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partial_degeneralize: force purge_unreachable in some corner case

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* spot/twaalgos/degen.cc: If an all-accepting transition has been
redirected, we need to force purge_unreachable_state() to be called,
otherwise we may have unreachable states.
* tests/python/pdegen.py: Add test case.
This commit is contained in:
Alexandre Duret-Lutz 2020-02-10 14:08:05 +01:00
parent 443f638b9c
commit dd8c00fff0
2 changed files with 38 additions and 5 deletions
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22
spot/twaalgos/degen.cc
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@ -266,7 +266,8 @@ namespace spot
static void
keep_bottommost_copies(twa_graph_ptr& res,
scc_info& si_orig,
std::vector<unsigned>* orig_states)
std::vector<unsigned>* orig_states,
bool force_purge = false)
{
unsigned res_ns = res->num_states();
auto a = si_orig.get_aut();
@ -276,7 +277,11 @@ namespace spot
scc_info si_res(res, scc_info_options::TRACK_STATES);
unsigned res_scc_count = si_res.scc_count();
if (res_scc_count <= si_orig.scc_count())
return;
{
if (force_purge)
res->purge_unreachable_states();
return;
}
// If we reach this place, we have more SCCs in the output than
// in the input. This means that we have created some redundant
@ -1064,18 +1069,25 @@ namespace spot
}
}
// Raise the destination of the "all-accepting" edges to the
// highest existing level.
// highest existing level. If we do such a redirection, we need
// to force keep_bottommost_copies to purge unreachable_states.
bool force_purge = false;
auto& ev = res->edge_vector();
for (unsigned idx: allaccedges)
{
unsigned dst = ev[idx].dst;
unsigned orig_dst = (*orig_states)[dst];
unsigned hl = highest_level[orig_dst];
ev[idx].dst = ds2num[degen_state{orig_dst, hl}];
unsigned new_dst = ds2num[degen_state{orig_dst, hl}];
if (dst != new_dst)
{
ev[idx].dst = new_dst;
force_purge = true;
}
}
//orders.print();
res->merge_edges();
keep_bottommost_copies(res, si_orig, orig_states);
keep_bottommost_copies(res, si_orig, orig_states, force_purge);
return res;
}