Software engineers are faced with a dilemma. They want to write general and wellstructured programs that are flexible and easy to maintain. On the other hand, generality has a price: efficiency. A specialized program solving a particular problem is often significantly faster than a general program. However, the development of specialized software is time-consuming, and is likely to exceed the production of today’s programmers. New techniques are required to solve this so-called software crisis. Partial evaluation is a program specialization technique that reconciles the benefits of generality with efficiency. This thesis presents an automatic partial evaluator for the Ansi C programming language. The content of this thesis is analysis and transformation of C programs. We develop several analyses that support the transformation of a program into its generating extension. A generating extension is a program that produces specialized programs when executed on parts of the input. The thesis contains the following main results.

Partial evaluation provides a unifying paradigm for a broad spectrum of work in

Partial evaluators can be separated into two classes: offline specializers, which make all of their reduce/residualize decisions before specialization, and online specializers, which make such decisions during specialization. The choice of which method to use is driven by a tradeoff between the efficiency of the specializer and the quality of the residual programs that it produces. Existing research describes some of the inefficiencies of online specializers, and how these are avoided using offline methods, but fails to address the price paid in specialization quality. This paper motivates research in online specialization by describing two fundamental limitations of the offline approach, and explains why the online approach does not encounter the same difficulties.

In functional programming, intermediate data structures are often used to "glue" together small programs. Deforestation is a program transformation to remove these intermediate data structures automatically. We present a simple algorithm for deforestation based on two fusion rules for hylomorphism, an expressive recursion pattern. A generic notation for hylomorphisms is introduced, where natural transformations are explicitly factored out, and it is used to represent programs. Our method successfully eliminates intermediate data structures of any algebraic type from a much larger class of compositional functional programs than previous techniques. 1 Introduction In functional programming, programs are often constructed by "gluing" together small components, using intermediate data structures to convey information between them. Such data are constructed in one component and later consumed in another component, but never appear in the result of the whole program. The compositional styl...

Languages that integrate functional and logic programming with a complete operational semantics are based on narrowing, a unification-based goal-solving mechanism which subsumes the reduction principle of functional languages and the resolution principle of logic languages. Formal methods of transformation of functional logic programs can be based on this well-established operational semantics. In this paper, we present a partial evaluation scheme for functional logic languages based on an automatic unfolding algorithm which builds narrowing trees. We study the semantic properties of the transformation and the conditions under which the technique terminates, is sound and complete, and is also generally applicable to a wide class of programs. We illustrate our method with several examples and discuss the relation with Supercompilation and Partial Evaluation. To the best of our knowledge this is the first formal approach to partial evaluation of functional logic programs.

Program fusion is the process whereby separate pieces of code are fused into a single piece, typically transforming a multi-pass algorithm into a single pass. Recent work has made it clear that the process is especially successful if the loops or recursions are expressed using catamorphisms (e.g.foldr) and constructor-abstraction (e.g. build). In this paper we show how to transform recursive programs into this form automatically, thus enabling the fusion transformation to be applied more easily than before. 1 Introduction There are significant advantages to multi-pass algorithms, in which intermediate data-structures are created and traversed. In particular, each of the passes may be relatively simple, so are both easier to write and are potentially more reusable. By separating many distinct phases it becomes possible to focus on a single task, rather than attempting to do many things at the same time. The classic toy example of this is to compute the sum of the squares of the numbe...

We extend positive supercompilation to handle negative as well as positive information. This is done by instrumenting the underlying unfold rules with a small rewrite system that handles constraints on terms, thereby ensuring perfect information propagation. We illustrate this by transforming a naively specialised string matcher into an optimal one. The presented algorithm is guaranteed to terminate by means of generalisation steps.

This paper presents a termination technique for positive supercompilation, based on notions from term algebra. The technique is not particularily biased towards positive supercompilation, but also works for deforestation and partial evaluation. It appears to be well suited for partial deduction too. The technique guarantees termination, yet it is not overly conservative. Our technique can be viewed as an instance of Martens ' and Gallagher's recent framework for global termination of partial deduction, but it is more general in some important respects, e.g. it uses well-quasi orderings rather than well-founded orderings. Its merits are illustrated on several examples.

The control of polyvariance is a key issue in partial deduction of logic programs. Certainly, only finitely many specialised versions of any procedure should be generated, while, on the other hand, overly severe limitations should not be imposed. In this paper, well-founded orderings serve as a starting point for tackling this so-called "global termination" problem. Polyvariance is determined by the set of distinct "partially deduced" atoms generated during partial deduction. Avoiding ad-hoc techniques, we formulate a quite general framework where this set is represented as a tree structure. Associating weights with nodes, we define a well-founded order among such structures, thus obtaining a foundation for certified global termination of partial deduction. We include an algorithm template, concrete instances of which can be used in actual implementations, prove termination and correctness, and report on the results of some experiments. Finally, we conjecture that the proposed framewor...

. This paper identifies and solves a class of problems that arise in binding time analysis and more generally in partial evaluation of programs: the approximation and loss of static information due to dynamic expressions with static subexpressions. Solving this class of problems yields substantial binding time improvements and thus dramatically better results not only in the case of partial evaluation but also for static analyses of programs --- this last point actually is related to a theoretical result obtained by Nielson. Our work can also be interpreted as providing a solution to the problem of conditionally static data, the dual of partially static data. We point out which changes in the control flow of a source program may improve its static data flow. Unfortunately they require one to iterate earlier phases of partial evaluation. We show how these changes are subsumed by transforming the source program into continuation-passing style (CPS). The transformed programs get specializ...