Typer inference builds a short cut to deforestation

ChitilOlaf,

doi:10.1145/317765.317907

Cited by 9 publications

(2 citation statements)

References 18 publications

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“…On the one hand, short cut fusion is easily generalized to arbitrary covariant recursive types -called algebraic data types below and elsewhere. Such generalizations have already been incorporated into a number of automatic fusion tools (Chitil, 1999;Gill, 1996;Johann, 1997;Johann & Visser, 2000;Németh, 2000). On the other hand, short cut fusion for lists can be generalized to accommodate more general list production.…”

Section: Proving Correctnessmentioning

confidence: 99%

Short cut fusion is correct

Johann

2003

J. Funct. Prog.

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Fusion is the process of removing intermediate data structures from modularly constructed functional programs. Short cut fusion is a particular fusion technique which uses a single, local transformation rule to fuse compositions of list-processing functions. Short cut fusion has traditionally been treated purely syntactically, and justifications for it have appealed either to intuition or to "free theorems" -even though the latter have not been known to hold in languages supporting higher-order polymorphic functions and fixpoint recursion. In this paper we use Pitts' recent demonstration that contextual equivalence in such languages is parametric to provide the first formal proof of the correctness in short cut fusion for them. In particular, we show that programs which have undergone short cut fusion are contextually equivalent to their unfused counterparts.

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Section: Proving Correctnessmentioning

confidence: 99%

Short cut fusion is correct

Johann

2003

J. Funct. Prog.

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“…Given the widespread use of monadic computations, it is natural to try to apply automatable program transformation techniques to improve the efficiency of modularly constructed monadic programs. Fusion is one technique which is suitable for this purpose, and a number of fusion transformations appropriate to the non-monadic functional setting have been developed in recent years (Chitil, 1999;Gill et al, 1993;Hu at al., 1996;Johann, 2002;Jürgensen, 2005;Sheard and Fegaras, 1993;Svenningsson, 2002;Takano and Meijer, 1995;Voigtländer, 2002). Perhaps the best known of these is short cut fusion (Gill et al, 1993), a local transformation based on two combinators -namely, build, which produces lists in a uniform manner, and foldr, which uniformly consumes them -and a single, oriented replacement rule known as the foldr/build rule (see Section 3).…”

Section: Introductionmentioning

confidence: 99%

Monadic augment and generalised short cut fusion

Ghani¹,

Johann²

2007

J. Funct. Prog.

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Monads are commonplace programming devices that are used to uniformly structure computations; in particular, they are often used to mimic the effects of impure features such as state, error handling, and I/O. This paper further develops the monadic programming paradigm by investigating the extent to which monadic computations can be optimised by using generalisations of short cut fusion to eliminate monadic structures whose sole purpose is to “glue together” monadic program components. Ghani, Uustalu, and Vene have recently shown that every inductive type has an associated build combinator and an associated short cut fusion law. They have also used the notion of a parameterised monad to describe those monads that give rise to inductive types, and have shown that the standard augment combinators and cata/augment fusion rules for algebraic data types can be generalised to fixed points of all parameterised monads. We revisit these augment combinators and generalised short cut fusion rules for such types but consider them from a functional programming perspective, rather than a categorical one. In addition to making the category-theoretic ideas of Ghani, Uustalu, and Vene more easily accessible to a wider audience of functional programmers, we demonstrate their practical applicability by developing nontrivial application programs and performing modest benchmarking on them. We also show how the cata/augment rules can serve as the basis for deriving additional generic fusion laws, thus opening the way for an algebra of fusion. Finally, we offer deep theoretical insights, arguing that the augment combinators are monadic in nature, and thus that the cata/build and cata/augment rules are arguably the best generally applicable fusion rules obtainable.

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Type-Inference Based Short Cut Deforestation (Nearly) without Inlining

Chitil

2000

Lecture Notes in Computer Science

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Deforestation optimises a functional program by transforming it into another one that does not create certain intermediate data structures. In [Chi99] we presented a type-inference based deforestation algorithm which performs extensive inlining. However, across module boundaries only limited inlining is practically feasible. Furthermore, inlining is a non-trivial transformation which is therefore best implemented as a separate optimisation pass. To perform short cut deforestation (nearly) without inlining, Gill suggested to split definitions into workers and wrappers and inline only the small wrappers, which transfer the information needed for deforestation. We show that Gill's use of a function build limits deforestation and note that his reasons for using build do not apply to our approach. Hence we develop a more general worker/wrapper scheme without build. We give a type-inference based algorithm which splits definitions into workers and wrappers. Finally, we show that we can deforest more expressions with the worker/wrapper scheme than the algorithm with inlining.

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Typer inference builds a short cut to deforestation

Abstract: The version in the Kent Academic Repository may differ from the final published version. Users are advised to check http://kar.kent.ac.uk for the status of the paper. Users should always cite the published version of record.

Cited by 9 publications

References 18 publications

Short cut fusion is correct

Short cut fusion is correct

Monadic augment and generalised short cut fusion

Type-Inference Based Short Cut Deforestation (Nearly) without Inlining

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