Implementation and comparison of iSCSI over RDMA

iSCSI is an emerging storage network technology that allows for block-level access to disk drives over a computer network. Since iSCSI runs over the very ubiquitous TCP/IP protocol it has many advantages over its more proprietary alternatives. Due to the recent movement toward 10 gigabit Ethernet, storage vendors are interested to see how this large increase in network bandwidth could benefit the iSCSI protocol. In order to make full use of the bandwidth provided by a 10 gigabit Ethernet link, specialized Remote Direct Memory Access hardware is being developed to offload processing and reduce the data-copy-overhead found in a standard TCP/IP network stack. This thesis focuses on the development of an iSCSI implementation that is capable of supporting this new hardware and the evaluation of its performance. This thesis depicts the approach used to implement the iSCSI Extensions for Remote Direct Memory Access (iSER) with the UNH iSCSI reference implementation. This approach involves a three step process: moving UNH-iSCSI from the Linux kernel to the Linux user-space, adding support for the iSER extensions to our user-space iSCSI and finally moving everything back into the Linux kernel. In addition to a description of the implementation, results are given that demonstrate the performance of the completed iSER-assisted iSCSI implementation

Planning under time pressure

Heuristic search is a technique used pervasively in artificial intelligence and automated planning. Often an agent is given a task that it would like to solve as quickly as possible. It must allocate its time between planning the actions to achieve the task and actually executing them. We call this problem planning under time pressure. Most popular heuristic search algorithms are ill-suited for this setting, as they either search a lot to find short plans or search a little and find long plans. The thesis of this dissertation is: when under time pressure, an automated agent should explicitly attempt to minimize the sum of planning and execution times, not just one or just the other. This dissertation makes four contributions. First we present new algorithms that use modern multi-core CPUs to decrease planning time without increasing execution. Second, we introduce a new model for predicting the performance of iterative-deepening search. The model is as accurate as previous offline techniques when using less training data, but can also be used online to reduce the overhead of iterative-deepening search, resulting in faster planning. Third we show offline planning algorithms that directly attempt to minimize the sum of planning and execution times. And, fourth we consider algorithms that plan online in parallel with execution. Both offline and online algorithms account for a user-specified preference between search and execution, and can greatly outperform the standard utility-oblivious techniques. By addressing the problem of planning under time pressure, these contributions demonstrate that heuristic search is no longer restricted to optimizing solution cost, obviating the need to choose between slow search times and expensive solutions

Best-first heuristic search for multicore machines

To harness modern multicore processors, it is imperative to develop parallel versions of fundamental algorithms. In this paper, we compare different approaches to parallel best-first search in a shared-memory setting. We present a new method, PBNF, that uses abstraction to partition the state space and to detect duplicate states without requiring frequent locking. PBNF allows speculative expansions when necessary to keep threads busy. We identify and fix potential livelock conditions in our approach, proving its correctness using temporal logic. Our approach is general, allowing it to extend easily to suboptimal and anytime heuristic search. In an empirical comparison on STRIPS planning, grid pathfinding, and sliding tile puzzle problems using 8-core machines, we show that A*, weighted A* and Anytime weighted A* implemented using PBNF yield faster search than improved versions of previous parallel search proposals

Experimental Real-time Heuristic Search Results in a Video Game

In real-time domains such as video games, a planning algorithm has a strictly bounded time before it must return the next action for the agent to execute. We introduce a realistic video game benchmark domain that is useful for evaluating real-time heuristic search algorithms. Unlike previous benchmarks such as grid pathfinding and the sliding tile puzzle, this new domain includes dynamics and induces a directed graph. Using both the previous and new domains, we investigate several enhancements to a leading real-time search algorithm, LSS-LRTA*. We show experimentally that 1) it is not difficult to outperform A * when optimizing goal achievement time, 2) it is better to plan after each action than to commit to multiple actions or to use a dynamically sized lookahead, 3) A*-based lookahead can cause undesirable actions to be selected, and 4) on-line de-biasing of the heuristic can lead to improved performance. We hope that this new domain and results will stimulate further research on applying real-time search to dynamic real-time domains

Implementation and Evaluation of iSCSI over RDMA

iSCSI is an emerging storage network technology that al-lows block-level access to storage devices, such as disk drives, over a computer network. Since iSCSI runs over the ubiquitous TCP/IP protocol, it has many advantages over its more proprietary alternatives. Due to the recent movement toward 10 gigabit Ethernet, storage vendors are interested to see the benefits this large increase in network bandwidth could bring to iSCSI. In order to make full use of the bandwidth provided by a 10 gigabit Ethernet link, specialized Remote Direct Memory Access hardware is being developed to offload processing and reduce the data-copy-overhead found in a standard TCP/IP network stack. This paper focuses on the development of an iSCSI implementation that is capa

\u3ci\u3eIn Vitro\u3c/i\u3e Validation of Patient-Specific Hemodynamic Simulations in Coronary Aneurysms Caused by Kawasaki Disease

To perform experimental validation of computational fluid dynamics (CFD) applied to patient specific coronary aneurysm anatomy of Kawasaki disease. We quantified hemodynamics in a patient-specific coronary artery aneurysm physical phantom under physiologic rest and exercise flow conditions. Using phase contrast MRI (PCMRI), we acquired 3-component flow velocity at two slice locations in the aneurysms. We then performed numerical simulations with the same geometry and inflow conditions, and performed qualitative and quantitative comparisons of velocities between experimental measurements and simulation results. We observed excellent qualitative agreement in flow pattern features. The quantitative spatially and temporally varying differences in velocity between PCMRI and CFD were proportional to the flow velocity. As a result, the percent discrepancy between simulation and experiment was relatively constant regardless of flow velocity variations. Through 1D and 2D quantitative comparisons, we found a 5–17% difference between measured and simulated velocities. Additional analysis assessed wall shear stress differences between deformable and rigid wall simulations. This study demonstrated that CFD produced good qualitative and quantitative predictions of velocities in a realistic coronary aneurysm anatomy under physiological flow conditions. The results provide insights on factors that may influence the level of agreement, and a set of in vitro experimental data that can be used by others to compare against CFD simulation results. The findings of this study increase confidence in the use of CFD for investigating hemodynamics in the specialized anatomy of coronary aneurysms. This provides a basis for future hemodynamics studies in patient-specific models of Kawasaki disease

Assessing Concussion Potential in Youth Sports for the CPSC

This project was conducted with the U.S. Consumer Product Safety Commission to investigate physical causes of concussions and prevention methods to address them, particularly in youth sports. Concussions are a form of traumatic brain injury, a leading cause of death and disability among children. After evaluating occurrence data from the Commission’s NEISS database and surveying student athletes, we determined which physical causes of concussions in sports presented potential for a reduction in concussions and encouraged action to address these concerns

The Vehicle, Fall 1998

Vol. 40, No. 1 Table of Contents Poetry 23 years across 1000 milesAudre Hillyerpage 1 UntitledEthan Heicherpage 2 glimpseMandy Watsonpage 4 In a Nut ShellSylvia Whippopage 5 Flat Tortilla PagesAudre Hillyerpage 6 AlexeiNicole Cordinpage 7 GracePatty Burnspage 8 sacrementMandy Watsonpage 12 Dream of Your RejectionStephanie Kavanaughpage 13 A hollowed moonMandy Watsonpage 14 UntitledEthan Heicherpage 15 The Blue NoteSylvia Whippopage 16 the six senses of eveEthan Heicherpage 18 Visual art UntitledDawn Kehrkornpage 20 Prose Still LifeKim Hunterpage 21https://thekeep.eiu.edu/vehicle/1070/thumbnail.jp