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degen: do not mark initial trivial SCCs as accepting

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Doing so is not wrong, but it's superfluous, and the extra accepting
state will cause additional work in emptiness checks based on NDFS.
Report from Jan Strejček.

* src/tgbaalgos/degen.cc: Here.
* src/tgbatest/degenid.test: Add a test case.
This commit is contained in:
Alexandre Duret-Lutz 2015-04-01 15:26:05 +02:00
parent 54a8ce502d
commit 6e8170e386
2 changed files with 36 additions and 0 deletions
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4
src/tgbaalgos/degen.cc
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@ -72,6 +72,7 @@ namespace spot
acc_cond::mark_t common = a_->acc().all_sets();
acc_cond::mark_t union_ = 0U;
bool has_acc_self_loop = false;
bool seen = false;
for (auto& t: a_->out(s))
{
// Ignore transitions that leave the SCC of s.
@ -85,7 +86,10 @@ namespace spot
// an accepting self-loop?
has_acc_self_loop |= (t.dst == s) && a_->acc().accepting(t.acc);
seen = true;
}
if (!seen)
common = 0U;
cache_[s] = std::make_tuple(common, union_, has_acc_self_loop);
}