Program synthesis with algebraic library specifications

Abstract

A key challenge in program synthesis is synthesizing programs that use libraries, which most real-world software does. The current state of the art is to model libraries with mock library implementations that perform the same function in a simpler way. However, mocks may still be large and complex, and must include many implementation details, both of which could limit synthesis performance. To address this problem, we introduce JLibSketch, a Java program synthesis tool that allows library behavior to be described with algebraic specifications, which are rewrite rules for sequences of method calls, e.g., encryption followed by decryption (with the same key) is the identity. JLibSketch implements rewrite rules by compiling JLibSketch problems into problems for the Sketch program synthesis tool. More specifically, after compilation, library calls are represented by abstract data types (ADTs), and rewrite rules manipulate those ADTs. We formalize compilation and prove it sound and complete if the rewrite rules are ordered and non-unifiable. We evaluated JLibSketch by using it to synthesize nine programs that use libraries from three domains: data structures, cryptography, and file systems. We found that algebraic specifications are, on average, about half the size of mocks. We also found that algebraic specifications perform better than mocks on seven of the nine programs, sometimes significantly so, and perform equally well on the last two programs. Thus, we believe that JLibSketch takes an important step toward synthesis of programs that use libraries. CCS Concepts: • Software and its engineering → Automatic programming; Source code generation.

Program Sketching by Automatically Generating Mocks from Tests

“…While Sketcham relies on the core algorithm of that work, Sketcham frees the Sketch user from needing to write models, because we create mocks automatically from normal sketches. Mariano et al [18] use algebraic specifications to model libraries. In contrast, our approach derives specifications from the input program's assertions, without requiring the programmer to add annotations.…”

“…Program synthesis by sketching, as embodied by the Sketch synthesis tool [30], is a popular technique that has been applied to a wide variety of problems [5,7,13,14,15,16,18,22,29]. A Sketch input (henceforth a sketch) is a program written in a C-like language augmented with holes, unknown constants, and generators, unknown expressions.…”