Showing papers on "Tree (data structure) published in 1982"

Decidability of reachability in vector addition systems (Preliminary Version)

Abstract: A convincing proof of the decidability of reachability in vector addition systems is presented. No drastically new ideas beyond those in Sacerdote and Tenney, and Mayr are made use of. The complicated tree constructions in the earlier proofs are completely eliminated.

Automatic Floorplan Design

Abstract: The problem of allocating area to modules at the highest level of a top-down decomposition is treated in this paper. A theorem of Schoenberg is applied to obtain a good embedding of the module space into the plane. The dutch metric is introduced to transform netlist information - if available - into a distance matrix. This metric is flexible enough to enable the user to steer the design in an interactive environment, and rigorous enough to yield results satisfying optimality criterions. The embedding is used to derive the topology of the floorplan in the form of the structure tree of a slicing structure. To store the partial structure tree during the construction a concise and convenient data structure, the shorthand tree, is introduced. For any aspect ratio of the chip a minimum area floorplan can be generated. The paper also shows how wiring space predictions can be incorporated, how varying degrees of module flexibility can be accounted for, and how fixing bonding pad macros affects the procedure.

A linear decomposition method for large optimization problems. Blueprint for development

Abstract: A method is proposed for decomposing large optimization problems encountered in the design of engineering systems such as an aircraft into a number of smaller subproblems. The decomposition is achieved by organizing the problem and the subordinated subproblems in a tree hierarchy and optimizing each subsystem separately. Coupling of the subproblems is accounted for by subsequent optimization of the entire system based on sensitivities of the suboptimization problem solutions at each level of the tree to variables of the next higher level. A formalization of the procedure suitable for computer implementation is developed and the state of readiness of the implementation building blocks is reviewed showing that the ingredients for the development are on the shelf. The decomposition method is also shown to be compatible with the natural human organization of the design process of engineering systems. The method is also examined with respect to the trends in computer hardware and software progress to point out that its efficiency can be amplified by network computing using parallel processors.

Multicast communication tree creation and control method and apparatus

Abstract: In a multicast network communication system, administration of the communication path making up the multicast tree itself has been separated from control and administration of the network. Creation of a multicast distribution tree and control over the membership thereof, is separately controlled independently from the creation and use of the tree transmission path used to communicate among the members of a multicast set. Transmission distribution trees are set up when a transmission request is received and the properties of the transmission path that is required are known. Transmission paths are created and controlled by all nodes in the communications system, each node having necessary control code and processors for responding to requests from set members to transmit a message to groups of users by creating and activating the necessary tree communication path distribution linkages. A distribution tree is created by the Tree Leader by generating a tree address using a random number generator. A tree address correlator is generated utilizing network and node identifiers unique for the network, and a list of subnodes or users connected for each member of the multicast tree set is generated. Using this information, a tree distribution path is computed to cover all of the subnodes required and a tree set up request message is sent by the Tree Leader along a computed path to each involved subnode. Each subnode returns a message indicating whether the tree address is already in use or is available for use. Successfully negotiated tree addresses are marked at the path link initiation and termination points at each node through the network.

Spatial versus Tree Representations of Proximity Data.

Abstract: In this paper we investigated two of the most common representations of proximities, two-dimensional euclidean planes and additive trees. Our purpose was to develop guidelines for comparing these representations, and to discover properties that could help diagnose which representation is more appropriate for a given set of data. In a simulation study, artificial data generated either by a plane or by a tree were scaled using procedures for fitting either a plane (KYST) or a tree (ADDTREE). As expected, the appropriate model fit the data better than the inappropriate model for all noise levels. Furthermore, the two models were roughly comparable: for all noise levels, KYST accounted for plane data about as well as ADDTREE accounted for tree data. Two properties of the data proved useful in distinguishing between the models: the skewness of the distribution of distances, and the proportion of elongated triangles, which measures departures from the ultrametric inequality, Applications of KYST and ADDTREE to some twenty sets of real data, collected by other investigators, showed that most of these data could be classified clearly as favoring either a tree or a two-dimensional representation.

Message routing in a computer network

Abstract: An adaptive distributed message routing algorithm that may be implemented in a computer program to control the routing of data messages in a packet message switching digital computer network. Network topology information is exchanged only between neighbor nodes in the form of minimum spanning trees, referred to as exclusionary trees. An exclusionary tree is formed by excluding the neighbor node and its links from the tree. From the set of exclusionary trees received a route table and transmitted exclusionary trees are constructed.

A description of STEMS-- the stand and tree evaluation and modeling system.

Abstract: This paper describes STEMS (Stand and Tree Evaluation and Modeling System), the current computerized Lake State tree growth projection system. It presents the program structure, discusses the growth and mortality components, the management subsystem, and the regeneration subsystem. Some preliminary results of model testing are presented and an application is discussed.

DADO: a tree-structured machine architecture for production systems

Abstract: DADO is a parallel tree-structured machine designed to provide highly significant performance improvements in the execution of large Production Systems. The DADO machine comprises a large (on the order of a hundred thousand) set of processing elements (PE's), each containing its own processor, a small amount (2K bytes, in the current design) of local random access memory, and a specialized I/O switch. The PE's are interconnected to form a complete binary tree. This paper describes a general procedure for the parallel execution of production systems on the DADO machine, and outlines in general terms how this procedure can be extended to include commutative and multiple, independent production systems.

The Quad-CIF Tree: A Data Structure for Hierarchical On-Line Algorithms

Abstract: In this paper we describe the quad-CIF tree data structure and its application to hierarchical on-line computer-aided design algorithms. The main idea is to overlay a tree of coordinates on top of the hierarchical representation of an integrated circuit. The coordinate tree enables one to find quickly the set of all objects that intersect a given window. We outline how one can use the data structure in order to implement hierarchical, on-line design rule checking and node extraction. We also describe some applications to plotting.

Obtaining the Layout of Water Distribution Systems

Abstract: An essential first step in the design of a municipal water distribution system is the determination of the locational placement or layout of the links of pipe that will form the system. A two-level hierarchically integrated system of models is developed for the layout of both single and multiple source water distribution systems. The first level, a nonlinear programming model, selects an economical tree layout for the major pipe links. The second level, an integer programming model, chooses the loop- forming links to add to the first level tree layout in order to minimize the cost of providing a specified level of reliability in case of failure of the larger first level links. The system of models is applied to an example two-source water distribution system layout problem.

Post-event human decision errors: operator action tree/time reliability correlation

Abstract: This report documents an interim framework for the quantification of the probability of errors of decision on the part of nuclear power plant operators after the initiation of an accident. The framework can easily be incorporated into an event tree/fault tree analysis. The method presented consists of a structure called the operator action tree and a time reliability correlation which assumes the time available for making a decision to be the dominating factor in situations requiring cognitive human response. This limited approach decreases the magnitude and complexity of the decision modeling task. Specifically, in the past, some human performance models have attempted prediction by trying to emulate sequences of human actions, or by identifying and modeling the information processing approach applicable to the task. The model developed here is directed at describing the statistical performance of a representative group of hypothetical individuals responding to generalized situations.

Locating mobile servers on a network with markovian properties

Abstract: The median problem has been generalized to the case in which facilities (“servers”) can be moved, at a cost, on the network in response to changes in the state of the network. Such changes are brought about by changes in travel times on the links of the network due to the occurrence of probabilistic events. For the case examined here, transitions among states of the network are assumed to be Markovian. The problem is examined for an objective which is a weighted function of demand travel times and of server relocation costs. It is shown that when these latter costs are a concave function of the time to travel from the current server location to the new server location, an optimal set of server locations exists solely on the nodes of the network. The location-relocation problem can be formulated as an integer programming problem. The problem of locating a single server on a network which is a tree is shown to have a simple solution. A heuristic algorithm for the single server on a general network is also described. The paper develops simple bounds for the general multifacility, multistate problem and concludes with the description of a relaxed version of this model and with a discussion of the model's applicability.

Design, Analysis, and Implementation of a Parallel Tree Search Algorithm

Abstract: The alpha-beta algorithm for searching decision trees is adapted to allow parallel activity in different parts of a tree during the search. The algorithm has been implemented in a procedural simulation language (GASP IV). The simulation environment provides the illusion of multiple software processes and multiple hardware processors. A number of preliminary experiments have been done to gather statistics on run time, nodes scored, and nodes visited. Results indicate that a substantial reduction in time of search occurs because of the use of parallelism. An analytic expression for the storage requirements of the algorithm is derived. The analysis provides an example of the classical tradeoff between time and storage.

LINGUIST-86: Yet another translator writing system based on attribute grammars

Abstract: LINGUIST-86 is a commercially-developed translator-writing-system based on attribute grammars [K]. From an input attribute grammar it generates a set of high-level language source modules that form an alternating-pass attribute evaluator [JW]. LINGUIST-86 generates attribute evaluators efficient enough to run on a microcomputer at speeds competitive with other translators on the system. The Attributed Program Tree is kept on secondary storage rather than in randomly-accessed memory, thus allowing non-trivial inputs to be evaluated on a microcomputer system. LINGUIST-86 also applies an optimization called static subsumption that eliminates many copy rules from the generated evaluators. LINGUIST-86 is itself written as an 1800 line attribute grammar and is self-generating.

Method and apparatus for on-line monitoring of the operation of a complex non-linear process control system

Abstract: The operation of a nuclear fueled, electric power generating unit is monitored by utilizing decision tree analysis of selected system parameters to generate a representation of the real time system status. Current system status is presented to the operator either in the form of conclusory indications, such as verbal statements, representative of system status, or in the form of a visual display of the entire decision tree including indications of the path through the tree representative of current conditions. In either case, indications of off-normal conditions are accompanied by directions as to appropriate action to be taken, either by the operator or the automatic control system, to steer the system toward more acceptable conditions. In addition, the status indications are prioritized to indicate the seriousness of the off-normal conditions and to direct the sequence of corrective action to be taken when multiple off-normal conditions exist. The decision tree displays are generated either on a color cathode ray tube by a programmed digital computer, or manually on a hard wired panel by an operator who operates switches to illuminate the appropriate branches of the tree based upon meter readings of the selected parameters incorporated into the panel at each branch point. In one embodiment, the invention is applied to monitoring system status when the unit is at power, and in another, it is applied to providing clear, unambiguous indications of the real time status of selected critical safety functions and of appropriate corrective action to be taken, if necessary, following a reactor trip.