Evaluation of an Evolutionary Algorithm to Dynamically Alter Partition Sizes in Web Caching Systems

There has been an explosion in the volume of data that is being accessed from the Internet. As a result, the risk of a Web server being inundated with requests is ever-present. One approach to reducing the performance degradation that potentially comes from Web server overloading is to employ Web caching where data content is replicated in multiple locations. In this paper, we investigate the use of evolutionary algorithms to dynamically alter partition size in Web caches. We use established modeling techniques to compare the performance of our evolutionary algorithm to that found in statically-partitioned systems. Our results indicate that utilizing an evolutionary algorithm to dynamically alter partition sizes can lead to performance improvements especially in environments where the relative size of large to small pages is high.

Aging effect in the BESIII drift chamber

As the main tracking detector of BESIII, the drift chamber provides accurate measurements of the position and the momentum of the charged particles produced in e＋e- collisions at BEPCII. After six years of operation, the drift chamber is suffering from aging problems due to huge beam-related background. The gains of the cells in the first ten layers show an obvious decrease, reaching a maximum decrease of about 29% for the first layer cells. Two calculation methods for the gain change （Bhabha events and accumulated charges with 0.3% aging ratio for inner chamber cells） give almost the same results. For the Malter effect encountered by the inner drift chamber in January 2012, about 0.2% water vapor was added to the MDC gas mixture to solve this cathode aging problem. These results provide an important reference for MDC operating high voltage settings and the upgrade of the inner drift chamber.

A cache-friendly sampling strategy for texture-based volume rendering on GPU

The texture-based volume rendering is a memory-intensive algorithm.Its performance relies heavily on the performance of the texture cache.However,most existing texture-based volume rendering methods blindly map computational resources to texture memory and result in incoherent memory access patterns,causing low cache hit rates in certain cases.The distance between samples taken by threads of an atomic scheduling unit(e.g.a warp of 32 threads in CUDA)of the GPU is a crucial factor that affects the texture cache performance.Based on this fact,we present a new sampling strategy,called Warp Marching,for the ray-casting algorithm of texture-based volume rendering.The effects of different sample organizations and different thread-pixel mappings in the ray-casting algorithm are thoroughly analyzed.Also,a pipeline manner color blending approach is introduced and the power of warp-level GPU operations is leveraged to improve the efficiency of parallel executions on the GPU.In addition,the rendering performance of the Warp Marching is view-independent,and it outperforms existing empty space skipping techniques in scenarios that need to render large dynamic volumes in a low resolution image.Through a series of micro-benchmarking and real-life data experiments,we rigorously analyze our sampling strategies and demonstrate significant performance enhancements over existing sampling methods.

Replacement Policy for Caching World-Wide Web Documents Based on Site-Graph Model

The hit rate, a major metric for evaluating proxy caches, is mostly limited by the replacement strategy of proxy caches. However, in traditional proxy caches, the hit rate does not usually successfully predict how well a proxy cache will perform because the proxy cache counts any hit in its caching space which has many pages without useful information, so its replacement strategy fails to determine which pages to keep and which to release. The proxy cache efficiency can be measured more accurately using the valid hit rate introduced in this paper. An efficient replacement strategy based on the Site Graph model for WWW (World Wide Web) documents is also discussed in this paper. The model analyzes user access behavior as a basis for the replacement strategy. Simulation results demonstrate that the replacement strategy improves proxy cache efficiency.