Homomorphisms are functions which can be parallelized by the divide-and-conquer paradigm. A class of distributable homomorphisms (DH) is introduced and an efficient parallel implementation schema for all functions of the class is derived by transformations in the Bird-Meertens formalism. The schema can be directly mapped on the hypercube with an unlimited or an arbitrary fixed number of processors, providing provable correctness and predictable performance. The popular scan-function (parallel prefix) illustrates the presentation: the systematically derived implementation for scan coincides with the practically used "folklore" algorithm for distributed-memory machines.

We propose a new visual programming language, called GRAPNEL (GRAphical Process's NEt Language), for designing distributed parallel programs based on the message passing programming paradigm. GRAPNEL is a high level graphical interface for creating distributed applications, and can be useful for both non-professional and professional programmers dealt with parallel programming. GRAPNEL provides high level abstraction mechanisms in order to support the structured design at level of processes. These mechanisms include the Process Group abstraction and the automatic generation of several regular process topology based on predefined topology templates. Dynamic process creation and destruction are possible, but can be applied only in a well structured manner. GRAPNEL is a hybrid language, where the communication related parts of the program are described using graphical symbols but textual descriptions are applied where they are more appropriate. It makes possible to incorporate large ordin...

A majority of the MPP systems designed to date have been MIMD distributed memory systems. For almost all of these systems, message passing environments have provided the primary mechanism for programming multiprocessor applications. In this paper we provide an introduction to MPP systems in general. We then introduce current MPP message passing interfaces, by tracing their historical development over the last 10 years. In addition to their use within a single MPP architecture, we discuss the use of message passing systems to interconnect more loosely coupled processors in heterogeneous environments. Finally we review the development of "portability platforms" - message passing systems that have been devised solely to allow portability of message passing programs between different systems. * Research supported in part by NSF Grand Challenges Applications Group grant ASC-9217394 and by NASA HPCC Group Grant NAG5-2218. + To appear in Parallel Computing, April 1994. TABLE OF CONTENTS ...

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In this paper, we report on a project to develop a unified approach for building a library of collective communication operations that performs well on a cross-section of problems encountered in real applications. The target architecture is a two-dimensional mesh with worm-hole routing, but the techniques are more general. The approach differs from traditional library implementations in that we address the need for implementations that perform well for various sized vectors and grid dimensions, including non-power-oftwo grids. We show how a general approach to hybrid algorithms yields performance across the entire range of vector lengths. Moreover, many scalable implementations of application libraries require collective communication within groups of nodes. Our approach yields the same kind of performance for group collective communication. Results from the Intel Paragon system are included. To obtain this library for Intel systems contact intercom@cs.utexas.edu. 1 Introduction The I...

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A greedy randomized adaptive search procedure (GRASP) is a metaheuristic for combinatorial optimization. Given an undirected graph with weights associated with its nodes, the Steiner tree problem consists in finding a minimum weight subgraph spanning a given subset of (terminal) nodes of the original graph. In this paper, we describe a parallel GRASP for the Steiner problem in graphs. We review basic concepts of GRASP: construction and local search algorithms. The implementation of a sequential GRASP for the Steiner problem in graphs is described in detail. Feasible solutions are characterized by their nonterminal nodes. A randomized version of Kruskal's algorithm for the minimum spanning tree problem is used in the construction phase. Local search is based on insertions and eliminations of nodes to/from the current solution. Parallelization is done through the distribution of the GRASP iterations among the processors on a demand-driven basis, in order to improve load balancing. The ...

Fairness is an important issue when benchmarking parallel computers using application codes. The best parallel algorithm on one platform may not be the best on another. While it is not feasible to reevaluate parallel algorithms and reimplement large codes whenever new machines become available, it is possible to embed algorithmic options into codes that allow them to be "tuned" for a particular machine without requiring code modifications. In this paper, we describe a code in which such an approach was taken. PSTSWM was developed for evaluating parallel algorithms for the spectral transform method in atmospheric circulation models. Many levels of runtimeselectable algorithmic options are supported. We discuss these options and our evaluation methodology. We also provide empirical results from a number of parallel machines, indicating the importance of tuning for each platform before making a comparison. 1 Introduction Benchmarking parallel (and sequential) computers is a varied activi...

this paper, we study functions called list homomorphisms, which represent a particular pattern of parallelism.

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