Test-Delivery Optimization in Manycore SOCs

We present two test-data delivery optimization algorithms for system-on-chip (SOC) designs with hundreds of cores, where a network-on-chip (NOC) is used as the interconnection fabric. We first present an e ective algorithm based on a subsetsum formulation to solve the test-delivery problem in NOCs with arbitrary topology that use dedicated routing. We further propose an algorithm for the important class of NOCs with grid topology and XY routing. The proposed algorithm is the first to co-optimize the number of access points, access-point locations, pin distribution to access points, and assignment of cores to access points for optimal test resource utilization of such NOCs. Testtime minimization is modeled as an NOC partitioning problem and solved with dynamic programming in polynomial time. Both the proposed methods yield high-quality results and are scalable to large SOCs with many cores. We present results on synthetic grid topology NOC-based SOCs constructed using cores from the ITC’02 benchmark, and demonstrate the scalability of our approach for two SOCs of the future, one with nearly 1,000 cores and the other with 1,600 cores. Test scheduling under power constraints is also incorporated in the optimization framework

Exploiting partial reconfiguration through PCIe for a microphone array network emulator

The current Microelectromechanical Systems (MEMS) technology enables the deployment of relatively low-cost wireless sensor networks composed of MEMS microphone arrays for accurate sound source localization. However, the evaluation and the selection of the most accurate and power-efficient network’s topology are not trivial when considering dynamic MEMS microphone arrays. Although software simulators are usually considered, they consist of high-computational intensive tasks, which require hours to days to be completed. In this paper, we present an FPGA-based platform to emulate a network of microphone arrays. Our platform provides a controlled simulated acoustic environment, able to evaluate the impact of different network configurations such as the number of microphones per array, the network’s topology, or the used detection method. Data fusion techniques, combining the data collected by each node, are used in this platform. The platform is designed to exploit the FPGA’s partial reconfiguration feature to increase the flexibility of the network emulator as well as to increase performance thanks to the use of the PCI-express high-bandwidth interface. On the one hand, the network emulator presents a higher flexibility by partially reconfiguring the nodes’ architecture in runtime. On the other hand, a set of strategies and heuristics to properly use partial reconfiguration allows the acceleration of the emulation by exploiting the execution parallelism. Several experiments are presented to demonstrate some of the capabilities of our platform and the benefits of using partial reconfiguration

임베디드 시스템에서 여러 컨볼루션 뉴럴 네트워크를 위한 하드웨어를 고려하는 소프트웨어 최적화 기법

학위논문 (박사) -- 서울대학교 대학원 : 공과대학 컴퓨터공학부, 2021. 2. 하순회.임베디드 기기는 대개 계산량, 메모리 크기, 에너지 소모량 등의 제약 사항이 있기 때문에, 딥 러닝 응용을 임베디드 기기에서 수행하는 것은 쉽지 않다. 딥 러닝 응용의 계산량 증가를 해결하기 위해서 에너지 효율적인 모바일 GPU, 디지털 신호 처리 프로세서을 사용하거나, 또는 새로운 뉴럴 프로세서 칩을 만드려는 하드웨어 영역의 최적화 방법이 있다. 반면에 딥 러닝 응용 영역에서는 새로운 딥 러닝 응용을 만들거나, 딥 러닝의 통계적인 특성을 이용한 근사 계산 방법을 이용하여 최적화 방법을 제안하고 있다. 그리고 또 다른 최적화 방법으로는 먼저 하드웨어 플랫폼의 성능 병목 부분을 찾고, 일을 동등하게 여러 계산 자원에 분배하여 최적화하는 하드웨어를 고려한 최적화 방법이 있다. 본 논문에서는 하드웨어를 고려한 소프트웨어 최적화 방법들을 고안하였다. 먼저, LPIRC 대회에 참가한 경험을 바탕으로 임베디드 딥 러닝 시스템을 최적화하는 체계적인 방법론을 고안하고, 그 방법론에 따른 C-GOOD이라는 딥 러닝 프레임워크를 구현하였다. C-GOOD은 하드웨어 플랫폼에 독립적으로 작동하기 위해 대부분의 임베디드 기기에서 컴파일, 수행이 가능한 C 코드를 생성한다. 또한 여러 가지 딥 러닝 응용 영역의 최적화 방법을 적용할 수 있는 옵션과 시스템 성능을 측정할 수 있는 기능을 제공하였다. 이 방법론을 Jetson TX2, Odroid XU4, SRP 등의 서로 다른 3개의 기기에 적용해 봄으로써, 고안된 방법론이 하드웨어 플랫폼에 독립적이며 C-GOOD을 통해 쉽게 여러 딥 러닝 응용 최적화 방법을 적용할 수 있음을 확인하였다. 최근 임베디드 기기에 이종 프로세서들이 많이 탑재되고 있고, 동시에 자율 주행 자동차와 스마트폰 등의 하나의 임베디드 기기에서 여러 개의 딥 러닝 응용을 동시에 수행하는 것이 필요해지고 있다. 본 논문에서는 여러 딥 러닝 응용을 이종 프로세서들을 탑재한 임베디드 기기에 스케줄하는 방법을 고안하고, 스케줄링 프레임워크를 구현하였다. 이 방법론은 실제 기기에서의 프로파일링부터 스케줄 결과를 실제 기기에서 확인하는 과정까지 포함하며, 실제 기기에서 발생하는 이슈들인 DVFS, CPU Hot-plug 등을 고려하였다. 이종 프로세서로의 스케줄링 기법으로는 많이 사용되는 메타 휴리스틱 알고리즘은 유전 알고리즘을 사용하였다. 특히, 서로 다른 주기와 상대 오프셋을 가지고 있는 여러 응용을 동시에 스케줄하기 위해서 모든 태스크들의 스케줄 가능성을 고려하여 스케줄하였다. 스케줄 결과를 검증하기 위해서, ACL의 코어 라이브러리를 이용하여 딥 러닝 추론 응용을 구현하였으며, 스케줄 결과와 같이 각 레이어들을 실제 하드웨어의 서로 다른 프로세서 매핑하도록 구현하였다. 갤럭시 S9 스마트폰과 Hikey 970 보드에서 서로 다른 두개의 딥 러닝 네트워크를 수행하고, 스케줄 결과와 비교하여 방법론을 검증할 수 있었다. 이전 최적화 방법들이 딥 러닝 응용의 계산량과 프로세서들에 집중하였는데, 딥 러닝 가속기 또는 NPU의 성능 병목이 생기는 원인은 오프 칩 메모리와 온 칩 사이의 통신이다. 더욱이 오프 칩 메모리 DRAM 접근은 NPU의 전력소모의 많은 부분을 차지한다고 알려져있다. 따라서 이와 같은 오프 칩 DRAM 접근으로 인한 NPU의 성능과 에너지 영향을 줄이고자 본 논문에서는 온 칩 메모리 뱅크를 관리하는 컴파일러 기법을 고안하였다. 온 칩 메모리를 여러 개의 뱅크로 구성하고 연산 도중에 인풋 데이터를 미리 로드함으로써 연산 지연 시간을 줄일 수 있다는 점과 레이어의 아웃풋을 온 칩 메모리에서 재사용하여 오프 칩 메모리 접근을 줄일 수 있다는 점을 이용하여 서로 다른 두 가지의 목적 함수를 가진 두 가지 기법을 고안하였다. 목적 함수는 각각 오프 칩 메모리 접근을 최소화하는 것과 오프 칩 메모리 접근으로 인한 프로세서들의 처리 지연시간을 줄이는 것이다. 서로 다른 5개의 딥 러닝 네트워크를 사이클 레벨 NPU 시뮬레이터에서 수행하여 두 목적 함수에 따른 절충 (Trade-off) 관계 를 확인하였다. 또한 온 칩 메모리 뱅크 관리 기법을 레이어 간 피처 데이터를 최대한 재사용하는 레이어 융합 방법으로 확장하였다. 기존의 순수한 레이어 융합 방법의 경우에는 중복 계산하는 오버헤드와 추가적인 필터 웨이트 로드가 생긴다. 따라서 본 논문에서는 기존의 레이어 별로 처리하는 방법과 순수한 레이어 융합 방법 사이의 하이브리드 레이어 융합 방법을 고안하였다. 두 온 칩 메모리 뱅크 관리 기법을 기반으로 하이브리드 레이어 융합 방법이 기존의 레이어 별 처리하는 기법과 순수한 레이어 융합 방법보다 좋은 성능을 보임을 확인할 수 있었다.Executing deep learning algorithms on mobile embedded devices is challenging because embedded devices usually have tight constraints on the computational power, memory size, and energy consumption, while the resource requirements of deep learning algorithms achieving high accuracy continue to increase. To cope with increasing computation complexity, it is common to use an energy-efficient accelerator, such as a mobile GPU or digital signal processor (DSP) array, or to develop a customized neural processor chip called neural processing unit (NPU). In the application domain, many optimization techniques have been proposed to change the application algorithm in order to reduce the computational amount and memory usage by developing new deep learning networks or software optimization techniques that take advantage of the statistical nature of deep learning algorithms. Another approach is hardware-ware software optimization, which finds the performance bottleneck first and then distributes the workload evenly by scheduling the workloads. This dissertation covers hardware-aware software optimization, which is based on a hardware processor or platform. First, we devise a systematic optimization methodology through the experience of participating in the Low Power Image Recognition Challenge (LPIRC) and build a deep learning framework called C-GOOD (C-code Generation Framework for Optimized On-device Deep Learning) based on the devised methodology. For hardware independence, C-GOOD generates a C code that can be compiled for and run on any embedded device. Also, C-GOOD is facilitated with various options for application domain optimization that can be performed according to the devised methodology. By applying the devised methodology to three hardware platforms, NVIDIA Jetson TX2, Odroid XU4, and the Samsung Reconfigurable Processor (SRP), we demonstrate that the devised methodology is independent of the hardware platforms and application domain optimizations can be performed easily with C-GOOD. Recently, embedded devices are equipped with heterogeneous processing elements (PEs), and the need for running multiple deep learning applications concurrently in the embedded systems such as self-driving cars and smartphones is increasing at the same time. In those systems, we devise an end-to-end methodology to schedule deep learning applications onto heterogeneous PEs and implement a scheduling framework according to the methodology. It covers from profiling on real embedded devices to verifying the schedule results on the devices. In this methodology, we use a genetic algorithm (GA)-based scheduling technique for scheduling deep learning applications onto heterogeneous PEs and consider several practical issues in the profile step. Furthermore, we schedule multiple applications with different throughput constraints considering the schedulability of mapped tasks on each processor. After implementing a deep learning inference engine that can utilize heterogeneous PEs using a low-level library of the ARM compute library (ACL), we verify the devised methodology by running two widely used convolution neural networks (CNNs) on a Galaxy S9 smartphones and a Hikey970 board. While the previous optimization methods focus on the computation and processing elements, the performance bottleneck of deep learning accelerators is the communication between off-chip and on-chip memory. Moreover, the off-chip DRAM access volume has a significant effect on the energy consumption of an NPU. To reduce the impact of off-chip DRAM access on the performance and energy of an NPU, we devise compiler techniques for an NPU to manage multi-bank on-chip memory with two different objectives: one is to minimize the off-chip memory access volume, and the other is to minimize the processing delay caused by unhidden DRAM accesses. The main idea is that by organizing on-chip memory into multiple banks, we may hide the off-chip DRAM access delay by prefetching data into unused banks during computation and reduce the off-chip DRAM access volume by storing the output feature map data of each layer to on-chip memory. By running CNN benchmarks on a cycle-level NPU simulator, we demonstrate the trade-off relation between two objectives. The devised multi-bank on-chip memory management (MOMM) techniques are extended to consider layer fusion that aims to reuse feature maps between layers maximally. Since the pure layer fusion technique incurs extra computation overhead and increases DRAM access for filter weights, a hybrid fusion technique is presented between a per-layer processing technique and the pure layer fusion techniques, based on the devised MOMM techniques with two different objectives. Experiment results confirm the superiority of the hybrid fusion technique to the per-layer processing technique and the pure layer fusion technique.Abstract Contents List of Figures List of Tables List of Algorithms Chapter 1 Introduction 1 1.1 Motivation 1 1.2 Contribution 7 1.3 Dissertation Organization 8 Chapter 2 Background 9 2.1 Target Hardware 9 2.1.1 Commodity Hardware Platform 9 2.1.2 Application-specific Hardware Accelerator 10 2.2 Convolutional Neural Network 11 2.2.1 Convolution 11 2.2.2 Optimization Methods for Convolutional Neural Network 11 Chapter 3 Optimization for a Commodity Hardware Platform 14 3.1 Joint Optimization Method of Multiple Objectives 15 3.1.1 Hardware Platform 16 3.1.2 Deep Neural Network and Software Framework 17 3.1.3 Software Optimization Techniques 19 3.2 C-code Generation Framework for Optimized On-device Deep Learning 29 3.2.1 C-GOOD Framework 29 3.2.2 Experiments 36 3.3 Scheduling Deep Learning Applications Onto Heterogeneous Processors 44 3.3.1 Search Space Size 45 3.3.2 Hardware Platform and System Model 45 3.3.3 Proposed Scheduling Framework and Profiling 48 3.3.4 Scheduling a Single Deep Learning Application 53 3.3.5 Scheduling Multiple Deep Learning Applications 61 3.3.6 Verification with Real Hardware Platforms 65 3.4 Related Work 69 3.4.1 Deep Learning Framework 69 3.4.2 Deep Learning Compiler 70 3.4.3 Scheduling Deep Learning Application 70 3.4.4 Scheduling Multiple Applications on Heterogeneous Processors 72 Chapter 4 Optimization for an Application-specific Hardware Accelerator 75 4.1 Multi-Bank On-chip Memory Management Problem 75 4.1.1 Main Idea 75 4.1.2 Assumed Dataflow 76 4.1.3 Multi-bank On-chip Memory Management Problem 79 4.2 Proposed Multi-bank On-chip Memory Management Techniques 83 4.2.1 DRAM-first Storing Policy 84 4.2.2 DRAM Access Minimization Policy (MIN policy) 85 4.2.3 DRAM Access Hiding Policy (HIDE policy) 89 4.2.4 Multiple Path Consideration 91 4.3 Layer Fusion Technique 92 4.3.1 Layer Fusion Technique 92 4.3.2 Hybrid Fusion Technique 94 4.4 Experiments 96 4.4.1 Setup 96 4.4.2 Performance Comparison of MOMM Techniques 98 4.4.3 Multiple Path 100 4.4.4 Design Space Exploration of NPU Architecture 101 4.4.5 Hybrid Fusion Technique 104 4.5 Related Work 106 Chapter 5 Conclusion 108 Bibliography 111 Appendix 120 A Proposed Multi-bank On-chip Memory Management Algorithm 120 A.1 Multi-bank On-chip Memory (MOM) Manager 120 A.2 MIN policy 122 A.3 HIDE policy 124 요 약 126Docto

Power constrained test scheduling in system-on-chip design

With the development of VLSI technologies, especially with the coming of deep sub-micron semiconductor process technologies, power dissipation becomes a critical factor that cannot be ignored either in normal operation or in test mode of digital systems. Test scheduling has to take into consideration of both test concurrency and power dissipation constraints. For satisfying high fault coverage goals with minimum test application time under certain power dissipation constraints, the testing of all components on the system should be performed in parallel as much as possible. The main objective of this thesis is to address the test-scheduling problem faced by SOC designers at system level. Through the analysis of several existing scheduling approaches, we enlarge the basis that current approaches based on to minimize test application time and propose an efficient and integrated technique for the test scheduling of SOCs under power-constraint. The proposed merging approach is based on a tree growing technique and can be used to overlay the block-test sessions in order to reduce further test application time. A number of experiments, based on academic benchmarks and industrial designs, have been carried out to demonstrate the usefulness and efficiency of the proposed approaches

Exploring Processor and Memory Architectures for Multimedia

Multimedia has become one of the cornerstones of our 21st century society and, when combined with mobility, has enabled a tremendous evolution of our society. However, joining these two concepts introduces many technical challenges. These range from having sufficient performance for handling multimedia content to having the battery stamina for acceptable mobile usage. When taking a projection of where we are heading, we see these issues becoming ever more challenging by increased mobility as well as advancements in multimedia content, such as introduction of stereoscopic 3D and augmented reality. The increased performance needs for handling multimedia come not only from an ongoing step-up in resolution going from QVGA (320x240) to Full HD (1920x1080) a 27x increase in less than half a decade. On top of this, there is also codec evolution (MPEG-2 to H.264 AVC) that adds to the computational load increase. To meet these performance challenges there has been processing and memory architecture advances (SIMD, out-of-order superscalarity, multicore processing and heterogeneous multilevel memories) in the mobile domain, in conjunction with ever increasing operating frequencies (200MHz to 2GHz) and on-chip memory sizes (128KB to 2-3MB). At the same time there is an increase in requirements for mobility, placing higher demands on battery-powered systems despite the steady increase in battery capacity (500 to 2000mAh). This leaves negative net result in-terms of battery capacity versus performance advances. In order to make optimal use of these architectural advances and to meet the power limitations in mobile systems, there is a need for taking an overall approach on how to best utilize these systems. The right trade-off between performance and power is crucial. On top of these constraints, the flexibility aspects of the system need to be addressed. All this makes it very important to reach the right architectural balance in the system. The first goal for this thesis is to examine multimedia applications and propose a flexible solution that can meet the architectural requirements in a mobile system. Secondly, propose an automated methodology of optimally mapping multimedia data and instructions to a heterogeneous multilevel memory subsystem. The proposed methodology uses constraint programming for solving a multidimensional optimization problem. Results from this work indicate that using today’s most advanced mobile processor technology together with a multi-level heterogeneous on-chip memory subsystem can meet the performance requirements for handling multimedia. By utilizing the automated optimal memory mapping method presented in this thesis lower total power consumption can be achieved, whilst performance for multimedia applications is improved, by employing enhanced memory management. This is achieved through reduced external accesses and better reuse of memory objects. This automatic method shows high accuracy, up to 90%, for predicting multimedia memory accesses for a given architecture

Cognition-Based Networks: A New Perspective on Network Optimization Using Learning and Distributed Intelligence

IEEE Access Volume 3, 2015, Article number 7217798, Pages 1512-1530 Open Access Cognition-based networks: A new perspective on network optimization using learning and distributed intelligence (Article) Zorzi, M.a , Zanella, A.a, Testolin, A.b, De Filippo De Grazia, M.b, Zorzi, M.bc a Department of Information Engineering, University of Padua, Padua, Italy b Department of General Psychology, University of Padua, Padua, Italy c IRCCS San Camillo Foundation, Venice-Lido, Italy View additional affiliations View references (107) Abstract In response to the new challenges in the design and operation of communication networks, and taking inspiration from how living beings deal with complexity and scalability, in this paper we introduce an innovative system concept called COgnition-BAsed NETworkS (COBANETS). The proposed approach develops around the systematic application of advanced machine learning techniques and, in particular, unsupervised deep learning and probabilistic generative models for system-wide learning, modeling, optimization, and data representation. Moreover, in COBANETS, we propose to combine this learning architecture with the emerging network virtualization paradigms, which make it possible to actuate automatic optimization and reconfiguration strategies at the system level, thus fully unleashing the potential of the learning approach. Compared with the past and current research efforts in this area, the technical approach outlined in this paper is deeply interdisciplinary and more comprehensive, calling for the synergic combination of expertise of computer scientists, communications and networking engineers, and cognitive scientists, with the ultimate aim of breaking new ground through a profound rethinking of how the modern understanding of cognition can be used in the management and optimization of telecommunication network