This is the native version of the AbsSynthe tool, used to synthesize controllers from succinct safety specifications.

• Version: 2.1
• Maintainer: Guillermo A. Perez (University of Antwerp)
• Contributors: Nicolas Basset, Romain Brenguier, Ocan Sankur, Jean-Francois Raskin

We provide a building script for your convenience, but you may have to customize it for your set up.

The tool uses a simple version of the aiger library developed by the team of Armin Biere (available at http://fmv.jku.at/aiger/). Specifically, we use slightly modified versions of the aiger.c, aigtocnf.c, and aiger.h files.

We also make use of the cudd BDD library (version 2.5.1) included in the source sub-folder.

If you use AbsSynthe for your academic purposes, please cite the original paper describing the tool:

@inproceedings{DBLP:journals/corr/BrenguierPRS14,
  author    = {Romain Brenguier and
               Guillermo A. P{\'{e}}rez and
               Jean{-}Fran{\c{c}}ois Raskin and
               Ocan Sankur},
  editor    = {Krishnendu Chatterjee and
               R{\"{u}}diger Ehlers and
               Susmit Jha},
  title     = {AbsSynthe: abstract synthesis from succinct safety specifications},
  booktitle = {Proceedings 3rd Workshop on Synthesis, {SYNT} 2014, Vienna, Austria,
               July 23-24, 2014},
  series    = {{EPTCS}},
  volume    = {157},
  pages     = {100--116},
  year      = {2014},
  url       = {https://doi.org/10.4204/EPTCS.157.11},
  doi       = {10.4204/EPTCS.157.11},
  timestamp = {Fri, 02 Nov 2018 09:30:18 +0100},
  biburl    = {https://dblp.org/rec/journals/corr/BrenguierPRS14.bib},
  bibsource = {dblp computer science bibliography, https://dblp.org}
}

The idea behind the winning region that AbsSynthe can output is outlined in the rules of the synthesis-competition website (http://www.syntcomp.org/rules/).

For the winning region generation, I take a BDD representing the set of latch valuations (i.e. states) that are safe with respect to the specification. I then generate a new AIG file in which each latch becomes an input and the output of the encoded circuit has value 1 if and only if the given values for the latches correspond to a safe/winning state. Otherwise the value is 0. In AIGER terms, we started with a file whose input, latch, and output sets were I, L, O respectively. I create a new AIGER file with I', L', O' as new sets of inputs, latches, and outputs such that I' = L, O' = Win(I') and L' is empty.

For the inductive certificate we go beyond just safe states and want to capture all the controllable-input valuations that make it so that the uncontrollable-input valuation does not take the system outside of the safe/winning region. Again, starting from the BDD for the safe latch valuations, one can use the transition relation of the system and intersect it with the winning region so as to obtain precisely the desired transitions and build an AIG for it. Latches and inputs both become inputs in the new circuit and its output is 1 if and only if the given values correspond to an uncontrollable-input valuation and a controllable-input valuation so that, from the chosen latch valuation, we reach again a safe latch valuation. In AIGER terms, we create a file with I', L', O' as new sets of inputs, latches, and outputs such that I' = I U L, O' = T(L,I,L'') ^ Win(L''), and L' is empty.

Besides bug fixing, this version includes options for

• a forced reordering just before generating the output circuit (so as to minimize the size of the BDDs on which the circuit is based)
• a way of reducing the number of subgames for the compositional algorithms based on the idea that subgames that do not depend on the same variables may be easy to solve but do not give much information; hence, we combine them into more complicated games which are (hopefully) more instructive regarding the realizability of the global game
• generation of the winning refion being inductively invariant in AIGER (previously available only in QDIMACS format)

For this new version of Swiss AbsSynthe we have implemented a new abstraction algorithm and one more compositional algorithm.

Additionally, there are new options to output

1. an aag version of the winning region if the given input spec is realizable and
2. a QDIMACS certificate of the winning region being inductively invariant, that is there is some way to choose controllable inputs -- which depends on the latches and uncontrollable inputs -- which allows the controller to stay in the winning region if it started from the winning region. The latter can be fed into a QBF solver to obtain Skolem functions: a strategy.