消除拥挤的多层总体布线新流程

提出一种在布线前进行层分配的总体布线算法,基于一个多层布线的新流程,使用包含线网所有端点的边界盒来估计线网拥挤度,并基于拥挤度均匀的目标把线网分配到不同层对上.该算法已经实现并进行了测试,实验结果证明了其有效性.     

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.     

确定区域详细布线算法

提出了一种确定区域的详细布线算法,它能对不同设计模式进行布线。该算法能适用于任意多层布线情况,并且支持不同布线层具有的不同工艺参数,在构造布线树时,考虑芯片当前的走线拥挤度,使布线比较平均,并加快了算法运行速度、改善了布线质量,在连接两点线网时,构造基于二维迷宫布线结果的分层图,提出了一种对分层图的启发式染色算示来进行布线层分配,大大提高算法布线速度,采用拆线重布的方法来处理布线失败的线网。     

VLSI积木块布图设计的通道划分和总体布线

本文提出了用ＶＬＳＩ积木声布科设计（ＢＢＬ）中的通道划分和总体布线有效算法，通道划分是在角逢数据结构的基础上，对空瓦片进行适当分割和合并，总体布线以通道图和线网排序的为基础，提出了扩张－收缩优化总体布线算法，在保证获得很高布通率的前提下，将线网按最短路径和最少通孔数进行布线，算法已用于Ｃ语言实现，结果令人满意。     

一种基于通孔数最小化的多层通道布线算法

该文提出了一种基于通孔数量小化的多层通道布线算法，算法采用非预留层模，首先根据线网之间的位置关系利用模拟退火算法将各线网合理地分配到对应的布线层中去，然后利用遗传算法得到相关布线层中线网的最佳布线顺序向量，最的根据得到的顺序向量利用“沉积法”将各线网布于合理的通道上，该算法克服了传统通孔优化算法中原始布线对优化结果的不利影响，使通孔的优化达到很好的效果。     

基于线网分类的模拟电路自动布线器

提出一种基于线网分类的模拟电路自动布线方法,并设计实现了一种基于线网分类的模拟电路布线器NCARouter．基于模拟电路性能要求,布线器中的线网被分为关键线网、普通线网和电源／地线网3种类型．同时,模拟电路的性能约束被转化为线网的属性描述,包括几何约束（如对称）、电学约束（如匹配）、寄生参数描述等．此外,针对不同类型的线网,该布线器使用了不同的布线算法,以满足总体性能约束．实验结果表明,该布线器不仅能很好地完成布线,还能确保满足模拟电路各种性能要求．     

VLSI中高性能X结构多层总体布线器

X结构带来物理设计诸多性能的提高,该结构的引入和多层工艺的普及,使得总体布线算法更复杂.为此,在XGRouter布线器的基础上,本文设计了三种有效的加强策略,包括:1)增加新类型的布线方式;2)粒子群优化(Particle swarm optimization,PSO)算法与基于新布线代价的迷宫布线的结合;3)初始阶段中预布线容量的缩减策略,继而引入了多层布线模型,简化了XGRouter的整数线性规划模型,最终构建了一种高性能的X结构多层总体布线器,称为ML-XGRouter.在标准测试电路的仿真实验结果表明,ML-XGRouter相对其他各类总体布线器,在多层总体布线中最重要的优化目标|溢出数和线长总代价两个指标上均取得最佳.     

基于多阶段拆线重布的总体布线算法

超大规模集成电路总体布线是集成电路物理设计的关键环节之一,对芯片的可布线性、线长、通孔数等性能指标有重大影响.针对拆线重布方法容易陷入局部最优解的问题,提出一种基于多阶段拆线重布的总体布线算法.该算法根据不同布线阶段对最小化溢出值和最小化线长这两个目标的侧重点不同,通过构造不同的布线代价函数、确定不同的布线顺序、选取不同的布线模型及布线算法对线网进行拆线重布,使得基于多阶段拆线重布的总体布线算法可以有效地跳出局部最优解,快速地提高布线质量.采用ISPD08总体布线竞赛中的标准测试例子集的实验结果表明,与NTUgr,NTHU-Route2.0和NCTU-GR2.0相比,所提出的总体布线算法在平均总溢出方面分别减少了1.4%,2.4%和21.5%,在平均运行时间方面分别快了10.4倍,1.6倍和1.3倍.     

拥挤度驱动的总体布线层分配算法

针对多层布线问题，提出以拥挤度为驱动目标，完成布线资源的合理分配，同时达到布线层资源占用少和通孔数少等优化目标的层分配算法．首先采用启发式方法获得初始分配方案，然后通过模拟退火技术优化分配结果，最后采用试探策略优化层资源占用．工业实验数据表明，该算法能够实现线网层合理分配，获得满足拥挤度的优化解．     

一种基于线网划分的并行FPGA布线算法

针对在现场可编程门阵列(FPGA)软件系统中大规模电路设计布线时间较长的问题,提出一种基于线网引脚位置划分且具有平台独立性的多线程FPGA布线算法。对高扇出线网采用将单根线网拆分成子线网并同时布线的方法,对低扇出线网采用选择若干位置不相交叠的线网进行同时布线的方法,给出线网边界框图的数据结构来缩短选择若干低扇出线网的时间,采取负载平衡机制和同步措施,分别提高布线效率和保证布线结果的确定性。实验结果证明,在Intel 4核处理器平台上,与单线程VPR算法相比,该并行算法的平均布线效率提高了90%,平均布线质量下降不超过2.3%,并能够得到确定的布线结果,在EDA方面具有重要的理论与实用价值。     

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).     

Fuzzy-based Adaptive Routing Algorithm for Networks-on-Chip

In this paper, we propose two adaptive routing algorithms to alleviate congestion in the network. In the first algorithm, the routing decision is assisted by the number of occupied buffer slots at the corresponding input buffer of the next router and the congestion level of that router. Although this algorithm performs better than the conventional method, DyXY, in some cases the proposed algorithm leads to non-optimal decisions. Fuzzy controllers compensate for ambiguities in the data by giving a level of confidence rather than declaring the data simply true or false. To make a better routing decision, we propose an adaptive routing algorithm based on fuzzy logic for Networks-on-chip where the routing path is determined based on the current condition of the network. The proposed algorithm avoids congestion by distributing traffic over the routers that are less congested or have a spare capacity. The output of the fuzzy controller is the congestion level, so that at each router, the neighboring router with the lowest congestion value is chosen for routing a packet. To evaluate the proposed routing method, we use two multimedia applications and two synthetic traffic profiles. The experimental results show that the fuzzy-based routing scheme improves the performance over the DyXY routing algorithm by up to 25% with a negligible hardware overhead.     

PFR:一个基于平面的完全自适应路由器

互连网络路由器是ＭＰＰ系统的关键部件，其性能优劣直接影响系统性能。路由器根据其所采用的路由算法可分为确定性和自适应路由器两种，其中自适应路由器有灵活性好，网络的通道利用率高和网络容错能力强等优点，正逐步为新一代的ＭＰＰ系统所采用，但其工程实现难度较大。本文在ｍｅｓｈ结构上，采用虫孔路由切换技术，给出了一个可扩展性好，自适应性强的基于平面的完全自适应路由算法ＰＢＦＡＡ，并采用基于虚通道的综合流控策略     

Software-based rerouting for fault-tolerant pipelined communication

This paper presents a software-based approach to fault-tolerant routing in networks using wormhole or virtual cut-through switching. When a message encounters a faulty output link, it is removed from the network by the local router and delivered to the messaging layer of the local node's operating system. The message passing software can reroute this message, possibly along nonminimal paths. Alternatively, the message may be addressed to an intermediate node, which will forward the message to the destination. A message may encounter multiple faults and pass through multiple intermediate nodes. The proposed techniques are applicable to both obliviously and adaptively routed networks. The techniques are specifically targeted toward commercial multiprocessors where the mean time to repair (MTTR) is much smaller than the mean time between router failures (MTBF), i.e., it is sufficient to tolerate a maximum of three failures. This paper presents requirements for buffer management, deadlock freedom, and livelock freedom. Simulation results are presented to evaluate the degradation in latency and throughput as a function of the number and distribution of faults. There are several advantages of such an approach. Router designs are minimally impacted, and thus remain compact and fast. Only messages that encounter faulty components are affected, while the machine is ensured of continued operation until the faulty components can be replaced. The technique leverages existing network technology, and the concepts are portable across evolving switch and router designs. Therefore, we feel that the technique is a good candidate for incorporation into the next generation of multiprocessor networks     

带有引线端预处理的区域布线算法

提出一种带有引线端优化处理的多层区域布线算法，能处理端点障碍在区域内任意分布的大量布线问题，首先将多端线网划分为二端子线网，并在此基础上根据二端子线网之间的相对位置关系进行分类；然后对每个类型的二端子线网，采用双向迷宫和朝向目标的深度优先搜索策略依次布线；最后通过拆线-重布策略来解决布线冲突．在进行布线搜索之前，对引线端映射到网格点上这一过程引入了一种有效的优化预处理机制，采用二分图中多目标约束寻找最佳匹配的思想和策略来解决引线端优化映射问题．测试并比较了有／无这种优化处理的2种情况，实验结果表明，该算法有效地改善了网格映射的精度和准确性，可缩短线长和提高布通率．     

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.     

LCFAA:一个低代价的完全自适应路由算法

大规模并行处理机系统（ＭＰＰ）中路由算法对互联网络通信性能和系统性能起着重要作用。自适应路由算法具有灵活性好、网络的通道利用率高和网络容错能力强等优点,但其实现难度较大,因而目前仅在少数ＭＰＰ系统中得以实现。文中在ｍｅｓｈ结构上提出了一个低代价无死锁的安全自适应最短虫孔路由算法ＬＣＦＡＡ,该算法所需虚通道数少,具有代价低、自适应性强的特点。文中证明了算法的无死锁、无活锁性和完全自适应性,并模拟验证