11801606
Efficient communication in metacube: a new interconnection network
This paper introduces a new interconnection network for very large parallel computers called metacube (MC). An MC network has a 2-level cube structure. An MC(k,m) network connects 2(m2/sup k/+k) nodes with m + k links per node, where k is the dimension of a high-level cube and m is the dimension of low-level cubes (clusters). An MC network is a symmetric network with short diameter, easy and efficient routing similar to that of hypercubes. However, an MC network can connect more than one hundred of millions of nodes with only 6 links per node. Design of efficient routing algorithms for collective communications is the key issue for any interconnection network. In this paper we also show that total exchange (all-to-all personalized communication) can be done efficiently in metacube.
12134443
From dual-cube to metacube: efficient low-degree alternatives to hypercube
The hypercube has been widely used as the interconnection network in parallel computers. However, when dealing with the parallel computers of very large scale, the port limitation due to the technology greatly forbid the use of hypercube networks. The hypercube-based SGI Origin2000, a newly developed multiprocessor system, tried to solve this problem by introducing a Cray router. In this paper we first describe a hypercube-like network, called dual-cube, that was motivated by the structure of Origin2000. A dual-cube DC(m) has m+1 links per node where m is the degree of a cluster (m-cube), one more link is used for connecting to a node in another cluster. The dual-cube mitigates the problem of port limitation in the large-scale hypercube network while keeps most of the topological properties of the hypercube network. Then, we describe an interconnection network that extends dual-cube into a more general network called metacube. The metacube has a two-level cube structure with two parameters representing the dimensions of the two-level cubes. Metacube is much more flexible than dual-cube and can solve the port limitation problem completely. The dual-cube and metacube networks can be applied to SGI Origin2000 to connect large number of processors without using Cray router.
8653140
Multibaseline stereo in the presence of specular reflections
We address the problem of accurate depth estimation using multibaseline stereo in the presence of specular reflections. Specular reflections can cause the intensity and color of corresponding points to change dramatically according to different viewpoints, thus producing severe matching errors for various stereo algorithms. In this paper we propose a new method to deal with this problem by treating specular reflections as occlusions. Our idea is to first detect specular pixels by computing the uncertainty of depth estimates. Then we combine the use of flexible windows and an adaptively selected subset of images to avoid these specular areas in all the multibaseline stereo images. Even though specularities may exist in the reference image, accurate depth is nevertheless estimated for all pixels. Experiments show that our consideration of specular reflections leads to improved stereo results.
32291231
Face Recognition with Region Division and Spin Images
This paper explores how spin images can be constructed using shape-from-shading information and used for the purposes of face recognition. We commence by extracting needle-maps from gray-scale images of faces, using a mean needle-map to enforce the correct pattern of facial convexity and concavity. Spin images [4] are estimated from the needle maps using local spherical geometry to approximate the facial surface. Our representation is based on the spin image histograms for an arrangement of image patches. We demonstrate how this representation can be used to perform face recognition across different subjects and illumination conditions. Experiments show the method to be reliable and accurate, and the recognition precision reaches 98% on CMU PIE sub- database.
8401209
Optimal Traffic-Oblivious Energy-Aware Routing for Multihop Wireless Networks
Energy efficiency is an important issue in multihop wireless networks with energy concerns. Usually it is achieved with accurate knowledge of the traffic pattern and/or the current network information such as the remaining energy level. We investigate the problem of designing a routing scheme to minimize the maximum energy utilization of a multihop wireless network with weak assumption of the traffic pattern and without ongoing collection of network information. We develop polynomial size LP models to design such a routing scheme. We discuss generalizations of the LP models to various radio transmission models. In an interference-limited scenario, we show how to guarantee schedulability of the oblivious routing. We present an extension to consider lossy links. We also discuss implementation issues. The LP models achieve performance close to what an oracle can achieve in the performance study. The results for multihop wireless networks with a single sink are especially good. We make a first stride in designing a traffic-oblivious energy-aware routing framework in multihop wireless networks.
43234278
A Ramsey Goodness Result for Graphs with Many Pendant Edges
14632183
Collection of network information in active networks
Collection of information about the state of the network is very important for applications both in active networks and in traditional passive networks. However, the existing methods for the collection and prediction of network state cannot meet the needs of complex and intelligent applications. Active networks provide an environment that supports the injection and execution of application-specified codes in the network nodes, and consequently suggest possibilities for the solving of such a problem. In this article we present a new method for the collection of network state information by describing how active network techniques can be used to collect this information more freely and in a user-specific way. We give also an implementation of this approach to collect network resource information and evaluate it by measurements. By using this method, users can specify both the content and the format of the network resource information that they want to acquire as well as nodes at which they want to gather these information.