In principle, pure functional languages promise straightforward architecture-independent parallelism. We investigate the validity of this claim in the context of our highly-portable implementation of an implicitly-parallel functional language: the GUM implementation of Glasgow Parallel Haskell (GpH). We discuss architecture independence at two levels: lowlevel (i.e. the implementation) and high-level (i.e. the programmer). Low-level architecture independence is achieved by chosing a message-passing model for GUM, and implementing it using portable C and a widely-supported message-passing library like PVM. In fact GUM is largely independent of the message-passing library, and has been adapted to use MPI and the CM-5 CMMD libraries as well as PVM. As a result, GUM is easily ported, and is currently available on seven platforms including shared-memory machines, distributed-memory machines, and networks of workstations. We provide indicative measurements of how efficient and effective our...

The static single assignment (SSA) form is central to a range of optimisation algorithms relying on data flow information, and hence, to the correctness of compilers employing those algorithms. It is well known that the SSA form is closely related to lambda terms (i.e., functional programs), and, considering the large amount of energy expended on theories and frameworks for formal reasoning in the lambda calculus, it seems only natural to leverage this connection to improve our capabilities to reason about compiler optimisations. In this paper, we discuss a new formalisation of the mapping from SSA programs to a restricted form of lambda terms, called administrative normal form (ANF). We conjecture that this connection improves our ability to reason about SSA-based optimisation algorithms and provide a first data point by presenting an ANF variant of a well known SSA-based conditional constant propagation algorithm.

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We present a compiler for the functional language HDC, which aims at the generation of efficient code from high-level programs. HDC, which is syntactically a subset of the widely used language Haskell, facilitates the clean integration of skeletons with a predefined efficient parallel implementation into a functional program. Skeletons are higher-order functions which represent program schemata that can be specialized by providing customizing functions as parameters. The only restriction on customizing functions is their type. Skeletons can be composed of skeletons again. With HDC, we focus on the divide-and-conquer paradigm, which has a high potential for an efficient parallelization. We describe the most important phases of the compiler: desugaring, elimination of higher-order functions, generation of an optimized directed acyclic graph and code generation, with a focus on the integration of skeletons. The effect of the transformations on the target code is demonstrated on the examp...

Optimizing compilers for function-oriented and object-oriented languages exploit type and flow information for efficient implementation. Although type and flow information (both control and data flow) are inseparably intertwined, compilers usually compute and represent them separately. Partially, this has been a result of the usual polymorphic type systems using 8 and 9 quantifiers, which are difficult to use in combination with flow annotations. In the Church Project, we are experimenting with intermediate languages that integrate type and flow information into a single flow type framework. This integration facilitates the preservation of flow and type information through program transformations. In this paper we describe CIL, an intermediate language supporting polymorphic types and polyvariant flow information and describe its application in program optimiziation. We are experimenting with this intermediate language in a flow and typedirected compiler for a functional language. ...

Correctness-preserving program transformation has recently received a particular attention for compiler optimization in functional programming [Kelsey and Hudak 1989; Appel 1992; Peyton Jones 1996]. By implementing a compiler using many passes, each of which is a transformation for a particular optimization, one can attain a modular compiler. It is no surprise that the modularity would increase if transformations are structured, i.e. constructed in a modular way. Indeed, the program transformation in calculational form (or program calculation) can help us to attain this goal.

This copy of the thesis has been supplied on the condition that anyone who consults it is understood to recognise that the copyright rests with its author and that no quotation from the thesis and no information derived from it may be published without the prior written consent of the author or the university (as may be appropriate). I hereby declare that the work presented in this the-sis was carried out by myself at Heriot-Watt University, Edinburgh, except where due acknowledgement is made, and has not been submitted for any other degree.

Refactoring is a technique for improving the design of existing programs without changing their external behaviour. HaRe is the refactoring tool we have built to support refactoring Haskell 98 programs. Along with the development of HaRe, we have also investigated the formal specification and proof of validity of refactorings. This formalisation process helps to clarify the meaning of refactorings, improves our confidence in the behaviour-preservation of refactorings, and reduces the need for testing. This paper gives an overview of HaRe, and shows our approach to the formalisation of refactorings. 1

The application of natural semantic specifications of lazy evaluation to areas such as usage analysis, formal profiling and abstract machine construction has shown it to be a useful formalism. This paper introduces several variants and extensions of this specification. The first variant

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