性能驱动总体布线的关键技术及研究进展

在计算机软件领域,超大规模集成电路技术的迅猛发展迫切需要高性能CAD工具——电子设计自动化(EDA)软件工具的支持.与物理设计相关的CAD技术称为布图设计,总体布线是布图设计中一个极为重要的环节.目前,在深亚微米、超深亚微米工艺下的超大规模、甚大规模集成电路设计中,性能驱动总体布线算法已成为布图设计中的一个国际研究热点.针对这一热点,分析了性能驱动总体布线算法研究中亟待解决的关键技术,并详细阐述了国内外的重要相关研究工作进展情况.  

一种新的与线网顺序无关的随机优化总体布线算法

针对目前总体布线中仍然存在的3个关键问题；布线结果受布线顺序的影响、总体布线图中拥挤区域的不可预见性、线网连接式样受到算法的限制等，该文提出了一种新的不受线网顺序影响的总体布线算法，并实现了相应的总体布线器RINO－Router。该算法采用随机优化方法来保 证先后被拆线重布的线网有相同的通过拥挤区域的机会，并能得到GRG边的拥挤度估计值；采用高效的Steiner树改造算法构造避开拥挤区域的布线树，采用典型电路实例进行了测试，并将布线结果与基于多商品流算法的总体布线器Matula-Router进行了对比。结果表明，RINO－Router能够在短得多的运行时间内求得质量与Matula-Router相近的总体布线解。  

SSTT: Efficient Local Search for GSI Global Routing

In this paper, a novel global routing algorithm is presented for congestion opti-mization based on efficient local search, named SSTT (search space traversing technology). This method manages to traverse the whole search space. A hybrid optimization strategy is adopted,consisting of three optimization sub-strategies: stochastic optimization, deterministic optimiza-tion and local enumeration optimization, to dynamically reconstruct the problem structure. Thus,“transition” can be made from a local minimum point to reach other parts of the search space,traverse the whole search space, and obtain the global (approximate) optimal routing solution.Since any arbitrary initial routing solution can be used as the start point of the search, the initial-ization in SSTT algorithm is greatly simplified. SSTT algorithm has been tested on both MCNC benchmark circuits and industrial circuits, and the experimental results were compared with those of typical existing algorithms. The experimental results show that SSTT algorithm can obtain the global (approximate) optimal routing solution easily and quickly. Moreover, it can meet the needs of practical applications. The SSTT global routing algorithm gives a general-purpose routing solution.  

一种以电性能优化为目标的Steiner树算法

本文提出了一种以电性能优化为目标的Ｓｔｅｉｎｅｒ树算法，它把从线网的源点到漏点的时间延迟最小作为求解Ｓｔｅｉｎｅｒ树的目标，文中首先给出一种多端线网连线延迟模型，然后导出它的上界，它是线网连线总长和从源点到漏点路径长度的函数。  

CNB: A Critical-Network-Based Timing Optimization Method for Standard Cell Global Routing

A novel method, named critical-network-based (CNB),for timing optimization in global routing is presented in this paper.The essence of this method is different from that of the typical existing ones,named nets-based (NB) and critical-path-based (CPB).The main contribution of this paper is that the CNB delay reduction method is more efficient than the typical existing ones.This new method makes it possible to reduce the delay in an overall survey.Based on CNB,a timing optimization algorithm for global routing is implemented and tested on Microelectronics Center of North Carolina (MCNC) benchmarks in this paper.The experimental results axe compared between this algorithm and the existing ones.The experimental results show that this algorithm is able to control the delay efficiently.  

用非常快速模拟重复退火算法实现的模拟电路模块布局

提出了基于非常快速模拟重复退火算法实现模拟电路模块布局的方法,该算法指数倍地快于传统的Cauchy 或 Bolzmann退火算法.其中使用一个滑行函数将绝对布局问题转化为相对布局问题,这样极大地减少了算法的搜索空间,而不会降低搜索成功率.价值函数根据模拟集成电路固有的特点设计而成,模拟电路设计者可根据电路的具体要求选择合适的网络长度估算器.使用最小steiner树方法的全局布线器与布局器同时工作,减轻了后续细节布线环节的工作量,并保证最后布局结果的可用性.最后,给出了使用该布局方法实现运算放大器的版图事例.  

Multiterminal global routing: A deterministic approximation scheme

We consider the problem of routing multiterminal nets in a two-dimensional gate-array. Given a gate-array and a set of nets to be routed, we wish to find a routing that uses as little channel space as possible. We present a deterministic approximation algorithm that uses close to the minimum possible channel space. We cast the routing problem as a new form of zero-one multicommodity flow, an integer-programming problem. We solve this integer program approximately by first solving its linear-program relaxation and then rounding any fractions that appear in the solution to the linear program. The running time of the rounding algorithm is exponential in the number of terminals in a net but polynomial in the number of nets and the size of the array. The algorithm is thus best suited to cases where the number of terminals on each net is small.This work was done while the authors were with the Computer Science Division, University of California at Berkeley. The work of Prabhakar Raghavan was supported by an IBM Doctoral Fellowship, and the work of Clark Thompson was supported by a California State MICRO grant (AT&T Foundation).  

矩形Steiner最小树布线灵活度

矩形Steiner最小树(RSMT)的布线灵活度影响其结构变形能力,直接影响芯片布线的收敛性.文中从树边形态、结构固有变形和拓扑变形3方面对线网的RSMT的布线灵活度进行刻画,给出了更能反映RSMT结构变形能力的计算模型.针对布线灵活度的"瓶颈"问题,提出了拥挤驱动的RSMT布线灵活度挖掘算法:根据树形的最短布线路径布线可能情况,定义了树边的布线灵活度;进而考虑RSMT结构中所有树边布线灵活度的组合情况和RSMT拓扑的变形性,得到RSMT布线灵活度.实验结果表明:将计算模型应用到拥挤驱动的RSMT布线灵活度挖掘算法,良好地改善了布线拥挤;将该挖掘算法应用到FastRoute4.1总体布线算法中,能够缩短14%的运行时间.  

无线传感器网络最优路由算法研究

无线传感器网络存在拓扑规模庞大、Mesh组网及传感器结点能量有限和处理能力差的缺点。为提高无线传感器网络路由效率，提出一种简单的全局路由最优算法。该算法根据变量r的不同取值，使算法输出路径不同，进而预防网络拥塞的发生。仿真实验表明，并行近似最短路由算法所耗时间是Dijkstra算法的1/3，该算法既能满足无线传感器路由需求，又能解决无线传感器网络拥塞的问题。  

基于分段时延凸函数的最小斯坦纳树方法

针对超大规模集成电路的互连时延问题，提出一种利用互连时延为搜索距离分段凸函数性质建立的最小时延斯坦纳Elmore(Steiner Elmore)布线树的方法，采用扩大搜索空间的方法寻找最佳连接点，同时建立一种有效的查找方法对布线树进行反复修改以减小树的总长度。实验结果表明，该方法可以缩小布线树的搜索空间，加快搜索速度，在阻抗占优的情况下，具有较好的性能。