A Critique of the llc Parallel Language and Some Solutions

llc is an extension of C that has been implemented on the Dado2 machine at Columbia University. In an llc program, a single controlling processor invokes operations in parallel in subsets of a set of attached processors, which themselves can invoke parallel operations in remaining processors. llc allocates one element of a parallel object per physical processor. Removing this restriction allows programs to use parallel vectors of arbitrary size without reference to the number of processors in the machine. A program in the resulting language, mpc, contains a single main process. Each mpc process can create sets of attached processes statically or dynamically by declaring arrays of process type, and can invoke operations in parallel in these processes. mpc retains much of llc's power while adding generality, clarity, and portability

Dado2 llc User's Manual

llc is an ex.tension of C for hierarchically parallel processing on distributed-memory parallel processors. The language has been implemented on Dado2, a massively parallel tree-structured MIMD multicomputer. This manual explains the features of the language as it is implemented on Dado2, its compilation, and execution. The manual complements the Ilc tutorial, the Ilc reference manual, and the llc report

llc Reference Manual

llc is an extension of C for hierarchically parallel processing on distributed-memory parallel processors. In an llc program, a single controlling processor invokes operations in parallel in subsets of a set of attached processors, which themselves can invoke parallel operations in remaining processors. This manual succinctly describes the language syntax and the implementation-independent aspects of its semantics

An Algorithmic Taxonomy of Production System Machines

This paper presents a survey of computer architectures designed to execute production systems. After a brief description of production systems and production system languages, the paper summarizes match algorithms, particularly the Rete algorithm, and outlines suggested parallelizations. Most parallel production system algorithms have as their unit of sequential computation a single production's left-hand side, activations of a single Rete node, a single activation of a Rete node, or a single comparison in a Rete node. The paper discusses a number of proposed production system machine architectures in terms of the parallel and sequential computations performed in the algorithms suggested for each machine. A taxonomy of parallel production system algorithms, describing in detail the distribution and replication of data and computations, concludes the paper

Dado2 llc User's Manual

llc is an ex.tension of C for hierarchically parallel processing on distributed-memory parallel processors. The language has been implemented on Dado2, a massively parallel tree-structured MIMD multicomputer. This manual explains the features of the language as it is implemented on Dado2, its compilation, and execution. The manual complements the Ilc tutorial, the Ilc reference manual, and the llc report

More Rules May Mean Faster Parallel Execution

In this brief paper we report a simple scheme to extract implicit parallelism in the low-level match phase of the parallel execution of production system programs. The essence of the approach is to replicate rules while introducing new constraints within each copy to restrict each individual rule to match a potentially smaller set of data elements. Speed up is achieved by matching each copy of a rule in parallel. Variations of this approach may be applicable to logic-based programming systems, such as PROLOG, executed in a parallel environment. Indeed, sequential implementations of OPS-style production systems based on the RETE match algorithm may enjoy performance advantages as well. This scheme may be implemented by a simple preprocessing stage which requires no modification to the underlying match algorithms

A simple preprocessing scheme to extract and balance implicit parallelism in the concurrent match of production rules

In this brief paper we report a simple scheme to extract implicit parallelism in the low-level match phase of the parallel execution of production system programs. The essence of the approach is to replicate rules while introducing new constraints within each copy to restrict each individual rule to match a potentially smaller set of data elements. Speed up is achieved by matching each copy of a rule in parallel. Variations of this approach may be applicable to logic-based programming systems, such as PROLOG, executed in a parallel environment. Indeed, sequential implementations of OPS-style production systems based on the Rete match algorithm may enjoy performance advantages as well. This scheme may be implemented by a simple preprocessing stage which requires no modification to the underlying match algorithms

On the multispacecraft determination of periodic surface wave phase speeds and wavelengths

Observations of surface waves on the magnetopause indicate a wide range of phase velocities and wavelengths. Their multispacecraft analysis allows a more precise determination of wave characteristics than ever before and reveal shortcomings of approximations to the phase speed that take a predetermined fraction of the magnetosheath speed or the average flow velocity in the boundary layer. We show that time lags between two or more spacecraft can give a qualitative upper estimate, and we confirm the unreliability of flow approximations often used by analyzing a few cases. Using two‐point distant magnetic field observations and spectral analysis of the tailward magnetic field component, we propose an alternative method to estimate the wavelength and phase speed at a single spacecraft from a statistical fit to the data at the other site

Perspectives and Forecasts

As the twenty-first century approaches it is accompanied by dramatic changes for the South. Southerners have been inundated with demographic, technological, and social developments which have exercised and will continue to effect dramatic changes in the traditional southern life-style. Once sleeping villages have become busy cities complete with shopping malls and burgeoning industry. All white public schools, businesses, and even churches have yielded to pressures for social equality and racial integration. An equable climate and multitudinous recreational and retirement opportunities have magnetized millions of Americans from the Northeast and Midwest, luring them to the Southland. All of these developments will, or at least should have far-reaching implications for southern archives and professional archivists for years to come