30326495
Performance-driven channel pin assignment algorithms
In this paper we consider two channel pin assignment problems which take circuit performance into account. The first one is the module implementation selection problem. We are given a net span bound for each critical net and each module has several possible placements of its pins. Our objective is to minimize channel density while satisfying net span constraints. We proved that this problem is NP-complete. For the case when each module has at most 2 pin placements, the problem can be transformed to the 2-SAT problem and hence is polynomial time solvable. We present a heuristic based on this algorithm to solve the general case. The second problem we consider is the module shifting problem. We are given a set of modules whose relative ordering is fixed on each side of the channel but their exact positions are not fixed. We present a polynomial time algorithm to test the feasibility of satisfying the net span constraints by shifting the modules. The algorithm is based on formulating the problem as a special integer linear programming problem which is solvable in polynomial time. We also extend our algorithms to handle multiple channels. >
195349922
Routing for symmetric FPGAs and FPICs
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. >
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>>
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.
2339232
Maze routing with OPC consideration
14267974
Sample Rate Conversion Technology in Software Defined Radio
In this paper, a reconfigurable integer factor sample rate converter is proposed for software defined radio (SDR) receivers. A general principle for digital filter design in sample rate conversion (SRC) in SDR receivers can be summarized as that implementation efficiency is emphasized in the front stages, while high performance must be emphasized in the back stages. Based on this principle, a cascaded integrate comb (CIC) filter with factor-16 down sampler is used to realize large-factor and multiplier-free decimation in the front stage, while a multistage decimator is implemented together with the CIC filter to provide finer integral down sample rate. The multistage decimator is consisted of three stages, with each stage serving as a factor-2 down sampler. The Nyquist filters are used as anti-aliasing filter in the first two stages, and the linear phase equiripple filter is used in the last stage. In the end, the results of the sample rate conversion in SDR receiver are provided in this paper
9564557
An Object-Oriented Approach to Shadow Generation in Computer Graphics
This paper presents an object-oriented shadow generation algorithm for a large number of convex polyhedra (objects) in a 3-D scene. In the past, the shadow volume binary space partitioning (SVBSP) tree algorithm is known to be efficient in a static environment in which the point light source can be changed. However, if a scene consists of many objects and each object consists of many polygons, the time complexity for generating and traversing an SVBSP tree increases rapidly because the SVBSP tree algorithm only deals with polygons which are components of objects. Furthermore, the SVBSP tree algorithm suffers from polygon-splitting problems resulting in a high cost as the number of polygons increases. Our approach is object-oriented in the sense that an object is used as the basic logical unit instead of polygons. In the preprocessing stage the object ordering for shadow generation is determined for all possible light source positions. At the run time, the shadow detection algorithm is executed, and if nec...
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.
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.
15371718
Automatic Chromosome Classification Using Medial Axis Approximation and Band Profile Similarity
Automated chromosome classification is an essential task in cytogenetics and has been an important pattern recognition problem. Numerous attempts were made in the past to characterize chromosome to perform clinical and cancer cytogenetics research. It is important to determine optimum features and develop feature extraction schemes for chromosome classification. In this paper we propose novel approaches for medial axis determination and profile matching of human chromosome. The medial axis determination plays a critical role for precise and complete extraction of band patterns of chromosomes. The features of the band profile obtained along the axis are then used in the classification process. In particular, the medial axis is obtained by simple cross-section analysis and the classification is accomplished through iterative pairing of band profiles. According to the experimental results, the developed automatic system can efficiently extract band profiles of the chromosomes along their medial axes, and satisfactory chromosome classification results can be obtained.