Programming by sketching for bit-streaming programs

Abstract

This paper introduces the concept of programming with sketches, an approach for the rapid development of high-performance applications. This approach allows a programmer to write clean and portable reference code, and then obtain a high-quality implementation by simply sketching the outlines of the desired implementation. Subsequently, a compiler automatically fills in the missing details while also ensuring that a completed sketch is faithful to the input reference code. In this paper, we develop StreamBit as a sketching methodology for the important class of bit-streaming programs (e.g., coding and cryptography). A sketch is a partial specification of the implementation, and as such, it affords several benefits to programmer in terms of productivity and code robustness. First, a sketch is easier to write compared to a complete implementation. Second, sketching allows the programmer to focus on exploiting algorithmic properties rather than on orchestrating low-level details. Third, a sketch-aware compiler rejects "buggy" sketches, thus improving reliability while allowing the programmer to quickly evaluate sophisticated implementation ideas. We evaluated the productivity and performance benefits of our programming methodology in a user-study, where a group of novice StreamBit programmers competed with a group of experienced C programmers on implementing a cipher. We learned that, given the same time budget, the ciphers developed in StreamBit ran 2.5× faster than ciphers coded in C. We also produced implementations of DES and Serpent that were competitive with hand optimized implementations available in the public domain. Copyright 2005 ACM.