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simulation: fix merging transiant SCCs

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This fixes #452, and also fix a bug related to transiant SCCs
incorrectly merged in cosimulation: the source of the edges was
updated without fixing the chaining of the edges.

* spot/twaalgos/simulation.cc: Fix all the above.
* tests/python/simstate.py: Add test case from issue #452.
* tests/core/det.test, tests/core/ltlsynt.test,
tests/core/satmin.test: Lower expected sizes.
* tests/python/decompose.ipynb: Adjust for changed order.
This commit is contained in:
Alexandre Duret-Lutz 2021-04-19 23:38:50 +02:00
parent cfa3417449
commit fca6513604
6 changed files with 203 additions and 142 deletions
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49
spot/twaalgos/simulation.cc
View file

@ -550,16 +550,16 @@ namespace spot
// All states in p.second have the same class, so just
// pick the class of the first one first one.
bdd src = previous_class_[p->second.front()];
assert(gb->get_state(src.id()) == srcst);
// Get the signature to derive successors.
bdd sig = compute_sig(p->second.front());
assert(signatures.size() == srcst);
signatures.push_back(sig);
if (Cosimulation)
sig = bdd_compose(sig, bddfalse, bdd_var(bdd_initial));
assert(gb->get_state(src.id()) == srcst);
assert(signatures.size() == srcst);
signatures.push_back(bdd_exist(sig, all_proms_));
// Get all the variables in the signature.
bdd sup_sig = bdd_support(sig);
@ -656,6 +656,7 @@ namespace spot
}
}
bool need_another_pass = false;
// Attempt to merge trivial SCCs
if (!record_implications_ && res->num_states() > 1)
{
@ -664,7 +665,10 @@ namespace spot
unsigned nstates = res->num_states();
std::vector<unsigned> redirect(nstates);
std::iota(redirect.begin(), redirect.end(), 0);
for (unsigned s = 0; s < nstates; ++s)
signatures[s] = bdd_exist(signatures[s], all_proms_);
bool changed = false;
bool unchanged = false;
for (unsigned scc = 0; scc < nscc; ++scc)
if (si.is_trivial(scc))
{
@ -676,8 +680,10 @@ namespace spot
{
changed = true;
redirect[s] = i;
break;
goto if_changed;
}
unchanged = true;
if_changed:;
}
if (changed)
{
@ -688,16 +694,28 @@ namespace spot
for (auto& e: res->edges())
e.dst = redirect[e.dst];
res->set_init_state(redirect[res->get_init_state_number()]);
if (Cosimulation)
// Fix chaining of edges with changed sources.
res->merge_edges();
if (unchanged)
need_another_pass = true;
}
}
// If we recorded implications for the determinization
// procedure, we should not remove unreachable states, as that
// will invalidate the contents of the IMPLICATIONS vector.
// It's OK not to purge the result, as the determinization
// will only explore the reachable part anyway.
if (!record_implications_)
res->purge_unreachable_states();
// Remove unreachable states.
// In the case of co-simulation, changing the sources
// of edges, might have created dead states.
//
// If we recorded implications for the determinization
// procedure, we should not remove unreachable states, as
// that will invalidate the contents of the IMPLICATIONS
// vector. It's OK not to purge the result in that case,
// as the determinization will only explore the reachable
// part anyway.
if (Cosimulation)
res->purge_dead_states();
else
res->purge_unreachable_states();
}
// Push the common incoming sets to the outgoing edges.
// Doing so cancels the preprocessing we did in the other
@ -751,7 +769,12 @@ namespace spot
res->prop_universal(true);
if (Sba)
res->prop_state_acc(true);
return res;
if (!need_another_pass)
return res;
direct_simulation<Cosimulation, Sba> sim(res);
return sim.run();
}