sccfilter: improve the new version to simplify acceptance sets
* src/tgbaalgos/sccinfo.cc, src/tgbaalgos/sccinfo.hh: Implement the acc_filter_simplify filter, and generalize composition to be n-ary. * src/tgbaalgos/sccfilter.cc (used_acc): New method.
This commit is contained in:
Alexandre Duret-Lutz
parent
84f92541f3
commit
af6cb049f2
3 changed files with 333 additions and 18 deletions
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@ -609,13 +609,17 @@ namespace spot
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return ret;
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}
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//////////////////////////////////////////////////////////////////////
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// The goal is to remove all the code above this line eventually, so
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// do not waste your time code common to both sides of this note.
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//////////////////////////////////////////////////////////////////////
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namespace
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{
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typedef std::tuple<bool, bdd, bdd> filtered_trans;
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typedef std::pair<bdd, bdd> acc_pair;
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// SCC filters are objects with two methods:
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// state(src) return true iff s should be kept
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@ -637,6 +641,11 @@ namespace spot
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return true;
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}
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acc_pair accsets(bdd all, bdd all_neg)
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{
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return acc_pair(all, all_neg);
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}
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// Accept all transitions, unmodified
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filtered_trans trans(unsigned, unsigned, bdd cond, bdd acc)
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{
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@ -698,11 +707,250 @@ namespace spot
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}
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};
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template<typename F1, typename F2>
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//
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struct acc_filter_simplify: id_filter
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{
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std::vector<bdd> acc_;
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typedef std::map<int, bdd> map_t;
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typedef std::vector<map_t> remap_t;
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remap_t remap_;
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acc_filter_simplify(scc_info* si)
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: id_filter(si)
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{
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}
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acc_pair accsets(bdd in_all, bdd in_all_neg)
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{
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unsigned scc_count = si->scc_count();
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remap_table_t remap_table(scc_count);
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std::vector<unsigned> max_table(scc_count);
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std::vector<bdd> useful_table(scc_count);
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std::vector<bdd> useless_table(scc_count);
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unsigned max_num = 1;
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const tgba_digraph* aut = si->get_aut();
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std::vector<bdd> used_acc = si->used_acc();
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for (unsigned n = 0; n < scc_count; ++n)
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{
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if (!si->is_accepting_scc(n))
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continue;
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bdd all = used_acc[n];
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//std::cerr << "SCC #" << n << "; used = " << all << std::endl;
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// Compute a set of useless acceptance sets.
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// If the acceptance combinations occurring in
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// the automata are { a, ab, abc, bd }, then
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// ALL contains (a&!b&!c&!d)|(a&b&!c&!d)|(a&b&c&!d)|(!a&b&!c&d)
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// and we want to find that 'a' and 'b' are useless because
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// they always occur with 'c'.
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// The way we check if 'a' is useless is to look whether ALL
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// implications (x -> a) for some other acceptance set x.
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//
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// The two while() loops in the code perform the equivalent of
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// for all a in allconds_a:
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// for all x in allconds_x:
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// check whether x -> a
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// ...
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//
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// Initially allconds_a = allconds_x contains all acceptance
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// sets. However when an acceptance set 'a' is determined to
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// be useless, it can be removed from allconds_x from future
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// iterations.
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bdd allconds_a = bdd_support(in_all_neg);
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bdd allconds_x = allconds_a;
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bdd useless = bddtrue;
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while (allconds_a != bddtrue)
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{
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// Speed-up the computation of implied acceptance sets by
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// removing those that are always present. We detect
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// those that appear as conjunction of positive variables
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// at the start of ALL.
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bdd prefix = bdd_satprefix(all);
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if (prefix != bddtrue)
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{
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assert(prefix == bdd_support(prefix));
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allconds_a = bdd_exist(allconds_a, prefix);
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if (allconds_a != bddtrue)
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{
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useless &= prefix;
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}
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else
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{
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// Never erase all conditions: at least keep one.
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useless &= bdd_high(prefix);
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break;
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}
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allconds_x = bdd_exist(allconds_x, prefix);
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}
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// Pick an acceptance set 'a'.
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bdd a = bdd_ithvar(bdd_var(allconds_a));
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// For all acceptance sets 'x' that are not already
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// useless...
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bdd others = allconds_x;
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while (others != bddtrue)
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{
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bdd x = bdd_ithvar(bdd_var(others));
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// ... check whether 'x' always implies 'a'.
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if (x != a && bdd_implies(all, x >> a))
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{
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// If so, 'a' is useless.
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all = bdd_exist(all, a);
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useless &= a;
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allconds_x = bdd_exist(allconds_x, a);
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break;
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}
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others = bdd_high(others);
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}
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allconds_a = bdd_high(allconds_a);
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}
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// We never remove ALL acceptance marks.
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assert(in_all_neg == bddtrue || useless != bdd_support(in_all_neg));
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useless_table[n] = useless;
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bdd useful = bdd_exist(in_all_neg, useless);
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//std::cerr << "SCC #" << n << "; useful = " << useful << std::endl;
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// Go over all useful sets of acceptance marks, and give them
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// a number.
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unsigned num = 1;
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// First compute the number of acceptance conditions used.
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for (BDD c = useful.id(); c != 1; c = bdd_low(c))
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++num;
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max_table[n] = num;
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if (num > max_num)
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max_num = num;
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useful_table[n] = useful;
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}
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// Now that we know about the max number of acceptance
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// conditions, add extra acceptance conditions to those SCC
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// that do not have enough.
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for (unsigned n = 0; n < scc_count; ++n)
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{
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if (!si->is_accepting_scc(n))
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continue;
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//std::cerr << "SCC " << n << '\n';
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bdd useful = useful_table[n];
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int missing = max_num - max_table[n];
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bdd useless = useless_table[n];
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while (missing--)
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{
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//std::cerr << useful << " : " << useless << std::endl;
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useful &= bdd_nithvar(bdd_var(useless));
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useless = bdd_high(useless);
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}
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int num = max_num;
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// Then number all of these acceptance conditions in the
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// reverse order. This makes sure that the associated number
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// varies in the same direction as the bdd variables, which in
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// turn makes sure we preserve the acceptance condition
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// ordering (which matters for degeneralization).
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for (BDD c = useful.id(); c != 1; c = bdd_low(c))
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remap_table[n].insert(std::make_pair(bdd_var(c), --num));
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max_table[n] = max_num;
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}
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acc_.resize(max_num);
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acc_[0] = bddfalse;
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bdd tmp = in_all;
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assert(aut->number_of_acceptance_conditions() >= max_num - 1);
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bdd all = bddfalse;
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bdd all_neg = bddtrue;
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if (tmp != bddfalse)
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{
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for (unsigned n = max_num - 1; n > 0; --n)
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{
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assert(tmp != bddfalse);
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int v = bdd_var(tmp);
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bdd vn = bdd_nithvar(v);
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all = (all & vn) | (all_neg & bdd_ithvar(v));
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all_neg &= vn;
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tmp = bdd_low(tmp);
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}
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tmp = in_all;
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for (unsigned n = max_num - 1; n > 0; --n)
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{
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int v = bdd_var(tmp);
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acc_[n] = bdd_compose(all_neg, bdd_nithvar(v), v);
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tmp = bdd_low(tmp);
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}
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}
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else
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{
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assert(max_num == 1);
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}
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remap_.resize(scc_count);
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bdd all_orig_neg = in_all_neg;
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bdd all_sup = bdd_support(all_orig_neg);
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for (unsigned n = 0; n < scc_count; ++n)
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{
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//std::cerr << "SCC #" << n << '\n';
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if (!si->is_accepting_scc(n))
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continue;
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bdd all = used_acc[n];
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while (all != bddfalse)
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{
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bdd one = bdd_satoneset(all, all_sup, bddtrue);
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all -= one;
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bdd res = bddfalse;
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bdd resacc = bddfalse;
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while (one != bddtrue)
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{
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if (bdd_high(one) == bddfalse)
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{
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one = bdd_low(one);
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continue;
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}
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int vn = bdd_var(one);
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bdd v = bdd_ithvar(vn);
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resacc |= bdd_exist(all_orig_neg, v) & v;
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res |= acc_[remap_table[n][vn]];
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one = bdd_high(one);
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}
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int id = resacc.id();
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//std::cerr << resacc << " -> " << res << '\n';
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remap_[n][id] = res;
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}
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}
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return acc_pair{all, all_neg};
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}
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filtered_trans trans(unsigned src, unsigned, bdd cond, bdd acc)
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{
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if (acc != bddfalse)
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{
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unsigned u = si->scc_of(src);
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auto i = remap_[u].find(acc.id());
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if (i != remap_[u].end())
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acc = i->second;
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else
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acc = bddfalse;
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}
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return filtered_trans{true, cond, acc};
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}
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};
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template<typename F1, typename... F2>
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struct compose_filters
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{
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F1 f1;
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F2 f2;
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compose_filters<F2...> f2;
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compose_filters(scc_info* si)
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: f1(si), f2(si)
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@ -714,6 +962,12 @@ namespace spot
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return f1.state(s) && f2.state(s);
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}
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acc_pair accsets(bdd all, bdd all_neg)
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{
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auto t = f1.accsets(all, all_neg);
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return f2.accsets(t.first, t.second);
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}
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filtered_trans trans(unsigned src, unsigned dst,
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bdd cond, bdd acc)
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{
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@ -724,15 +978,25 @@ namespace spot
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}
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};
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// If there is nothing to compose, use the filter as-is.
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template<typename F1>
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struct compose_filters<F1>: F1
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{
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compose_filters(scc_info* si)
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: F1(si)
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{
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}
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};
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template<class F>
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tgba_digraph* scc_filter_apply(const tgba_digraph* aut, scc_info* given_si)
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tgba_digraph* scc_filter_apply(const tgba_digraph* aut,
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scc_info* given_si)
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{
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// Compute scc_info if not supplied.
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scc_info* si = given_si;
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if (!si)
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si = new scc_info(aut);
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F filter(si);
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// Renumber all useful states.
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@ -749,7 +1013,11 @@ namespace spot
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bdd_dict* bd = aut->get_dict();
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tgba_digraph* filtered = new tgba_digraph(bd);
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bd->register_all_variables_of(aut, filtered);
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filtered->copy_acceptance_conditions_of(aut);
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{
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bdd all = aut->all_acceptance_conditions();
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bdd neg = aut->neg_acceptance_conditions();
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filtered->set_acceptance_conditions(filter.accsets(all, neg).first);
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}
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const tgba_digraph::graph_t& ing = aut->get_graph();
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tgba_digraph::graph_t& outg = filtered->get_graph();
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outg.new_states(out_n);
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@ -797,10 +1065,14 @@ namespace spot
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{
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if (remove_all_useless)
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return scc_filter_apply<compose_filters<state_filter,
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acc_filter_all>>(aut, given_si);
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acc_filter_all,
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acc_filter_simplify>>
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(aut, given_si);
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else
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return scc_filter_apply<compose_filters<state_filter,
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acc_filter_some>>(aut, given_si);
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acc_filter_some,
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acc_filter_simplify>>
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(aut, given_si);
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}
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}
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@ -23,6 +23,7 @@
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#include <queue>
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#include "tgba/bddprint.hh"
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#include "misc/escape.hh"
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#include "priv/accconv.hh"
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namespace spot
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{
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@ -45,6 +46,7 @@ namespace spot
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}
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scc_info::scc_info(const tgba_digraph* aut)
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: aut_(aut)
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{
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unsigned n = aut->num_states();
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sccof_.resize(n, -1U);
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@ -225,6 +227,29 @@ namespace spot
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}
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}
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std::vector<bdd> scc_info::used_acc() const
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{
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auto& g = aut_->get_graph();
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unsigned n = g.num_states();
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std::vector<bdd> result(scc_count());
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acceptance_convertor conv(aut_->neg_acceptance_conditions());
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for (unsigned src = 0; src < n; ++src)
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{
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unsigned src_scc = scc_of(src);
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if (!is_accepting_scc(src_scc))
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continue;
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for (auto& t: g.out(src))
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{
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if (scc_of(t.dst) != src_scc)
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continue;
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result[src_scc] |= conv.as_full_product(t.acc);
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}
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}
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return result;
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}
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std::ostream&
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dump_scc_info_dot(std::ostream& out,
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const tgba_digraph* aut, scc_info* sccinfo)
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@ -66,8 +66,9 @@ namespace spot
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std::vector<unsigned> sccof_;
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std::vector<scc_node> node_;
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const tgba_digraph* aut_;
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const scc_node& node(unsigned scc)
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const scc_node& node(unsigned scc) const
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{
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assert(scc < node_.size());
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return node_[scc];
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@ -76,52 +77,69 @@ namespace spot
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public:
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scc_info(const tgba_digraph* aut);
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unsigned scc_count()
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const tgba_digraph* get_aut() const
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{
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return aut_;
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}
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unsigned scc_count() const
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{
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return node_.size();
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}
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unsigned scc_of(unsigned st)
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unsigned scc_of(unsigned st) const
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{
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assert(st < sccof_.size());
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return sccof_[st];
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}
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const std::list<unsigned>& states_of(unsigned scc)
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const std::list<unsigned>& states_of(unsigned scc) const
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{
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return node(scc).states;
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}
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const scc_succs& succ(unsigned scc)
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const scc_succs& succ(unsigned scc) const
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{
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return node(scc).succ;
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}
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bool is_trivial(unsigned scc)
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bool is_trivial(unsigned scc) const
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{
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return node(scc).trivial;
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}
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bdd acc(unsigned scc)
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bdd acc(unsigned scc) const
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{
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return node(scc).acc;
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}
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bool is_accepting_scc(unsigned scc)
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bool is_accepting_scc(unsigned scc) const
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{
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return node(scc).accepting;
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}
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bool is_useful_scc(unsigned scc)
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bool is_useful_scc(unsigned scc) const
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{
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return node(scc).useful;
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}
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bool is_useful_state(unsigned st)
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bool is_useful_state(unsigned st) const
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{
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return node(scc_of(st)).useful;
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}
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/// \brief Return the set of all used acceptance combinations, for
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/// each accepting SCC.
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///
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/// If SCC #i use {a,b} and {c}, which
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/// are normally respectively encoded as
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/// Acc[a]&!Acc[b]&!Acc[c] | !Acc[a]&Acc[b]&!Acc[c]
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/// and
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/// !Acc[a]&!Acc[b]&Acc[c]
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/// then the vector will contain
|
||||
/// Acc[a]&Acc[b] | Acc[c]
|
||||
/// at position #i.
|
||||
std::vector<bdd> used_acc() const;
|
||||
};
|
||||
|
||||
|
||||
|
|
|
|||
Loading…
Add table
Add a link
Reference in a new issue