One of the disadvantages of Microsoft's disk operating system MS-DOS TM is its restriction to only one process running at a time. Consequently the integration of standard application programs to more complex appli...
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One of the disadvantages of Microsoft's disk operating system MS-DOS TM is its restriction to only one process running at a time. Consequently the integration of standard application programs to more complex application systems is rather limited. This paper shows how to use Modula-2 for integrating several standard MS-DOS applications. To perform this task, a Modula supervisor program implements a shell between application, MS-DOS operating system and BIOS (basic input output system). This shell provides all services needed for loading and executing programs as concurrent processes as well as a communication environment for these processes.
This paper considers a number of ways in which concurrent programs may be expressed within an object-oriented framework. It goes on to describe work investigating the expression of highly parallel programs in a conven...
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This paper considers a number of ways in which concurrent programs may be expressed within an object-oriented framework. It goes on to describe work investigating the expression of highly parallel programs in a conventional object-oriented language (Smalltalk-80). The relevance of this work to a new parallel object-oriented system is discussed. An implementation of an ‘eager’ evaluator is described, together with a ‘throttling’ mechanism capable of limiting the generation of concurrent processes. A system for suspending all processes performing a parallel computation is discussed. Finally, further work in investigating debugging environments for concurrent object-oriented systems is outlined.
This paper addresses the following question: What is the complexity of sorting n numbers x 1 ,…, x n (by comparisons), if it is known in advance that x 1 ,…, x n are all sums of up to d out m numbers (n= Σ 0⩽s⩽d m ...
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This paper addresses the following question: What is the complexity of sorting n numbers x 1 ,…, x n (by comparisons), if it is known in advance that x 1 ,…, x n are all sums of up to d out m numbers (n= Σ 0⩽s⩽d m s ) ? A lower bound due to Fredman concerning “Sorting X + Y ” is extended to the following result: Let d ⩾ 2 be fixed, n , m as above. Then every comparison tree for n inputs that sorts all inputs of the form ( Σ rϵS w r ∣ S ⊆ {1,…, m }, ∣ S ∣ ⩽ d ), for w ϵ R m , has depth Ω(m d ) = ϵ(n) . This lower bound is optimal. Furthermore, the case of sorting all subset sums of a vector is considered ( d = m ): Let n = 2 m . Then every comparison tree for n inputs that sorts all inputs of the form (Σ rϵS w r ∣S ⊆ {1,…,m}), w ϵ R m , has depth ⩾ 2 ⌞ m 3 ⌟ = Ω(n 1 3 . This lower bound is exponentially larger than those previously known for this problem.
Sorting algorithms are traditionally classified according to their main operational characteristic. More recently, program synthesis has been used as a basis for classification. We briefly survey previous work in the ...
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Sorting algorithms are traditionally classified according to their main operational characteristic. More recently, program synthesis has been used as a basis for classification. We briefly survey previous work in the synthesis and classification of sorting algorithms, and outline a more comprehensive scheme derived by synthesising many sorting algorithms in a top-down fashion on a semi-automated logic programming system.
Leslie Lamport presented a set of axioms in 1979 that capture the essential properties of the temporal relationships between complex and perhaps unspecified activities within any system, and proceeded to use this axio...
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Leslie Lamport presented a set of axioms in 1979 that capture the essential properties of the temporal relationships between complex and perhaps unspecified activities within any system, and proceeded to use this axiom system to prove the correctness of sophisticated algorithms for reliable communication and mutual exclusion in systems without shared memory. As a step toward a more complete metatheory of Lamport's axiom system, this paper determines the extent to which that system differs from systems based on 'atomic,' or indivisible, actions. Theorem 1 shows that only very weak conditions need be satisfied in addition to the given axioms to guarantee the existence of an atomic 'model,' while Proposition 1 gives sufficient conditions under which any such model must be a 'faithful' representation. Finally, Theorem 2 restates a result of Lamport showing exactly when a system can be thought of as made up of a set of atomic events that can be totally ordered temporally. A new constructive proof is offered for this result.
Despite the widely acknowledged importance of reader feedback in the assessment of application software documentation, few studies have sought to establish what subjective factors readers use when evaluating documenta...
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Despite the widely acknowledged importance of reader feedback in the assessment of application software documentation, few studies have sought to establish what subjective factors readers use when evaluating documentation and how to reliably measure those factors. This paper reports the development and validation of an instrument which measures seven important reader-oriented factors: credibility, demonstrative, fitness, personal affect, systematic arrangement, task relevance, and understandability.
A description is given of the unification of the document production cycle. The author introduces documentation tools and techniques useful to enhancing productivity. An incentive system is presented which is intended...
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ISBN:
(纸本)081861918X
A description is given of the unification of the document production cycle. The author introduces documentation tools and techniques useful to enhancing productivity. An incentive system is presented which is intended to reduce development costs. A summary lists several key ways in which this contributes to development environment productivity issues.
Interior-point methods for linear programming, developed in the context of sequential computation, are used to obtain a parallel algorithm for the bipartite matching problem. The algorithm runs in O*(√m) time. The re...
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ISBN:
(纸本)0818619821
Interior-point methods for linear programming, developed in the context of sequential computation, are used to obtain a parallel algorithm for the bipartite matching problem. The algorithm runs in O*(√m) time. The results extend to the weighted bipartite matching problem and to the zero-one minimum-cost flow problem, yielding O*(√m log C) algorithms. This improves previous bounds on these problems and illustrates the importance of interior-point methods in parallel algorithm design.
The computational power of a tree of processors is investigated. It is demonstrated that a tree of processors can solve certain problems impressively fast by exploiting the internal pipelining capabilities. Efficient ...
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ISBN:
(纸本)0818619821
The computational power of a tree of processors is investigated. It is demonstrated that a tree of processors can solve certain problems impressively fast by exploiting the internal pipelining capabilities. Efficient tree algorithms are designed for two different problems: selection and maintaining dictionaries. It is shown that an O(log n)-height tree of processors can find the kth smallest element of n numbers in deterministic O((log n)2+o(1)) steps, an impressive improvement over previous results. The main tools are the development of a new sampling technique and an elegant internal pipelining strategy. A lower bound is established for this selection problem. Another variant of the sampling technique reduces the storage requirement of R. M. Karp et al.'s (1986) tree searching algorithm while maintaining its speed. It is established that dictionary operations can be performed with a pipelined interval of O(1) and a response time of O(height of the tree), which again improves a known result and settles an open problem. This is based on being able to make the tree operate like a complete tree viewed from the root.
Optimal algorithms for sorting on parallel CREW (concurrent read, exclusive write) and EREW (exclusive read, exclusive write) versions of the pointer machine model are presented. Intuitively, these methods can be view...
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ISBN:
(纸本)0818619821
Optimal algorithms for sorting on parallel CREW (concurrent read, exclusive write) and EREW (exclusive read, exclusive write) versions of the pointer machine model are presented. Intuitively, these methods can be viewed as being based on the use of linked lists rather than arrays (the usual parallel data structure). It is shown how to exploit the 'locality' of the approach to solve a problem with applications to database querying and logic programming (set-expression evaluation) in O(log n) time using O(n) processors.
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