Prefetching J<Superscript>+</Superscript>-Tree: A Cache-Optimized Main Memory Database Index Structure

As the speed gap between main memory and modern processors continues to widen, the cache behavior becomes more important for main memory database systems (MMDBs). Indexing technique is a key component of MMDBs. Unfortunately, the predominant indexes — B⁺-trees and T-trees — have been shown to utilize cache poorly, which triggers the development of many cache-conscious indexes, such as CSB⁺-trees and pB⁺-trees. Most of these cache-conscious indexes are variants of conventional B⁺-trees, and have better cache performance than B⁺-trees. In this paper, we develop a novel J ⁺ -tree index, inspired by the Judy structure which is an associative array data structure, and propose a more cache-optimized index — Prefetching J ⁺ -tree (pJ⁺-tree), which applies prefetching to J⁺-tree to accelerate range scan operations. The J⁺-tree stores all the keys in its leaf nodes and keeps the reference values of leaf nodes in a Judy structure, which makes J⁺-tree not only hold the advantages of Judy (such as fast single value search) but also outperform it in other aspects. For example, J⁺-trees can achieve better performance on range queries than Judy. The pJ⁺-tree index exploits prefetching techniques to further improve the cache behavior of J⁺-trees and yields a speedup of 2.0 on range scans. Compared with B⁺-trees, CSB⁺-trees, pB⁺-trees and T-trees, our extensive experimental study shows that pJ⁺-trees can provide better performance on both time (search, scan, update) and space aspects.     

Cache-Conscious Data Cube Computation on a Modern Processor

As the speed gap between main memory and modern processors continues to widen,the cache behavior becomes more important for main memory database systems(MMDBs).Indexing technique is a key component of MMDBs. Unfortunately,the predominant indexes—B~+-trees and T-trees—have been shown to utilize cache poorly,which triggers the development of many cache-conscious indexes,such as CSB~+-trees and pB~+-trees.Most of these cache-conscious indexes are variants of conventional B~+-trees,and have better cache perf...     

塑料热气焊接设备的进展

概述了目前主要几种热气焊接机的牌号、功能和应用。     

2极中型异步电动机振动产生的原因及处理

结合生产实践,从机械、电磁等方面系统阐述了2极中型异步电动机振动产生的原因,提出了可行的处理方法,如针对刚性转子与挠性转子的特点,提出的不同设计方案;针对滑动轴承电动机,采取控制轴瓦间隙、加强支承刚度解决振动问题等;简要介绍了整机平衡在解决电机振动问题上的应用,为高转速电动机振动的解决提供了有效的手段.     

鱼尾式机头设计

<正> 一、引言目前,用于挤出塑料板的平口机头有:1.T 型机头2.鱼尾式机头3.衣架式机头4.螺杆式机头应用衣架式机头内聚合物熔融流动方程,获得机头各部分尺寸之间的关系,有关的研究结果,在本人过去的文章中,已有报导。     

面向互联网新闻的在线事件检测

为了提高互联网上新闻事件在线检测的效率,利用加窗策略、命名实体识别及后缀树聚类等技术提出了一种新的检测算法.该算法基于实体识别技术解析出新闻数据特有的信息元素(例如日期、地点、人物等),并在限定的时间窗口内,通过新闻特征的语义匹配实现了新事件的快速识别,从而大幅降低了基于文本相似度计算的检测算法带来的巨大时间消耗.实验结果证明,该算法能够实现在保障检测准确率的同时显著提高检测的效率.