33246096
Optimal net assignment
We study in this paper the net assignment problem subject to the capacity constraint, selection constraint and routing constraint. Given two adjacent channels separated by a cell row, and a set of nets in each of the two channels, this problem is to assign to the cell row a subset of nets in each channel such that without violating any given constraint, the sum of the remaining densities of the two channels is minimized. The capacity constraint requires the density caused by the nets, which are assigned to the cell row, to be no more than a user-specified number k, where k is no more than the number of tracks available for routing over that cell row. The selection constraint specifies in each channel the subset of nets which are candidates to be assigned to the cell row. The routing constraint requires each net to be either completely assigned to the cell row or to stay in its channel. This problem can find its application in modeling a practical over-the-cell routing problem in which the whole region over the cell row is two-layer routable for the nets in the two adjacent channels. We present an optimal algorithm to solve this problem and provide experimental results to support our algorithm. >
2339232
Maze routing with OPC consideration
47136995
Routing for symmetric FPGAs and FPICs
A new class of routing structures with fixed orthogonal wire segments and field programmable switches at the intersections of the wire segments is proposed. In comparison with the conventional two-dimensional field-programmable gate array (FPGA) routing structure, this class of routing structures has the advantage of using a smaller number of active programmable switches. An existing field-programmable interconnect chip (FPIC) routing structure can be included as a special case in our class of routing structures. Using a probabilistic model, we prove that complete routing can be achieved with a high degree of probability in a routing structure of this class in which the number of tracks in each channel approaches the lower bound asymptotically. We present a sequential routing algorithm based on the solution of the single net routing problem. We take into account the delay introduced by the active programmable switches on a routing path and formulate the single net routing problem as a node-weighted Steiner minimum tree (NWSMT) problem in a bipartite graph G. Since our single net routing problem is NP-complete, a polynomial time approximate algorithm is proposed. We prove that our single net routing algorithm produces an optimal solution for some special classes of bipartite graphs. In general, the solution obtained by our algorithm bas a performance bound of min{/spl Delta/(V/Z), |Z|-1}. Experimental results for several industrial circuits show a reduction of up to 41% in the number of active programmable switches when compared with corresponding results for the conventional FPGA routing structure.
195837988
An optimal algorithm for floorplan area optimization
An optimal algorithm for the VLSI floorplan area optimization problem is presented. The algorithm is an extension of the technique described by L. Stockmeyer (Information and Control, vol.59, p.91-101, 1983). Experimental results indicate that this algorithm pruned a very large number of redundant implementations. In addition, since the algorithm basically exploits the geometric property of the topology of the given floorplan it does not need to depend on the polar dual graphs to calculate the longest paths. Consequently it is able to run more efficiently than the branch-and-bound algorithm.<<ETX>>
42475732
An object-oriented approach to visual databases
As the demand for virtual reality systems increases, a new approach is needed to meet the following requirements: a world consists of a large number of objects; a camera is allowed to move and a world should be displayed in near real-time depending on the position of the camera as well as the angle of its lens; and minimum effort should be needed when objects are moving. We satisfy these requirements with the following: an object-oriented rendering approach is developed; and an approach based on spatial indexing (specifically R/sup +/-tree) is developed to manage operations on objects (i.e., retrieval, insertion and deletion) effectively.
33719933
Possibilistic C-Template Clustering and Its Application in Object Detection in Images
We present in this paper a new type of alternating-optimization based possibilistic c-shell clustering algorithm called possibilistic c-template (PCT). A template is represented by a set of line segments. A cluster prototype consists of a copy of the template after translation, scaling, and rotation transforms. This extends the capability of shell clustering beyond a few standard geometrical shapes that have been studied so far. We use a number of 2-dimensional data sets to illustrate the application of our algorithm in detecting generic template-based shapes in images. Techniques taken to relax the requirements of known number of clusters and good initialization are also described. Results for both synthetic and actual image data are presented.
9613111
Strategies for distributed search
The problem of locating information among cooperating agents within a distributed computing environment is considered. Such collections of agents can be collectively thought of as a single distributed application providing a single set of services; the X.500 distributed directory is an example of such an application. A central problem in such applications is the cooperative search for certain information which might be located at one of the agents. One approach to this problem relies on flooding messages throughout the distributed environment, such as that which might be used in routing algorithms to locate entries. Although the use of such algorithms, in principle, takes advantage of reaching many different agents via parallel data communication paths, the additional number of messages may be a distinct disadvantage in “higher layer” applications. This paper presents a variant of such approaches which rely on a depth-first method of distributing messages. Results of simulations illustrating the savings in messages of this approach to one relying on traditional flooding are presented for different network configurations.
42266951
TMO-structured cluster-based real-time management of location data on massive volume of moving items
A major challenge in the field of location based service (LBS) system engineering, is to establish a highly scalable system architecture which can be instantiated in moderate-size configurations handling thousands of moving items as well as in upper-end configurations handling millions of moving items. We are exploring an approach of using a cluster of database server nodes and effecting efficient distributed and parallel computing in both real-time update of location records of moving items and processing of location-related queries. The approach of developing efficient middleware which is layered on a cluster of nodes running commercial off-the-shelf database servers, has been adopted. The middleware design is substantially based on the TMO scheme for real-time distributed object programming and real-time distributed computing system design, which enables low-overhead coordination of distributed computations and highly abstract distributed programming styles.
12394125
Using compressed bytecode traces for slicing Java programs
Dynamic slicing is a well-known program debugging technique. Given a program P and input I, it finds all program statements which directly/indirectly affect the values of some variables' occurrences when P is executed with I. Dynamic slicing algorithms often proceed by traversing the execution trace of P produced by input I (or a dependence graph which captures control/data flow in the execution trace). Consequently, it is important to develop space efficient representations of the execution trace. In this paper, we use results from data compression to compactly represent bytecode traces of sequential Java programs. The major space savings come from the optimized representation of data (instruction) addresses used by memory reference (branch) bytecodes as operands. We give detailed experimental results on the space efficiency and time overheads for our compact trace representation. We then show how dynamic slicing algorithms can directly traverse our compact traces without resorting to costly decompression. We also develop an extension of dynamic slicing which allows us to explain omission errors (i.e. why some events did not happen during program execution).