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Distributed agreement-based (DAB) systems use common distributed agreement protocols such as leader election and consensus as building blocks for their target functionality. While automated verification for DAB systems is undecidable in general, recent work identifies a large class of DAB systems for which verification is efficiently-decidable. Unfortunately, the conditions characterizing such a class can be opaque and non-intuitive, and can pose a significant challenge to system designers trying to model their systems in this class. In this paper, we present a synthesis-driven tool, CINNABAR, to help system designers building DAB systems ensure that their intended designs belong to an efficiently-decidable class. In particular, starting from an initial sketch provided by the designer, CINNABAR generates sketch completions using a counterexample-guided procedure. The core technique relies on compactly encoding root-causes of counterexamples to varied properties such as efficient-decidability and safety. We demonstrate CINNABAR ’s effectiveness by successfully and efficiently synthesizing completions for a variety of interesting DAB systems including a distributed key-value store and a distributed consortium system. 

Scheduling transformations reorder operations in a program to improve locality and/or parallelism. There are mature loop transformation frameworks such as the polyhedral model for composing and applying instance-wise scheduling transformations for loop nests.In recent years, there have been efforts to build frameworks for composing and applying scheduling transformations for nested recursion and loops, but these frameworks cannot employ the full power of transformations for loop nests since they have overly-restrictive representations. This paper describes a new framework, UniRec, that not only generalizes prior frameworks for reasoning about transformations on recursion, but also generalizes the unimodular framework, and hence unifies reasoning about perfectly-nested loops and recursion.