Message-passing Programming Paradigm Research Articles

Uniqueness typing for resource management in message-passing concurrency

We view channels as the main form of resources in a message-passing programming paradigm. These channels need to be carefully managed in settings where resources are scarce. To study this problem, we extend the pi-calculus with primitives for channel allocation and deallocation and allow channels to be reused to communicate values of different types. Inevitably, the added expressiveness increases the possibilities for runtime errors. We define a substructural type system, which combines uniqueness typing and affine typing to reject these ill-behaved programs.

Uniqueness Typing for Resource Management in Message-Passing Concurrency

We view channels as the main form of resources in a message-passing programming paradigm. These channels need to be carefully managed in settings where resources are scarce. To study this problem, we extend the pi-calculus with primitives for channel allocation and deallocation and allow channels to be reused to communicate values of different types. Inevitably, the added expressiveness increases the possibilities for runtime errors. We define a substructural type system which combines uniqueness typing and affine typing to reject these ill-behaved programs.

A Coupled-Mode, Phase-Resolving Model for the Transformation of Wave Spectrum Over Steep 3D Topography: Parallel-Architecture Implementation

The problem of transformation of the directional spectrum of an incident wave system over an intermediate-depth region of strongly varying 3D bottom topography is studied in the context of linear theory. The consistent coupled-mode model, developed by Athanassoulis and Belibassakis (J. Fluid Mech. 389, pp. 275–301 (1999)) and extended to three dimensions by Belibassakis et al. (Appl. Ocean Res. 23(6), pp. 319–336 (2001)) is exploited for the calculation of the linear transfer function, connecting the incident wave with the wave conditions at each point in the field. This model is fully dispersive and takes into account reflection, refraction, and diffraction phenomena, without any simplification apart the standard intermediate-depth linearization. The present approach permits the calculation of spectra of all interesting wave quantities (e.g., surface elevation, velocity, pressure) at every point in the liquid domain. The application of the present model to realistic geographical areas requires a vast amount of calculations, calling for the exploitation of advanced computational technologies. In this work, a parallel implementation of the model is developed, using the message passing programming paradigm on a commodity computer cluster. In that way, a direct numerical solution is made feasible for an area of 25km2 over Scripps and La Jolla submarine canyons in Southern California, where a large amount of wave measurements are available. A comparison of numerical results obtained by the present model with field measurements of free-surface frequency spectra transformation is presented, showing excellent agreement. The present approach can be extended to treat weakly nonlinear waves, and it can be further elaborated for studying wave propagation over random bottom topography.

An Object-Oriented Parallel Particle-in-Cell Code for Beam Dynamics Simulation in Linear Accelerators

We present an object-oriented three-dimensional parallel particle-in-cell (PIC) code for simulation of beam dynamics in linear accelerators (linacs). An important feature of this code is the use of split-operator methods to integrate single-particle magnetic optics techniques with parallel PIC techniques. By choosing a splitting scheme that separates the self-fields from the complicated externally applied fields, we are able to utilize a large step size and still retain high accuracy. The method employed is symplectic and can be generalized to arbitrarily high order accuracy if desired. A two-dimensional parallel domain decomposition approach is employed within a message-passing programming paradigm along with a dynamic load balancing scheme. Performance tests on an SGI/Cray T3E-900 and an SGI Origin 2000 show good scalability of the object-oriented code. We present, as an example, a simulation of high current beam transport in the accelerator production of tritium (APT) linac design.

IMPI: Making MPI Interoperable.

The Message Passing Interface (MPI) is the de facto standard for writing parallel scientific applications in the message passing programming paradigm. Implementations of MPI were not designed to interoperate, thereby limiting the environments in which parallel jobs could be run. We briefly describe a set of protocols, designed by a steering committee of current implementors of MPI, that enable two or more implementations of MPI to interoperate within a single application. Specifically, we introduce the set of protocols collectively called Interoperable MPI (IMPI). These protocols make use of novel techniques to handle difficult requirements such as maintaining interoperability among all IMPI implementations while also allowing for the independent evolution of the collective communication algorithms used in IMPI. Our contribution to this effort has been as a facilitator for meetings, editor of the IMPI Specification document, and as an early testbed for implementations of IMPI. This testbed is in the form of an IMPI conformance tester, a system that can verify the correct operation of an IMPI-enabled version of MPI.

Designing parallel programs by the graphical language GRAPNEL

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 supports graphically 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. The first prototype of the GRAPNEL programming environment uses the PVM as the basis of the message passing mechanism. Textual program parts can be written in standard C. Other message passing libraries (e.g. MPI) and ordinary textual languages (e.g. FORTRAN) are to be supported in the future.

Distributed shared virtual memory on RISC System/6000 clusters and large scale computations: Two case studies

Many of today's moderately parallel and massively parallel multicomputers are non-shared memory systems, using the message passing programming paradigm for parallel applications. This is significant, since the shared memory paradigm is a well established programming paradigm on high performance computers, like the vector multiprocessors (vmp). Distributed shared virtual memory (dsvm) provides a way of using the shared memory programming paradigm on a set of loosely coupled computer systems. The work to date suggests that one can implement some moderately parallel applications on dsvm loosely coupled systems and achieve performances comparable to those on message passing non-shared memory systems. This paper reports first on DSVM6K, a dsvm system implemented in the AIX version 3 operating system on IBM's RISC System/6000, and then describes MTF6K, a prototypal implementation of MultiTasking Fortran on a cluster of RISC/6000 engines: MTF is a component of the IBM VS FORTRAN library which provides FORTRAN programmers with coarse grain, explicit multitasking primitives. In the last two sections of the paper two large scale applications are analyzed, a large scale 2D seismic modeling application and a 3D aerodynamic simulation.