Routing Tasks Research Articles

SIGIR workshop on interactive retrieval at TREC and beyond

The annual Text Retrieval Conference (TREC) has become a major event in information retrieval (IR) research. Over the last few years, its main focus has changed from the common ad hoc and routing tasks to tracks focused on special interests, such as cross-language retrieval, question answering, and large database/Web retrieval. In each of the tracks, a common task and test collection is developed each year for all participating groups to undertake. One problem the tracks have is a paucity of face-to-face meetings, since the only certain time each track actually meets is at the annual TREC meeting. For many tracks, this time is too early to work out all the details of the coming year’s track, and most additional work is done via email.

Predicting the effectiveness of na�ve data fusion on the basis of system characteristics

Effective automation of the information retrieval task has long been an active area of research, leading to sophisticated retrieval models. With many IR schemes available, researchers have begun to investigate the benefits of combining the results of different IR schemes to improve performance, in the process called data fusion. There are many successful data fusion experiments reported in IR literature, but there are also cases in which it did not work well. Thus, if would be quite valuable to have a theory that can predict, in advance, whether fusion of two or more retrieval schemes will be worth doing. In previous study (Ng & Kantor, 1998), we identified two predictive variables for the effectiveness of fusion: (a) a list-based measure of output dissimilarity, and (b) a pair-wise measure of the similarity of performance of the two schemes. In this article we investigate the predictive power of these two variables in simple symmetrical data fusion. We use the IR systems participating in the TREC 4 routing task to train a model that predicts the effectiveness of data fusion, and use the IR systems participating in the TREC 5 routing task to test that model. The model asks, when will fusion perform better than an oracle who uses the best scheme from each pair? We explore statistical techniques for fitting the model to the training data and use the receiver operating characteristic curve of signal detection theory to represent the power of the resulting models. The trained prediction methods predict whether fusion will beat an oracle, at levels much higher than could be achieved by chance.

Experimentation as a way of life: Okapi at TREC

The Okapi system has been used in a series of experiments on the TREC collections, investigating probabilistic models, relevance feedback and query expansion, and interaction issues. The TREC-6 ad hoc task was used to test an application of a new relevance weighting formula, which takes account of documents judged nonrelevant. The application was to a form of blind feedback (using the top-ranked documents from an initial search to improve the query formulation for a subsequent search, without actual relevance feedback, on the assumption that these top-ranked documents are likely to be relevant). In the routing task, the problem is one of query optimization based on a training set with known relevant documents; investigations for TREC-6 included using a form of simulated annealing for this purpose. A significant feature of this work is the need to avoid overfitting of the training sample. In the interactive track, methodology remains the major problem: we do not yet know how to conduct controlled laboratory experiments which provide good information about information retrieval interaction. The Okapi team has been particularly interested in the relation between the functionalities associated with relevance feedback and the ability of searchers to make use of these functionalities. TREC provides an excellent environment and set of tools for investigating automatic systems; its value for interactive systems is not yet proven.

Passage-based query refinement: (MultiText experiments for TREC-6)

The MultiText information retrieval system finds arbitrary passages of text, as opposed to complete documents, that are likely to be relevant to a particular topic. Passage retrieval provides the basis for the relevance ranking, term expansion, interactive user interface, and distributed searching used in the MultiText experiments for TREC-6. The essence of the relevance ranking technique is that shorter passages containing a particular set of terms are more likely to be relevant than longer ones. For the routing task, we used training data to compute an estimate of the probability of relevance as a function of passage length and used this estimate to construct compound queries which were then applied to new data. For the ad hoc task (automatic query formulation), we retrieved passages containing terms from the title and description, and automatically selected words from these passages to expand the set of terms. For the ad hoc task (manual query formulation), we used an interactive user interface that displayed passages and allowed users to judge the relevance of documents based on these passages. A similar, more streamlined, user interface was used for the high precision track, in which the objective was to retrieve ten relevant documents in five minutes. In addition, we participated in the Very Large Collection and Chinese language tracks. Our Very Large Collection experiment achieved high performance using distributed retrieval on a network of low cost workstations, with manually constructed queries and no user interaction. For the Chinese track, we used manually constructed queries.

Timing driven cell replication during placement for cycle time optimization

This paper presents a new timing driven approach for cell replication tailored to the practical needs of standard cell layout design. Cell replication methods have been studied extensively in the context of generic partitioning problems. However, until now it has remained unclear what practical benefit can be obtained from this concept in a realistic environment for timing-driven layout synthesis. Therfore, this paper presents a timing-driven cell replication procedure, demonstrates its incorporation into a standard cell placement and routing tool and, for the first time, examines its benefit on the final circuit performance in comparison with conventional gate- or transistor-sizing techniques. The proposed method relies on recursively duplicating cells located on timing-critical paths. Cell duplications are selected with the objective to reduce the length of the critical nets as well as to simplify the routing task for these nets. Additionally, the fanout load of a cell driving such a net is reduced. Experimental results demonstrate the usefulness of the proposed methodology and suggest that cell replication should be an integral part of the physical design flow complementing traditional gate sizing techniques.

Automatic router for the pin grid array package

A pin grid array (PGA) package router is described. Given a chip cavity with a number of I/O pads around its boundary and an equivalent number of pins distributed on the substrate, the objective of the router is to complete the planar interconnection of pad-to-pin nets on one or more layers. This router consists of three phases: layer assignment, topological routing and geometrical routing. Examples tested on a windows-based environment show that our router is efficient and can complete the routing task with less substrate layers. Compared to manual routing, this router has a user-friendly graphic interface and can be applied practically to industrial strength VLSI packaging.

INTERCONNECTION WIRE-LENGTH ESTIMATION IN VLSI STANDARD CELL PLACEMENT VIA NEURAL NETWORK

Neural Network is used as a tool for estimating interconnection wire-length in VLSI standard cell placement problem. Conventional methods for estimating the interconnection wire-length viz., Bounding Rectangle method, provide inaccurate estimate of the interconnection wire-length and does not depict the interconnection procedure in a layout and separates routing and placement tasks distinctly. The proposed mechanism utilizes the neural network characteristics in understanding the functional mapping between input and output, to estimate the interconnection wire-length. Experiments were performed for different number of cells with varying complexity of interconnections. In all the cases, the performance of the Neural Network is found to be superior to the results obtained using Bounding Rectangle procedure.

The Text REtrieval Conferences (TRECs): Providing a Test‐Bed for Information Retrieval Systems

Les congres de la TREC (Text REtrieval Conferences) ont pour sujet d'etude les methodes de recherche d'information ainsi que l'evaluation de ces methodes. La TREC fournit des collection-test

Microoptical elements for single mode fibre arrays free-space interconnections

The purpose of this paper is to investigate the performance of microoptics for telecommunication systems using free-space interconnects. This concerns mainly distribution or switching and routing tasks. In order to evaluate the interconnection capability of free-space microoptics, we impose severe conditions on the interconnects. These conditions correspond to the use of single mode fibre arrays at both the input and the output systems. This point is shown to become very critical when dealing with optical switches involving reconfigu-rable links. These points are illustrated by two examples : one with fixed and the other with reconfigurable interconnects but both using arrays of microoptical elements.

Synthesis of Optimal Nonorthogonal Routes

This paper introduces a novel approach to three dimensional routing optimization. Examples of routing tasks for engineering applications include routing of pipes, wires and air ducts. Traditionally, routing algorithms perform Manhattan, or orthogonal, routing. Nonorthogonal routing can be less costly than Manhattan routing and for applications such as automotive or aerospace design, Manhattan routing is impractical due to spatial limitations. The research presented in this paper uses simulated annealing as the basis of a nonorthogonal routing optimization algorithm. Several examples comparing the two approaches are given.

A neural network model for the free-ranging AGV route-planning problem

This paper describes the development of a prototype neural network model for the free-ranging AGV route-planning problem. The vehicle planner operates in quasi-real time. A small planning horizon is set and all transport requests existing at the beginning of a planning horizon are examined. A neural network model is proposed to perform dispatching and routing tasks for the AGVs. Its goal is to satisfy the transport requests in the shortest time and in a non-conflicting manner, subject to the global manufacturing objective of maximizing throughputs. Based on Kohonen's self-organizing feature maps, we develop three efficient planning algorithms for the single and multiple AGV problems. The simulation results indicate that the proposed neural network approach gives very efficient solutions.

The performance evaluation of a new neural network-based traffic management scheme for a satellite communication network

This paper presents the first attempt to incorporate the map configuration task with the routing task in the traffic management scheme of a satellite communication network. The map configuration task, which is automated by a self-organization scheme modified from Kohonen's model, consists of three stages. The first stage is the pattern recognition task, which selects an exemplar map that best meets the current network requirement. The second stage consists of analyzing the discrepancy between the chosen exemplar map and the state of the network, and adaptively modifying the chosen exemplar map to conform closely to the network requirement (input data pattern) by self-organization. Based on certain performance criteria, whether a new map is generated to replace the original chosen map is decided in the third stage. The routing task is implemented by a state-dependent routing algorithm which arranges the incoming call to some proper path to make the network more efficient, and lowers the call block rate. The new scheme inheriting merits of both the map configuration and routing tasks provides the best compromised performance in terms of block rates at various load conditions as compared to status quo approaches — schemes with either only the map configuration task or only the routing task.

Large test collection experiments on an operational, interactive system: Okapi at TREC

The Okapi system has been used in a series of experiments on the TREC collections, investigating probabilistic models, relevance feedback, and query expansion, and interaction issues. Some new probabilistic models have been developed, resulting in simple weighting functions that take account of document length and within-document and within-query term frequency. All have been shown to be beneficial. Relevance feedback and query expansion are highly beneficial when based on large quantities of relevance data (as in the routing task). Interaction issues are much more difficult to evaluate in the TREC framework, and no benefits have yet been demonstrated from feedback based on small numbers of “relevant” items identified by intermediary searchers.

学習とロボット 力学系に基づく自律移動ロボットの行動学習

This paper describes an experimental results based on our prior-proposed scheme : learning of sensory-based, goal-directed navigation. The emphasis is that learning a task-based behavior could be formulated as an embedding problem of dynamical systems : desired trajectories in a task space should be embedded into an adequate sensory-based internal state space so that an unique mapping from the internal state space to the motor command could be established. In this study, two types of neural architecture were tested for constructing such an adequate internal state space based on sensory information. A simple homing task was conducted on Feed Forward Neural Network that is fed with a regression of sensory sequence as time-delayed manner. A task of complex cyclic routing was conducted on Recurrent Neural Network (RNN) . In both cases, sufficient supervised training of robots generated rigid internal structure of attractor dynamics which realized desired navigations in robust manner, even against limited environmental changes as well as miscellaneous noises in the real world. It was confirmed that RNN architecture has more flexiblity adapting to various tasks.

PVM-Parallel Virtual Machine: AUsers' Guide and Tutorial for Networked Parallel Computing

Part 1 Introduction: heterogeneous network computing trends in distributed computing PVM overview other packages. Part 2 The PVM system. Part 3 Using PVM: how to obtain the PVM software setup to use PVM setup summary starting PVM common startup problems running PVM programs PVM console details host file options. Part 4 Basic programming techniques: common parallel programming paradigms workload allocation porting existing applications to PVM. Part 5 PVM user interface: process control information dynamic configuration signalling setting and getting options message passing dynamic process groups. Part 6 Program examples: fork-join dot product failure matrix multiply one-dimensional heat equation. Part 7 How PVM works: components messages PVM daemon libpvm library protocols message routing task environment console program resource limitations multiprocessor systems. Part 8 Advanced topics: XPVM porting PVM to new architectures. Part 9 Troubleshooting: geting PVM installed getting PVM running compiling applications running applications debugging and tracing debugging the system. Appendices: history of PVM versions PVM 3 routines.

A PARALLEL SIMULATED ANNEALING-BASED CHANNEL ROUTER

The routing problem of VLSI layout design is very compute intensive. Consequently, the routing task often turns out to be a bottleneck in the layout design of large circuits. Parallel processing of the routing problem holds promise for mitigating this situation. In this context, we present a parallel channel routing algorithm that is targetted to run on loosely coupled computers like hypercubes. The proposed parallel algorithm employs the simulated annealing technique for obtaining near- optimum solutions. Initially, the number of tracks in the channel is made equal to the number of nets, and partitions of the channel are appropriately assigned to the nodes of the hypercube. Each node carries out concurrent perturbations to obtain new channel states that satisfy the constraints for a given net list. The algorithm minimizes the number of tracks iteratively by using the simulated annealing technique. For efficient execution, we attempt to reduce the communication overheads by restricting the broadcast updates to cases of interprocessor net transfers only. Performance evaluation studies of the algorithm show promising results.

Learning goal-directed sensory-based navigation of a mobile robot

This paper presents a novel scheme for sensory-based navigation of a mobile robot: the robot is trained to learn a goal-directed task under adequate supervision, utilizing local sensory inputs. Focusing on the topological changes of temporal sensory flow, our scheme constructs a correct mapping from sensory input sequences to the maneuvering outputs through neural adaptation such that a hypothetical vector field that achieves the goal can be generated. The simulation experiments show that a robot, utilizing our scheme, can learn tasks of homing and sequential routing successfully in the work space of a certain geometrical complexity.

Coprocessor design for multilayer surface-mounted PCB routing

The authors present the issues involved in the design of a special-purpose processing array system, called HAM, which accelerates computationally intensive wire routing tasks. It is especially suited for double-sided surface-mounted boards, which require complex three-dimensional search operations over multiple wiring planes. The novel features of the design include a hexagonal interconnection scheme to improve workload distributions during multilayer concurrent search operations and the VLSI custom design of the processors. Particular emphasis has been placed on the demands of maze routing. A cell-address propagation scheme, which is quite different from the traditional grid-coordinate approach, is discussed. It provides rapid lookup of pertinent routing information and can be extended to any distributed memory multiprocessor system. A global pipelining scheme of cell updates and expands is discussed. Experimental results are presented relating the speedup to various criteria for two different modes of parallel wave propagation. >

Constant queue routing on a mesh

Packet routing is an important problem in parallel computation since a single step of interprocessor communication can be thought of as a packet routing task. In this paper we present an optimal algorithm for packet routing on a mesh-connected computer. Two important criteria for judging a routing algorithm are (1) its run time, i.e., the number of parallel steps it takes for the last packet to reach its destination, and (2) its queue size, i.e., the maximum number of packets that any node will have to store at any time during routing. We present a 2 n − 2 step routing algorithm for an n × n MIMD mesh that requires a queue size of only 112. The previous best known result is a routing algorithm with the same time bound but with a queue size of 1008. The time bound of 2 n − 2 is optimal. A queue size of 1008 is rather large for practical use. We believe that the queue size of our algorithm is practical. The improvement in the queue size is possible due to (among other things) a new sorting algorithm for the MIMD mesh.

Switch box routing: a retrospective

Detailed routing is a crucial task in physical design of VLSI chips. Many routing algorithms have been proposed and most of them, besides the maze and line search, are oriented towards handling specified detailed routing tasks. In this paper, we discuss routing strategies for switch box problems. Switch boxes are closed, rectilinear regions with terminals on all of their sides. They create the most difficult detailed routing tasks. Here, we discuss problems which make switch box routing so difficult and give an overview of representative heuristics for solving it.