A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> In this work we describe significant improvements to core routing technologies and outperform the best results from the ISPD '07 Global Routing Contest, as well as previous literature, in terms of route completion, runtime and total wirelength. In particular, our router, FGR, improves upon wirelengths produced by BoxRouter and MaizeRouter in March 2007 by 9.9% and 8.4%, respectively. Additionally, we reveal the mathematical basis of negotiated-congestion routing, offer comprehensive analysis of existing routing techniques and discuss several applications at the nanometer scale. <s> BIB001 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> This paper gives a broad overview of swarm intelligence in three parts: biological basis, artificial literature and swarm engineering. In biological basis part, the paper gives some operational principles from biological systems by naturalists and biologists. In artificial literature part, two fundamental approaches are provided to analyze swarm topology. The prevalent swarm models and techniques such as Reynolds's rules, discrete and continuum theory of flocking, coordination stability of the swarm motion, etc, are also summarized in this part. In swarm engineering part, the paper discusses Kazadi's “two-step” process. Many engineering applications come from Kazadi's researches. Also, the main application of swarm intelligence on robot systems and other applications are introduced in this part. We say this paper provides concepts for a better understanding of swarm intelligence both in principles and in applications. <s> BIB002 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> Swarm intelligence (SI) algorithms, including ant colony optimization, particle swarm optimization, bee-inspired algorithms, bacterial foraging optimization, firefly algorithms, fish swarm optimization and many more, have been proven to be good methods to address difficult optimization problems under stationary environments. Most SI algorithms have been developed to address stationary optimization problems and hence, they can converge on the (near-) optimum solution efficiently. However, many real-world problems have a dynamic environment that changes over time. For such dynamic optimization problems (DOPs), it is difficult for a conventional SI algorithm to track the changing optimum once the algorithm has converged on a solution. In the last two decades, there has been a growing interest of addressing DOPs using SI algorithms due to their adaptation capabilities. This paper presents a broad review on SI dynamic optimization (SIDO) focused on several classes of problems, such as discrete, continuous, constrained, multi-objective and classification problems, and real-world applications. In addition, this paper focuses on the enhancement strategies integrated in SI algorithms to address dynamic changes, the performance measurements and benchmark generators used in SIDO. Finally, some considerations about future directions in the subject are given. <s> BIB003 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> This paper presents an application of the modified version of Differential Evolution, call 2-Stage DE (2S-DE), for solving the transshipment of multiple product types in a multi-door cross docking system when a storage is allowed to be temporarily hold at the shipping dock. The objective is to find the truck schedule that minimizes the makespan. The performances of the proposed 2S-DE are evaluated and compared with the original DE and the GLNPSO previously published in literature. Using a set of generated instances, the experimental results show that all algorithms are able to find optimal solutions in small-size problems easily. However, when the problem becomes more complex, 2S-DE is superior to the GLNPSO and the original DE since it statistically shows outstanding results in terms of solution quality and convergence behavior. <s> BIB004 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> Abstract Today, VLSI technology has taken a fundamental role in developing most of the high-tech electronic circuits. Even though VLSI design is renowned for its smaller size, lower cost, lower power, high reliability and high functionality, the design process takes long time and produces high risk. So, to obtain the knowledge regarding the different contributions on VLSI design, about 52 papers on the design of VLSI using optimization are reviewed here. Accordingly, VLSI design optimization is analyzed through different bio-inspired algorithms and the performance measures of different VLSI experimentations are compared. Further, various improvements on Self-Adaptive Particle Swarm Optimization (SA-PSO) and VLSI design optimization, without the adoption of bio-inspired algorithms, are examined. Additionally, the floor planning problem of VLSI is considered and reviewed. Eventually, this paper provides the diverse research gaps and challenges in VLSI design, which may be helpful for the authors and the philosophers to contribute for further research. <s> BIB005 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> This paper proposed a novel hybrid optimization algorithm, particle swarm optimization-artificial bee colony (PSO-ABC), based on the PSO and ABC algorithms. The ABC algorithm can offset defects in the PSO algorithm that easily fall into a local optimization; combining the algorithms can improve the optimization ability of the PSO algorithm to a certain extent. Therefore, this paper applied the PSO-ABC hybrid algorithm and the finite-element method to systematically optimize the mechanical performance of the disc rotor of a bike and verified the numerical computation model via the wireless sensor network technology. The experimental test was completed with wireless sensor network technologies. To verify the optimized effects of the proposed PSO-ABC hybrid algorithm after parameter selection, the algorithm was compared with the traditional PSO and ABC models. The PSO, ABC, and PSO-ABC models adopted the same population to conduct a multi-objective optimization for vibration accelerations of the disc rotor. Comparing the results from these models proved that the proposed PSO-ABC method is superior for the optimization of vibration characteristics of the disc rotors. <s> BIB006 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> A rotational d–q current control scheme is prepared with the particle swarm optimization-PI controller, which drives an induction motor through an ultra-sparse Z -source matrix converter. To minimize the total size of the system, the lowest feasible values of Z -source elements are calculated by considering both timing and circuit aspects. A meta-heuristic method is integrated with the control system in order to find the optimum coefficients values in a single multimodal problem. Henceforth, the effect of all coefficients in minimizing the THD and balancing the stator current are considered simultaneously. By changing the reference point of magnitude or frequency, the modulation index can be automatically adjusted and respond to changes without heavy computational cost. The focus of this research is on having a reliable and lightweight system with no extensive computing time demand. The proposed scheme is validated by the promising simulation and experimental results. <s> BIB007 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> Shunt active power filter (SAPF) is widely used for compensating harmonic current produced by nonlinear loads. As one of the critical technologies, the current control strategy has an important influence on the compensation precision and dynamic response performance. In this paper, the essential of the current-limiting demands for the comprehensive protection of SAPF are revealed, namely the limiting control objects: first, rms of the compensation current (mainly for the overheat protection of IGBTs and inductors), second, the instantaneous wave of compensating current (mainly for the accurate current control and IGBT I cnom specification), and third, the instantaneous wave of PWM-VSC modulation voltage (for the need of liner close-loop control). To avoid the over-current fault and over-modulation fault of SAPF, this paper proposes an improved current-limiting scheme based on particle swarm optimization (PSO) to achieve the two optimization targets: the minimization THD for the grid-side current, and the maximization utilization ratio for the capacity of SAPF. The main advantage lies on the optimum limiting ratios of each harmonic order calculated in real time, respectively, to achieve the flexible and liner limiting control. In addition, taking the control structure consisting of selective harmonic detection under the multiple rotating reference frame and the single PI current loop, for example, this paper gives the method for steady-state error correction qualitatively and quantitatively, which employs the method based on the frequency response characteristics analysis. Finally, simulation and experimental results verify the effectiveness of the proposed strategy. <s> BIB008 </s> A Survey of Swarm Intelligence Techniques in VLSI Routing Problems <s>  <s> Abstract Vehicle routing problem (VRP) is one of the widely researched areas in transportation science, mainly due to the potential cost savings and service improvement opportunities which brings to organizations involved in physical distribution of goods. In this paper, we develop a multi-depot green vehicle routing problem (MDGVRP) by maximizing revenue and minimizing costs, time and emission, and then, apply an improved ant colony optimization (IACO) algorithm that aims to efficiently solve the problem. The IACO model developed in this research uses an innovative approach in updating the pheromone that results in better solutions. The results achieved through the IACO demonstrate satisfying performance, which have higher solution quality when compared to the conventional ACO. The IACO algorithm used in this paper demonstrated a good level of responsiveness and simplicity when solving MDGVRP with multiple objectives. <s> BIB009
Very Large Scale Integration (VLSI) is a process of forming an Integrated Circuit (IC) by incorporating thousands of transistors into a single chip BIB005 . As integration continues to increase, more and more features, even a complete system can be integrated into a single chip. As the pillar of information industry, the design and manufacturing of VLSI are playing an increasingly important role in driving economic development, deepening industrial structure and lifestyle changes. Physical design is the most time-consuming step in the design process of IC, and it is also one of the most important and active research field in VLSI computer-aided design technology. Due to its complexity, the whole process of physical design is often divided into partition, floorplanning, placement and routing. Routing plays a key role in VLSI physical design as it determines the specific shape and layout of interconnect, impacting performance, power and manufacturability, which is traditionally divided into the two steps of global and detailed routing. Global routing needs to connect all nets with all capacity constraints satisfied. While detailed routing takes a global routing solution with a small number of capacity violations (overflows), or none at all. And under the premise of ensuring spacing constraints and more sophisticated design rules, detailed routing completes the assignment of wires within the routing area. With the rapid development of IC, these characteristics are presented: the feature size is getting smaller and smaller, the chip area is getting larger and larger, the power supply voltage is getting lower and lower, and the number of routing metal layers is also increasing. Traditional routing algorithms, which operate in isolated layout regions-channels or switch-boxes, are usually assumed to be routed on the premise of a small number of metal layers, making it difficult to accommodate more metal layers. Gradually, overthe-cell routing with six or multi-layer routing lead to the adoption of similar graph-theoretical techniques in global and detailed routing, perhaps with different layouts, resource and delay models BIB001 . The routing algorithms require a better balance between wirelength minimization and congestion. In general, congestion is optimized by considering constraints such as obstacles, number of vias, and capacitance. However, the continuous reduction of process size and the increase of integration complexity make traditional routing algorithms unable to perform such multi-objective tasks well, and the design of routing algorithms faces new challenges. Swarm Intelligence (SI) is an important category of optimization technique, which is inspired from simple behaviors and self-organizing interaction among agents like ant colonies foraging, bird flocking, animal herding, bacterial growth, honey bees, fish schooling, and so on BIB003 . Each SI algorithm has its own unique advantages. The specific behaviors of these animals in solving problems have different help for searching optimal solutions, so the performance of each SI algorithm is different for different problems. But these SI algorithms have one thing in common, that is, each of them has several agents working simultaneously. And experience learning or information sharing or competition among individuals can enable swarm to grow rapidly, improving search efficiency and precision. Therefore, many researchers have started applying various SI algorithms with great promise because of their high computational efficiency, reliability, scalability, self-organizing, longevity and low-cost BIB002 . In recent years, SI techniques have been widely used on many practical real-world problems in the fields of scheduling BIB004 , production BIB006 , facility control BIB007 , BIB008 , transportation BIB009 and so on. The survey has the following four main objectives. First, we give an introduction about key concepts in VLSI routing, such as Minimum Spanning Tree (MST), Steiner tree and related routing issues including global and detailed routing. Second, the applications of some SI techniques in routing problems are listed to provide an overview of the current state of this hot field. Thirdly, we investigate and research some advanced processes, and give a discussion about the construction of routing models and evaluation models that are suitable for such processes. The final important goal is to identify future trends and research directions to better guide subsequent research efforts. This study discussed the contributions which were published in the relevant journals, conference proceedings and theses. The rest of the paper is organized as follows. The core definitions and related concepts of SI techniques and VLSI routing issues are respectively presented in Sections II and III, so that they are easily linked to the rest of the research in this paper. Then, Section IV focuses on the investigated routing problems using the five SI algorithms to present a current state of the art. Section V provides a discussion of related issues, including multi-layer routing based on X-architecture, global routing in a Multiple Dynamic Supply Voltage (MDSV) chip design environment, and routing problems under the via-pillar process. Section VI clarifies the future trends and opportunities under each type of problems, while Section VII is to make a conclusion for this paper. 