Transit

Abstract

With the maturing of technology for model checking and constraint solving, there is an emerging opportunity to develop programming tools that can transform the way systems are specified. In this paper, we propose a new way to program distributed protocols using concolic snippets. Concolic snippets are sample execution fragments that contain both concrete and symbolic values. The proposed approach allows the programmer to describe the desired system partially using the traditional model of communicating extended finite-state-machines (EFSM), along with high-level invariants and concrete execution fragments. Our synthesis engine completes an EFSM skeleton by inferring guards and updates from the given fragments which is then automatically analyzed using a model checker with respect to the desired invariants. The counterexamples produced by the model checker can then be used by the programmer to add new concrete execution fragments that describe the correct behavior in the specific scenario corresponding to the counterexample.We describe TRANSIT, a language and prototype implementation of the proposed specification methodology for distributed protocols. Experimental evaluations of TRANSIT to specify cache coherence protocols show that (1) the algorithm for expression inference from concolic snippets can synthesize expressions of size 15 involving typical operators over commonly occurring types, (2) for a classical directory-based protocol, TRANSIT automatically generates, in a few seconds, a complete implementation from a specification consisting of the EFSM structure and a few concrete examples for every transition, and (3) a published partial description of the SGI Origin cache coherence protocol maps directly to symbolic examples and leads to a complete implementation in a few iterations, with the programmer correcting counterexamples resulting from underspecified transitions by adding concrete examples in each iteration.

Synthesizing highly expressive SQL queries from input-output examples

“…Results showed that SCYTHE quickly and precisely solved more than 74% of the benchmarks and 80% out of these solved benchmarks were solved within a few seconds. Our algorithm solved 51 more cases within 600 seconds compared to the enumerative search algorithm [25,37] and outperformed SQLSynthesizer [40] on their project benchmarks with 4 more cases solved.…”

“…Such algorithms enumerate all programs in the program space of a given depth limit and retain only those consistent with the provided I/O examples. Previous enumerative synthesizers [2,25,37] adopt the concept of equivalence classes to optimize the search process: they group programs into equivalence classes based on their behaviors on the input example to compress the search space. The search then proceeds iteratively: within each stage, the algorithms enumerate all programs in the current search space, group them based on an equivalence metric, and proceed to the next stage.…”

CLS-SMT: Bringing Together Combinatory Logic Synthesis and Satisfiability Modulo Theories

“…A user specifies the behaviour of the desired program by a number of input-output examples [19]. Singh and Gulwani transformed strings and data types in spreadsheets [17,28] and Udupa et al were able to synthesize protocols from a given skeleton and examples [32].…”

“…The main difference is the way of specification. Like in many traditional synthesis approaches [16,17,28,32], targets in [27] are specified by using properties of executed programs. More specifically, relations on inputs and outputs are defined.…”

“…Software synthesis is an established research topic that offers a broad range of specification formalisms such as examples [16,17,28,32], types [16,20,25] or first-order-logic [27,31]. For this paper, we followed the intuition that the joint usage of (complementary) formalisms can yield a synthesis approach that combines the respective strengths of the underlying techniques.…”