Efficient and Reliable Lock-Free Memory Reclamation Based on Reference Counting

We present an efficient and practical lock-free method for semiautomatic (application-guided) memory reclamation based on reference counting, aimed for use with arbitrary lock-free dynamic data structures. The method guarantees the safety of local as well as global references, supports arbitrary memory reuse, uses atomic primitives that are available in modern computer systems, and provides an upper bound on the amount of memory waiting to be reclaimed. To the best of our knowledge, this is the first lock-free method that provides all of these properties. We provide analytical and experimental study of the method. The experiments conducted have shown that the method can also provide significant performance improvements for lock-free algorithms of dynamic data structures that require strong memory management.     

多寄存器组网络处理器上的寄存器分配技术

针对传统的图着色寄存器分配算法不能直接处理网络处理器的操作问题,提出了一种多寄存器组网络处理上的寄存器分配技术．在依次分析了一个符号寄存器可能位于哪些寄存器组？如果没有候选组,该如何解决这种冲突？如果有多个候选组,该选用哪个组等问题的基础上,通过将这些方法与图着色寄存器分配算法相融合,在IXP上实现了这种多寄存器组的寄存器分配,提高了它的可编程性．这种方法也可运用到其它具有类似寄存器结构的处理器上．     

Counting Beans

Our current body politic is looking for a more robust voting mechanism that is secured by technology rather than by the competence and integrity of bean counters.     

通过寄存器队列模型实现寄存器分配和指令调度

寄存器分配与指令调度是编译器优化过程中的两项重要任务．由于这两个阶段通常是独立完成的，寄存器分配往往会引入不必要的伪相关，从而影响指令调度的效率和结果，影响最终性能的提高．本文提出了寄存器队列模型，并在其基础上提出了一种结合实现寄存器分配和指令调度的算法，该算法能够在保证每条指令的执行时间最早的同时使用最少数目的寄存器．它的另外一个优点是具有线性的时间和空间复杂度，而且易于硬件实现．     

二进制翻译中的寄存器映射与剪裁的实现

如何进行异构机之间可执行程序的高效移植是二进制翻译面对的难点问题.从寄存器映射的角度分析了这一问题,提出了分段映射和特殊寄存器功能剪裁相结合的方法,以trend系统为平台进行了实验和测试.NPB-serail测试包和SPEC2000测试包的测试结果显示:使用该方法,可以简化指令翻译,减少代码膨胀,有效提高翻译后代码的执行效率.     

Semantical Counting Circuits

Abstract. Counting functions can be defined syntactically or semantically depending on whether they count the number of witnesses in a non-deterministic or in a deterministic computation on the input. In the Turing-machine-based model these two ways of defining counting were proven to be equivalent for many important complexity classes. In the circuit-based model it was done for #P, but for low-level complexity classes such as #AC ⁰ and #NC ¹ only the syntactical definitions were considered. We give appropriate semantical definitions for these two classes and prove them to be equivalent to the syntactical ones. We also consider semantically defined probabilistic complexity classes corresponding to AC ⁰ and NC ^{1} and prove that in the case of unbounded error, they are identical to their syntactical counterparts.     

Register allocation via coloring

Register allocation may be viewed as a graph coloring problem. Each node in the graph stands for a computed quantity that resides in a machine register, and two nodes are connected by an edge if the quantities interfere with each other, that is, if they are simultaneously live at some point in the object program. This approach, though mentioned in the literature, was never implemented before. Preliminary results of an experimental implementation in a PL/I optimizing compiler suggest that global register allocation approaching that of hand-coded assembly language may be attainable.     

基于分层计数型Bloom过滤器的进化数据流计数

许多应用场景所产生的数据流中,元素的频数分布符合重尾分布的特点,即大部分元素的频数较小而少部分元素的频数较大.为了解决数据流中所有相异元素及其频数的高效存储问题,提出了一个基于分层的计数型布卢姆过滤器(hierarchical counting Bloom filter,HCBF)保存所有元素频数的方法.该方法采用长度递减、计数单位递增的多层计数型布卢姆过滤器作为存储数据结构,多层过滤器共同组成元素的频数.与两个经典的计数型布卢姆过滤器CBF和DCF相比,HCBF更加适合真实数据流元素频数分布的重尾特点,在不影响查询性能和错误率的前提下,能够显著地降低空间开销.理论分析与实验结果验证了该结论.     

注册表与系统安全性

介绍了 Windows注册表的组织结构和大量重要的子键 ,并通过这些子键的设置来改善系统安全性和可靠性。     

注册电子邮箱的探讨

用户注册电子邮箱应当注意以下几个方面:选择适当的服务商,根据自己的需要确定收费方式,构思严肃合适的用户名,设置安全可靠的密码。     

位宽感知的寄存器绑定算法

寄存器绑定是高层次综合中的一个基础优化问题,主要目标是在保证电路功能的同时最小化寄存器资源的使用.传统的方法尝试将编译器的寄存器分配算法应用于寄存器绑定中,但却忽略了分配问题与绑定问题的差异性,因此在绑定过程中引入了额外的资源约束,或采用了不适合电路设计的编译优化技巧,从而导致资源浪费.为了解决这些问题, 本文将寄存器绑定问题转化为连续多重着色问题,并提出了一种基于位宽与顶点度结合的启发式求解方法.该方法通过对变量的位宽和活跃区间等信息的细粒度刻画和建模,能够进一步优化寄存器资源的开销,同时无需插入额外的指令.我们将该算法与两种典型算法进行了比较,实验结果表明, 我们的算法在Mibench测试集的96.72%的测试用例中达到了理论最优解,比其他两种方法分别提高了31.5%和25.1%;在Rosetta测试集的所有测试用例中均表现为最优解,比其他两种方法分别提高了7.41%和7.39%.