODPOR_RACING_EVENTS with `%u` : `%u` is a valid racing event", target, e_i);
racing_events.insert(e_i);
disqualified_events.insert(e_i);
}
return racing_events;
}
-bool Execution::happens_before(Execution::EventHandle e1_handle, Execution::EventHandle e2_handle) const
+std::unordered_set<Execution::EventHandle> Execution::get_reversible_races_of(EventHandle handle) const
{
- // 1. "happens-before" is a subset of "occurs before"
- if (e1_handle > e2_handle) {
- return false;
+ std::unordered_set<EventHandle> reversible_races;
+ for (EventHandle race : get_racing_events_of(handle)) {
+ if (ReversibleRaceCalculator::is_race_reversible(*this, race, handle)) {
+ reversible_races.insert(race);
+ }
}
+ return reversible_races;
+}
- // Each execution maintains a stack of clock vectors which are updated
- // according to the procedure outlined in section 4 of the original DPOR paper
- const Event& e2 = get_event_with_handle(e2_handle);
- const aid_t proc_e1 = get_actor_with_handle(e1_handle);
- return e1_handle <= e2.get_clock_vector().get(proc_e1).value_or(0);
+Execution Execution::get_prefix_before(Execution::EventHandle handle) const
+{
+ return Execution(std::vector<Event>{contents_.begin(), contents_.begin() + handle});
}
-Execution Execution::get_prefix_up_to(Execution::EventHandle handle)
+std::unordered_set<aid_t>
+Execution::get_missing_source_set_actors_from(EventHandle e, const std::unordered_set<aid_t>& backtrack_set) const
{
- if (handle == static_cast<Execution::EventHandle>(0)) {
- return Execution();
+ // If this execution is empty, there are no initials
+ // relative to the last transition added to the execution
+ // since such a transition does not exist
+ if (empty()) {
+ return std::unordered_set<aid_t>{};
}
- return Execution(std::vector<Event>{contents_.begin(), contents_.begin() + (handle - 1)});
+
+ // To actually compute `I_[E'](v) ∩ backtrack(E')`, we must
+ // first compute `E'` and "move" in the direction of `v`.
+ // We perform a scan over `E` (this execution) and make
+ // note of any events which occur after `e` but don't
+ // "happen-after" `e` by pushing them onto `E'`. Note that
+ // correctness is still preserved in computing `v` "on-the-fly"
+ // to determine if an event `e` by actor `q` is an initial for `E'`
+ // after `v`: only those events that "occur-before" `e` in `v` could
+ // "happen-before" `ve for any valid "happens-before" relation
+ // (see property 1 in the ODPOR paper, viz. "is included in <_E")
+
+ // First, grab `E' := pre(e, E)` and determine what actor `p` is
+ const auto next_E_p = get_latest_event_handle().value();
+ xbt_assert(e != next_E_p,
+ "This method assumes that the event `e` (%u) and `next_[E](p)` (%u)"
+ "are in a reversible race, yet we claim to have such a race between the"
+ "same event. This indicates the the SDPOR pseudocode implementation is broken "
+ "as it supplies these values.",
+ e, next_E_p);
+ Execution E_prime_v = get_prefix_before(e);
+ std::vector<sdpor::Execution::EventHandle> v;
+ std::unordered_set<aid_t> I_E_prime_v;
+ std::unordered_set<aid_t> disqualified_actors;
+
+ // Note `e + 1` here: `notdep(e, E)` is defined as the
+ // set of events that *occur-after* but don't *happen-after* `e`
+ for (auto e_prime = e + 1; e_prime <= next_E_p; ++e_prime) {
+ // Any event `e*` which occurs after `e` but which does not
+ // happen after `e` is a member of `v`. In addition to marking
+ // the event in `v`, we also "simulate" running the action `v`
+ // from E'
+ if (not happens_before(e, e_prime) || e_prime == next_E_p) {
+ // First, push the transition onto the hypothetical execution
+ E_prime_v.push_transition(get_event_with_handle(e_prime).get_transition());
+ const EventHandle e_prime_in_E_prime_v = E_prime_v.get_latest_event_handle().value();
+
+ // When checking whether any event in `dom_[E'](v)` happens before
+ // `next_[E'](q)` below for thread `q`, we must consider that the
+ // events relative to `E` (this execution) are different than those
+ // relative to `E'.v`. Thus e.g. event `7` in `E` may be event `4`
+ // in `E'.v`. Since we are asking about "happens-before"
+ // `-->_[E'.v]` about `E'.v`, we must build `v` relative to `E'`.
+ //
+ // Note that we add `q` to v regardless of whether `q` itself has been
+ // disqualified since we've determined that `e_prime` "occurs-after" but
+ // does not "happen-after" `e`
+ v.push_back(e_prime_in_E_prime_v);
+
+ const aid_t q = E_prime_v.get_actor_with_handle(e_prime_in_E_prime_v);
+ if (disqualified_actors.count(q) > 0) { // Did we already note that `q` is not an initial?
+ continue;
+ }
+ const bool is_initial = std::none_of(v.begin(), v.end(), [&](const auto& e_star) {
+ return E_prime_v.happens_before(e_star, e_prime_in_E_prime_v);
+ });
+ if (is_initial) {
+ // If the backtrack set already contains `q`, we're done:
+ // they've made note to search for (or have already searched for)
+ // this initial
+ if (backtrack_set.count(q) > 0) {
+ return std::unordered_set<aid_t>{};
+ } else {
+ I_E_prime_v.insert(q);
+ }
+ } else {
+ // If `q` is disqualified as a candidate, clearly
+ // no event occurring after `e_prime` in `E` executed
+ // by actor `q` will qualify since any (valid) happens-before
+ // relation orders actions taken by each actor
+ disqualified_actors.insert(q);
+ }
+ }
+ }
+ xbt_assert(not I_E_prime_v.empty(),
+ "For any non-empty execution, we know that "
+ "at minimum one actor is an initial since "
+ "some execution is possible with respect to a "
+ "prefix before event `%u`, yet we didn't find anyone. "
+ "This implies the implementation of this function is broken.",
+ e);
+ return I_E_prime_v;
}
-void Execution::push_transition(const Transition* t)
+std::optional<PartialExecution> Execution::get_odpor_extension_from(EventHandle e, EventHandle e_prime,
+ const State& state_at_e) const
{
- if (t == nullptr) {
- throw std::invalid_argument("Unexpectedly received `nullptr`");
+ // `e` is assumed to be in a reversible race with `e_prime`.
+ // If `e > e_prime`, then `e` occurs-after `e_prime` which means
+ // `e` could not race with if
+ if (e > e_prime) {
+ throw std::invalid_argument("ODPOR extensions can only be computed for "
+ "events in a reversible race, which is claimed, "
+ "yet the racing event 'occurs-after' the target");
}
- ClockVector max_clock_vector;
- for (const Event& e : this->contents_) {
- if (e.get_transition()->depends(t)) {
- max_clock_vector = ClockVector::max(max_clock_vector, e.get_clock_vector());
+
+ if (empty()) {
+ return std::nullopt;
+ }
+
+ PartialExecution v;
+ std::vector<Execution::EventHandle> v_handles;
+ std::unordered_set<aid_t> WI_E_prime_v;
+ std::unordered_set<aid_t> disqualified_actors;
+ Execution E_prime_v = get_prefix_before(e);
+ const std::unordered_set<aid_t> sleep_E_prime = state_at_e.get_sleeping_actors();
+
+ // Note `e + 1` here: `notdep(e, E)` is defined as the
+ // set of events that *occur-after* but don't *happen-after* `e`
+ //
+ // SUBTLE NOTE: ODPOR requires us to compute `notdep(e, E)` EVEN THOUGH
+ // the race is between `e` and `e'`; that is, events occurring in `E`
+ // that "occur-after" `e'` may end up in the partial execution `v`.
+ //
+ // Observe that `notdep(e, E).proc(e')` will contain all transitions
+ // that don't happen-after `e` in the order they appear FOLLOWED BY
+ // THE **TRANSITION** ASSOCIATED WITH **`e'`**!!
+ //
+ // SUBTLE NOTE: Observe that any event that "happens-after" `e'`
+ // must necessarily "happen-after" `e` as well, since `e` and
+ // `e'` are presumed to be in a reversible race. Hence, we know that
+ // all events `e_star` such that `e` "happens-before" `e_star` cannot affect
+ // the enabledness of `e'`; furthermore, `e'` cannot affect the enabledness
+ // of any event independent with `e` that "occurs-after" `e'`
+ for (auto e_star = e + 1; e_star <= get_latest_event_handle().value(); ++e_star) {
+ // Any event `e*` which occurs after `e` but which does not
+ // happen after `e` is a member of `v`. In addition to marking
+ // the event in `v`, we also "simulate" running the action `v` from E'
+ // to be able to compute `--->[E'.v]`
+ if (not happens_before(e, e_star)) {
+ xbt_assert(e_star != e_prime,
+ "Invariant Violation: We claimed events %u and %u were in a reversible race, yet we also "
+ "claim that they do not happen-before one another. This is impossible: "
+ "are you sure that the two events are in a reversible race?",
+ e, e_prime);
+ E_prime_v.push_transition(get_event_with_handle(e_star).get_transition());
+ v.push_back(get_event_with_handle(e_star).get_transition());
+
+ const EventHandle e_star_in_E_prime_v = E_prime_v.get_latest_event_handle().value();
+
+ // When checking whether any event in `dom_[E'](v)` happens before
+ // `next_[E'](q)` below for thread `q`, we must consider that the
+ // events relative to `E` (this execution) are different than those
+ // relative to `E'.v`. Thus e.g. event `7` in `E` may be event `4`
+ // in `E'.v`. Since we are asking about "happens-before"
+ // `-->_[E'.v]` about `E'.v`, we must build `v` relative to `E'`
+ v_handles.push_back(e_star_in_E_prime_v);
+
+ // Note that we add `q` to v regardless of whether `q` itself has been
+ // disqualified since `q` may itself disqualify other actors
+ // (i.e. even if `q` is disqualified from being an initial, it
+ // is still contained in the sequence `v`)
+ const aid_t q = E_prime_v.get_actor_with_handle(e_star_in_E_prime_v);
+ if (disqualified_actors.count(q) > 0) { // Did we already note that `q` is not an initial?
+ continue;
+ }
+ const bool is_initial = std::none_of(v_handles.begin(), v_handles.end(), [&](const auto& handle) {
+ return E_prime_v.happens_before(handle, e_star_in_E_prime_v);
+ });
+ if (is_initial) {
+ // If the sleep set already contains `q`, we're done:
+ // we've found an initial contained in the sleep set and
+ // so the intersection is non-empty
+ if (sleep_E_prime.count(q) > 0) {
+ return std::nullopt;
+ } else {
+ WI_E_prime_v.insert(q);
+ }
+ } else {
+ // If `q` is disqualified as a candidate, clearly
+ // no event occurring after `e_prime` in `E` executed
+ // by actor `q` will qualify since any (valid) happens-before
+ // relation orders actions taken by each actor
+ disqualified_actors.insert(q);
+ }
+ }
+ }
+
+ // Now we add `e_prime := <q, i>` to `E'.v` and repeat the same work
+ // It's possible `proc(e_prime)` is an initial
+ //
+ // Note the form of `v` in the pseudocode:
+ // `v := notdep(e, E).e'^
+ E_prime_v.push_transition(get_event_with_handle(e_prime).get_transition());
+ v.push_back(get_event_with_handle(e_prime).get_transition());
+
+ const EventHandle e_prime_in_E_prime_v = E_prime_v.get_latest_event_handle().value();
+ v_handles.push_back(e_prime_in_E_prime_v);
+
+ const bool is_initial = std::none_of(v_handles.begin(), v_handles.end(), [&](const auto& handle) {
+ return E_prime_v.happens_before(handle, e_prime_in_E_prime_v);
+ });
+ if (is_initial) {
+ if (const aid_t q = E_prime_v.get_actor_with_handle(e_prime_in_E_prime_v); sleep_E_prime.count(q) > 0) {
+ return std::nullopt;
+ } else {
+ WI_E_prime_v.insert(q);
+ }
+ }
+
+ const Execution pre_E_e = get_prefix_before(e);
+ const auto sleeping_actors = state_at_e.get_sleeping_actors();
+
+ // Check if any enabled actor that is independent with
+ // this execution after `v` is contained in the sleep set
+ for (const auto& [aid, astate] : state_at_e.get_actors_list()) {
+ const bool is_in_WI_E =
+ astate.is_enabled() and pre_E_e.is_independent_with_execution_of(v, astate.get_transition());
+ const bool is_in_sleep_set = sleeping_actors.count(aid) > 0;
+
+ // `action(aid)` is in `WI_[E](v)` but also is contained in the sleep set.
+ // This implies that the intersection between the two is non-empty
+ if (is_in_WI_E && is_in_sleep_set)
+ return std::nullopt;
+ }
+
+ return v;
+}
+
+bool Execution::is_initial_after_execution_of(const PartialExecution& w, aid_t p) const
+{
+ auto E_w = *this;
+ std::vector<EventHandle> w_handles;
+ for (const auto& w_i : w) {
+ // Take one step in the direction of `w`
+ E_w.push_transition(w_i);
+
+ // If that step happened to be executed by `p`,
+ // great: we know that `p` is contained in `w`.
+ // We now need to verify that it doens't "happen-after"
+ // any events which occur before it
+ if (w_i->aid_ == p) {
+ const auto p_handle = E_w.get_latest_event_handle().value();
+ return std::none_of(w_handles.begin(), w_handles.end(),
+ [&](const auto handle) { return E_w.happens_before(handle, p_handle); });
+ } else {
+ w_handles.push_back(E_w.get_latest_event_handle().value());
}
}
- // The entry in the vector for `t->aid_` is the size
- // of the new stack, which will have a size one greater
- // than that before we insert the new events
- max_clock_vector[t->aid_] = this->size() + 1;
- contents_.push_back(Event({t, max_clock_vector}));
+ return false;
}
-void Execution::pop_latest()
+bool Execution::is_independent_with_execution_of(const PartialExecution& w, std::shared_ptr<Transition> next_E_p) const
{
- contents_.pop_back();
+ // INVARIANT: Here, we assume that for any process `p_i` of `w`,
+ // the events of this execution followed by the execution of all
+ // actors occurring before `p_i` in `v` (`p_j`, `0 <= j < i`)
+ // are sufficient to enable `p_i`. This is fortunately the case
+ // with what ODPOR requires of us, viz. to ask the question about
+ // `v := notdep(e, E)` for some execution `E` and event `e` of
+ // that execution.
+ auto E_p_w = *this;
+ E_p_w.push_transition(std::move(next_E_p));
+ const auto p_handle = E_p_w.get_latest_event_handle().value();
+
+ // As we add events to `w`, verify that none
+ // of them "happen-after" the event associated with
+ // the step `next_E_p` (viz. p_handle)
+ for (const auto& w_i : w) {
+ E_p_w.push_transition(w_i);
+ const auto w_i_handle = E_p_w.get_latest_event_handle().value();
+ if (E_p_w.happens_before(p_handle, w_i_handle)) {
+ return false;
+ }
+ }
+ return true;
+}
+
+std::optional<PartialExecution> Execution::get_shortest_odpor_sq_subset_insertion(const PartialExecution& v,
+ const PartialExecution& w) const
+{
+ // See section 4 of Abdulla. et al.'s 2017 ODPOR paper for details (specifically
+ // where the [iterative] computation of `v ~_[E] w` is described)
+ auto E_v = *this;
+ auto w_now = w;
+
+ for (const auto& next_E_p : v) {
+ // Is `p in `I_[E](w)`?
+ if (const aid_t p = next_E_p->aid_; E_v.is_initial_after_execution_of(w_now, p)) {
+ // Remove `p` from w and continue
+
+ // INVARIANT: If `p` occurs in `w`, it had better refer to the same
+ // transition referenced by `v`. Unfortunately, we have two
+ // sources of truth here which can be manipulated at the same
+ // time as arguments to the function. If ODPOR works correctly,
+ // they should always refer to the same value; but as a sanity check,
+ // we have an assert that tests that at least the types are the same.
+ const auto action_by_p_in_w =
+ std::find_if(w_now.begin(), w_now.end(), [=](const auto& action) { return action->aid_ == p; });
+ xbt_assert(action_by_p_in_w != w_now.end(), "Invariant violated: actor `p` "
+ "is claimed to be an initial after `w` but is "
+ "not actually contained in `w`. This indicates that there "
+ "is a bug computing initials");
+ const auto& w_action = *action_by_p_in_w;
+ xbt_assert(w_action->type_ == next_E_p->type_,
+ "Invariant violated: `v` claims that actor `%ld` executes '%s' while "
+ "`w` claims that it executes '%s'. These two partial executions both "
+ "refer to `next_[E](p)`, which should be the same",
+ p, next_E_p->to_string(false).c_str(), w_action->to_string(false).c_str());
+ w_now.erase(action_by_p_in_w);
+ }
+ // Is `E ⊢ p ◇ w`?
+ else if (E_v.is_independent_with_execution_of(w_now, next_E_p)) {
+ // INVARIANT: Note that it is impossible for `p` to be
+ // excluded from the set `I_[E](w)` BUT ALSO be contained in
+ // `w` itself if `E ⊢ p ◇ w` (intuitively, the fact that `E ⊢ p ◇ w`
+ // means that are able to move `p` anywhere in `w` IF it occurred, so
+ // if it really does occur we know it must then be an initial).
+ // We assert this is the case here
+ const auto action_by_p_in_w =
+ std::find_if(w_now.begin(), w_now.end(), [=](const auto& action) { return action->aid_ == p; });
+ xbt_assert(action_by_p_in_w == w_now.end(),
+ "Invariant violated: We claimed that actor `%ld` is not an initial "
+ "after `w`, yet it's independent with all actions of `w` AND occurs in `w`."
+ "This indicates that there is a bug computing initials",
+ p);
+ } else {
+ // Neither of the two above conditions hold, so the relation fails
+ return std::nullopt;
+ }
+
+ // Move one step forward in the direction of `v` and repeat
+ E_v.push_transition(next_E_p);
+ }
+ return std::optional<PartialExecution>{std::move(w_now)};
+}
+
+bool Execution::happens_before(Execution::EventHandle e1_handle, Execution::EventHandle e2_handle) const
+{
+ // 1. "happens-before" (-->_E) is a subset of "occurs before" (<_E)
+ // and is an irreflexive relation
+ if (e1_handle >= e2_handle) {
+ return false;
+ }
+
+ // Each execution maintains a stack of clock vectors which are updated
+ // according to the procedure outlined in section 4 of the original DPOR paper
+ const Event& e2 = get_event_with_handle(e2_handle);
+ const aid_t proc_e1 = get_actor_with_handle(e1_handle);
+
+ if (const auto e1_in_e2_clock = e2.get_clock_vector().get(proc_e1); e1_in_e2_clock.has_value()) {
+ return e1_handle <= e1_in_e2_clock.value();
+ }
+ // If `e1` does not appear in e2's clock vector, this implies
+ // not only that the transitions associated with `e1` and `e2
+ // are independent, but further that there are no transitive
+ // dependencies between e1 and e2
+ return false;
}
-} // namespace simgrid::mc::odpor
\ No newline at end of file
+} // namespace simgrid::mc::odpor
