Approaches to Interpreter Composition

In this paper, we compose six different Python and Prolog VMs into 4 pairwise compositions: one using C interpreters; one running on the JVM; one using meta-tracing interpreters; and one using a C interpreter and a meta-tracing interpreter. We show that programs that cross the language barrier frequently execute faster in a meta-tracing composition, and that meta-tracing imposes a significantly lower overhead on composed programs relative to mono-language programs.Comment: 33 pages, 1 figure, 9 table

Transforming specifications of observable behaviour into programs

A methodology for deriving programs from specifications of observable behaviour is described. The class of processes to which this methodology is applicable includes those whose state changes are fully definable by labelled transition systems, for example communicating processes without internal state changes. A logic program representation of such labelled transition systems is proposed, interpreters based on path searching techniques are defined, and the use of partial evaluation techniques to derive the executable programs is described

Fine-grained Language Composition: A Case Study

Although run-time language composition is common, it normally takes the form of a crude Foreign Function Interface (FFI). While useful, such compositions tend to be coarse-grained and slow. In this paper we introduce a novel fine-grained syntactic composition of PHP and Python which allows users to embed each language inside the other, including referencing variables across languages. This composition raises novel design and implementation challenges. We show that good solutions can be found to the design challenges; and that the resulting implementation imposes an acceptable performance overhead of, at most, 2.6x.Comment: 27 pages, 4 tables, 5 figure

Making an Embedded DBMS JIT-friendly

While database management systems (DBMSs) are highly optimized, interactions across the boundary between the programming language (PL) and the DBMS are costly, even for in-process embedded DBMSs. In this paper, we show that programs that interact with the popular embedded DBMS SQLite can be significantly optimized - by a factor of 3.4 in our benchmarks - by inlining across the PL / DBMS boundary. We achieved this speed-up by replacing parts of SQLite's C interpreter with RPython code and composing the resulting meta-tracing virtual machine (VM) - called SQPyte - with the PyPy VM. SQPyte does not compromise stand-alone SQL performance and is 2.2% faster than SQLite on the widely used TPC-H benchmark suite.Comment: 24 pages, 18 figure

Fundamental Constructs in Programming Languages

Specifying the semantics of a programming language formally can have many benefits. However, it can also require a huge effort. The effort can be significantly reduced by translating language syntax to so-called fundamental constructs (funcons). A translation to funcons is easy to update when the language evolves, and it exposes relationships between individual language constructs. The PLanCompS project has developed an initial collection of funcons (primarily for translation of functional and imperative languages). The behaviour of each funcon is defined, once and for all, using a modular variant of structural operational semantics. The definitions are available online. This paper introduces and motivates funcons. It illustrates translation of language constructs to funcons, and how funcons are defined. It also relates funcons to notation used in previous frameworks, including monadic semantics and action semantics.Comment: 20 pages plus appendix, submitted to ISoLA 202

Using Prolog techniques to guide program composition

It is possible to build complex programs by repeated combination of pairs of simpler programs. However, naive combination often produces programs that are far too inefficient. We would like to have a system that would produce the optimal combination of two programs, and also work with minimal supervision by the user. In this thesis we make a significant step towards such an ideal, with the presentation of an interactive system based on program transformation complemented with knowledge of the program development. No single method is known that will combine all programs efficiently and so a variety of different combination methods must be used. However, to get good results it is necessary that the methods have access to knowledge about the program structure. To provide this knowledge we have decided to require that the initial programs be constructed in a spe¬ cialised editor which embodies knowledge of certain standard Prolog practices (techniques) to aid the program construction, but more importantly can record pertinent parts of the program development into a structure called the program history. This program history contains the initial control flow (skeleton) and the techniques that the user applied in the construction of the program. Hence it carries knowledge about the program that would otherwise be very difficult to extract from just the program itself. The first contribution of this thesis is to recognise that knowledge contained in the program history can be used in program transformation, reducing the need for user interaction. The interactive composition system presented can automatically take major decisions, such as the selection of which subgoal should be unfolded or the laws to be applied in order to get a more efficient combined program. Furthermore, a component of our system called the selection procedure can decide automatically which is the most suitable combination method by analysing the characteristics of the initial pair of programs as given by their program histories. Approaches that do not use the program history suffer from the problem that it is not always practical to extract the required information about the structure of the program. Our second contribution is to provide a range of new methods which exploit the program history in order to produce more efficient programs, and to deal with a wider range of combination problems. The new methods not only combine programs with the same control flow, but can also deal with some cases in which the control flows are different. All of these methods are completely automatic with the exception of our "mutant" method in which the combined clause needs to be approved by the user. The third contribution is to present relevant properties in our composition system. These properties fall into the following three groups: (i) properties which hold after applying each combination method, (ii) properties about the type of program which is obtained after the combination, (iii) properties of the join specification which defines the characteristics of the combined program