考虑总线时序匹配的多策略层分配算法

在总体布线的过程中,层分配阶段通过控制总线线网的层次影响总线的时序匹配效果.为此,提出考虑总线时序匹配的多策略层分配算法.首先基于线网属性的线网优先级策略,针对线网不同属性的特点得到一个兼顾线长和总线偏差的布线顺序;然后基于贪心策略的初始布线策略,每次布线都对正在布线的线网选择当前最短路径,使相同总线内的线网都尽可能等...     

非默认规则线技术下基于多策略的时延驱动层分配算法

层分配作为超大规模集成电路物理设计中的关键环节,在决定布线方案的时延起到非常重要作用.为了优化集成电路的时延性能,现有的层分配工作通常注重优化互连时延和通孔数量,但要么未考虑到对线网中时序关键段的分配问题,要么对线网段的时序关键性的表示不够合理,最终使得算法的时延优化不够理想.为此,本文提出一种非默认规则线技术下基于多策略的时延驱动层分配算法,主要包含4种关键策略:(1)提出轨道数感知的层选择策略,增强层分配器为线网段选择合适布线层的能力;(2)提出多指标驱动的初始线网排序策略,综合考虑线长、信号接收器数和可布线轨道资源等多个指标为线网确定层分配优先级,从而获得高质量的初始层分配结果;(3)提出线网段调整策略,通过重绕线网,将时序关键段调整至上层布线层,优化线网时延;(4)提出线网段时延优化策略,对存在溢出线网进行拆线重绕,从而可同时优化时延和溢出数.实验结果表明,本文提出的算法相比于现有的层分配算法能够在时延和通孔数两个指标上均取得最佳,并且保证不产生溢出.     

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.     

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。     

一种通孔最小化的三层通道布线算法

本文提出的连通孔最小化的三层通道布线算法,根据线网的接点位置建立线网分层图,并对此图进行三着色,确定出初始布线集和分拆线网集,通过引进线网次序图、压缩空段长度、填充原则和逐步排障法等,将初始布线集和拆网集的线网分配到相应的走线道上.实现线网的互连.本算法已用PASCAL语言编程,并在XT/286机上实现.结果表明,该算法不仅使通孔数大大减少,而且有些例子的走线道数也较一般布线法少.     

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。     

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．     

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。     

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．     

WEAVER: A Knowledge-Based Routing Expert

WEAVER, a channel/switchbox knowledge-based routing program, simultaneously considers all the important routing metrics including 100 percent routability, minimum routing area, minimum wire length, and the minimum number of vias. It allows prerouted nets and user interaction throughout the entire routing process, while relaxing the unnecessary contraints of assigning different directions?constraints imposed by all of the current channel and switchbox routers. A grid-based router using two interconnection layers, WEAVER can be easily expanded to route any shape routing area such as T or +. Implemented in OPSS, a production system language, WEAVER routinely produces routings requiring less area than routers that focus on a single routing metric.     

Crosstalk-Aware Routing Resource Assignment

Crosstalk noise is one of the emerging issues in deep sub-micrometer technology which causes many undesired effects on the circuit performance. In this paper, a Crosstalk-Aware Routing Resource Assignment (CARRA) algorithm is proposed, which integrates the routing layers and tracks to address the crosstalk noise issue during the track/layer assignment stage. The CARRA problem is formulated as a weighted bipartite matching problem and solved using the linear assignment algorithm. The crosstalk risks between nets are represented by an undirected graph and the maximum number of the concurrent crosstalk risking nets is computed as the max clique of the graph. Then the nets in each max clique are assigned to disadjacent tracks. Thus the crosstalk noise can be avoided based on the clique concept. The algorithm is tested on IBM benchmarks and the experimental results show that it can improve the final routing layout a lot with little loss of the completion rate.     

认知无线Mesh网络中基于干扰模型的信道分配策略*

从信道干扰的角度为认知无线Mesh网络提出一种新的信道分配策略。首先对网络进行分层并按层对节点设置不同的层数权值,以此来选择最佳路径,再利用信道干扰模型来选择最佳信道。新策略有效整合了路由和信道分配过程,通过路由的实现来协助节点的信道分配以获得整个网络的最优化性能。仿真结果表明,新算法相比于无线多信道网络中基于链接的信道分配算法,在时延、吞吐量上有明显的优势。     

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.     

An on-demand routing protocol for improving channel use efficiency in multichannel ad hoc networks

In wireless ad hoc networks, end-to-end delivery over network is a critical concern for routing protocols. The capacity of routing protocols is constrained by the intra-flow interference introduced by adjacent nodes on the same path, and inter-flow interference generated by nodes from neighboring paths. In this paper, we develop an on-demand routing protocol M-AODV-R that solves the channel assignment, reuse and routing problem jointly. The proposed channel reuse scheme and channel assignment scheme can enhance channel reuse rate. This cross-layer design approach can significantly improve the performance of multichannel ad hoc networks over existing routing protocols. Simulation results show that the proposed routing M-AODV-R can effectively increase throughput and reduce delay, as compared to AODV protocol.     

Finding All Minimal Shapes in a Routing Channel

We present an algorithm to find a set of all optimal solutions for a channel placement problem. A channel consists of two rows of horizontal line segments (representing components). Each line segment contains some terminals with fixed positions. Sets of terminals, called nets, are to be connected. The relative ordering of line segments in each row is fixed. The line segments can be shifted left or right, which will affect the width needed for routing and the length of the channel. We want to find the tradeoff between channel length and routing width. Since the channel routing problem is NP-complete, we use a lower bound on routing width, called density. The density of a placement is the maximum number of nets crossing each vertical cut. We can increase the total length to minimize the channel density, or minimize the total length by increasing the channel density. The pair (density, total length) is called the shape of a placement. A shape is minimal if a decrease in density would cause an increase in total length, and vice versa. Our algorithm computes all the minimal shapes in O (N ⁴ ) time, where N is the number of nets. This is the first known algorithm for this problem whose running time is polynomial in the number of nets and independent of the length of the channel. Received January 18, 1996; revised December 2, 1996.     

MANET中有利于信道重用的按需信道分配和路由协议

从信道重用的角度出发,设计出一种简单而有效的按需固定信道分配机制和路由的协议(CA-AODV-R)。该协议将信道分配放到路由层进行,通过在路由发现时的RREQ和RREP中携带信道信息来分配固定信道,避免了MAC层动态信道分配协议(如DCA等)需要频繁地调用信道分配算法的问题。CA-AODV-R使用的固定信道分配算法为把数据信道按编号从小到大排列后按每3个划分为一个小组,同一条路由发现路径上的后继节点分配固定信道时优先在其前驱节点的固定信道所在小组内选择空闲信道。仿真结果表明,CA-AODV-R协议相对于单信道AODV能够大幅度提高网络吞吐量和分组投递率并降低网络的端到端时延。