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15
Comprehending Monads
 Mathematical Structures in Computer Science
, 1992
"... Category theorists invented monads in the 1960's to concisely express certain aspects of universal algebra. Functional programmers invented list comprehensions in the 1970's to concisely express certain programs involving lists. This paper shows how list comprehensions may be generalised to an arbit ..."
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Cited by 458 (13 self)
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Category theorists invented monads in the 1960's to concisely express certain aspects of universal algebra. Functional programmers invented list comprehensions in the 1970's to concisely express certain programs involving lists. This paper shows how list comprehensions may be generalised to an arbitrary monad, and how the resulting programming feature can concisely express in a pure functional language some programs that manipulate state, handle exceptions, parse text, or invoke continuations. A new solution to the old problem of destructive array update is also presented. No knowledge of category theory is assumed.
Models and Languages for Parallel Computation
 ACM COMPUTING SURVEYS
, 1998
"... We survey parallel programming models and languages using 6 criteria [:] should be easy to program, have a software development methodology, be architectureindependent, be easy to understand, guranatee performance, and provide info about the cost of programs. ... We consider programming models in ..."
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Cited by 135 (4 self)
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We survey parallel programming models and languages using 6 criteria [:] should be easy to program, have a software development methodology, be architectureindependent, be easy to understand, guranatee performance, and provide info about the cost of programs. ... We consider programming models in 6 categories, depending on the level of abstraction they provide.
The BirdMeertens Formalism as a Parallel Model
 Software for Parallel Computation, volume 106 of NATO ASI Series F
, 1993
"... The expense of developing and maintaining software is the major obstacle to the routine use of parallel computation. Architecture independent programming offers a way of avoiding the problem, but the requirements for a model of parallel computation that will permit it are demanding. The BirdMeertens ..."
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Cited by 41 (0 self)
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The expense of developing and maintaining software is the major obstacle to the routine use of parallel computation. Architecture independent programming offers a way of avoiding the problem, but the requirements for a model of parallel computation that will permit it are demanding. The BirdMeertens formalism is an approach to developing and executing dataparallel programs; it encourages software development by equational transformation; it can be implemented efficiently across a wide range of architecture families; and it can be equipped with a realistic cost calculus, so that tradeoffs in software design can be explored before implementation. It makes an ideal model of parallel computation. Keywords: General purpose parallel computing, models of parallel computation, architecture independent programming, categorical data type, program transformation, code generation. 1 Properties of Models of Parallel Computation Parallel computation is still the domain of researchers and those ...
Semantic Lego
, 1995
"... Denotational semantics [Sch86] is a powerful framework for describing programming languages; however, its descriptions lack modularity: conceptually independent language features influence each others' semantics. We address this problem by presenting a theory of modular denotational semantics. Follo ..."
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Cited by 37 (0 self)
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Denotational semantics [Sch86] is a powerful framework for describing programming languages; however, its descriptions lack modularity: conceptually independent language features influence each others' semantics. We address this problem by presenting a theory of modular denotational semantics. Following Mosses [Mos92], we divide a semantics into two parts, a computation ADT and a language ADT (abstract data type). The computation ADT represents the basic semantic structure of the language. The language ADT represents the actual language constructs, as described by a grammar. We define the language ADT using the computation ADT; in fact, language constructs are polymorphic over many different computation ADTs. Following Moggi [Mog89a], we build the computation ADT from composable parts, using monads and monad transformers. These techniques allow us to build many different computation ADTs, and, since our language constructs are polymorphic, many different language semantics. We autom...
Optimising the Parallel Behaviour of Combinations of Program Components
, 1995
"... The skeleton approach to programming parallel machines promises to offer a highlevel of abstraction to the programmer, whilst providing the implementation with sufficient information to effectively manage the resources available. Each skeleton captures a common pattern of computation and has associ ..."
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Cited by 19 (2 self)
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The skeleton approach to programming parallel machines promises to offer a highlevel of abstraction to the programmer, whilst providing the implementation with sufficient information to effectively manage the resources available. Each skeleton captures a common pattern of computation and has associated with it parallel implementations. Functional programming languages are a suitable framework for exploring this approach as skeletons can be elegantly represented as higherorder functions. Applications are naturally expressed as combinations of several skeletons. This thesis explores the problem of optimising combinations of skeletons, where each skeleton may have more than one underlying parallel implementation. A skeleton approach suitable for expressing programs as combinations of skeletons is presented. The primitive skeletons of this approach are operators of parallel abstract data types. Skeletons are combined together using a set of combining skeletons which abstract patterns of...
A Cost Analysis for a Higherorder Parallel Programming Model
, 1996
"... Programming parallel computers remains a difficult task. An ideal programming environment should enable the user to concentrate on the problem solving activity at a convenient level of abstraction, while managing the intricate lowlevel details without sacrificing performance. This thesis investiga ..."
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Cited by 17 (1 self)
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Programming parallel computers remains a difficult task. An ideal programming environment should enable the user to concentrate on the problem solving activity at a convenient level of abstraction, while managing the intricate lowlevel details without sacrificing performance. This thesis investigates a model of parallel programming based on the BirdMeertens Formalism (BMF). This is a set of higherorder functions, many of which are implicitly parallel. Programs are expressed in terms of functions borrowed from BMF. A parallel implementation is defined for each of these functions for a particular topology, and the associated execution costs are derived. The topologies which have been considered include the hypercube, 2D torus, tree and the linear array. An analyser estimates the costs associated with different implementations of a given program and selects a costeffective one for a given topology. All the analysis is performed at compiletime which has the advantage of reducing run...
Embedding prolog in haskell
 Department of Computer Science, University of Utrecht
, 1999
"... The distinctive merit of the declarative reading of logic programs is the validity ofallthelaws of reasoning supplied by the predicate calculus with equality. Surprisingly many of these laws are still valid for the procedural reading � they can therefore be used safely for algebraic manipulation, pr ..."
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Cited by 16 (4 self)
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The distinctive merit of the declarative reading of logic programs is the validity ofallthelaws of reasoning supplied by the predicate calculus with equality. Surprisingly many of these laws are still valid for the procedural reading � they can therefore be used safely for algebraic manipulation, program transformation and optimisation of executable logic programs. This paper lists a number of common laws, and proves their validity for the standard (depth rst search) procedural reading of Prolog. They also hold for alternative search strategies, e.g. breadth rst search. Our proofs of the laws are based on the standard algebra of functional programming, after the strategies have been given a rather simple implementation in Haskell. 1
From Dynamic Programming to Greedy Algorithms
 Formal Program Development, volume 755 of Lecture Notes in Computer Science
, 1992
"... A calculus of relations is used to reason about specifications and algorithms for optimisation problems. It is shown how certain greedy algorithms can be seen as refinements of dynamic programming. Throughout, the maximum lateness problem is used as a motivating example. 1 Introduction An optimisat ..."
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Cited by 14 (3 self)
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A calculus of relations is used to reason about specifications and algorithms for optimisation problems. It is shown how certain greedy algorithms can be seen as refinements of dynamic programming. Throughout, the maximum lateness problem is used as a motivating example. 1 Introduction An optimisation problem can be solved by dynamic programming if an optimal solution is composed of optimal solutions to subproblems. This property, which is known as the principle of optimality, can be formalised as a monotonicity condition. If the principle of optimality is satisfied, one can compute a solution by decomposing the input in all possible ways, recursively solving the subproblems, and then combining optimal solutions to subproblems into an optimal solution for the whole problem. By contrast, a greedy algorithm considers only one decomposition of the argument. This decomposition is usually unbalanced, and greedy in the sense that at each step the algorithm reduces the input as much as poss...
Virtual Data Structures
 Formal Program Development, Lecture Notes in Computer Science 755
, 1992
"... this paper is to demonstrate a number of techniques which may be used in calculating algorithms for sequenceoriented problems. It may be considered as a further step in the development of a programming method which started with [5]. The basic observation underlying this method is that algorithms ca ..."
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Cited by 14 (3 self)
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this paper is to demonstrate a number of techniques which may be used in calculating algorithms for sequenceoriented problems. It may be considered as a further step in the development of a programming method which started with [5]. The basic observation underlying this method is that algorithms can be the result of a systematic development, in which all design decisions and applied insights are clearly identifiable. One might even claim that the essence of an algorithm is its derivation, and not the program text that results from such a derivation
Tuning Task Granularity and Data Locality of Data Parallel GpH Programs
, 2001
"... The performance of data parallel programs often hinges on two key coordination aspects: the computational costs of the parallel tasks relative to their management overhead  task granularity ; and the communication costs induced by the distance between tasks and their data  data locality . In da ..."
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Cited by 7 (4 self)
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The performance of data parallel programs often hinges on two key coordination aspects: the computational costs of the parallel tasks relative to their management overhead  task granularity ; and the communication costs induced by the distance between tasks and their data  data locality . In data parallel programs both granularity and locality can be improved by clustering, i.e. arranging for parallel tasks to operate on related subcollections of data.