# Practical Synthesis of Reactive Systems from LTL Specifications via Parity Games

## TL;DR

This paper introduces an efficient, structured, and incremental automata-theoretic approach for synthesizing reactive systems from LTL specifications, implemented in the Strix tool, which outperforms other tools on benchmark sets.

## Contribution

The paper presents a structured, forward, and incremental synthesis method with heuristics and symbolic representations, improving efficiency and scalability in LTL synthesis.

## Key findings

- Strix outperforms other tools on Syntcomp benchmarks.
- The approach reduces runtime and memory consumption.
- Techniques for extracting implementations from automata are effective.

## Abstract

The synthesis of reactive systems from linear temporal logic (LTL) specifications is an important aspect in the design of reliable software and hardware. We present our adaption of the classic automata-theoretic approach to LTL synthesis, implemented in the tool Strix which has won the two last synthesis competitions (Syntcomp2018/2019). The presented approach is (1) structured, meaning that the states used in the construction have a semantic structure that is exploited in several ways, it performs a (2) forward exploration such that it often constructs only a small subset of the reachable states, and it is (3) incremental in the sense that it reuses results from previous inconclusive solution attempts. Further, we present and study different guiding heuristics that determine where to expand the on-demand constructed arena. Moreover, we show several techniques for extracting an implementation (Mealy machine or circuit) from the witness of the tree-automaton emptiness check. Lastly, the chosen constructions use a symbolic representation of the transition functions to reduce runtime and memory consumption. We evaluate the proposed techniques on the Syntcomp2019 benchmark set and show in more detail how the proposed techniques compare to the techniques implemented in other leading LTL synthesis tools.