Routing with locality in partitioned-bus meshes

We show that adding partitioned-buses (as opposed to long buses that span an entire row or column) to ordinary meshes can reduce the routing time by approximately one-third for permutation routing with locality. A matching time lower bound is also proved. The result can be generalized to multi-packet routing.published_or_final_versio

Efficient computations on meshes with express links

At head of title: Computer science publication.Cover title.Includes bibliographical references (p. 10-12).published_or_final_versio

NGS: An application layer network game simulator

In the last five years the popularity of Massively Multiplayer Online Games (MMOGs) has exploded. Unfortunately, the demand has far outweighed the resources developers can provide. Many MMOGs are suffering from scalability issues, resulting in sharding, down time, and server crashes. To solve these problems, the research community is investigating peer-to-peer (P2P) overlay networks to support MMOGs, as P2P networks are theoretically and practically scalable. The majority of analysis of P2P gaming architectures has been qualitative, making it difficult to understand the strengths and weaknesses of each system. This is partially due to the lack of appropriate simulation tools. To address this problem we have developed an application layer network game simulator - NGS - for modelling network game architectures. NGS includes mechanisms to collect quantitative metrics, which may then be used to perform comparisons with other architectures. NGS is flexible enough to model Client/Server, Region based, Neighbour based, and hybrid architectures. It is extensible and modular, and will enable the research community to evaluate the benefits and weaknesses of existing and new network gaming architectures. Results demonstrating the extensibility and performance of NGS, and comparisons of the performance of several different architectures are included

Enhanced mirrored servers for network games

The Mirrored Server (MS) architecture uses multiple mirrored servers across multiple locations to alleviate the bandwidth bottleneck in the Client/Server (C/S) architecture. Each mirror receives and multicasts player updates to the others, simulates the game, and disseminates the new game state to players. However, keeping the game state consistent between mirrors in the presence of network delay, and maintaining game responsiveness requires each server in MS to simulate the game multiple times for each game update, and additional times in the event of costly rollbacks. In this paper we propose the Enhanced Mirrored Server (EMS) architecture. Like in the Peer-to-Peer architecture, EMS allows peers to exchange updates directly, resulting in a higher tolerance to delay at the mirrors. We propose using bucket synchronization in the mirrors so that each server in EMS simulates the game only once for each update and does not require rollbacks. The server disseminates updates to clients only in the event of inconsistency, and thus its outgoing bandwidth is lower than in MS. Our EMS uses cryptographic techniques to provide security equivalent to C/S, and prevents the timestamp cheat possible in MS. Our analytical analysis and simulations show the advantages of EMS over MS

Effective Heuristic Methods for Finding Non-Optimal Solutions of Interest in Constrained Optimization Models

This paper introduces the SoI problem, that of finding non-optimal solutions of interest for constrained optimization models. SoI problems subsume finding FoIs (feasible solutions of interest), and IoIs (infeasible solutions of interest). In all cases, the interest addressed is post-solution analysis in one form or another. Post-solution analysis of a constrained optimization model occurs after the model has been solved and a good or optimal solution for it has been found. At this point, sensitivity analysis and other questions of import for decision making (discussed in the paper) come into play and for this purpose the SoIs can be of considerable value. The paper presents examples that demonstrate this and reports on a systematic approach, using evolutionary computation, for obtaining both FoIs and IoIs

Interleukin 1 production during accessory cell-dependent mitogenesis of T lymphocytes

We have studied the control and significance of IL-1 production in human leukocyte cultures during accessory cell-dependent, T lymphocyte mitogenesis using sensitive bioassays and immunolabeling techniques. In primary antigen-dependent systems like the MLR, IL-1 production was not detected in accessory cells (monocytes, dendritic cells) or T cells, suggesting that it is not an early product in these responses. However, monocytes could be induced to make IL-1 after interacting with sensitized antigen-specific T cells. Both alloreactive T cell clones or freshly prepared lymphoblasts induced IL-1 provided the monocytes carried the HLA-DR antigens to which the T cells were initially sensitized. Even in these circumstances, dendritic cells and B cells failed to make IL-1. The mechanism whereby activated T cells induce IL-1 in monocytes was explored. Supernatants from cocultures of monocytes and T cells or several recombinant cytokines induced little or no IL-1. A more potent antigen independent pathway of IL-1 induction was identified. IL-1 could be induced in third-party HLA-DR nonspecific monocytes in cocultures of alloreactive T cell clones or blasts and HLA-DRE-specific dendritic cells. The induction was factor independent since dendritic cells and T blasts placed in a chamber separate from third-party monocytes by a semipermeable membrane did not induce monocyte IL-1. These results suggest that a cell contact mechanism rather than an IL-1-inducing factor leads to IL-1 production. The role of IL-1 in T cell proliferation was tested with a polyclonal anti-IL-1 antibody. The antibody failed to block the proliferation of primary T cells, or alloreactive T cell clones and blasts stimulated with HLA-specific monocytes or dendritic cells, even though IL-1 in the medium was neutralized

Air Insufflation of the Stomach Following Laparoscopic Pyloromyotomy May Not Detect Perforation

Air insufflation of the stomach during laparoscopic pyloromyotomy does not reliably rule-out perforation