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...

Xab (X-window Analysis and deBugging) is a tool for run time monitoring of PVM (Parallel Virtual Machine) programs. PVM supports the programming of a network of heterogeneous computers as a single parallel computer. Using Xab, PVM programs can easily be instrumented and monitored. Xab uses PVM to monitor PVM programs. This makes Xab very portable but it leads to interesting issues of how to make Xab peacefully coincide with the programs it monitors. Xab consists of three main components, a user library, a monitoring program, and an X windows front end. The user library provides instrumented versions of the PVM calls. The monitoring program runs as a PVM process and gathers monitor events in the form of PVM messages. The Xab front end displays information graphically about PVM processes and messages. This paper discusses the design, implementation, and use of the Xab tool. Related work is briefly presented and contrasted with the approach taken with Xab. How Xab works and how it is use...

Zipcode is a message-passing and process-management system that was designed for multicomputers and homogeneous networks of computers in order to support libraries and large-scale multicomputer software. The system has evolved significantly over the last five years, based on our experiences and identified needs. Features of Zipcode that were originally unique to it, were its simultaneous support of static process groups, communication contexts, and virtual topologies, forming the "mailer" data structure. Point-to-point and collective operations reference the underlying group, and use contexts to avoid mixing up messages. Recently, we have added "gather-send" and "receive-scatter" semantics, based on persistent Zipcode "invoices," both as a means to simplify message passing, and as a means to reveal more potential runtime optimizations. Key features in Zipcode appear in the forthcoming MPI standard. Keywords: Static Process Groups, Contexts, Virtual Topologies, Point-to-Point Communica...

We discuss timing and performance modeling of a routine to nd all the eigenvalues and eigenvectors of a dense symmetric matrix on distributed memory computers. The routine, PDSYEVX, is part of the ScaLAPACK library. It is based on bisection and inverse iteration, but is not designed to guarantee orthogonality of eigenvectors in the presence of clustered eigenvalues. We use our validated performance model to conclude that PDSYEVX is very e cient for large enough problem sizes, nearly independently of input and output data layouts. However, e ciency will be low ifinterprocessor communication is too slow, such asonconventional workstation networks, or if per processor memory is too small, such as on the Intel Gamma. Modeling also helps us choose the appropriate algorithm to deal with clusters. 1

The statistical analysis of traces taken from the NAS Parallel Benchmarks can tell one much about the type of network traffic that can be expected from scientific applications run on distributed memory parallel computers. For instance, such applications utilize a relatively few number of communication library functions, the length of their messages is widely varying, they use many more short messages than long ones, and within a single application the messages tend to follow relatively simple patterns. Hardware and software designers can use information such as this to optimize their systems for the highest possible performance. This paper presents specific data on how these generally known characteristics about distributed memory applications are exhibited in the NAS Parallel Benchmarks. 1

This paper describes a compilation approach for a Fortran 90D/HPF compiler, a source-tosource parallel compiler for distributed memory systems. Different from Fortran 77 parallelizing compilers, a Fortran90D/HPF compiler does not parallelize sequential constructs. Only parallelism expressed by Fortran 90D/HPF parallel constructs is exploited. The methodoly of parallelizing Fortran programs such as computation partitioning, communication detection and generation, and the run-time support for the compiler are discussed. An example of Gaussian Elimination is used to illustrate the compilation techniques with performance results. This work was supported in part by NSF under CCR-9110812 (Center for Research on Parallel Computation) and DARPA under contract # DABT63-91-C-0028. The content of the information does not necessarily reflect the position or the policy of the Government and no official endorsement should be inferred. y Corresponding Author: Alok Choudhary, 121 Link Hall, ECE De...

Concurrent and distributed computing, using portable software systems or environments on general purpose networked computing platforms, has recently gained widespread attention. Many such systems have been developed, and several are in production use. This paper describes the evolution of the PVM system, a software infrastructure for concurrent computing in networked environments. PVM has evolved over the past three years; it is currently in use at several hundred institutions worldwide for applications ranging from scientific supercomputing to high performance computations in medicine, discrete mathematics, and databases, and for learning parallel programming. We describe the historical evolution of the PVM system, outline the programming model and supported features, present results gained from its use, list representative applications from a variety of disciplines that PVM has been used for, and comment on future trends and ongoing research projects. 1 Introduction High-performance...

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program follows its specification, a testing phase must be included in the program development process, and also a complementary debugging phase, to help locating the program's bugs. This paper presents an environment which results of the composition and integration of two basic tools: STEPS (a testing tool) and DDBG (a debugging tool). The two tools are presented individually as stand-alone tools, and we describe how they were combined through the use of another intermediate tool. We claim that the result achieved is a very effective testing and debugging environment.

We need a programming language for distributed systems which makes it possible to benefit from the potential interests of distributed platforms: e.g., performances, high availability. Ada 95 defines a general framework for programming distributed applications but there is still no language for configuring. Our paper presents our proposal for such a language and we have implemented some of its features. This is part of our effort to make GNAT an environment for programming distributed systems. keywords: Distributed systems programming - configuration language - GNAT 1 Introduction Distributed systems are available thanks to the emergence of networks, workstations and PCs. Programming distributed systems still implies low level interactions with the operating system or communication network interfaces. This is incompatible with a well disciplined programming approach and leads to non portable application codes. Advances in computer science have made possible the transition from ass...