基于流水线计算的3D NoC测试规划研究

为了提高三维片上网络(3D NoC)资源内核的测试效率,提出一种在功耗约束条件下多播流水线并行测试同构核与单播测试异构核相结合的方法对IP核进行测试。为了减少测试数据因资源冲突而进行等待的时间,设计一种改进XYZ路由算法,并采用改进人工蜂群(ABC)算法求解最佳测试规划方案。以国际标准电路测试集ITC'02作为实验对象,结果表明,测试时间最大优化率达到15.45%,与其他测试规划方法相比该文方法能有效地提高并行测试效率。

Pattern recognition in multi-synaptic photonic spiking neural networks based on a DFB-SA chip

Spiking neural networks(SNNs)utilize brain-like spatiotemporal spike encoding for simulating brain functions.Photonic SNN offers an ultrahigh speed and power efficiency platform for implementing high-performance neuromorphic computing.Here,we proposed a multi-synaptic photonic SNN,combining the modified remote supervised learning with delayweight co-training to achieve pattern classification.The impact of multi-synaptic connections and the robustness of the network were investigated through numerical simulations.In addition,the collaborative computing of algorithm and hardware was demonstrated based on a fabricated integrated distributed feedback laser with a saturable absorber(DFB-SA),where 10 different noisy digital patterns were successfully classified.A functional photonic SNN that far exceeds the scale limit of hardware integration was achieved based on time-division multiplexing,demonstrating the capability of hardware-algorithm co-computation.

Groundwater Level Prediction Using Artificial Neural Networks: A Case Study in Tra Noc Industrial Zone, Can Tho City, Vietnam

The objective of this study is to predict groundwater levels (GWLs) under different impact factors using Artificial Neural Network (ANN) for a case study in Tra Noc Industrial Zone, Can Tho City, Vietnam. This can be achieved by evaluating the current state of groundwater resources (GWR) exploitation, use and dynamics;setting-up, calibrating and validating the ANN;and then predicting GWLs at different lead times. The results show that GWLs in the study area have been found to reduce rapidly from 2000 to 2015, especially in the Middle-upper Pleistocene (qp2-3) and upper Pleistocene (qp3) due to the over-withdrawals from the enterprises for production purposes. Concerning this problem, an Official Letter of the People’s Committee of Can Tho City was issued and taken into enforcement in 2012 resulting in the reduction of exploitation. The calibrated ANN structures have successfully demonstrated that the GWLs can be predicted considering different impact factors. The predicted results will help to raise awareness and to draw an attention of the local/central government for a clear GWR management policy for the Mekong delta, especially the industrial zones in the urban areas such as Can Tho city.

ARTIFICIAL NEURAL NETWORK MODELLING OF A WOOD CHIP REFINER

1 INTRODUCTIONWood chip refining is the most critical step in mechanical pulping.Commercical experi-ences have been gained for years.Modelling and control of chip refiners,however,pose a challenge mainly because of the stochastic nature of the process.Some attemptshave been made to employ factor analysis technique[1]in the modelling andsimulating of refiner operation[2,3].Strand[2]used common factors as links betweenintrinsic fibre properties and pulp quality.He believed that a qualitative concept onthe physical nature of these common factors could be arrived at,and thus would helpto understand what refining variables need to be controlled or adjusted in order to im-prove pulp quality.However,the linear model used in factor analysis is based on theassumption that the interactions among the system variables are linear,which,ofcourse,is not true in practice.

A PRIORITY-BASED POLLING SCHEDULING ALGORITHM FOR ARBITRATION POLICY IN NETWORK ON CHIP

A solution is imperatively expected to meet the efficient contention resolution schemes for managing simultaneous access requests to the communication resources on the Network on Chip (NoC). Based on the ideas of conflict-free transmission, priority-based service, and dynamic self-adaptation to loading, this paper presents a novel scheduling algorithm for Medium Access Control (MAC) in NoC with the researches of the communication structure features of 2D mesh. The algorithm gives priority to guarantee the Quality of Service (QoS) for local input port as well as dynamic adjustment of the performance of the other ports along with input load change. The theoretical model of this algorithm is established with Markov chain and probability generating function. Mathematical analysis is made on the mean queue length and the mean inquiry cyclic time of the system. Simulated experiments are conducted to test the accuracy of the model. It turns out that the findings from theoretical analysis correspond well with those from simulated experiments. Further more, the analytical findings of the system performance demonstrate that the algorithm enables effectively strengthen the fairness and stability of data transmissions in NoC.

Designs of 3D Mesh and Torus Optical Network-on-Chips:Topology,Optical Router and Routing Module

As a nanometer-level interconnection,the Optical Network-on-Chip(ONoC)was proposed since it was typically characterized by low latency,high bandwidth and power efficiency. Compared with a 2-Dimensional(2D)design,the 3D integration has the higher packing density and the shorter wire length. Therefore,the 3D ONoC will have the great potential in the future. In this paper,we first discuss the existing ONoC researches,and then design mesh and torus ONoCs from the perspectives of topology,router,and routing module,with the help of 3D integration. A simulation platform is established by using OPNET to compare the performance of 2D and 3D ONoCs in terms of average delay and packet loss rate. The performance comparison between 3D mesh and 3D torus ONoCs is also conducted. The simulation results demonstrate that 3D integration has the advantage of reducing average delay and packet loss rate,and 3D torus ONoC has the better performance compared with 3D mesh solution. Finally,we summarize some future challenges with possible solutions,including microcosmic routing inside optical routers and highly-efficient traffic grooming.

Design and simulation of a Torus topology for network on chip

Aiming at the applications of NOC （network on chip） technology in rising scale and complexity on chip systems, a Torus structure and corresponding route algorithm for NOC is proposed. This Torus structure improves traditional Torus topology and redefines the denotations of the routers. Through redefining the router denotations and changing the original router locations, the Torus structure for NOC application is reconstructed. On the basis of this structure, a dead-lock and live-lock free route algorithm is designed according to dimension increase. System C is used to implement this structure and the route algorithm is simulated. In the four different traffic patterns, average, hotspot 13%, hotspot 67% and transpose, the average delay and normalization throughput of this Torus structure are evaluated. Then, the performance of delay and throughput between this Torus and Mesh structure is compared. The results indicate that this Torus structure is more suitable for NOC applications.

New Latency Model for Dynamic Frequency Scaling on Network-on-Chip

Modulating both the clock frequency and supply voltage of the network-on-chip （NoC） during runtime can reduce the power consumption and heat flux, but will lead to the increase of the latency of NoC. It is necessary to find a tradeoff between power consumption and communication latency. So we propose an analytical latency model which can show us the relationship of them. The proposed model to analyze latency is based on the M/G/1 queuing model, which is suitable for dynamic frequency scaling. The experiment results show that the accuracy of this model is more than 90%.

MSONoC: a non-blocking optical interconnection network for inter cluster communication

Electric router is widely used for multi-core system to interconnect each other. However, with the increasing number of processor cores, the probability of communication conflict between processor cores increases, and the data delay increases dramatically. With the advent of optical router, the traditional electrical interconnection mode has changed to optical interconnection mode. In the packet switched optical interconnection network, the data communication mechanism consists of 3 processes: link establishment, data transmission and link termination, but the circuit-switched data transmission method greatly limits the utilization of resources. The number of micro-ring resonators in the on-chip large-scale optical interconnect network is an important parameter affecting the insertion loss. The proposed λ-route, GWOR, Crossbar structure has a large overall network insertion loss due to the use of many micro-ring resonators. How to use the least micro-ring resonator to realize non-blocking communication between multiple cores has been a research hotspot. In order to improve bandwidth and reduce access latency, an optical interconnection structure called multilevel switching optical network on chip(MSONoC) is proposed in this paper. The broadband micro-ring resonators(BMRs) are employed to reduce the number of micro-ring resonators(MRs) in the network, and the structure can provide the service of non-blocking point to point communication with the wavelength division multiplexing(WDM) technology. The results show that compared to λ-route, GWOR, Crossbar and the new topology structure, the number of micro-ring resonators of MSONoC are reduced by 95.5%, 95.5%, 87.5%, and 60% respectively. The insertion loss of the minimum link of new topology, mesh and MSONoC structure is 0.73 dB, 0.725 dB and 0.38 dB.

Designing cost-effective network-on-chip by dual-channel access mechanism

A dual-channel access mechanism to overcome the drawback of traditional single-channel access mechanism for network-on-chip （NoC） is proposed. In traditional single-channel access mechanism, every Internet protocol （IP） has only one chan- nel to access the on-chip network. When the network is relatively idle, the injection rate is too small to make good use of the network resource. When the network is relatively busy, the ejection rate is so small that the packets in the network cannot leave immediately, and thus the probability of congestion is increased. In the dual-channel access mechanism, the injection rate of IP and the ejection rate of the network are increased by using two optional channels in network interface （NI） and local port of routers. Therefore, the communication performance is improved. Experimental results show that compared with traditional single-channel access mechanism, the proposed scheme greatly increases the throughput and cuts down the average latency with reasonable area increase.

Cluster Based Hierarchical Routing Algorithm for Network on Chip

This paper presents a new logical mechanism called as Cluster Based Hierarchical Routing (CBHR) to improve the efficiency of NoC. This algorithm comprises the following steps: 1) the network is segmented logically into clusters with same size or different sizes;2) algorithms are assigned for internal and global routing;3) routers working functions are modified logically to support local and global communication. The experiments have conducted for CBHR algorithm for two dimensional mesh and torus architectures. The performance of this mechanism is analyzed and compared with other deterministic and adaptive routing algorithms in terms of energy, throughput with different packet injection ratios.

Design of an unbuffered switch for network on-chip

In the complex multicore chip system,network on-chip(NoC)is viewed as a kind of system interconnection that can substitute the traditional interconnect networks,which will improve the system performance and communication efficiency.With regard to the complex and large scale NoC,simple and efficient routing nodes are the critical factors to achieve low-cost and low-congestion communication performance.This paper proposes an unbuffered switch architecture and makes detailed analysis of the mechanism of buffer in the switch architecture.According to the simulation results,the S-mesh using the unbuffered switch architecture is better in terms of the optimal performance in message latency than some typical NoC architectures,such as 2D-mesh,Fat-tree,Butterfly,Octagon and so on.The synthesis results of design compiler indicate that the unbuffered switch has obvious advantages of achieving cost and operating speed for the chips.

Reliability-aware mapping and links voltage assignment for energy-efficient networks-on-chip

As feature sizes shrink,low energy consumption,high reliability and high performance become key objectives of network-on-chip(NoC) design.In this paper,an integrated approach is presented to map IP cores onto NoC architecture and assign voltage levels for each link,such that the communication energy is minimized under constraints of bandwidth and reliability.The design space is explored using tabu search.In order to select optimal voltage level for the links,an energy-efficiency driven heuristic algorithm is proposed to perform energy/reliability trade-off by exploiting communication slack.Experimental results show that the ordinary energy optimization techniques ignoring the influence of voltage on fault rates could lead to drastically decreased communication reliability of NoCs,and the proposed approach can produce reliable and energy-efficient implementations.

分层立方体网络在NoC线性阵列中的最优嵌入

随着大数据时代的到来,大规模计算的需求使得人们对芯片性能的要求日益提高,片上网络(Network-on-Chip,NoC)作为芯片内部以网络通信为中心的互连结构,在通信的各个方面实现了良好的平衡。NoC组件的物理布局及互连方式对芯片的总体性能(如信号延迟、电路成本等)有着很大的影响,因芯片面积有限,最小化连接组件的导线总长度,即最小化线长,被作为芯片设计的重点。分层立方体网络(Hierarchical Cubic Network,HCN)具有通信延迟低、可靠性和扩展性高等优点,而线性阵列是NoC常用的拓扑结构之一,将分层立方体网络移植到线性阵列上,就可以在线性阵列上模拟分层立方体网络的结构和算法。图嵌入是实现网络移植的关键技术。在图嵌入中,最小化导线总长度的目标可以通过求解具有最小线长的最优嵌入来达成。文中主要研究了分层立方体网络在线性阵列中的最优嵌入问题。首先,通过研究分层立方体网络的最优集,提出了分层立方体网络在线性阵列中的一种嵌入方案hel,并证明在嵌入方案hel下的线长相比其他嵌入方案下的线长是最小的,即hel为最优嵌入;然后给出了嵌入hel下线长的精确值以及一个时间复杂度为O(N)的嵌入算法,其中N为n维分层立方体网络的顶点数且N=22n;其次,还给出了分层立方体网络在NoC上的线性物理布局算法;最后,通过对比实验评估了嵌入hel的性能。

An Evaluation of Routing Algorithms in Traffic Engineering and Quality of Service Provision of Network on Chips

Nowadays the number of cores that are integrated into NoC (Network on Chip) systems is steadily increasing, and real application traffic, running in such multi-core environments requires more and more bandwidth. In that sense, NoC architectures should be properly designed so as to provide efficient traffic engineering, as well as QoS support. Routing algorithm choice in conjunction with other parameters, such as network size and topology, traffic features (time and spatial distribution), as well as packet injection rate, packet size, and buffering capability, are all equivalently critical for designing a robust NoC architecture, on the grounds of traffic engineering and QoS provision. In this paper, a thorough numerical investigation is achieved by taking into consideration the criticality of selecting the proper routing algorithm, in conjunction with all the other aforementioned parameters. This is done via implementation of four routing evaluation traffic scenarios varying each parameter either individually, or as a set, thus exhausting all possible combinations, and making compact decisions on proper routing algorithm selection in NoC architectures. It has been shown that the simplicity of a deterministic routing algorithm such as XY, seems to be a reasonable choice, not only for random traffic patterns but also for non-uniform distributed traffic patterns, in terms of delay and throughput for 2D mesh NoC systems.

一种基于混合加固的容软错误NoC路由器

片上网络已成为众核处理器互连网络的标准范式。然而,随着电源电压的逐渐降低,工艺尺寸的逐渐缩减,片上网络中出现软错误的概率逐渐增大。错误纠正码常用于容软错误的片上网络路由器设计中。然而,传统的路由器设计往往只采用汉明码进行纠错,这样的设计结构简单却存在纠错能力不足的问题。提出了一种基于错误纠正码的混合加固容软错误路由器设计方案,该设计方案的核心思想是,依据信息位重要性的不同,采取不同的容错码设计,实现了路由器可靠性与容错开销之间的权衡。实验结果显示,该设计方案相较于基准设计在合成流量和PARSEC benchmark下实现了系统可靠性的提升;同时,硬件综合结果也表明该设计方案可以缩短4%的关键路径延迟。

Twist-Routing Algorithm for Faulty Network-on-Chips

This paper introduces Twist-routing, a new routing algorithm for faulty on-chip networks, which improves Maze-routing, a face-routing based algorithm which uses deflections in routing, and archives full fault coverage and fast packet delivery. To build Twist-routing algorithm, we use bounding circles, which borrows the idea from GOAFR+ routing algorithm for ad-hoc wireless networks. Unlike Maze-routing, whose path length is unbounded even when the optimal path length is fixed, in Twist-routing, the path length is bounded by the cube of the optimal path length. Our evaluations show that Twist-routing algorithm delivers packets up to 35% faster than Maze-routing with a uniform traffic and Erdos-Rényi failure model, when the failure rate and the injection rate vary.

Design of Efficient Router with Low Power and Low Latency for Network on Chip

The NoC consists of processing element (PE), network interface (NI) and router. This paper proposes a hybrid scheme for Netwok of Chip (NoC), which aims at obtaining low latency and low power consumption by concerning wired and wireless links between routers. The main objective of this paper is to reduce the latency and power consumption of the network on chip architecture using wireless link between routers. In this paper, the power consumption is reduced by designing a low power router and latency is reduced by implementing a on-chip wireless communication as express links for transferring data from one subnet routers to another subnet routers. The average packet latency and normalized power consumption of proposed hybrid NoC router are analyzed for synthetic traffic loads as shuffle traffic, bitcomp traffic, transpose traffic and bitrev traffic. The proposed hybrid NoC router reduces the normalized power over the wired NoC by 12.18% in consumer traffic, 12.80% in AutoIndust traffic and 12.5% in MPEG2 traffic. The performance is also analyzed with real time traffic environments using Network simulator 2 tool.

Application Aware Topology Generation for Surface Wave Networks-on-Chip

The networks-on-chip （NoC） communication has an increasingly larger impact on the system power consumption and performance. Emerging technologies, like surface wave, are believed to have lower transmission latency and power consumption over the conventional wireless NoC. Therefore, this paper studies how to optimize the network performance and power consumption by giving the packet-switching fabric and traffic pattern of each application. Compared with the conventional method of wire-linked, which adds wireless transceivers by using the genetic algorithm （GA）, the proposed maximal declining sorting algorithm （MDSA） can effectively reduce time consumption by as much as 20.4% to 35.6%. We also evaluate the power consumption and configuration time to prove the effective of the proposed algorithm.