Showing papers on "Routing (electronic design automation) published in 1978"

Optimization algorithms for networks and graphs

Abstract: Introduction to Graphs and Networks Computer Representation and Solution Tree Algorithms Shortest-Path Algorithms Minimum-Cost Flow Algorithms Matching and Assignment Algorithms The Postman and Related Arc Routing Problems The Traveling Salesman and Related Vertex Routing Problems Location Problems Project Networks NETSOLVE User's Manual

Analysis of Circuit-Switched Networks Employing Originating-Office Control with Spill-Forward

Abstract: This paper presents a single-moment method for determining the node-to-node grades of service of a circuit-switched communication network employing a routing strategy called "originating-office control with spill-forward." An example of such a network is the European AUTOVON. The new method makes use of the concept of "path-loss sequence" and the techniques in system reliability analysis to determine the probability of each route being used to complete a call. Results from a digital computer implementation of the method and comparisons with other methods are discussed.

A Dynamic Programming approach to the Aircraft Sequencing problem

Abstract: This report is excerpted from the author's Ph. D. dissertation 'Dynamic programming algorithms for specially structured sequencing and routing problems in transportation' (Dept. of Ocean Engineering, M.I.T., September, 1978.)"

Methods for Hierarchical Automatic Layout of Custom LSI Circuit Masks

Abstract: A new automatic IC mask layout code is described which avoids most of the problems inherent in the present generation of layout codes such as lack of flexibility, inefficient use of area, and restricted design complexity. The structured hierarchical layout approach, construction graphs, and placement and routing algorithms are outlined.

Route guidance system for roadway vehicles

Abstract: A central station of a route guidance system collects traffic data from various points of a city area and updates aural routing information stored in roadside remote stations at periodic intervals. A moving vehicle senses the location of a roadside station to transmit a coded destination signal thereto where it is decoded to retrieve desired routing information. The latter is compressed in time dimension and transmitted back to the vehicle for storage in a storage device which is later retrieved at such a rate as to reproduce the original aural information.

ARPANET Routing Algorithm Improvements

Abstract: : This report describes progress during the first six months of a contract to make several improvements to ARPANET routing. Some principal conclusions are: Several problems have been discovered in the present congestion control, line up/down procedures, and loop suppression techniques through the use of a new real-time monitoring capability. Solutions to most of these problems have been developed; operational experience with these changes is presented. A new set of line up/down procedures with much better performance was developed and analyzed. Extensive measurements of network delay were carried out; delays fluctuate rapidly over a large range, making it difficult to devise effective estimation techniques. The present routing algorithm is itself a major contributor to network delay due to the computations and update messages it requires. A set of improvements was designed for the present routing algorithm to make it more efficient and effective. However, a new algorithm, based on performing the entire shortest path calculation at each node, incrementally for each network change, appears to be a better choice for installation in work change, appears to be a better choice for installation in the ARPANET.

Pin Assignment on a Printed Circuit Board

Abstract: The design of a Printed Circuit Board is complete when the board is routed. All effort prior to activating the router is aimed at insuring successful routing, often involving the following steps: 1) Assigning elements to packages (this is known as the assignment problem). 2) Placing the packages on the board (the placement problem). 3) Assigning the connections of the nets to specific pins on the packages (the pin assignment problem). Each of these steps is designed to help produce a routable board. This paper describes a method of solving the pin assignment problem that achieves routability of the board by reducing prospective wire crossings. Routability is improved by ordering the nets to be assigned to a specific set of pins according to their location relative to this set of pins, and then assigning them, in this order, to the nearest available pin.

Wire-guidance apparatus

Abstract: Routing decisions for vehicles following current-carrying guidewires and carrying destination addresses are made at intersections of a guidewire system without the need for storing large amounts of data at the intersections by making inequality and equality comparisons of destination addresses with one or a few numbers stored at each intersection and basing routing on the results of one or a combination of two such comparisons.

A Topologically Based Non-Minimum Distance Routing Algorithm

Abstract: In this paper, a unique topologically based non-minimum distance routing algorithm is presented. It offers both maximal completion rates and minimal via usage. The algorithm is based on a topological transformation of a significant subset of the PC routing problem: A broad channel encompassing a full row of DIPs and all routes within it. This transformation eliminates the need to consider detailed path shapes during routing. The routing problem is transformed into a permutation of nets. It is coupled with a backtrack search to produce a powerful routing algorithm. The search is conducted in a planar environment.

Validation of algorithms for optimal routing of flow in networks

Abstract: This paper presents computational results relating to solution of convex multicommodity network flow problems by using several recently developed optimization algorithms. These algorithms are based on the ideas of Gallager's method for distributed optimization of delay in data communication networks [1], and gradient projection ideas from nonlinear programming [2], [3]. They can be used both with and without a line search. An important common feature of the algorithms which distinguishes them from other existing methods is that they utilize second derivatives and are geared towards approximating a constrained version of Newton's method. The computational results confirm that the algorithms tend to employ good search directions as well as automatically generate a satisfactory stepsize regardless of the level and pattern of traffic input to the network. This latter advantage is of crucial importance when the algorithms are used for distributed routing of flow in data communication networks where the use of line search is nearly impossible.

An automatic layout system for masterslice LSI: MARC

Abstract: An LSI layout software system MARC is described, which places functional blocks on a chip and wires between the blocks for a masterslice LSI. Up to a 1200-cell masterslice, which can contain 300 functional blocks, can be handled by the system. The placement procedure is based on the attractive and repulsive force method, and the routing procedure is implemented using the two-phase assignment algorithm. The efficient combination of placement and routing procedures brings about a high-quality result. Manual modification can be performed easily by the stand-alone graphic system interfaced with the main computer. It is shown that satisfactory run results have been obtained in the application to practical data.

Drilling and routing machine for printed circuit boards

Abstract: A machine for drilling and routing of printed circuit boards comprises a support mechanism for supporting a stack of superimposed boards in a support plane and for moving the stack of boards in a first predetermined direction parallel to the support plane. A tool spindle is disposed above the stack of boards and is movable in a second direction parallel to the support plane and perpendicular to the first direction, so that the positions of the holes to be drilled in the PC-boards can be determined in a coordinate system having the first and second directions as its X-axis and Y-axis respectively. For holding the stack of PC-boards pressed together during the drilling or routing operation, the machine comprises press rollers, which exert a pressure force upon the stack of PC-boards towards the support mechanism. The press rollers are arranged on both sides of the tool spindle with their axes of rotation parallel to the direction in which the tool spindle can be moved, i.e. the Y-direction.

On Reliable Topological Structures for Message-Switching Communication Networks

Abstract: The synthesis of optimal reliable (invulnerable) topological structures for message-switching communication networks is considered. The connectivity of the underlying graphs is used as a measure of the network invulnerability. The maximal average message delay value is utilized as the network delay measure. Simultaneously with choosing the topological structure, optimal line capacities are assigned. Therefore, the performance measure of a given network structure is chosen to be given by its delay-capacity product function, incorporating the product of the prescribed network maximal delay value and the associated minimal overall line capacity value. The latter involves a distance-independent link cost function incorporating the line capacity. A general routing discipline is used to account for dynamic updating of fixed routing procedures, needed to accomodate terminal traffic flow fluctuations. n -node k -connected graphs yielding networks with minimal delaycapacity product functions are characterized and realized. Complete networks (utilizing direct dedicated lines) are shown to be optimal if the resulting lines have a high average line utilization value. Otherwise (under appropriate symmetry conditions on the network traffic matrix), the optimal message-switching reliable network structures are characterized by a family of graphs of diameter two. The latter thus allow between any pair of nodes a route which is either a direct line or contains a single intermediate node. Also noted is a family of k -connected networks, for which the delay-capacity product function is not increased by more than twice upon the failure of (k-1) or less nodes or lines.

Implementation of an Interactive Printed Circuit Design System

Abstract: This paper describes the implementation and performance of SPRINT, an interactive system for printed circuit board design developed at the Stanford Linear Accelerator Center (SLAC). Topics discussed include the placement subsystem, the routing subsystem consisting of an interactive manual router, an automatic batch router, and a via elimination program, as well as the structure of the design file around which the entire system is centered.

A Multi-Pass, Multi-Algorithm Approach to PCB Routing

Abstract: This paper describes a multi-pass routing technique in which each connection is initially generated in its optimum path irrespective of all other connections. Subsequent passes are utilized to resolve Pass 1 conflicts by repositioning wires. Each pass has its own algorithm which operates on a single class of connection and resolves local groups of wires at a time with respect to each other. Wires may be moved from one area of the board to another and from one side of the board to the other.

A Minicomputer Based Interactive Graphics System as Used for Electronic Design and Automation

Abstract: Described in this paper is the use of a commercially available Interactive Graphics System for electronic design, drafting and documentation. The system is used starting from a rough schematic and ending with a tested, manufactured printed circuit board.Discussed in the paper are major aspects and quantitative results obtained in a range of computer aided tasks. These range from initial P.C. design and prototyping to final production, documentation and testing as performed in a relatively small engineering department. The turnkey system employed is Computervision's Designer TM System, with output to Computer Automation's Capable TM printed circuit board tester.Major uses of the system include its use in a novel way at the prototyping stage to produce P.C. prototype circuit boards. Others include the use of its integral minicomputer based P.C. board routing programs supplemented by interactive graphics as well as the use of a series of computer based design verification features both for checking physical constraints and for ensuring data integrity and consistency within the entire documentation package. These verifications eliminate many forms of manual checking. Actual examples are presented.

An Approach to Gate Assignment and Module Placement for Printed Wiring Boards

Abstract: High density packaging is one of the most urgent requirements in the design of digital systems. In the assembly of such systems, printed wiring boards (PWB's) are used very often to provide the necessary interconnection among circuit modules. Thus, methods to raise wiring density of PWB's are continually under investigation. Given a router to realize 100 percent wiring, an efficient method for assigning logical gates to circuit modules and for determining the placement of the modules on a given PWB may contribute more toward raising the wirability than improving the existing routing scheme, especially when all available sophisticated routing algorithms have been attempted. The present paper proposes an algorithm to the problem of gate assignment and module placement, to be added to an existing router. It operates on a PDP 11/40 with 24K words core memory and 1.2M words disk storage coupled with a TEKTRONIX 4014 graphics terminal. We also show how effectively the described assignment and placement scheme improves the wirability of the router.

Routing at sea--1857-1977

Abstract: This paper deals with the following topics relative to ship routing. (1) Introduction which includes the development of ships' routing and traffic separation from 1857-1977, (2) Safety at Sea legislation; (3) changes in instrumentation and navigational practice; (4) The problem of traffic growth; (5) New environmental risks; (6) International solutions to navigational problems; (7) Ocean weather routing; (8) Ocean traffic separation; (9) Traffic separation in the Great Lakes; (10) Naval routing; (11) The origins of modern traffic separation in converging areas; (12) The Institutes' First working group on traffic separation; (13) The second working group on traffic separation; (14) Further developments in traffic separation; (15) The development of routing systems; (16) Ships' routing and the Rule of the Road; (17) The development of deep water routes; (18) Routing around and through fishing areas; (19) Routing to avoid specific areas; (20) Traffic flow in areas of offshore exploitation; (21) Traffic surveillance and information services; (22) Operational research for ships' routing; (23) The success of traffic separation, and (24) Conclusions.

The design of a dense PCB using an interactive DA system

Abstract: Historically, there have been two approaches to the use of computers for the design of printed circuit boards: Computer Aided Design (CAD) wherein a designer carries out the design of the board and a computer, coupled with graphics hardware (usually a storage tube) and software is used to carry out graphic handling and bookkeeping tasks; and Design Automation (DA) wherein a sophisticated placement and routing program, usually installed on a large computer, is used in a batch process mode to carry out the design according to necessarily limited algorithms When either of these approaches is used in conjunction with dense PCB designs, the results have been unsatisfactory: From CAD because of a feeling that "the computer should be able to help me more in solving this knotty problem"; and from DA because the results of the automated process are usually so poor as to approach being worthless: that is, the effort to complete the design approaches the level of difficulty of designing the card manually from the beginning The use of a computer-based design system for the design of dense printed circuit boards (PCB's) has thus been an elusive goal

Optimization of ship routing

Abstract: An automated system for optimal ship routing is presented in this report. The optimal ship routing is essentially treated as a dynamic control process of a multi-stage, stochastic nature under the constraints of operational requirements, ocean environmental conditions and ship dynamic response characteristics.

Railway track monitoring system

Abstract: Railway track monitoring system has processing circuit receiving signals from sensor pick=up and voltage from tachometer applied to routing circuit

A Modified Lockset Approach for Enhancing Routing Effectiveness

Abstract: In a recent attempt to emulate by simulation and then to improve upon a farm supply cooperative's distribution system, a lockset algorithm that included a backhaul routing capacity was constructed. The author describes the problem that motivated that modification, the modification itself, and a possible methodological improvement for applying routing models to firm-level distribution problems. The modified lockset's simulation capability is discussed with respect to capacity control and “load size/loading time” trade-off. Finally, the potential for determining visit frequency within a distribution routing analysis rather than accepting it as a given is discussed.

An optimal control approach to dynamic routing in data communication networks : part I--principles

Abstract: : A continuous state space model for the problem of dynamic routing in data communication networks has been recently proposed. In this paper we present an algorithm for finding the feedback solution to the associated linear optimal control problem with linear state and control variable inequality constraints when the inputs are assumed to be constant in time. The Constructive Dynamic Programming Algorithm, as it is called, employs a combination of necessary conditions, dynamic programming and linear programming to construct a set of convex polyhedral cones which cover the admissible state space with optimal controls. Due to several complicating features which appear in the general case the algorithms is presented in a conceptual form which may serve as a framework for the development of numerical schemes for special situations. In this vein the authors present in a forthcoming paper the case of single destination network problems with all equal weightings in the cost functional.

Distributed Control for a Variable Length Message Store-and-Forward System

Abstract: This paper describes the performance of a store-store-and-forward communications network with an adaptive routing strategy. The network chosen is a simplification of the AUTODIN network (described below) and the strategy is a modification of the routing of ARPANET. The objective is to make a network such as AUTODIN, with its wide variation in message length, effectively responsive for computercomputer and terminal-computer messages as well as record traffic. A second objective is to increase survivability following isolated equipment failures. A simulation study is used to show that improved performance is achieved.

Classification of PCB Types for Cost Effective Solutions

Abstract: Printed Circuit Board implementation has been described as the most expensive and time-consuming effort in the product design cycle Experience has proven modern design automation systems are capable of significant reductions in design time This does not say that all PCB design should be done on design automation systems This paper addresses three classes of PCB's, and describes proven techniques for methods of classification and cost effective solutions The oral presentation will be accompanied by visual aids (slides) of actual designs in each classification