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zlktree: use a cache in the construction of zielonka_tree

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This largely speeds up the computation for conditions
like "Rabin n" sharing a lot of subtrees.

Also implement options to stop the construction if the shape is wrong.

* spot/twaalgos/zlktree.cc, spot/twaalgos/zlktree.hh: Implement the
cache and the options.
* tests/python/zlktree.ipynb, tests/python/zlktree.py: New tests.
This commit is contained in:
Alexandre Duret-Lutz 2022-05-20 16:51:16 +02:00
parent f784e40548
commit b11208440b
5 changed files with 517 additions and 151 deletions
Download patch file Download diff file Expand all files Collapse all files

5
NEWS
View file

@ -85,6 +85,11 @@ New in spot 2.10.6.dev (not yet released)
- complement() used to always turn tautological acceptance conditions
into Büchi. It now only does that if the automaton is modified.
- The zielonka_tree construction was optimized using the same
memoization trick that is used in ACD. Additionally it can now be
run with additional option to abort when the tree as an unwanted
shape, or to turn the tree into a DAG.
New in spot 2.10.6 (2022-05-18)
Bugs fixed:

70
spot/twaalgos/zlktree.cc
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@ -1,5 +1,5 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2021 Laboratoire de Recherche et Developpement de
// Copyright (C) 2021, 2022 Laboratoire de Recherche et Developpement de
// l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
@ -109,7 +109,8 @@ namespace spot
}
}
zielonka_tree::zielonka_tree(const acc_cond& cond)
zielonka_tree::zielonka_tree(const acc_cond& cond,
zielonka_tree_options opt)
{
const acc_cond::acc_code& code = cond.get_acceptance();
auto all = cond.all_sets();
@ -120,11 +121,47 @@ namespace spot
nodes_[0].colors = all;
nodes_[0].level = 0;
robin_hood::unordered_node_map<acc_cond::mark_t, unsigned> nmap;
std::vector<size_model> models;
// This loop is a BFS over the increasing set of nodes.
for (unsigned node = 0; node < nodes_.size(); ++node)
{
acc_cond::mark_t colors = nodes_[node].colors;
unsigned nextlvl = nodes_[node].level + 1;
// Have we already seen this combination of colors previously?
// If yes, simply copy the children.
if (auto p = nmap.emplace(colors, node); !p.second)
{
unsigned fc = nodes_[p.first->second].first_child;
if (!fc) // this is a leaf
{
++num_branches_;
continue;
}
if (!!(opt & zielonka_tree_options::MERGE_SUBTREES))
{
nodes_[node].first_child = fc;
continue;
}
unsigned child = fc;
unsigned first = nodes_.size();
nodes_[node].first_child = first;
do
{
auto& c = nodes_[child];
child = c.next_sibling;
nodes_.push_back({node, static_cast<unsigned>(nodes_.size() + 1),
0, nextlvl, c.colors});
}
while (child != fc);
nodes_.back().next_sibling = first;
// We do not have to test the shape since this is the second time
// we see these colors;
continue;
}
bool is_accepting = code.accepting(colors);
if (node == 0)
is_even_ = is_accepting;
@ -145,15 +182,32 @@ namespace spot
nodes_.reserve(first + num_children);
for (auto& m: models)
nodes_.push_back({node, static_cast<unsigned>(nodes_.size() + 1),
0, nodes_[node].level + 1, m.model});
0, nextlvl, m.model});
nodes_.back().next_sibling = first;
if (num_children > 1)
{
bool abort = false;
if (is_accepting)
{
has_rabin_shape_ = false;
if (!!(opt & zielonka_tree_options::ABORT_WRONG_SHAPE)
&& !!(opt & zielonka_tree_options::CHECK_RABIN))
abort = true;
}
else
{
has_streett_shape_ = false;
if (!!(opt & zielonka_tree_options::ABORT_WRONG_SHAPE)
&& !!(opt & zielonka_tree_options::CHECK_STREETT))
abort = true;
}
if (abort)
{
nodes_.clear();
num_branches_ = 0;
return;
}
}
}
@ -523,14 +577,18 @@ namespace spot
do
{
auto& c = nodes_[child];
// We have to read anything we need from C
// before emplace_back, which may reallocate.
acc_cond::mark_t colors = c.colors;
unsigned minstate = c.minstate;
child = c.next_sibling;
nodes_.emplace_back(c.edges, c.states);
auto& n = nodes_.back();
n.parent = node;
n.level = lvl + 1;
n.scc = ref.scc;
n.colors = c.colors;
n.minstate = c.minstate;
child = c.next_sibling;
n.colors = colors;
n.minstate = minstate;
}
while (child != fc);
chain_children(node, before, nodes_.size());

67
spot/twaalgos/zlktree.hh
View file

@ -1,5 +1,5 @@
// -*- coding: utf-8 -*-
// Copyright (C) 2021 Laboratoire de Recherche et Developpement de
// Copyright (C) 2021, 2022 Laboratoire de Recherche et Developpement de
// l'Epita (LRDE).
//
// This file is part of Spot, a model checking library.
@ -28,6 +28,68 @@
namespace spot
{
/// \ingroup twa_acc_transform
/// \brief Options to alter the behavior of acd
enum class zielonka_tree_options
{
/// Build the ZlkTree, without checking its shape.
NONE = 0,
/// Check if the ZlkTree has Rabin shape.
/// This actually has no effect unless ABORT_WRONG_SHAPE is set,
/// because zielonka_tree always check the shape.
CHECK_RABIN = 1,
/// Check if the ZlkTree has Streett shape.
/// This actually has no effect unless ABORT_WRONG_SHAPE is set,
/// because zielonka_tree always check the shape.
CHECK_STREETT = 2,
/// Check if the ZlkTree has Parity shape
/// This actually has no effect unless ABORT_WRONG_SHAPE is set,
/// because zielonka_tree always check the shape.
CHECK_PARITY = CHECK_RABIN | CHECK_STREETT,
/// Abort the construction of the ZlkTree if it does not have the
/// shape that is tested. When that happens, num_branches() is set
/// to 0.
ABORT_WRONG_SHAPE = 4,
/// Fuse identical substree. This cannot be used with
/// zielonka_tree_transform(). However it saves memory if the
/// only use of the zielonka_tree to check the shape.
MERGE_SUBTREES = 8,
};
#ifndef SWIG
inline
bool operator!(zielonka_tree_options me)
{
return me == zielonka_tree_options::NONE;
}
inline
zielonka_tree_options operator&(zielonka_tree_options left,
zielonka_tree_options right)
{
typedef std::underlying_type_t<zielonka_tree_options> ut;
return static_cast<zielonka_tree_options>(static_cast<ut>(left)
& static_cast<ut>(right));
}
inline
zielonka_tree_options operator|(zielonka_tree_options left,
zielonka_tree_options right)
{
typedef std::underlying_type_t<zielonka_tree_options> ut;
return static_cast<zielonka_tree_options>(static_cast<ut>(left)
| static_cast<ut>(right));
}
inline
zielonka_tree_options operator-(zielonka_tree_options left,
zielonka_tree_options right)
{
typedef std::underlying_type_t<zielonka_tree_options> ut;
return static_cast<zielonka_tree_options>(static_cast<ut>(left)
& ~static_cast<ut>(right));
}
#endif
/// \ingroup twa_acc_transform
/// \brief Zielonka Tree implementation
///
@ -41,7 +103,8 @@ namespace spot
{
public:
/// \brief Build a Zielonka tree from the acceptance condition.
zielonka_tree(const acc_cond& cond);
zielonka_tree(const acc_cond& cond,
zielonka_tree_options opt = zielonka_tree_options::NONE);
/// \brief The number of branches in the Zielonka tree.
///

513
tests/python/zlktree.ipynb
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File diff suppressed because one or more lines are too long

9
tests/python/zlktree.py
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@ -152,3 +152,12 @@ tc.assertTrue(a.equivalent_to(b))
b = spot.acd_transform_sbacc(a, False)
tc.assertEqual(str(b.acc()), '(2, Fin(0) & Inf(1))')
tc.assertTrue(a.equivalent_to(b))
# This used to be very slow.
c = spot.acc_cond("Rabin 9")
n = spot.zielonka_tree(c).num_branches()
tc.assertEqual(n, 362880)
opt = spot.zielonka_tree_options_MERGE_SUBTREES;
n = spot.zielonka_tree(c, opt).num_branches()
tc.assertEqual(n, 9)