Cunf: An Unfolder for Contextual Nets

Cunf is a set of research tools to carrying out unfolding-based formal verification of Petri nets extended with read arcs, also called contextual nets, or c-nets. The package specifically contains the tools:

• cunf: constructs the unfolding of a c-net;
• cna: performs reachability and deadlock analysis using unfoldings constructed by cunf;
• Scripts such as pep2dot or grml2pep to do format conversion between various Petri net formats, unfolding formats, etc.
• ptnet: a small Python module (see scripts/ptnet/) suitable to programmatically generate and manage Petri net models.

Installation

From Precompiled Binaries

1. Install dependencies. In Ubuntu, type:

   sudo apt-get install minisat python2.7 python-networkx
   

   In other operating systems, please ensure that the executable minisat is in your PATH, and that Python 2.7 and the Python package networkx are available in your system.

2. Check the latest release to find the link to the .tar.gz file with precompiled binaries that you want to download (currently only available for Linux x86_64). Download it and uncompress it:

   wget https://github.com/cesaro/cunf/releases/download/v?.?.?/cunf-x86_64-v1.6.1.tar.gz
   tar xzvf cunf-x86_64-v1.6.1.tar.gz
   cd cunf-x86_64-v1.6.1
   

3. All binaries are in the bin/ folder, you can directly run them from there. For instance, you can do deadlock detection on one of the examples:

   ./bin/cunf -i examples/dijkstra/dij04.ll_net -s out.unf
   ./bin/cna  -d out.unf
   

   The second command should print:

   NO , the net is deadlock-free
   

   together with other debugging information.

From Source Code

Please note that development takes place in the master branch of this repository. If you want a stable version of the tool you should download and compile the sources of the latest release available.

1. Ensure that you have all the necessary dependencies. In Ubuntu, install the following packages:

   sudo apt-get install libc-dev coreutils git make
   sudo apt-get install clang flex bison cpp minisat python3.5 python3-networkx
   

2. Check out the latest release:

   git clone git@github.com:cesaro/cunf.git
   cd cunf
   git checkout v1.6.1
   

2. Compile the source code:

   make all
   make dist
   

   This will put all binaries and libraries into the dist/ folder, from where you may directly run them or copy them to suitable locations in your machine.

3. To test the insallation, do deadlock detection on one of the examples:

   ./dist/bin/cunf -i dist/examples/dijkstra/dij04.ll_net -s out.unf
   ./dist/bin/cna  -d out.unf
   

   The second command should print:

   NO , the net is deadlock-free
   

   together with other debugging information.

Documentation

The Cunf user's manual (available with the latest release) contains all documentation available, including a guided tutorial of the tool.

Algorithms

Cunf implements the contextual net unfolding algorithm proposed by Baldan et al. in [BCKS08]. The algorithms and data structures actually implemented have been partially described in [RSB11], [BBCKRS12]. Cunf can only unfold 1-safe c-nets (i.e., no reachable marking puts more than one token on every place), and for the time being the tool will blindly assume the input is 1-safe.

Cna, whose name stands for Contextual Net Analyzer, checks for place coverability or deadlock-freedom of a c-net by examining its unfolding. The tool reduces these problems to the satisfiability of a propositional formula that it generates out of the unfolding, and uses Minisat as a back-end to solve the formula. The algorithms used by Cna has been described in [RS12].

[BBCKRS12]

Paolo Baldan, Alessandro Bruni, Andrea Corradini, Barbara König, César Rodríguez, and Stefan Schwoon. Efficient Unfolding of Contextual Petri Nets. Theoretical Computer Science 449, 2 – 22 (2012).

[BCKS08]

Paolo Baldan, Andrea Corradini, Barbara König, and Stefan Schwoon. McMillan's Complete Prefix for Contextual Nets. In Transactions on Petri Nets and Other Models of Concurrency I, p. 199-220, 2008. Springer-Verlag.

[RSB11]

César Rodríguez, Stefan Schwoon, and Paolo Baldan. Efficient contextual unfolding. In Proc. of CONCUR'11, volume 6901 of LNCS. Springer, 2011.

[RS12]

César Rodríguez and Stefan Schwoon. Verification of Petri Nets with Read Arcs. In Proc. of CONCUR'12, vol. 7454 of LNCS, pages 471–485, September 2012.

Related Tools

• Stefan Schwoon's Mole unfolder.
• Victor Khomenko's Punf unfolder.
• The PEP homepage.
• DPU, an unfolder for multithreaded C programs.

Author and Contact

The Cunf Tool is developed and maintained by César Rodríguez. Please feel free to contact me with questions or to send feedback.