
Predicting Winning Regions in Parity Games via
Graph Neural Networks
Tobias Hecking∗
German Aerospace Center (DLR)
Institute for Software Technology
Cologne, Germany
tobias.hecking@dlr.de
Swathy Muthukrishnan∗
University of Stuttgart
Stuttgart, Germany
swathy.muthukrishnan.24@gmail.com
Alexander Weinert∗
German Aerospace Center (DLR)
Institute for Software Technology
Cologne, Germany
alexander.weinert@dlr.de
Abstract
Solving parity games is a major building block for numerous
applications in reactive program verication and synthesis.
While they can be solved eciently in practice, no known
approach has a polynomial worst-case runtime complexity.
We present a incomplete polynomial-time approach to de-
termining the winning regions of parity games via graph
neural networks.
Our evaluation on 900 randomly generated parity games
shows that this approach is eective and ecient in prac-
tice. It correctly determines the winning regions of
∼
60% of
the games in our data set and only incurs minor errors in
the remaining ones. We believe that this approach can be
extended to eciently solve parity games as well.
ACM Reference Format:
Tobias Hecking, Swathy Muthukrishnan, and Alexander Weinert.
2023. Predicting Winning Regions in Parity Games via Graph Neural
Networks. In Proceedings of First International Workshop on Deep
Learning-aided Verication (DAV ’23). ACM, New York, NY, USA,
4pages. hps://doi.org/XXXXXXX.XXXXXXX
1 Introduction
Parity games are innite arena-based games between Player 0
and Player 1that capture all
𝜔
-regular languages. They are
the canonical model for specications of reactive systems,
where Player 0and Player 1represent the system and its
environment, respectively. Solving them is a major building
block for reactive program verication and synthesis. [
3
,
16
]
Solving comprises determining the winning regions of both
players as well as a winning strategy for both players.
∗
Authors are listed in alphabetical order and have contributed equally to
this work
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DAV ’23, July 18, 2023, Paris, France
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ACM ISBN 978-1-4503-XXXX-X/18/06. . . $15.00
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The problem of solving parity games is known to be in
UP∩coUP
[
9
] and to be solvable in quasi-polynomial time [
2
].
There exist parity game solvers that are ecient in prac-
tice [
4
,
15
,
17
], all of which suer from a non-polynomial
worst-case runtime complexity.
Here, we trade completeness for eciency in determining
the winning regions. Classically, parity games are solved by
building a correct-by-construction strategy, which yields the
winning regions as a by-product. We instead train graph neu-
ral networks (GNNs) [
1
] to determine the winning regions.
Applying the trained GNN to a parity game
G
then yields a
prediction of the winning region of G.
In a preliminary evaluation we constructed two GNNs and
trained these on 2 100 randomly generated parity games. We
then predicted the winning region of another 900 randomly
generated parity games using these GNNs. This approach
yields correct winning regions in 537 (433) cases, as well as
regions that dier by one vertices from the correct result in
245 (279) cases.
2 Preliminaries
We write
R
and
R𝑘,𝑙
to denote the real numbers and the set
of
𝑘×𝑙
-matrices over the reals, respectively. Moreover, given
a set
𝑆
, we write
𝑆𝑛
to denote the
𝑛
-ary cartesian power of
𝑆
.
Parity Games. An arena
A=(𝑉 ,𝑉0,𝑉1, 𝐸)
comprises
a nite set of vertices
𝑉
, a partition
(𝑉0, 𝑉1)
of
𝑉
, as well
as a set of edges
𝐸⊆𝑉×𝑉
with
∀𝑣∈𝑉 . ({𝑣}×𝑉) ∩
𝐸≠∅
. We call
𝑉𝑖
the vertices of Player
𝑖
. A play
𝜌=
𝑣0𝑣1𝑣2···
of
A
is an innite path through
(𝑉 , 𝐸)
. A par-
ity game
(A,Parity(Ω))
comprises an arena
A
with vertex
set
𝑉
and a coloring
Ω:𝑉→N
. The play
𝜌
is winning for
Player 𝑖if (max {Ω(𝑣𝑖) | 𝑖∈N})mod 2 =𝑖.
A strategy
𝜎:𝑉𝑖→𝑉
for Player
𝑖
is a mapping with
∀𝑣∈𝑉𝑖.(𝑣, 𝜎 (𝑣)) ∈ 𝐸
. A play
𝜌=𝑣0𝑣1𝑣2···
is consistent
with
𝜎
if
∀𝑗∈N. 𝑣𝑗∈𝑉𝑖⇒𝑣𝑗+1=𝜎(𝑣𝑗)
. We say that
Player
𝑖
wins
G
from vertex
𝑣∈𝑉
if she has a strategy
𝜎
such that all plays starting in
𝑣
and consistent with
𝜎
are
winning for her. The winning region
𝑊𝑖(G)
of Player
𝑖
in
G
is the set of all vertices from which Player 𝑖wins G.
Neural Network Layers. A
𝑘, 𝑙
-neural network layer is a
function
ℎ:R𝑘→R𝑙
. In this work we use the linear layer
ℎ𝐴,𝑏 (𝑥)=𝑥𝐴𝑇+𝑏
, where
𝐴∈R𝑙×𝑘
and
𝑏∈R1×𝑙
, the rectied
arXiv:2210.09924v2 [cs.GT] 27 Jul 2023