41399976
Characterizing Parallel Hierarchies by Reducibilities
Abstract Parallel time bounded reducibilities are discussed. The important parallel hierarchies NC and AC are characterized using a parallel time bounded reducibility. From this point of view, a structural property of the hierarchies NC and AC is easily obtained.
31382426
Strong Fault-Tolerance: Parallel Routing in Networks with Faults
A d-regular network G is strongly fault-tolerant if for any copy Gf of G with at most d - 2 faulty nodes, every pair of nonfaulty nodes u and v in Gf admits min{df(u), df (v)} node-disjoint paths in Gf from u to v, where df(u) and df(v) are the degrees of the nodes u and v in Gf. We show that popular network structures, such as hypercube and star networks, are strongly fault-tolerant. We develop efficient algorithms that construct the maximum number of node-disjoint paths of optimal or nearly optimal length in these networks with faulty nodes. Our algorithms are optimal in terms of their running time.
1021255
A minimal and complete set of operators for the development of robust manifold mesh modelers
In this paper, we identify a minimal and complete set of fundamental operators, which is necessary and sufficient for performing all homeomorphic and topological operations on 2- manifold mesh structures. Efficient algorithms are developed for the implementation of these operators. We also developed a set of powerful, user-friendly, and effective operators at the level of user-interface. Using these operators, we have developed a prototype system for robust, interactive, and user-friendly modeling of orientable 2-manifold meshes. Users of our system can perform a large set of homeomorphic and topological changes with these user-interface level operators. Our system is topologically robust in the sense that users will never create invalid 2-manifold mesh structure with these operators. In our system, the homeomorphic and topological surgery operations can be applied alternatively on 2-manifold meshes. With our system, users can blend surfaces, construct rinds, and open holes on these rind shapes. With our system, the shapes that look like solid, non-manifold, or 2-manifold with boundary can be manipulated. The system also provides automatic texture mapping during topology changes.
5242879
Interactive rind modeling
In this paper, we describe a technique, with roots in topological graph theory, that we call rind modeling. It provides for the easy creation of surfaces resembling peeled and punctured rinds. We show how the method's two main steps of: 1) creation of a shell or crust like the rind of an orange, and 2) opening holes in the crust by punching or peeling can be encapsulated into a real time semi-automatic interactive algorithm. We include a number of worked examples, some by students in a first modeling course, that demonstrate the ease with which a large variety of intricate rind shapes can be created.
2261180
Graph Ear Decompositions and Graph Embeddings
Ear decomposition of a graph has been extensively studied in relation to graph connectivity. In this paper, a connection of ear decomposition to graph embeddings is exhibited. It is shown that constructing a maximum-paired ear decomposition of a graph and constructing a maximum-genus embedding of the graph are polynomial-time equivalent. Applications of this connection are discussed.
16331940
Optimal Parallel Routing in Star Networks
Star networks have recently been proposed as attractive alternatives to the popular hypercube for interconnecting processors on a parallel computer. In this paper, we present an efficient algorithm that constructs an optimal parallel routing in star networks. Our result improves previous results for the problem.
43053494
Heaps with Bits
We show how to improve the complexity of heap operations and heapsort using extra bits. We first study the parallel complexity of implementing priority queue operations on a heap. The tradeoff betw ...
43754145
Heaps with Bits
In this paper, we show how to improve the complexity of heap operations and heapsort using extra bits. We first study parallel complexity of implementing priority queue operations on a heap. While the insertion of a new element into a heap can be done as fast as parallel searching, we show how to delete the smallest element from a heap in constant time with a sublinear number of processors, and in sublogarithmic time with a sublogarithmic number of processors. The models of parallel computation used are the CREW PRAM and the CRCW PRAM. Our results improve those of previously known algorithms.
24126539
A Behavior-Based Classification and Retrieval Technique for Object-Oriented Specification Reuse
This paper presents a classification and retrieval technique for object-oriented specification reuse, based on the assumption that existing specifications exhibiting behaviors similar to that of the system under development are appropriate for reuse. Existing specifications are classified and retrieved according to the semantic networks abstracted from their behaviors. Since semantic networks attach semantic meanings to certain degrees of detail, our technique is rather precise. Primary behavior is used to classify specifications because it can be obtained in the early phases of system analysis. Therefore, our technique allows early reuse. Moreover, subspecifications and classes of existing specifications are classified independently so that they can be retrieved for reuse separately. Thus, our technique encourages reusing subspecifications as well as classes. Since a subspecification is composed of classes and their relationships, reusing it corresponds to reusing all those classes and relationships. A technique that reuses subspecifications as well as classes is thus expected to save more time than those that reuse only classes.
10286772
Image segmentation by spatially adaptive color and texture features
An image segmentation algorithm that is based on spatially adaptive color and texture features is presented. The proposed algorithm is based on a previously proposed algorithm but introduces a number of new elements. We use a new set of texture features based on a steerable filter decomposition. The steerable filters combined with a new spatial texture segmentation scheme provide a finer and more robust segmentation into texture classes. The proposed algorithm includes an elaborate border estimation procedure, which extends the idea of Pappas (1992) adaptive clustering segmentation algorithm to color texture. The performance of the proposed algorithm is demonstrated in the domain of photographic images, including low resolution compressed images.
14690444
Fluid-flow analysis of TCP Westwood with RED
This paper concerns TCP Westwood (TCPW), a recently developed modification of TCP, in combination with RED queue management. We develop a fluid-flow model of TCPW with RED and use it to study both equilibrium and dynamic features. On the equilibrium side, we identify the scaling of window with loss-probability, and compare it to TCP NewReno. We also use the model to find the boundary of stability, beyond which we see large oscillations; we find that the stable region of TCPW is enhanced with respect to TCP NewReno. Furthermore we show preliminary evidence that oscillations, when they occur, have a limited impact on network throughput. Fairness and friendliness of TCPW is also analyzed and compared with NewReno. Our results show that TCPW is more fair than NewReno for flows with heterogenous round trip time. We also found that TCPW friendliness to NewReno is dependent on the difference between equilibrium queue size and the product of bandwidth and delay.