* src/tgbaalgos/bfssteps.hh, src/tgbaalgos/bfssteps.cc: New files.
* src/tgbaalgos/Makefile.am (tgbaalgos_HEADERS, libtgbaalgos_la_SOURCES): Add them. * src/tgbaalgos/gv04.cc (gv04::result::accepting_run): Use the new bfs_steps class.
This commit is contained in:
Alexandre Duret-Lutz
parent
df1bf80d1f
commit
2b74398a62
5 changed files with 218 additions and 160 deletions
|
|
@ -30,13 +30,12 @@
|
|||
|
||||
#include <cassert>
|
||||
#include <utility>
|
||||
#include <map>
|
||||
#include <deque>
|
||||
#include "tgba/tgba.hh"
|
||||
#include "misc/hash.hh"
|
||||
#include "emptiness.hh"
|
||||
#include "emptiness_stats.hh"
|
||||
#include "gv04.hh"
|
||||
#include "bfssteps.hh"
|
||||
|
||||
namespace spot
|
||||
{
|
||||
|
|
@ -242,6 +241,8 @@ namespace spot
|
|||
|
||||
struct result: public emptiness_check_result
|
||||
{
|
||||
gv04& data;
|
||||
|
||||
result(gv04& data)
|
||||
: data(data)
|
||||
{
|
||||
|
|
@ -253,7 +254,7 @@ namespace spot
|
|||
tgba_run* res = new tgba_run;
|
||||
|
||||
// Transitively update the lowlinks, so we can use them in
|
||||
// the BDS bellow.
|
||||
// the BFS bellow.
|
||||
for (int i = 0; i <= data.top; ++i)
|
||||
{
|
||||
int l = data.stack[i].lowlink;
|
||||
|
|
@ -293,179 +294,83 @@ namespace spot
|
|||
father = data.stack[father].pre;
|
||||
}
|
||||
|
||||
// Construct the cycle in two phases. A first BFS find the
|
||||
// Construct the cycle in two phases. A first BFS finds the
|
||||
// shortest path from scc_root to an accepting transition.
|
||||
// A second BFS then search a path back to scc_root. If
|
||||
// there is no acceptance conditions we just use the second
|
||||
// BFS to find a cycle around scc_root.
|
||||
|
||||
struct first_bfs: bfs_steps
|
||||
{
|
||||
const gv04& data;
|
||||
int scc_root;
|
||||
|
||||
first_bfs(const gv04& data, int scc_root)
|
||||
: bfs_steps(data.a), data(data), scc_root(scc_root)
|
||||
{
|
||||
}
|
||||
|
||||
virtual const state*
|
||||
filter(const state* s)
|
||||
{
|
||||
// Do not escape the SCC
|
||||
hash_type::const_iterator j = data.h.find(s);
|
||||
if (// This state was never visited so far.
|
||||
j == data.h.end()
|
||||
// Or it was discarded
|
||||
|| j->second >= data.stack.size()
|
||||
// Or it was discarded (but its stack slot reused)
|
||||
|| data.stack[j->second].s->compare(s)
|
||||
// Or it is still on the stack but not in the SCC
|
||||
|| data.stack[j->second].lowlink < scc_root)
|
||||
{
|
||||
delete s;
|
||||
return 0;
|
||||
}
|
||||
delete s;
|
||||
return j->first;
|
||||
}
|
||||
|
||||
virtual bool
|
||||
match(tgba_run::step& step, const state*)
|
||||
{
|
||||
return step.acc != bddfalse;
|
||||
}
|
||||
};
|
||||
|
||||
struct second_bfs: first_bfs
|
||||
{
|
||||
const state* target;
|
||||
second_bfs(const gv04& data, int scc_root, const state* target)
|
||||
: first_bfs(data, scc_root), target(target)
|
||||
{
|
||||
}
|
||||
|
||||
virtual bool
|
||||
match(tgba_run::step&, const state* s)
|
||||
{
|
||||
return s == target;
|
||||
}
|
||||
};
|
||||
|
||||
const state* bfs_start = data.stack[scc_root].s;
|
||||
const state* bfs_end = bfs_start;
|
||||
if (data.accepting != bddfalse)
|
||||
{
|
||||
trace << "1st BFS" << std::endl;
|
||||
|
||||
// Records backlinks to parent state during the BFS.
|
||||
// (This also stores the propositions of this link.)
|
||||
std::map<const state*, tgba_run::step,
|
||||
state_ptr_less_than> father;
|
||||
// BFS queue.
|
||||
std::deque<const state*> todo;
|
||||
// Initial state.
|
||||
todo.push_back(bfs_start);
|
||||
|
||||
while (!todo.empty())
|
||||
{
|
||||
const state* src = todo.front();
|
||||
todo.pop_front();
|
||||
tgba_succ_iterator* i = data.a->succ_iter(src);
|
||||
for (i->first(); !i->done(); i->next())
|
||||
{
|
||||
const state* dest = i->current_state();
|
||||
|
||||
trace << " state " << data.a->format_state(dest);
|
||||
|
||||
// Do not escape the SCC
|
||||
hash_type::const_iterator j = data.h.find(dest);
|
||||
if (// This state was never visited so far.
|
||||
j == data.h.end()
|
||||
// Or it was discarded
|
||||
|| j->second >= data.stack.size()
|
||||
// Or it was discarded (but its stack slot reused)
|
||||
|| data.stack[j->second].s->compare(dest)
|
||||
// Or it is still on the stack but not in the SCC
|
||||
|| data.stack[j->second].lowlink < scc_root)
|
||||
{
|
||||
trace << " ignored" << std::endl;
|
||||
delete dest;
|
||||
continue;
|
||||
}
|
||||
trace << " explored" << std::endl;
|
||||
delete dest;
|
||||
dest = j->first;
|
||||
|
||||
bdd cond = i->current_condition();
|
||||
bdd acc = i->current_acceptance_conditions();
|
||||
tgba_run::step s = { src, cond, acc };
|
||||
|
||||
if (acc != bddfalse)
|
||||
{
|
||||
// Found it!
|
||||
|
||||
tgba_run::steps p;
|
||||
while (s.s != bfs_start)
|
||||
{
|
||||
p.push_front(s);
|
||||
s = father[s.s];
|
||||
}
|
||||
p.push_front(s);
|
||||
res->cycle.splice(res->cycle.end(), p);
|
||||
// Exit this BFS, and start the next one at dest.
|
||||
todo.clear();
|
||||
bfs_start = dest;
|
||||
break;
|
||||
}
|
||||
|
||||
// Common case: record backlinks and continue BFS
|
||||
// for unvisited states.
|
||||
if (father.find(dest) == father.end())
|
||||
{
|
||||
todo.push_back(dest);
|
||||
father[dest] = s;
|
||||
}
|
||||
}
|
||||
delete i;
|
||||
}
|
||||
first_bfs b1(data, scc_root);
|
||||
bfs_start = b1.search(bfs_start, res->cycle);
|
||||
assert(bfs_start);
|
||||
}
|
||||
// Second BFS.
|
||||
if (bfs_start != bfs_end || res->cycle.empty())
|
||||
{
|
||||
trace << "2nd BFS" << std::endl;
|
||||
|
||||
// Records backlinks to parent state during the BFS.
|
||||
// (This also stores the propositions of this link.)
|
||||
std::map<const state*, tgba_run::step,
|
||||
state_ptr_less_than> father;
|
||||
// BFS queue.
|
||||
std::deque<const state*> todo;
|
||||
// Initial state.
|
||||
todo.push_back(bfs_start);
|
||||
|
||||
while (!todo.empty())
|
||||
{
|
||||
const state* src = todo.front();
|
||||
todo.pop_front();
|
||||
tgba_succ_iterator* i = data.a->succ_iter(src);
|
||||
for (i->first(); !i->done(); i->next())
|
||||
{
|
||||
const state* dest = i->current_state();
|
||||
|
||||
trace << " state " << data.a->format_state(dest);
|
||||
|
||||
// Do not escape the SCC
|
||||
hash_type::const_iterator j = data.h.find(dest);
|
||||
if (// This state was never visited so far.
|
||||
j == data.h.end()
|
||||
// Or it was discarded
|
||||
|| j->second >= data.stack.size()
|
||||
// Or it was discarded (but its stack slot reused)
|
||||
|| data.stack[j->second].s->compare(dest)
|
||||
// Or it is still on the stack but not in the SCC
|
||||
|| data.stack[j->second].lowlink < scc_root)
|
||||
{
|
||||
trace << " ignored" << std::endl;
|
||||
delete dest;
|
||||
continue;
|
||||
}
|
||||
trace << " explored" << std::endl;
|
||||
delete dest;
|
||||
dest = j->first;
|
||||
|
||||
bdd cond = i->current_condition();
|
||||
bdd acc = i->current_acceptance_conditions();
|
||||
tgba_run::step s = { src, cond, acc };
|
||||
|
||||
if (dest == bfs_end)
|
||||
{
|
||||
// Found it!
|
||||
tgba_run::steps p;
|
||||
while (s.s != bfs_start)
|
||||
{
|
||||
p.push_front(s);
|
||||
s = father[s.s];
|
||||
}
|
||||
p.push_front(s);
|
||||
res->cycle.splice(res->cycle.end(), p);
|
||||
// Exit this BFS.
|
||||
todo.clear();
|
||||
break;
|
||||
}
|
||||
|
||||
// Common case: record backlinks and continue BFS
|
||||
// for unvisited states.
|
||||
if (father.find(dest) == father.end())
|
||||
{
|
||||
todo.push_back(dest);
|
||||
father[dest] = s;
|
||||
}
|
||||
}
|
||||
delete i;
|
||||
}
|
||||
second_bfs b2(data, scc_root, bfs_end);
|
||||
bfs_start = b2.search(bfs_start, res->cycle);
|
||||
assert(bfs_start == bfs_end);
|
||||
}
|
||||
|
||||
// Clone every state in the cycle before returning it. (We
|
||||
// didn't do that before in the algorithm, because it's
|
||||
// easier to follow if every state manipulated in the BFS is
|
||||
// the instance in the hash table.)
|
||||
for (tgba_run::steps::iterator i = res->cycle.begin();
|
||||
i != res->cycle.end(); ++i)
|
||||
i->s = i->s->clone();
|
||||
|
||||
assert(res->cycle.begin() != res->cycle.end());
|
||||
|
||||
return res;
|
||||
}
|
||||
|
||||
gv04& data;
|
||||
};
|
||||
|
||||
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue