Showing papers on "Tree (data structure) published in 1992"

Tree visualization with tree-maps: 2-d space-filling approach

Abstract: The traditional approach to representing tree structures is as a rooted, directed graph with the root node at the top of the page and children nodes below the parent node with lines connecting them (Figure 1). Knuth (1968, p. 305-313) has a long discussion about this standard representation, especially why the root is at the top and he offers several alternatives including brief mention of a space-filling approach. However, the remainder of his presentation and most other discussions of trees focus on various node and edge representations. By contrast, this paper deals with a two-dimensional (2-d) space-filling approach in which each node is a rectangle whose area is proportional to some attribute such as node size.

Learning classification trees

Abstract: Algorithms for learning classification trees have had successes in artificial intelligence and statistics over many years. This paper outlines how a tree learning algorithm can be derived using Bayesian statistics. This introduces Bayesian techniques for splitting, smoothing, and tree averaging. The splitting rule is similar to Quinlan's information gain, while smoothing and averaging replace pruning. Comparative experiments with reimplementations of a minimum encoding approach,c4 (Quinlanet al., 1987) andcart (Breimanet al., 1984), show that the full Bayesian algorithm can produce more accurate predictions than versions of these other approaches, though pays a computational price.

A Further Comparison of Splitting Rules for Decision-Tree Induction

Abstract: One approach to learning classification rules from examples is to build decision trees. A review and comparison paper by Mingers (Mingers, 1989) looked at the first stage of tree building, which uses a “splitting rule” to grow trees with a greedy recursive partitioning algorithm. That paper considered a number of different measures and experimentally examined their behavior on four domains. The main conclusion was that a random splitting rule does not significantly decrease classificational accuracy. This note suggests an alternative experimental method and presents additional results on further domains. Our results indicate that random splitting leads to increased error. These results are at variance with those presented by Mingers.

Varieties of Increasing Trees

Abstract: An increasing tree is a labelled rooted tree in which labels along any branch from the root go in increasing order. Under various guises, such trees have surfaced as tree representations of permutations, as data structures in computer science, and as probabilistic models in diverse applications.

Limited lookahead policies in supervisory control of discrete event systems

Abstract: A supervisory control scheme which is based on limited lookahead control policies is proposed, using an online scheme where after the occurrence of an event, the next control action is determined on the basis of an N-step-ahead projection of the behavior of the process (represented as an N-level tree). This procedure then repeats after the execution of the next event. Different attitudes can be adopted to calculate a control action for the given N-level tree in order to resolve uncertainties about the process behavior beyond N steps. Two such attitudes, termed conservative and optimistic. are studied. Results are presented pertaining to monotonicity and convergence properties of the optimistic and conservative N-step policies in terms of N, and comparison of these policies with the optimal offline solution; closed-form expression for the language generated by the N-step conservative policy for prefix-closed legal languages; and lower bounds for N that guarantee that the online scheme performs as well as an offline scheme with complete information. >

BURG: fast optimal instruction selection and tree parsing

Abstract: 1 Overview BURG is a program that generates a fast tree parser using BURS (Bottom-Up Rewrite System) technology. It accepts a cost-augmented tree grammar and emits a C program that discovers in linear time an optimal parse of trees in the language described by the grammar. BURG has been used to construct fast optimal instruction selectors for use in code generation. BURG addresses many of the problems addressed by TWIG [AGT89, App87], but it is somewhat less flexible and much faster. BURG is available via anonymous ftp from kaese.cs.wisc.edu. The compressed shar file pub/burg, shar. Z holds the complete distribution. This document describes only that fraction of the BURS model that is required to use BURG. Readers interested in more detail might start with Reference [BDB90]. 2 Input BURG accepts a tree grammar and emits a BURS tree parser. Figure 1 shows a sample grammar that implements a very simple instruction selector. BURG grammars are structurally similar to YACC's. Comments follow C conventions. Text between \"%{\" and \"%}\" is called the configuration section; there may be several such segments. All are concatenated and copied verbatim into the head of the generated parser, which is called BURM. Text after the second \"%%\", if any, is also copied verbatim into BURM, at the end. The configuration section configures BURM for the trees being parsed and the client's environment. This section must define NODEPTR_TYPE to be a visible typedef symbol for a pointer to a node in the subject tree.

Tree Matching Problems with Applications to Structured Text Databases

Abstract: A venturi scrubber for the scrubbing of an inlet gas stream with a scrubbing liquid or slurry, to remove gaseous or vaporous components from the gas stream, or to remove entrained solid particulate or discrete liquid droplet (fog or mist) constituents, and thereby to prevent air pollution and/or to recover the component or constituent. The venturi scrubber has an adjustable throat characterized by the provision of structure to adjust the cross-sectional dimension of the gas passage at or adjacent to the throat section. The structure includes at least one movable baffle at the periphery of the gas passage, and a container. The container is disposed external to and contiguous with the baffle, and a controlled amount of a fluid is passed into the container so that the internal fluid pressure within the container, and resultant volumetric dimension of the container, and thereby also the resultant displacement of the baffle relative to the periphery of the throat section, are adjustable in proportion to a change in the flow rate of the inlet gas stream.

Method and system for processing and presenting on-line, multimedia information in a tree structure

Abstract: Method and system are provided for processing and presenting on-line, multimedia information such as diagnostic information for a machine tool. The system uses multimedia information tools (i.e. graphics, documentation, drawings, photographs, full motion video with audio, PLC ladder, etc.) and techniques to assist maintenance personnel. Diagnostic development and multimedia information assignment are accomplished through graphical visual programming, which requires no conventional software programming efforts. The system uses diagnostic trees having multimedia graphic icons which define the diagnostic components. In developing a visual diagnostic tree, the multimedia information can be assigned or mapped to each node of the tree by selecting an appropriate icon to represent the multimedia from an icon library. Then, an appropriate media information file or record and comments for that icon are further added to define that node assignments. The system is user friendly, uses conventional hardware and can be used on the plant floor. The system is immediately executable and is generic. The method and system can also be used for training, process planning, marketing, sales, help desk applications, other machine diagnostics, and engineering design.

A Simulated Annealing Algorithm for Allocating Space to Manufacturing Cells

Abstract: This paper describes a procedure that can be used by facility designers to allocate space to manufacturing cells. The procedure takes into consideration the area and shape requirements of individual cells as well as any occupied regions on a floor plan. A layout is represented as a collection of rectangular partitions organized as a slicing tree. The solution method involves searching through the space of all slicing trees of a given structure. An effective simulated annealing algorithm capable of minimizing inter-cell traffic flow and enforcing geometric constraints is presented. The algorithm is compared with two local search methods with encouraging results.

A spanning tree carry lookahead adder

Abstract: The design of the 56-b significant adder used in the Advanced Micro Devices Am29050 microprocessor is described. Originally implemented in a 1- mu m design role CMOS process, it evaluates 56-b sums in well under 4 ns. The adder employs a novel method for combining carries which does not require the back propagation associated with carry lookahead, and is not limited to radix-2 trees, as is the binary lookahead carry tree of R.P. Brent and H.T. Kung (1982). The adder also utilizes a hybrid carry lookahead-carry select structure which reduces the number of carriers that need to be derived in the carry lookahead tree. This approach produces a circuit well suited for CMOS implementation because of its balanced load distribution and regular layout. >

Parallel hierarchical N-body methods

Abstract: Recent algorithmic advances utilizing hierarchical data structures have resulted in a dramatic reduction in the time required for computer simulation of N-body systems with long-range interactions. Computations which required O($N\sp2$) operations can now be done in O(N log N) or O(N). We review these tree methods and find that they may be distinguished based on a few simple features. The Barnes-Hut (BH) algorithm has received a great deal of attention, and is the subject of the remainder of the dissertation. We present a generalization of the BH tree and analyze the statistical properties of such trees in detail. We also consider the expected number of operations entailed by an execution of the BH algorithm. We find an optimal value for m, the maximum number of bodies in a terminal cell, and confirm that the number of operations is O(N log N), even if the distribution of bodies is not uniform. The mathematical basis of all hierarchical methods is the multipole approximation. We discuss multipole approximations, for the case of arbitrary, spherically symmetric, and Newtonian Green's functions. We describe methods for computing multipoles and evaluating multipole approximations in each of these cases, emphasizing the tradeoff between generality and algorithmic complexity. N-body simulations in computational astrophysics can require 10$\sp6$ or even more bodies. Algorithmic advances are not sufficient, in and of themselves, to make computations of this size feasible. Parallel computation offers, a priori, the necessary computational power in terms of speed and memory. We show how the BH algorithm can be adapted to execute in parallel. We use orthogonal recursive bisection to partition space. The logical communication structure that emerges is that of a hypercube. A local version of the BH tree is constructed in each processor by iteratively exchanging data along each edge of the logical hypercube. We obtain speedups in excess of 380 on a 512 processor system for simulations of galaxy mergers with 180000 bodies. We analyze the performance of the parallel version of the algorithm and find that the overhead is due primarily to interprocessor synchronization delays and redundant computation. Communication is not a significant factor.

Classification trees with neural network feature extraction

Abstract: The ideal use of small multilayer nets at the decision nodes of a binary classification tree to extract nonlinear features is proposed. The nets are trained and the tree is grown using a gradient-type learning algorithm in the multiclass case. The method improves on standard classification tree design methods in that it generally produces trees with lower error rates and fewer nodes. It also reduces the problems associated with training large unstructured nets and transfers the problem of selecting the size of the net to the simpler problem of finding a tree of the right size. An efficient tree pruning algorithm is proposed for this purpose. Trees constructed with the method and the CART method are compared on a waveform recognition problem and a handwritten character recognition problem. The approach demonstrates significant decrease in error rate and tree size. It also yields comparable error rates and shorter training times than a large multilayer net trained with backpropagation on the same problems. >

Heterogeneous data translation system

Abstract: A method and apparatus facilitating the exchange of data between application programs written in a higher level language and running on separate heterogeneous computer platforms, without concern for possible differences in internal data formats in the separate platforms. Each message format to be the subject of exchange among heterogeneous computer platforms is preregistered with each such platform by writing and executing a computer program that contains a definition of the message format in the higher level language. Preregistration produces a message description file in each platform, which is used at initialization time to generate a field descriptor tree in each platform. When a message is to be transmitted, it is first translated to a universal meta format, making use of the field descriptor tree, and on receipt at another platform is translated back to the native format of the receiving platform. Thus, data messages are exchanged without concern for the internal data formats used by the separate platforms.

Progress with methods for constructing evolutionary trees

Abstract: Evolutionists dream of a tree-reconstruction method that is efficient (fast), powerful, consistent, robust and falsifiable. These criteria are at present conflicting in that the fastest methods are weak (in their use of information in the sequences) and inconsistent (even with very long sequences they may lead to an incorrect tree). But there has been exciting progress in new approaches to tree inference, in understanding general properties of methods, and in developing ideas for estimating the reliability of trees. New phylogenetic invariant methods allow selected parameters of the underlying model to be estimated directly from sequences. There is still a need for more theoretical understanding and assistance in applying what is already known.

Method and apparatus for maximum likelihood estimation direct integer search in differential carrier phase attitude determination systems

Abstract: A method for comparing the relative phase of carrier signals received from GPS satellites to determine the roll, pitch and azimuth attitude of ships, aircraft, land vehicles, or survey instruments, accomplishes a maximum likelihood estimation (MLE) optimum solution over the full range of integers and vehicle attitudes. The problem is formulated as an MLE optimization, where vehicle attitude and integers are regarded as parameters to be adjusted to maximize probability of first-difference carrier phase measurements that are actually generated by hardware. Formulation results in weighted-fit error W as the objective criterion to minimize. A Kalman filter is introduced, having same objective criterion. Minimizing computation in Kalman filter leads to a decision tree for the integers. Two ways are shown to prune decision tree. The first is to exclude impossible combinations, such as those that produce an antenna upside down. The second is to generate a lower bound for W at each branch of the tree. A running sum is kept at each stage moving down the tree. When that sum exceeds a reasonableness bound or the current best W found elsewhere in the search, it is guaranteed that all subsequent integer combinations further down the current branch will produce a larger W and the remainder of the current branch can be cut off, speeding up the search.

The generalized tree quorum protocol: an efficient approach for managing replicated data

Abstract: In this paper, we present a low-cost fault-tolerant protocol for managing replicated data. We impose a logical tree structure on the set of copies of an object and develop a protocol that uses the information available in the logical structure to reduce the communication requirements for read and write operations. The tree quorum protocol is a generalization of the static voting protocol with two degrees of freedom for choosing quorums. In general, this results in significantly lower communication costs for comparable data availability. The protocol exhibits the property of graceful degradation, i.e., communication costs for executing operations are minimal in a failure-free environment but may increase as failures occur. This approach in designing distributed systems is desirable since it provides fault-tolerance without imposing unnecessary costs on the failure-free mode of operations.

Equality and Disequality Constraints on Direct Subterms in Tree Automata

Abstract: We define an extension of tree automata by adding some tests in the rules. The goal is to handle non linearity. We obtain a family which has good closure and decidability properties and we give some applications.

Deterministic skip lists

Abstract: We explore techniques based on the notion of a skip list to guarantee logarithmic search, insert and delete costs. The basic idea is to insist that between any pair of elements above a given height are a small number of elements of precisely that height. The desired behaviour can be achieved by either using some extra space for pointers, or by adding the constraint that the physical sizes of the nodes be exponentially increasing. The first approach leads to simpler code, whereas the second is ideally suited to a buddy system of memory allocation. Our techniques are competitive in terms of time and space with balanced tree schemes, and, we feel, inherently simpler when taken from first principles.

Hierarchical Steiner tree construction in uniform orientations

Abstract: A hierarchical approach to Steiner tree construction in lambda -geometry is proposed. The algorithm runs in time O(n log n) and the length of the constructed tree is at most ( sigma /cos( pi /2 lambda )) times (for lambda =2, 3/2 times) the length of the optimal Steiner tree where n is the cardinality of the point set and it was recently proved that sigma is (2/ square root 3). How to trade off between the running time of the algorithm and the length of the produced Steiner tree is shown. Given enough time, an optimal Steiner tree will be obtained. The algorithm is extended to construct a Steiner tree of a set of subtrees (i.e., partial trees) and runs in O( lambda N log N) time, where N is the total number of edges of the subtrees. >

Using Segmented Right-Deep Trees for the Execution of Pipelined Hash Joins

Abstract: In this paper, we explore the execution of pipelined hash joins in a multiprocessor-based database system. To improve the query execution, an innovative approach on query execution tree selection is proposed to exploit segmented right-deep trees, which are bushy trees of right-deep subtrees. We first derive an analytical model for the execution of a pipeline segment, and then, in light of the model, develop heuristic schemes to determine the query execution plan based on a segmented right-deep tree so that the query can be efficiently executed. As shown by our simulation, the proposed approach, without incurring additional overhead on plan execution, possesses more flexibility in query plan generation, and leads to query plans of significantly better performance than those achievable by the previous schemes using right-deep trees.

Apparatus and method for communicating between nodes in a network

Abstract: A plurality of nodes in a network (100) are connected in a tree arrangement. A master control node (110) is at the root of the tree. Each connection (121-128) between a parent node and a child node (114-118) in the tree consists of only one pair of wires, over which data bits are transmitted serially. To avoid contention, communications are always initiated by the parent node. The child node detects the end of message when no more data is received for a set timeout period. The child node then has a specified time interval for response to the communication, during which interval it has control of the line. After the end of the interval, control reverts to the parent. If a message has been received from the child within that time, normal status is resumed; otherwise, the parent retries the message or takes other error recovery actions. In the preferred embodiment, the network is used to monitor power conditions at a plurality of nodes in a computer system.

The Scalable Tree Protocol-a cache coherence approach for large-scale multiprocessors

Abstract: The problem of cache coherence in large-scale shared-memory multiprocessors has been addressed using directory-schemes. Two problems arise when the number of processors increases: the network latency increases and the implementation cost must be kept acceptable. The authors present a tree-based cache coherence protocol called the scalable tree protocol (STP). They show that it can be implemented at a reasonable implementation cost and that the write latency is logarithmic to the size of the sharing set. How to maintain an optimal tree structure and how to handle replacements efficiently are critical issues the authors address for this type of protocol. They compare the performance of the STP with that of the scalable coherent interface (SCI) (IEEE standard P1596) by considering a classical matrix-oriented algorithm targeted for large-scale parallel processing. They show that the STP manages to reduce the execution time considerably by reducing the write latency. >

Feature classification using supervised statistical pattern recognition

Abstract: Feature classification using a novel supervised statistical pattern recognition approach is described. A tree-like hierarchical decomposition of n-dimensional feature space is created off-line from an image processing system. The hierarchical tree is created through a minimax-type decompositional segregation of n-dimensional feature vectors of different feature classifications within the corresponding feature space. Each cell preferably contains feature vectors of only one feature classification, or is empty, or is of a predefined minimum cell size. Once created, the hierarchical tree is made available to the image processing system for real-time defect classification of features in a static or moving pattern. Each feature is indexed to the classification tree by locating its corresponding feature vector in the appropriate feature space cell as determined by a depth-first search of the hierarchical tree. The smallest leaf node which includes that feature vector provides the statistical information on the vector's classification.

Access method concurrency with recovery

Abstract: Providing high concurrency in B+-trees has been studied extensively. But few efforts have been documented for combining concurrency methods with a recovery scheme that preserves well-formed trees across system crashes. We describe an approach for this that works for a class of index trees that is a generalization of the Blink-tree. A major feature of our method is that it works with a range of different recovery methods. It achieves this by decomposing structure changes in an index tree into a sequence of atomic actions, each one leaving the tree well-formed and each working on a separate level of the tree. All atomic actions on levels of the tree above the leaf level are independent of database transactions, and so are of short duration.