Supercompilation is a technique due to Turchin [1] which allows for the construction of program optimisers that are both simple and extremely powerful. Supercompilation is capable of achieving transformations such as deforestation [2], function specialisation and constructor specialisation [3]. Inspired by Mitchell’s promising results [4], we show how the call-by-need supercompilation algorithm can be recast to be based explicitly on an evaluator, and in the process extend it to deal with recursive let expressions.

The paper presents a number of improvements to the method of two-level supercompilation: a fast technique of lemma discovering by analyzing the expressions in the partial process tree, an enhancement to the algorithm of checking improvement lemmas based on the normalization of tick annotations, and a few techniques of finding simplified versions of lemmas discovered in the process of two-level supercompilation.

Supercompilation is a powerful technique for program optimisation and theorem proving. In this paper we describe and evaluate three improvements to the Cambridge Haskell Supercompiler (CHSC). We reduce supercompiled program size by the use of a weak normaliser and aggressive rollback, and we improve the performance of supercompiled programs by heap speculation and generalisation. Our generalisation method is simpler than those in the literature, and is better at generalising computations involving primitive operations such as those on machine integers. We also provide the first comprehensive account of the tag-bag termination mechanism.

The paper deals with some aspects of metasystem transitions in the context of supercompilation. We consider the manifestations of the law of branching growth of the penultimate level in the case of higher-level supercompilation and argue that this law provides some useful hints regarding the ways of constructing metasystems by combining supercompilers. In particular we show the usefulness of multi-result supercompilation for proving the equivalence of expressions and in two-level supercompilation.

Stencil convolution is a fundamental building block of many scientific and image processing algorithms. We present a declarative approach to writing such convolutions in Haskell that is both efficient at runtime and implicitly parallel. To achieve this we extend our prior work on the Repa array library with two new features: partitioned and cursored arrays. Combined with careful management of the interaction between GHC and its back-end code generator LLVM, we achieve performance comparable to the standard OpenCV library. Categories and Subject Descriptors D.3.3 [Programming Languages]: Language Constructs and Features—Concurrent programming

We describe a library-based approach to constructing termination tests suitable for controlling termination of symbolic methods such as partial evaluation, supercompilation and theorem proving. With our combinators, all termination tests are correct by construction. We show how the library can be designed to embody various optimisations of the termination tests, which the user of the library takes advantage of entirely transparently. Categories and Subject Descriptors D.3.2 [Programming Languages]: Language Classifications – Applicative (functional) languages

The paper explains the principles of multi-result supercompilation. We introduce a formalism for representing supercompilation algorithms as rewriting rules for graphs of congurations. Some low-level technical details related to the implementation of multi-result supercompilation in MRSC are discussed. In particular, we consider the advantages of using spaghetti stacks for representing graphs of configurations.