Showing papers on "Routing (electronic design automation) published in 1994"

Deadlock-free message routing in multiprocessor interconnection networks

Abstract: A deadlock-free routing algorithm can be generated for arbitrary interconnection networks using the concept of virtual channels. A necessary and sufficient condition for deadlockfree routing is the absence of cycles in the channel dependency graph. Given an arbitrary network and a routing function, the cycles of the channel dependency graph can be removed by splitting physical channels into groups of virtual channels. This method is used to develop deadlock-free routing algorithms for k-ary n-cubes, for cube connected cycles, and for shuffle? exchange networks. (This is a revised version of 5206-tr-86)

A tabu search heuristic for the vehicle routing problem

Abstract: The purpose of this paper is to describe TABUROUTE, a new tabu search heuristic for the vehicle routing problem with capacity and route length restrictions. The algorithm considers a sequence of adjacent solutions obtained by repeatedly removing a vertex from its current route and reinserting it into another route. This is done by means of a generalized insertion procedure previously developed by the authors. During the course of the algorithm, infeasible solutions are allowed. Numerical tests on a set of benchmark problems indicate that tabu search out performs the best existing heuristics, and TABUROUTE often produces the best known solutions.

The turn model for adaptive routing

Abstract: This paper presents a model for designing wormhole routing algorithms. A unique feature of the model is that it is not based on adding physical or virtual channels to direct networks (although it can be applied to networks with extra channels). Instead, the model is based on analyzing the directions in which packets can turn in a network and the cycles that the turns can form. Prohibiting just enough turns to break all of the cycles produces routing algorithms that are deadlock free, livelock free, minimal or nonminimal, and highly adaptive. This paper focuses on the two most common network topologies for wormhole routing, n-dimensional meshes and k-ary n-cubes without extra channels

Efficient routing in all-optical networks

Abstract: Communication in all-optical networks requires novel routing paradigms. The high bandwidth of the optic fiber is utilized through wavelengthdivision multiplexing: a single physical optical link can carry several logical signals, provided that they are transmitted on different wavelengths. We study the problem of routing a set of requests (each of which is a pair of nodes to be connected by a path) on sparse networks using a limited number of wavelengths, ensuring that different paths using the same wavelength never use the same physical link. The constraints on the selection of paths and wavelengths depend on the type of photonic switches used in the network. We present eflicient routing techniques for the two types of photonic switches that dominate current research in all-optical networks. Our results es*IBM T.J. Watson Research Center, Yorktown. This work was supported in part by grant MDA 97292-C-0075 from ARPA. t The Weizmann Institute, Israel, and IBM Alrnaden Research Center, California. Work at the Weizmann Institute supported in part by the Norman D. Cohen Professorial Chair of Computer Science. Permission to co y without fee all or part of this material is granted provicf~hatthecopies are not madeorcfistrfbutedfor direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association of Computing Machinery. To copy otherwke, or to republish, requires a fee andJor specific permission. STOC 945/84 Montreal, Quebec, Canada (!3 1984 ACM 0-89791 -663-6/94/0005.. $3.50 tablish a connection between the expansion of a network and the number of wavelengths required for routing on it.

RISA: accurate and efficient placement routability modeling

Abstract: The prevalence of net list synthesis tools raises great concern on routability of cell placement created with state-of-the-art placement techniques. In this paper, an accurate and efficient placement routability modeling technique is proposed and incorporated into the prevailing simulated annealing approach. This accurate and efficient modeling is based on the supply versus demand analysis of routing resource over an array of regions on a chip. Vertical and horizontal routability is analyzed separately due to the bias of routing resource in multiple-metal-layer ASIC designs. A special technique on net bounding box partitioning is also proposed and critical to the accuracy of this modeling at the presence of mega cells, which tend to cause local routing congestion. By incorporating this efficient modeling into the cost function of simulated annealing, experiments conducted on small to large industrial designs indicate that placement routability evaluated with a global router is greatly improved as a result of the proposed accurate modeling.

On optimal interconnections for VLSI

Abstract: List of Figures. List of Tables. 1: Preliminaries. 1.1. Preface. 1.2. The Domain of Discourse: Routing in VLSI Physical Design. 1.3. Overview of the Book. 1.4. Acknowledgements. 2: Area. 2.1. Introduction. 2.2. Performance Bounds for MST-Based Strategies. 2.3. Iterated 1-Steiner (I1S). 2.4. Enhancing I1S Performance. 2.5. Practical Implementation Options for I1S. 2.6. On the Maximum MST Degree. 2.7. Steiner Trees in Graphs. 3: Delay. 3.1. Preliminaries. 3.2. Geometric Approaches to Delay Minimization. 3.3. Minimization of Actual Delay. 3.4. New Directions. 4: Skew. 4.1. Preliminaries. 4.2. An Early Matching-Based Approach. 4.3. DME: Exact Zero Skew with Minimum Wirelength. 4.4. Planar-Embeddable Trees. 4.5. Remarks. 5: Multiple Objectives. 5.1. Minimum Density Trees. 5.2. Multi-Weighted Graphs. 5.3. Prescribed-Width Routing. A: Appendix: Signal Delay Estimators. A.1. Basics. A.2. Accuracy and Fidelity. References. Author Index. Term Index.

Improved approximation algorithms for the multi-commodity flow problem and local competitive routing in dynamic networks

Abstract: Improved Approximation Algorithms the Multi-Commodity Flow Problem and Competitive Routing in Dynamic Networks

Lightwave networks based on de Bruijn graphs

Abstract: Proposes de Bruijn graphs as logical topologies for multihop lightwave networks. After deriving bounds on the throughput and delay performance of any logical topology, the authors compute the throughput and delay performance of de Bruijn graphs for two different routing schemes and compare it with their bounds and the performance of shufflenets. For a given maximum nodal in- and out-degree and average number of hops between stations, a logical topology based on a de Bruijn graph can support a larger number of stations than a shufflenet and this number is close to the maximum that can be supported by any topology. The authors also propose de Bruijn graphs as good physical topologies for wavelength routing lightwave networks consisting of all-optical routing nodes interconnected by point-to-point fiber links. The worst-case loss experienced by a transmission is proportional to the maximum number of hops (diameter). For a given maximum nodal in- and out-degree and diameter, a physical topology based on a de Bruijn graph can support a large number of stations using a relatively small number of wavelengths. >

An optimization problem related to balancing loads on SONET rings

Abstract: We provide a model and a set of solution techniques for an important problem arising in the design of survivable telecommunication networks utilizing fiber-optics-based technologies. The emergence of a synchronous standard for optical signaling called "SONET" allows for an economic implementation of ring designs that provides protection for high capacity services. An objective is to choose a loading of the demands onto a ring design that minimizes associated equipment and facility costs while providing capacity for alternative routing should some link or node fail. After the computational complexity of the problem has been determined, three approximation heuristics, including a mathematical programming dual-ascent solution technique, are described and compared. The heuristics are being successfully applied to actual network design problems arising in Bell operating companies and other telecommunication providers.

Method for estimating routability and congestion in a cell placement for integrated circuit chip

Abstract: A cell placement for a microelectronic integrated circuit includes a plurality of cells interconnected by nets of wiring. A method for estimating routing density in the placement includes superimposing a pattern of contiguous tiles over the placement, with each of the tiles having edges. Bounding boxes are constructed around the nets, and net probable densities are calculated within each bounding box for the wiring required by each net for each edge respectively. The net probable densities are summed to produce total probable densities of wiring required by all of the nets for each edge respectively. The net probable density for each edge is calculated as being equal to a wiring capacity of the edge divided by the sum of the wiring capacity of the edge and all other unobscured edges within the bounding box that are collinear with the edge respectively. A congestion map can be constructed from the total probable densities and the capacities of the edges, and/or these calculations can be used to predict the routability or unroutability of the placement. Provisions are made for edges that are obscured by large megacells or other obstacles, including providing routing detours around the obstacles.

Efficient routing and scheduling algorithms for optical networks

Abstract: This paper studies the problems of dedicating routes and scheduling transmissions in optical networks. In optical networks, the vast bandwidth available in an optical fiber is utilized by partitioning it into several channels, each at a different optical wavelength. A connection between two nodes is assigned a specific wavelength, with the constraint that no two connections sharing a link in the network can be assigned the same wavelength. This paper classifies several models related to optical networks and presents optimal or near-optimal algorithms for permutation routing and/or scheduling problems in many of these models. tally important because the entire network can be constructed out of passive (unpowered) optical components and hence made reliable as well as easy to operate, with all the control being done outside the network.

Packet-switched self-routing multistage interconnection network having contention-free fanout, low-loss routing, and fanin buffering to efficiently realize arbitrarily low packet loss

Abstract: A new class of packet-switched extended generalized-shuffle self-routing multistage interconnection networks provides a continuous performance-cost tradeoff between, on the one hand, the knockout switch or buffered crossbar and, on the other hand, the tandem banyan network. Multiple copies of the new networks may be serially cascaded back-to-back, and connected in parallel. A particular concentrator circuit in the network concentrates active communications packets randomly distributed on many lines onto selected lines. Another, second, network communicates synchronization information communicable point-to-point and multipoint while performing arithmetic and logical operations on the synchronization information so communicated. A hybrid parallel combination of both the first and second networks serves to efficiently communicate information point-to-point while simultaneously communicating synchronization information both point-to-point and multipoint.

An adaptive and fault tolerant wormhole routing strategy for k -ary n -cubes

Abstract: The concept of virtual channels is extended to multiple virtual communication systems that provide adaptability and fault tolerance in addition to being deadlock-free. A channel dependency graph is taken as the definition of what connections are possible, and any routing function must use only those connections defined by it. Virtual interconnection networks allowing adaptive, deadlock-free routing are examined for three k-ary n-cube topologies: unidirectional, torus-connected bidirectional, and mesh-connected bidirectional. >

An edge-based heuristic for Steiner routing

Abstract: A new approximation heuristic for finding a rectilinear Steiner tree of a set of nodes is presented. It starts with a rectilinear minimum spanning tree of the nodes and repeatedly connects a node to the nearest point on the rectangular layout of an edge, removing the longest edge of the loop thus formed. A simple implementation of the heuristic using conventional data structures is compared with previously existing algorithms. The performance (i.e., quality of the route produced) of our algorithm is as good as the best reported algorithm, while the running time is an order of magnitude better than that of this best algorithm. It is also shown that the asymptotic time complexity for the algorithm can be improved to O(n log n), where n is the number of points in the set. >

Deadlock-free multicast wormhole routing in multicomputer networks

Abstract: Efficient routing of messages is the key to the performance of multicomputers. Multicast communication refers to the delivery of the same message from a source node to an arbitrary number of destination nodes. Wormhole routing is the most promising switching technique used in new generation multicomputers. In this paper, we present multicast wormhole routing methods for multicomputers adopting 2D-mesh and hypercube topologies. The dual-path routing algorithm requires less system resource, while the multipath routing algorithm creates less traffic. More import antly, both routing algorithms are deadlock-free, which is essential to wormhole networks.

Optimal routing and wavelength assignment in all-optical networks

Abstract: The author consider the problem of routing connections in an optical network using wavelength division multiplexing, where each connection between a pair of nodes in the network is assigned a path through the network and a wavelength on that path, such that connections whose paths share a common link in the network are assigned different wavelengths. They derive an upper bound on the carried traffic of connections (or equivalently, a lower bound on the blocking probability) for any routing and wavelength assignment (RWA) algorithm in such a network. The bound scales with the number of wavelengths and is achieved asymptotically (when a large number of wavelengths is available) by a fixed RWA algorithm. Although computationally intensive, this bound can be used as a metric against which the performance of different RWA algorithms can be compared for networks of moderate size. They illustrate this by comparing the performance of a simple RWA algorithm via simulation with our bound. They also derive a similar bound for optical networks using dynamic wavelength converters, which are equivalent to circuit-switched telephone networks, and compare the two cases for different examples. >

Hypercube communication delay with wormhole routing

Abstract: We present an analytical model for the performance evaluation of hypercube computers. This analysis is aimed at modeling a deadlock-free wormhole routing scheme prevalent on second generation hypercube systems. Probability of blocking and average message delay are the two performance measures discussed. We start with the communication traffic to find the probability of blocking. The traffic analysis can capture any message destination distribution. Next, we find the average message delay that consists of two parts. The first part is the actual message transfer delay between any source and destination nodes. The second part of the delay is due to blocking caused by the wormhole routing scheme. The analysis is also extended to virtual cut-through routing and random wormhole routing techniques. The validity of the model is demonstrated by comparing analytical results with those from simulation. >

Integrated circuit physical design automation system utilizing optimization process decomposition and parallel processing

Abstract: In a physical design automation system for producing an optimized cell placement for an integrated circuit chip, a placement optimization methodology is decomposed into a plurality of cell placement optimization processes that are performed simultaneously by parallel processors on input data representing the chip. The results of the optimization processes are recomposed to produce an optimized cell placement. The fitness of the optimized cell placement is analyzed, and the parallel processors are controlled to selectively repeat performing the optimization processes for further optimizing the optimized cell placement if the fitness does not satisfy a predetermined criterion. The system can be applied to initial placement, routing, placement improvement and other problems. The processors can perform the same optimization process on different placements, or on areas of a single placement. Alternatively, the processors can perform different optimization processes simultaneously on a single initial placement, with the resulting processed placement having the highest fitness being selected as the optimized placement. The processors can further selectively reprocess areas of a placement having high cell interconnect congestion or other low fitness parameters.

Analog Device-Level Layout Automation

Abstract: List of Figures. List of Tables. Preface. 1. Introduction. 2. Basic Placement. 3. Topological Placement. 4. Geometry Sharing Placement. 5. Line-Expansion Routing. 6. Integrated Rerouting. 7. Symmetric Routing. 8. Crosstalk Avoidance Routing. 9. Additional KOAN/ANAGRAM II Results. 10. Conclusions and Future Work. Subject Index.

On-line admission control and circuit routing for high performance computing and communication

Abstract: This paper considers the problems of admission control and virtual circuit routing in high performance computing and communication systems. Admission control and virtual circuit routing problems arise in numerous applications, including video-servers, real-lime database servers, and the provision of permanent virtual channel in large-scale communications networks. The paper describes both upper and lower bounds on the competitive ratio of algorithms for admission control and virtual circuit routing in trees, arrays, and hypercubes (the networks most commonly used in conjunction with nigh performance computing and communication). Our results include optimal algorithms for admission control and virtual circuit routing in trees, as well as the first competitive algorithms for these problems on non-tree networks. A key result of our research is the development of on-line algorithms that substantially outperform the greedy-based approaches that are used in practice. >

Printed circuit assembly with fine pitch flexible printed circuit overlay mounted to printed circuit board

Abstract: A printed circuit assembly includes a fine pitch flexible printed circuit overlay bonded to a normal pitch printed circuit board. The fine pitch flexible printed circuit overlay may provide increased packaging density, direct chip attachment and/or complex routing with a minimal cost impact on the overall printed circuit assembly.

Method and apparatus for an automatic decomposition of a network topology into a backbone and subareas

Abstract: The object of the invention is to perform an automatic decomposition of a packet switching network in backbone nodes and subareas nodes to speed up the routing path search without degrading the optimization criterion of the routing algorithm and without generating additional control messages on the network. Currently, routing algorithms compute all the available paths in the network, from the source node to the destination node before to select an optimal route. However, networks are rarely fully meshed. They are usually built around a hierarchical structure: a set of nodes, interconnected by high throughput lines,are used to build a backbone with a high degree of meshing and then, local nodes are grouped in geographical subareas themselves attached to the backbone. Routing algorithms can take advantage of this particular network topology to drastically reduce the complexity of paths computation. For a given connection, only a limited number of nodes are defined as usable and are taken in account by the algorithm in its path calculation.

Closing the gap: near-optimal Steiner trees in polynomial time

Abstract: The minimum rectilinear Steiner tree (MRST) problem arises in global routing and wiring estimation, as well as in many other areas. The MRST problem is known to be NP-hard, and the best performing MRST heuristic to date is the Iterated 1-Steiner (I1S) method recently proposed by Kahng and Robins (see ibid., vol. 11, p. 893-902, 1992). In this paper, we develop a straightforward, efficient implementation of I1S, achieving a speedup factor of three orders of magnitude over previous implementations. We also give a parallel implementation that achieves near-linear speedup on multiple processors. Several performance-improving enhancements enable us to obtain Steiner trees with average cost within 0.25% of optimal, and our methods produce optimal solutions in up to 90% of the cases for typical nets. We generalize I1S and its variants to three dimensions, as well as to the case where all the pins lie on k parallel planes, which arises in, e.g., multilayer routing. Motivated by the goal of reducing the running times of our algorithms, we prove that any pointset in the Manhattan plane has a minimum spanning tree (MST) with maximum degree 4, and that in three-dimensional Manhattan space every pointset has an MST with maximum degree of 14 (the best previous upper bounds on the maximum MST degree in two and three dimensions are 6 and 26, respectively); these results are of independent theoretical interest and also settle an open problem in complexity theory. >

Routing a multi-terminal critical net: Steiner tree construction in the presence of obstacles

Abstract: This paper presents a new model for VLSI routing in the presence of obstacles, that transforms any routing instance from a geometric problem into a graph problem. It is the first model that allows computation of optimal obstacle-avoiding rectilinear Steiner trees in time corresponding to the instance size (the number of terminals and obstacle border segments) rather than the size of the routing area. For the most common multi-terminal critical nets-those with three or four terminals-we observe that optimal trees can be computed as efficiently as good heuristic trees, and present algorithms that do so. For nets with five or more terminals, we present algorithms that heuristically compute obstacle-avoiding Steiner trees. Analysis and experiments demonstrate that the model and algorithms work well in both theory and practice. >

Optimal diverse routing in telecommunication fiber networks

Abstract: Telecommunication fiber networks can be more complicated than the traditional graph-theoretic networks of nodes and links. This is due to practical and economic considerations. The paper considers two major types of deviations from the traditional graph-theoretic network, and provide an algorithm for the shortest pair of physically-disjoint paths between a given pair of nodes in the network. Such disjoint paths can be used for improving the reliability of the network, e.g., one path may be used as a back up while the other is actually used for transmission of data. Alternatively, the entire traffic between the given pair of nodes in the network may be divided equally over the two disjoint paths so that if a node or link on one of the paths fails, not all of the traffic is lost. Optimizing the length of disjoint paths helps in reducing the amount of fiber usage and network costs. >

Subgradient methods for the service network design problem

Abstract: We present local-improvement heuristics for a Service Network Design Problem encountered in the motor carrier industry. The scheduled set of vehicle departures determines the right hand side of the capacity constraints of the shipment routing subproblem which is modeled as a multicommodity network flow problem. The heuristics, one for dropping a scheduled service and another for introducing a new service, are based upon subgradients derived from the optimal dual variables of the shipment routing subproblem. The basis of the multicommodity network flow problem is partitioned to facilitate the calculation of the dual variables, reduced costs and subgradients. These are determined in large part by additive and network operations, and only in small part by matrix multiplication. The results of our computational experimentation are presented.