1 /* Copyright (c) 2008-2023. The SimGrid Team. All rights reserved. */
3 /* This program is free software; you can redistribute it and/or modify it
4 * under the terms of the license (GNU LGPL) which comes with this package. */
6 #include "src/mc/explo/odpor/Execution.hpp"
7 #include "src/mc/api/State.hpp"
8 #include "src/mc/explo/odpor/ReversibleRaceCalculator.hpp"
9 #include "xbt/asserts.h"
10 #include "xbt/string.hpp"
15 namespace simgrid::mc::odpor {
17 std::vector<std::string> get_textual_trace(const PartialExecution& w)
19 std::vector<std::string> trace;
20 for (const auto& t : w) {
21 const auto a = xbt::string_printf("Actor %ld: %s", t->aid_, t->to_string(true).c_str());
22 trace.push_back(std::move(a));
27 Execution::Execution(const PartialExecution& w)
29 push_partial_execution(w);
32 void Execution::push_transition(std::shared_ptr<Transition> t)
35 throw std::invalid_argument("Unexpectedly received `nullptr`");
37 ClockVector max_clock_vector;
38 for (const Event& e : this->contents_) {
39 if (e.get_transition()->depends(t.get())) {
40 max_clock_vector = ClockVector::max(max_clock_vector, e.get_clock_vector());
43 max_clock_vector[t->aid_] = this->size();
44 contents_.push_back(Event({std::move(t), max_clock_vector}));
47 void Execution::push_partial_execution(const PartialExecution& w)
49 for (const auto& t : w) {
54 std::vector<std::string> Execution::get_textual_trace() const
56 std::vector<std::string> trace;
57 for (const auto& t : this->contents_) {
59 xbt::string_printf("Actor %ld: %s", t.get_transition()->aid_, t.get_transition()->to_string(true).c_str());
60 trace.push_back(std::move(a));
65 std::unordered_set<Execution::EventHandle> Execution::get_racing_events_of(Execution::EventHandle target) const
67 std::unordered_set<Execution::EventHandle> racing_events;
68 std::unordered_set<Execution::EventHandle> disqualified_events;
70 // For each event of the execution
71 for (auto e_i = target; e_i != std::numeric_limits<Execution::EventHandle>::max(); e_i--) {
72 // We need `e_i -->_E target` as a necessary condition
73 if (not happens_before(e_i, target)) {
77 // Further, `proc(e_i) != proc(target)`
78 if (get_actor_with_handle(e_i) == get_actor_with_handle(target)) {
79 disqualified_events.insert(e_i);
83 // There could an event that "happens-between" the two events which would discount `e_i` as a race
84 for (auto e_j = e_i; e_j < target; e_j++) {
86 // 1. e_i --->_E e_j; and
87 // 2. disqualified_events.count(e_j) > 0
88 // then e_i --->_E target indirectly (either through
89 // e_j directly, or transitively through e_j)
90 if (disqualified_events.count(e_j) > 0 && happens_before(e_i, e_j)) {
91 disqualified_events.insert(e_i);
96 // If `e_i` wasn't disqualified in the last round,
97 // it's in a race with `target`. After marking it
98 // as such, we ensure no other event `e` can happen-before
99 // it (since this would transitively make it the event
100 // which "happens-between" `target` and `e`)
101 if (disqualified_events.count(e_i) == 0) {
102 racing_events.insert(e_i);
103 disqualified_events.insert(e_i);
107 return racing_events;
110 std::unordered_set<Execution::EventHandle> Execution::get_reversible_races_of(EventHandle handle) const
112 std::unordered_set<EventHandle> reversible_races;
113 for (EventHandle race : get_racing_events_of(handle)) {
114 if (ReversibleRaceCalculator::is_race_reversible(*this, race, handle)) {
115 reversible_races.insert(race);
118 return reversible_races;
121 Execution Execution::get_prefix_before(Execution::EventHandle handle) const
123 return Execution(std::vector<Event>{contents_.begin(), contents_.begin() + handle});
126 std::unordered_set<aid_t>
127 Execution::get_missing_source_set_actors_from(EventHandle e, const std::unordered_set<aid_t>& backtrack_set) const
129 // If this execution is empty, there are no initials
130 // relative to the last transition added to the execution
131 // since such a transition does not exist
133 return std::unordered_set<aid_t>{};
136 // To actually compute `I_[E'](v) ∩ backtrack(E')`, we must
137 // first compute `E'` and "move" in the direction of `v`.
138 // We perform a scan over `E` (this execution) and make
139 // note of any events which occur after `e` but don't
140 // "happen-after" `e` by pushing them onto `E'`. Note that
141 // correctness is still preserved in computing `v` "on-the-fly"
142 // to determine if an event `e` by actor `q` is an initial for `E'`
143 // after `v`: only those events that "occur-before" `e` in `v` could
144 // "happen-before" `ve for any valid "happens-before" relation
145 // (see property 1 in the ODPOR paper, viz. "is included in <_E")
147 // First, grab `E' := pre(e, E)` and determine what actor `p` is
148 const auto next_E_p = get_latest_event_handle().value();
149 xbt_assert(e != next_E_p,
150 "This method assumes that the event `e` (%u) and `next_[E](p)` (%u)"
151 "are in a reversible race, yet we claim to have such a race between the"
152 "same event. This indicates the the SDPOR pseudocode implementation is broken "
153 "as it supplies these values.",
155 Execution E_prime_v = get_prefix_before(e);
156 std::vector<sdpor::Execution::EventHandle> v;
157 std::unordered_set<aid_t> I_E_prime_v;
158 std::unordered_set<aid_t> disqualified_actors;
160 // Note `e + 1` here: `notdep(e, E)` is defined as the
161 // set of events that *occur-after* but don't *happen-after* `e`
162 for (auto e_prime = e + 1; e_prime <= next_E_p; ++e_prime) {
163 // Any event `e*` which occurs after `e` but which does not
164 // happen after `e` is a member of `v`. In addition to marking
165 // the event in `v`, we also "simulate" running the action `v`
167 if (not happens_before(e, e_prime) || e_prime == next_E_p) {
168 // First, push the transition onto the hypothetical execution
169 E_prime_v.push_transition(get_event_with_handle(e_prime).get_transition());
170 const EventHandle e_prime_in_E_prime_v = E_prime_v.get_latest_event_handle().value();
172 // When checking whether any event in `dom_[E'](v)` happens before
173 // `next_[E'](q)` below for thread `q`, we must consider that the
174 // events relative to `E` (this execution) are different than those
175 // relative to `E'.v`. Thus e.g. event `7` in `E` may be event `4`
176 // in `E'.v`. Since we are asking about "happens-before"
177 // `-->_[E'.v]` about `E'.v`, we must build `v` relative to `E'`.
179 // Note that we add `q` to v regardless of whether `q` itself has been
180 // disqualified since we've determined that `e_prime` "occurs-after" but
181 // does not "happen-after" `e`
182 v.push_back(e_prime_in_E_prime_v);
184 const aid_t q = E_prime_v.get_actor_with_handle(e_prime_in_E_prime_v);
185 if (disqualified_actors.count(q) > 0) { // Did we already note that `q` is not an initial?
188 const bool is_initial = std::none_of(v.begin(), v.end(), [&](const auto& e_star) {
189 return E_prime_v.happens_before(e_star, e_prime_in_E_prime_v);
192 // If the backtrack set already contains `q`, we're done:
193 // they've made note to search for (or have already searched for)
195 if (backtrack_set.count(q) > 0) {
196 return std::unordered_set<aid_t>{};
198 I_E_prime_v.insert(q);
201 // If `q` is disqualified as a candidate, clearly
202 // no event occurring after `e_prime` in `E` executed
203 // by actor `q` will qualify since any (valid) happens-before
204 // relation orders actions taken by each actor
205 disqualified_actors.insert(q);
209 xbt_assert(not I_E_prime_v.empty(),
210 "For any non-empty execution, we know that "
211 "at minimum one actor is an initial since "
212 "some execution is possible with respect to a "
213 "prefix before event `%u`, yet we didn't find anyone. "
214 "This implies the implementation of this function is broken.",
219 std::optional<PartialExecution> Execution::get_odpor_extension_from(EventHandle e, EventHandle e_prime,
220 const State& state_at_e) const
222 // `e` is assumed to be in a reversible race with `e_prime`.
223 // If `e > e_prime`, then `e` occurs-after `e_prime` which means
224 // `e` could not race with if
226 throw std::invalid_argument("ODPOR extensions can only be computed for "
227 "events in a reversible race, which is claimed, "
228 "yet the racing event 'occurs-after' the target");
236 std::vector<Execution::EventHandle> v_handles;
237 std::unordered_set<aid_t> WI_E_prime_v;
238 std::unordered_set<aid_t> disqualified_actors;
239 Execution E_prime_v = get_prefix_before(e);
240 const std::unordered_set<aid_t> sleep_E_prime = state_at_e.get_sleeping_actors();
242 // Note `e + 1` here: `notdep(e, E)` is defined as the
243 // set of events that *occur-after* but don't *happen-after* `e`
245 // SUBTLE NOTE: ODPOR requires us to compute `notdep(e, E)` EVEN THOUGH
246 // the race is between `e` and `e'`; that is, events occurring in `E`
247 // that "occur-after" `e'` may end up in the partial execution `v`.
249 // Observe that `notdep(e, E).proc(e')` will contain all transitions
250 // that don't happen-after `e` in the order they appear FOLLOWED BY
251 // THE **TRANSITION** ASSOCIATED WITH **`e'`**!!
253 // SUBTLE NOTE: Observe that any event that "happens-after" `e'`
254 // must necessarily "happen-after" `e` as well, since `e` and
255 // `e'` are presumed to be in a reversible race. Hence, we know that
256 // all events `e_star` such that `e` "happens-before" `e_star` cannot affect
257 // the enabledness of `e'`; furthermore, `e'` cannot affect the enabledness
258 // of any event independent with `e` that "occurs-after" `e'`
259 for (auto e_star = e + 1; e_star <= get_latest_event_handle().value(); ++e_star) {
260 // Any event `e*` which occurs after `e` but which does not
261 // happen after `e` is a member of `v`. In addition to marking
262 // the event in `v`, we also "simulate" running the action `v` from E'
263 // to be able to compute `--->[E'.v]`
264 if (not happens_before(e, e_star)) {
265 xbt_assert(e_star != e_prime,
266 "Invariant Violation: We claimed events %u and %u were in a reversible race, yet we also "
267 "claim that they do not happen-before one another. This is impossible: "
268 "are you sure that the two events are in a reversible race?",
270 E_prime_v.push_transition(get_event_with_handle(e_star).get_transition());
271 v.push_back(get_event_with_handle(e_star).get_transition());
273 const EventHandle e_star_in_E_prime_v = E_prime_v.get_latest_event_handle().value();
275 // When checking whether any event in `dom_[E'](v)` happens before
276 // `next_[E'](q)` below for thread `q`, we must consider that the
277 // events relative to `E` (this execution) are different than those
278 // relative to `E'.v`. Thus e.g. event `7` in `E` may be event `4`
279 // in `E'.v`. Since we are asking about "happens-before"
280 // `-->_[E'.v]` about `E'.v`, we must build `v` relative to `E'`
281 v_handles.push_back(e_star_in_E_prime_v);
283 // Note that we add `q` to v regardless of whether `q` itself has been
284 // disqualified since `q` may itself disqualify other actors
285 // (i.e. even if `q` is disqualified from being an initial, it
286 // is still contained in the sequence `v`)
287 const aid_t q = E_prime_v.get_actor_with_handle(e_star_in_E_prime_v);
288 if (disqualified_actors.count(q) > 0) { // Did we already note that `q` is not an initial?
291 const bool is_initial = std::none_of(v_handles.begin(), v_handles.end(), [&](const auto& e_star) {
292 return E_prime_v.happens_before(e_star, e_star_in_E_prime_v);
295 // If the sleep set already contains `q`, we're done:
296 // we've found an initial contained in the sleep set and
297 // so the intersection is non-empty
298 if (sleep_E_prime.count(q) > 0) {
301 WI_E_prime_v.insert(q);
304 // If `q` is disqualified as a candidate, clearly
305 // no event occurring after `e_prime` in `E` executed
306 // by actor `q` will qualify since any (valid) happens-before
307 // relation orders actions taken by each actor
308 disqualified_actors.insert(q);
313 // Now we add `e_prime := <q, i>` to `E'.v` and repeat the same work
314 // It's possible `proc(e_prime)` is an initial
316 // Note the form of `v` in the pseudocode:
317 // `v := notdep(e, E).e'^
319 E_prime_v.push_transition(get_event_with_handle(e_prime).get_transition());
320 v.push_back(get_event_with_handle(e_prime).get_transition());
322 const EventHandle e_prime_in_E_prime_v = E_prime_v.get_latest_event_handle().value();
323 v_handles.push_back(e_prime_in_E_prime_v);
325 const bool is_initial = std::none_of(v_handles.begin(), v_handles.end(), [&](const auto& e_star) {
326 return E_prime_v.happens_before(e_star, e_prime_in_E_prime_v);
329 if (const aid_t q = E_prime_v.get_actor_with_handle(e_prime_in_E_prime_v); sleep_E_prime.count(q) > 0) {
332 WI_E_prime_v.insert(q);
337 const Execution pre_E_e = get_prefix_before(e);
338 const auto sleeping_actors = state_at_e.get_sleeping_actors();
340 // Check if any enabled actor that is independent with
341 // this execution after `v` is contained in the sleep set
342 for (const auto& [aid, astate] : state_at_e.get_actors_list()) {
343 const bool is_in_WI_E =
344 astate.is_enabled() and pre_E_e.is_independent_with_execution_of(v, astate.get_transition());
345 const bool is_in_sleep_set = sleeping_actors.count(aid) > 0;
347 // `action(aid)` is in `WI_[E](v)` but also is contained in the sleep set.
348 // This implies that the intersection between the two is non-empty
349 if (is_in_WI_E && is_in_sleep_set) {
357 bool Execution::is_initial_after_execution_of(const PartialExecution& w, aid_t p) const
360 std::vector<EventHandle> w_handles;
361 for (const auto& w_i : w) {
362 // Take one step in the direction of `w`
363 E_w.push_transition(w_i);
365 // If that step happened to be executed by `p`,
366 // great: we know that `p` is contained in `w`.
367 // We now need to verify that it doens't "happen-after"
368 // any events which occur before it
369 if (w_i->aid_ == p) {
370 const auto p_handle = E_w.get_latest_event_handle().value();
371 return std::none_of(w_handles.begin(), w_handles.end(),
372 [&](const auto handle) { return E_w.happens_before(handle, p_handle); });
374 w_handles.push_back(E_w.get_latest_event_handle().value());
380 bool Execution::is_independent_with_execution_of(const PartialExecution& w, std::shared_ptr<Transition> next_E_p) const
382 // INVARIANT: Here, we assume that for any process `p_i` of `w`,
383 // the events of this execution followed by the execution of all
384 // actors occurring before `p_i` in `v` (`p_j`, `0 <= j < i`)
385 // are sufficient to enable `p_i`. This is fortunately the case
386 // with what ODPOR requires of us, viz. to ask the question about
387 // `v := notdep(e, E)` for some execution `E` and event `e` of
390 E_p_w.push_transition(std::move(next_E_p));
391 const auto p_handle = E_p_w.get_latest_event_handle().value();
393 // As we add events to `w`, verify that none
394 // of them "happen-after" the event associated with
395 // the step `next_E_p` (viz. p_handle)
396 for (const auto& w_i : w) {
397 E_p_w.push_transition(w_i);
398 const auto w_i_handle = E_p_w.get_latest_event_handle().value();
399 if (E_p_w.happens_before(p_handle, w_i_handle)) {
406 std::optional<PartialExecution> Execution::get_shortest_odpor_sq_subset_insertion(const PartialExecution& v,
407 const PartialExecution& w) const
409 // See section 4 of Abdulla. et al.'s 2017 ODPOR paper for details (specifically
410 // where the [iterative] computation of `v ~_[E] w` is described)
414 for (const auto& next_E_p : v) {
415 // Is `p in `I_[E](w)`?
416 if (const aid_t p = next_E_p->aid_; E_v.is_initial_after_execution_of(w_now, p)) {
417 // Remove `p` from w and continue
419 // INVARIANT: If `p` occurs in `w`, it had better refer to the same
420 // transition referenced by `v`. Unfortunately, we have two
421 // sources of truth here which can be manipulated at the same
422 // time as arguments to the function. If ODPOR works correctly,
423 // they should always refer to the same value; but as a sanity check,
424 // we have an assert that tests that at least the types are the same.
425 const auto action_by_p_in_w =
426 std::find_if(w_now.begin(), w_now.end(), [=](const auto& action) { return action->aid_ == p; });
427 xbt_assert(action_by_p_in_w != w_now.end(), "Invariant violated: actor `p` "
428 "is claimed to be an initial after `w` but is "
429 "not actually contained in `w`. This indicates that there "
430 "is a bug computing initials");
431 const auto& w_action = *action_by_p_in_w;
432 xbt_assert(w_action->type_ == next_E_p->type_,
433 "Invariant violated: `v` claims that actor `%ld` executes '%s' while "
434 "`w` claims that it executes '%s'. These two partial executions both "
435 "refer to `next_[E](p)`, which should be the same",
436 p, next_E_p->to_string(false).c_str(), w_action->to_string(false).c_str());
437 w_now.erase(action_by_p_in_w);
440 else if (E_v.is_independent_with_execution_of(w_now, next_E_p)) {
441 // INVARIANT: Note that it is impossible for `p` to be
442 // excluded from the set `I_[E](w)` BUT ALSO be contained in
443 // `w` itself if `E ⊢ p ◇ w` (intuitively, the fact that `E ⊢ p ◇ w`
444 // means that are able to move `p` anywhere in `w` IF it occurred, so
445 // if it really does occur we know it must then be an initial).
446 // We assert this is the case here
447 const auto action_by_p_in_w =
448 std::find_if(w_now.begin(), w_now.end(), [=](const auto& action) { return action->aid_ == p; });
449 xbt_assert(action_by_p_in_w == w_now.end(),
450 "Invariant violated: We claimed that actor `%ld` is not an initial "
451 "after `w`, yet it's independent with all actions of `w` AND occurs in `w`."
452 "This indicates that there is a bug computing initials",
455 // Neither of the two above conditions hold, so the relation fails
459 // Move one step forward in the direction of `v` and repeat
460 E_v.push_transition(next_E_p);
462 return std::optional<PartialExecution>{std::move(w_now)};
465 bool Execution::happens_before(Execution::EventHandle e1_handle, Execution::EventHandle e2_handle) const
467 // 1. "happens-before" (-->_E) is a subset of "occurs before" (<_E)
468 // and is an irreflexive relation
469 if (e1_handle >= e2_handle) {
473 // Each execution maintains a stack of clock vectors which are updated
474 // according to the procedure outlined in section 4 of the original DPOR paper
475 const Event& e2 = get_event_with_handle(e2_handle);
476 const aid_t proc_e1 = get_actor_with_handle(e1_handle);
478 if (const auto e1_in_e2_clock = e2.get_clock_vector().get(proc_e1); e1_in_e2_clock.has_value()) {
479 return e1_handle <= e1_in_e2_clock.value();
481 // If `e1` does not appear in e2's clock vector, this implies
482 // not only that the transitions associated with `e1` and `e2
483 // are independent, but further that there are no transitive
484 // dependencies between e1 and e2
488 } // namespace simgrid::mc::odpor