Relatively computably enumerable reals

A real X is defined to be relatively c.e. if there is a real Y such that X is c.e.(Y) and Y does not compute X. A real X is relatively simple and above if there is a real Y <_T X such that X is c.e.(Y) and there is no infinite subset Z of the complement of X such that Z is c.e.(Y). We prove that every nonempty Pi^0_1 class contains a member which is not relatively c.e. and that every 1-generic real is relatively simple and above.Comment: 5 pages. Significant changes from earlier versio

Logic Simulation: Statistics and Machine Design

The high costs associated with logic simulation of large VLSI based systems have led to the need for new computer architectures tailored to the simulation task. Such architecture have the potential for significant speed-ups over standard software based logic simulators. Several commercial simulation engines have bene produced to satisfy needs in this area. To properly explore the space of alternative simulation architectures, data is required on the simulation process itself. This paper presents a framework for such data gathering activity and uses the data in estimating the maximum speed-up attainable with a particular type of special-purpose parallel/pipelined simulation machine. First, possible sources of speed-up in the logic simulation task are examined. Then, the sort of data needed in the design of simulation engines is discussed. Next, the data is presented and the implication on machine design are discussed. This data includes information on subtask times found in standard discrete-event simulation algorithms, event intensities, queue length distributions, and simultaneous event distributions. Finally, a simple performance model of one type of simulation machine is developed, and the maximum speed-up attainable with this type of machine is predicted

Radio-frequency discharges in Oxygen. Part 1: Modeling

In this series of three papers we present results from a combined experimental and theoretical effort to quantitatively describe capacitively coupled radio-frequency discharges in oxygen. The particle-in-cell Monte-Carlo model on which the theoretical description is based will be described in the present paper. It treats space charge fields and transport processes on an equal footing with the most important plasma-chemical reactions. For given external voltage and pressure, the model determines the electric potential within the discharge and the distribution functions for electrons, negatively charged atomic oxygen, and positively charged molecular oxygen. Previously used scattering and reaction cross section data are critically assessed and in some cases modified. To validate our model, we compare the densities in the bulk of the discharge with experimental data and find good agreement, indicating that essential aspects of an oxygen discharge are captured.Comment: 11 pages, 10 figure

PAN AIR: A computer program for predicting subsonic or supersonic linear potential flows about arbitrary configurations using a higher order panel method. Volume 4: Maintenance document (version 3.0)

The Maintenance Document Version 3.0 is a guide to the PAN AIR software system, a system which computes the subsonic or supersonic linear potential flow about a body of nearly arbitrary shape, using a higher order panel method. The document describes the overall system and each program module of the system. Sufficient detail is given for program maintenance, updating, and modification. It is assumed that the reader is familiar with programming and CRAY computer systems. The PAN AIR system was written in FORTRAN 4 language except for a few CAL language subroutines which exist in the PAN AIR library. Structured programming techniques were used to provide code documentation and maintainability. The operating systems accommodated are COS 1.11, COS 1.12, COS 1.13, and COS 1.14 on the CRAY 1S, 1M, and X-MP computing systems. The system is comprised of a data base management system, a program library, an execution control module, and nine separate FORTRAN technical modules. Each module calculates part of the posed PAN AIR problem. The data base manager is used to communicate between modules and within modules. The technical modules must be run in a prescribed fashion for each PAN AIR problem. In order to ease the problem of supplying the many JCL cards required to execute the modules, a set of CRAY procedures (PAPROCS) was created to automatically supply most of the JCL cards. Most of this document has not changed for Version 3.0. It now, however, strictly applies only to PAN AIR version 3.0. The major changes are: (1) additional sections covering the new FDP module (which calculates streamlines and offbody points); (2) a complete rewrite of the section on the MAG module; and (3) strict applicability to CRAY computing systems

Parallel Machines and Algorithms for Discrete-Event Simulations

A number of recent articles have focused on the design of high speed discrete-event simulation (DES) machines for digital logic simulation. These investigations are in response to the enormous costs associated with the simulation of complex (VLSI) digital circuits for logic verification and fault analysis. One approach to reducing simulation costs is to design special purpose digital computers that are tailored to the logic simulation test. This paper is concerned with the architecture of such logic machines. The paper has three principal parts. First, a taxonomy of logic machine architectures is presented. The taxonomy focuses on the central components of the logic simulation algorithms and on architectural alternatives for increasing the speed of the simulation process. It thus represents a basis for discussing and differentiating between proposed architectures and also results in the identification of several new architectures. Although developed for digital logic simulators., the taxonomy can be used for general DES machines. Second, a performance measure is presented which permits evaluation of DES machines. Finally several DES machine designs are described and categorized using the taxonomy