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- All Subjects: Computer Engineering
- Genre: Masters Thesis
- Creators: Seo, Jae-Sun
- Creators: Ren, Fengbo
Description
Graph theory is a critical component of computer science and software engineering, with algorithms concerning graph traversal and comprehension powering much of the largest problems in both industry and research. Engineers and researchers often have an accurate view of their target graph, however they struggle to implement a correct, and efficient, search over that graph.
To facilitate rapid, correct, efficient, and intuitive development of graph based solutions we propose a new programming language construct - the search statement. Given a supra-root node, a procedure which determines the children of a given parent node, and optional definitions of the fail-fast acceptance or rejection of a solution, the search statement can conduct a search over any graph or network. Structurally, this statement is modelled after the common switch statement and is put into a largely imperative/procedural context to allow for immediate and intuitive development by most programmers. The Go programming language has been used as a foundation and proof-of-concept of the search statement. A Go compiler is provided which implements this construct.
To facilitate rapid, correct, efficient, and intuitive development of graph based solutions we propose a new programming language construct - the search statement. Given a supra-root node, a procedure which determines the children of a given parent node, and optional definitions of the fail-fast acceptance or rejection of a solution, the search statement can conduct a search over any graph or network. Structurally, this statement is modelled after the common switch statement and is put into a largely imperative/procedural context to allow for immediate and intuitive development by most programmers. The Go programming language has been used as a foundation and proof-of-concept of the search statement. A Go compiler is provided which implements this construct.
ContributorsHenderson, Christopher (Author) / Bansal, Ajay (Thesis advisor) / Lindquist, Timothy (Committee member) / Acuna, Ruben (Committee member) / Arizona State University (Publisher)
Created2018
Description
Deep neural networks (DNN) have shown tremendous success in various cognitive tasks, such as image classification, speech recognition, etc. However, their usage on resource-constrained edge devices has been limited due to high computation and large memory requirement.
To overcome these challenges, recent works have extensively investigated model compression techniques such as element-wise sparsity, structured sparsity and quantization. While most of these works have applied these compression techniques in isolation, there have been very few studies on application of quantization and structured sparsity together on a DNN model.
This thesis co-optimizes structured sparsity and quantization constraints on DNN models during training. Specifically, it obtains optimal setting of 2-bit weight and 2-bit activation coupled with 4X structured compression by performing combined exploration of quantization and structured compression settings. The optimal DNN model achieves 50X weight memory reduction compared to floating-point uncompressed DNN. This memory saving is significant since applying only structured sparsity constraints achieves 2X memory savings and only quantization constraints achieves 16X memory savings. The algorithm has been validated on both high and low capacity DNNs and on wide-sparse and deep-sparse DNN models. Experiments demonstrated that deep-sparse DNN outperforms shallow-dense DNN with varying level of memory savings depending on DNN precision and sparsity levels. This work further proposed a Pareto-optimal approach to systematically extract optimal DNN models from a huge set of sparse and dense DNN models. The resulting 11 optimal designs were further evaluated by considering overall DNN memory which includes activation memory and weight memory. It was found that there is only a small change in the memory footprint of the optimal designs corresponding to the low sparsity DNNs. However, activation memory cannot be ignored for high sparsity DNNs.
To overcome these challenges, recent works have extensively investigated model compression techniques such as element-wise sparsity, structured sparsity and quantization. While most of these works have applied these compression techniques in isolation, there have been very few studies on application of quantization and structured sparsity together on a DNN model.
This thesis co-optimizes structured sparsity and quantization constraints on DNN models during training. Specifically, it obtains optimal setting of 2-bit weight and 2-bit activation coupled with 4X structured compression by performing combined exploration of quantization and structured compression settings. The optimal DNN model achieves 50X weight memory reduction compared to floating-point uncompressed DNN. This memory saving is significant since applying only structured sparsity constraints achieves 2X memory savings and only quantization constraints achieves 16X memory savings. The algorithm has been validated on both high and low capacity DNNs and on wide-sparse and deep-sparse DNN models. Experiments demonstrated that deep-sparse DNN outperforms shallow-dense DNN with varying level of memory savings depending on DNN precision and sparsity levels. This work further proposed a Pareto-optimal approach to systematically extract optimal DNN models from a huge set of sparse and dense DNN models. The resulting 11 optimal designs were further evaluated by considering overall DNN memory which includes activation memory and weight memory. It was found that there is only a small change in the memory footprint of the optimal designs corresponding to the low sparsity DNNs. However, activation memory cannot be ignored for high sparsity DNNs.
ContributorsSrivastava, Gaurav (Author) / Seo, Jae-Sun (Thesis advisor) / Chakrabarti, Chaitali (Committee member) / Berisha, Visar (Committee member) / Arizona State University (Publisher)
Created2018
Description
Hardware implementation of deep neural networks is earning significant importance nowadays. Deep neural networks are mathematical models that use learning algorithms inspired by the brain. Numerous deep learning algorithms such as multi-layer perceptrons (MLP) have demonstrated human-level recognition accuracy in image and speech classification tasks. Multiple layers of processing elements called neurons with several connections between them called synapses are used to build these networks. Hence, it involves operations that exhibit a high level of parallelism making it computationally and memory intensive. Constrained by computing resources and memory, most of the applications require a neural network which utilizes less energy. Energy efficient implementation of these computationally intense algorithms on neuromorphic hardware demands a lot of architectural optimizations. One of these optimizations would be the reduction in the network size using compression and several studies investigated compression by introducing element-wise or row-/column-/block-wise sparsity via pruning and regularization. Additionally, numerous recent works have concentrated on reducing the precision of activations and weights with some reducing to a single bit. However, combining various sparsity structures with binarized or very-low-precision (2-3 bit) neural networks have not been comprehensively explored. Output activations in these deep neural network algorithms are habitually non-binary making it difficult to exploit sparsity. On the other hand, biologically realistic models like spiking neural networks (SNN) closely mimic the operations in biological nervous systems and explore new avenues for brain-like cognitive computing. These networks deal with binary spikes, and they can exploit the input-dependent sparsity or redundancy to dynamically scale the amount of computation in turn leading to energy-efficient hardware implementation. This work discusses configurable spiking neuromorphic architecture that supports multiple hidden layers exploiting hardware reuse. It also presents design techniques for minimum-area/-energy DNN hardware with minimal degradation in accuracy. Area, performance and energy results of these DNN and SNN hardware is reported for the MNIST dataset. The Neuromorphic hardware designed for SNN algorithm in 28nm CMOS demonstrates high classification accuracy (>98% on MNIST) and low energy (51.4 - 773 (nJ) per classification). The optimized DNN hardware designed in 40nm CMOS that combines 8X structured compression and 3-bit weight precision showed 98.4% accuracy at 33 (nJ) per classification.
ContributorsKolala Venkataramanaiah, Shreyas (Author) / Seo, Jae-Sun (Thesis advisor) / Chakrabarti, Chaitali (Committee member) / Cao, Yu (Committee member) / Arizona State University (Publisher)
Created2018
Description
The last decade has witnessed a paradigm shift in computing platforms, from laptops and servers to mobile devices like smartphones and tablets. These devices host an immense variety of applications many of which are computationally expensive and thus are power hungry. As most of these mobile platforms are powered by batteries, energy efficiency has become one of the most critical aspects of such devices. Thus, the energy cost of the fundamental arithmetic operations executed in these applications has to be reduced. As voltage scaling has effectively ended, the energy efficiency of integrated circuits has ceased to improve within successive generations of transistors. This resulted in widespread use of Application Specific Integrated Circuits (ASIC), which provide incredible energy efficiency. However, these are not flexible and have high non-recurring engineering (NRE) cost. Alternatively, Field Programmable Gate Arrays (FPGA) offer flexibility to implement any application, but at the cost of higher area and energy compared to ASIC.
In this work, a spatially programmable architecture customized for image processing applications is proposed. The intent is to bridge the efficiency gap between ASICs and FPGAs, by offering FPGA-like flexibility and ASIC-like energy efficiency. This architecture minimizes the energy overheads in FPGAs, which result from the use of fine-grained programming style and global interconnect. It is flexible compared to an ASIC and can accommodate multiple applications.
The main contribution of the thesis is the feasibility analysis of the data path of this architecture, customized for image processing applications. The data path is implemented at the register transfer level (RTL), and the synthesis results are obtained in 45nm technology cell library from a leading foundry. The results of image-processing applications demonstrate that this architecture is within a factor of 10x of the energy and area efficiency of ASIC implementations.
In this work, a spatially programmable architecture customized for image processing applications is proposed. The intent is to bridge the efficiency gap between ASICs and FPGAs, by offering FPGA-like flexibility and ASIC-like energy efficiency. This architecture minimizes the energy overheads in FPGAs, which result from the use of fine-grained programming style and global interconnect. It is flexible compared to an ASIC and can accommodate multiple applications.
The main contribution of the thesis is the feasibility analysis of the data path of this architecture, customized for image processing applications. The data path is implemented at the register transfer level (RTL), and the synthesis results are obtained in 45nm technology cell library from a leading foundry. The results of image-processing applications demonstrate that this architecture is within a factor of 10x of the energy and area efficiency of ASIC implementations.
ContributorsSatapathy, Saktiswarup (Author) / Brunhaver, John (Thesis advisor) / Clark, Lawrence T (Committee member) / Ren, Fengbo (Committee member) / Arizona State University (Publisher)
Created2016
Description
Coarse-grained Reconfigurable Arrays (CGRAs) are promising accelerators capable
of accelerating even non-parallel loops and loops with low trip-counts. One challenge
in compiling for CGRAs is to manage both recurring and nonrecurring variables in
the register file (RF) of the CGRA. Although prior works have managed recurring
variables via rotating RF, they access the nonrecurring variables through either a
global RF or from a constant memory. The former does not scale well, and the latter
degrades the mapping quality. This work proposes a hardware-software codesign
approach in order to manage all the variables in a local nonrotating RF. Hardware
provides modulo addition based indexing mechanism to enable correct addressing
of recurring variables in a nonrotating RF. The compiler determines the number of
registers required for each recurring variable and configures the boundary between the
registers used for recurring and nonrecurring variables. The compiler also pre-loads
the read-only variables and constants into the local registers in the prologue of the
schedule. Synthesis and place-and-route results of the previous and the proposed RF
design show that proposed solution achieves 17% better cycle time. Experiments of
mapping several important and performance-critical loops collected from MiBench
show proposed approach improves performance (through better mapping) by 18%,
compared to using constant memory.
of accelerating even non-parallel loops and loops with low trip-counts. One challenge
in compiling for CGRAs is to manage both recurring and nonrecurring variables in
the register file (RF) of the CGRA. Although prior works have managed recurring
variables via rotating RF, they access the nonrecurring variables through either a
global RF or from a constant memory. The former does not scale well, and the latter
degrades the mapping quality. This work proposes a hardware-software codesign
approach in order to manage all the variables in a local nonrotating RF. Hardware
provides modulo addition based indexing mechanism to enable correct addressing
of recurring variables in a nonrotating RF. The compiler determines the number of
registers required for each recurring variable and configures the boundary between the
registers used for recurring and nonrecurring variables. The compiler also pre-loads
the read-only variables and constants into the local registers in the prologue of the
schedule. Synthesis and place-and-route results of the previous and the proposed RF
design show that proposed solution achieves 17% better cycle time. Experiments of
mapping several important and performance-critical loops collected from MiBench
show proposed approach improves performance (through better mapping) by 18%,
compared to using constant memory.
ContributorsDave, Shail (Author) / Shrivastava, Aviral (Thesis advisor) / Ren, Fengbo (Committee member) / Ogras, Umit Y. (Committee member) / Arizona State University (Publisher)
Created2016
Description
Integrated circuits must be energy efficient. This efficiency affects all aspects of chip design, from the battery life of embedded devices to thermal heating on high performance servers. As technology scaling slows, future generations of transistors will lack the energy efficiency gains as it has had in previous generations. Therefore, other sources of energy efficiency will be much more important. Many computations have the potential to be executed for extreme energy efficiency but are not instigated because the platforms they run on are not optimized for efficient execution. ASICs improve energy efficiency by reducing flexibility and leveraging the properties of a specific computation. However, ASICs are fixed in function and therefore have incredible opportunity cost. FPGAs offer a reconfigurable solution but are 25x less energy efficient than ASIC implementation. Spatially programmable architectures (SPAs) are similar in design and structure to ASICs and FPGAs but are able bridge the ASIC-FPGA energy efficiency gap by trading flexibility for efficiency. However, SPAs are difficult to program because they do not share the same programming model as normal architectures that execute in time. This work addresses compiler challenges for coarse grained, locally interconnected SPA for domain efficiency (SPADE). A novel SPADE topology, called the wave pipeline, is introduced that is designed for the image signal processing domain that is both efficient and simple to compile to. A compiler for the wave pipeline is created that solves for maximum energy and area efficiency using low complexity, greedy methods. The wave pipeline topology and compiler allow for us to investigate and experiment with image signal processing applications to prove the feasibility of SPADE compilers.
ContributorsMackay, Curtis (Author) / Brunhaver, John (Thesis advisor) / Karam, Lina J (Committee member) / Seo, Jae-Sun (Committee member) / Arizona State University (Publisher)
Created2016
Description
Caches pose a serious limitation in scaling many-core architectures since the demand of area and power for maintaining cache coherence increases rapidly with the number of cores. Scratch-Pad Memories (SPMs) provide a cheaper and lower power alternative that can be used to build a more scalable many-core architecture. The trade-off of substituting SPMs for caches is however that the data must be explicitly managed in software. Heap management on SPM poses a major challenge due to the highly dynamic nature of of heap data access. Most existing heap management techniques implement a software caching scheme on SPM, emulating the behavior of hardware caches. The state-of-the-art heap management scheme implements a 4-way set-associative software cache on SPM for a single program running with one thread on one core. While the technique works correctly, it suffers from signifcant performance overhead. This paper presents a series of compiler-based efficient heap management approaches that reduces heap management overhead through several optimization techniques. Experimental results on benchmarks from MiBenchGuthaus et al. (2001) executed on an SMM processor modeled in gem5Binkert et al. (2011) demonstrate that our approach (implemented in llvm v3.8Lattner and Adve (2004)) can improve execution time by 80% on average compared to the previous state-of-the-art.
ContributorsLin, Jinn-Pean (Author) / Shrivastava, Aviral (Thesis advisor) / Ren, Fengbo (Committee member) / Ogras, Umit Y. (Committee member) / Arizona State University (Publisher)
Created2017
Description
The information era has brought about many technological advancements in the past
few decades, and that has led to an exponential increase in the creation of digital images and
videos. Constantly, all digital images go through some image processing algorithm for
various reasons like compression, transmission, storage, etc. There is data loss during this
process which leaves us with a degraded image. Hence, to ensure minimal degradation of
images, the requirement for quality assessment has become mandatory. Image Quality
Assessment (IQA) has been researched and developed over the last several decades to
predict the quality score in a manner that agrees with human judgments of quality. Modern
image quality assessment (IQA) algorithms are quite effective at prediction accuracy, and
their development has not focused on improving computational performance. The existing
serial implementation requires a relatively large run-time on the order of seconds for a single
frame. Hardware acceleration using Field programmable gate arrays (FPGAs) provides
reconfigurable computing fabric that can be tailored for a broad range of applications.
Usually, programming FPGAs has required expertise in hardware descriptive languages
(HDLs) or high-level synthesis (HLS) tool. OpenCL is an open standard for cross-platform,
parallel programming of heterogeneous systems along with Altera OpenCL SDK, enabling
developers to use FPGA's potential without extensive hardware knowledge. Hence, this
thesis focuses on accelerating the computationally intensive part of the most apparent
distortion (MAD) algorithm on FPGA using OpenCL. The results are compared with CPU
implementation to evaluate performance and efficiency gains.
few decades, and that has led to an exponential increase in the creation of digital images and
videos. Constantly, all digital images go through some image processing algorithm for
various reasons like compression, transmission, storage, etc. There is data loss during this
process which leaves us with a degraded image. Hence, to ensure minimal degradation of
images, the requirement for quality assessment has become mandatory. Image Quality
Assessment (IQA) has been researched and developed over the last several decades to
predict the quality score in a manner that agrees with human judgments of quality. Modern
image quality assessment (IQA) algorithms are quite effective at prediction accuracy, and
their development has not focused on improving computational performance. The existing
serial implementation requires a relatively large run-time on the order of seconds for a single
frame. Hardware acceleration using Field programmable gate arrays (FPGAs) provides
reconfigurable computing fabric that can be tailored for a broad range of applications.
Usually, programming FPGAs has required expertise in hardware descriptive languages
(HDLs) or high-level synthesis (HLS) tool. OpenCL is an open standard for cross-platform,
parallel programming of heterogeneous systems along with Altera OpenCL SDK, enabling
developers to use FPGA's potential without extensive hardware knowledge. Hence, this
thesis focuses on accelerating the computationally intensive part of the most apparent
distortion (MAD) algorithm on FPGA using OpenCL. The results are compared with CPU
implementation to evaluate performance and efficiency gains.
ContributorsGunavelu Mohan, Aswin (Author) / Sohoni, Sohum (Thesis advisor) / Ren, Fengbo (Thesis advisor) / Seo, Jae-Sun (Committee member) / Arizona State University (Publisher)
Created2017
Description
Achieving human level intelligence is a long-term goal for many Artificial Intelligence (AI) researchers. Recent developments in combining deep learning and reinforcement learning helped us to move a step forward in achieving this goal. Reinforcement learning using a delayed reward mechanism is an approach to machine intelligence which studies decision making with control and how a decision making agent can learn to act optimally in an environment-unaware conditions.
Q-learning is one of the model-free reinforcement directed learning strategies which uses temporal differences to estimate the performances of state-action pairs called Q values. A simple implementation of Q-learning algorithm can be done using a Q table memory to store and update the Q values. However, with an increase in state space data due to a complex environment, and with an increase in possible number of actions an agent can perform, Q table reaches its space limit and would be difficult to scale well. Q-learning with neural networks eliminates the use of Q table by approximating the Q function using neural networks.
Autonomous agents need to develop cognitive properties and become self-adaptive to be deployable in any environment. Reinforcement learning with Q-learning have been very efficient in solving such problems. However, embedded systems like space rovers and autonomous robots rarely implement such techniques due to the constraints faced like processing power, chip area, convergence rate and cost of the chip. These problems present a need for a portable, low power, area efficient hardware accelerator to accelerate the process of such learning.
This problem is targeted by implementing a hardware schematic architecture for Q-learning using Artificial Neural networks. This architecture exploits the massive parallelism provided by neural network with a dedicated fine grain parallelism provided by a Field Programmable Gate Array (FPGA) thereby processing the Q values at a high throughput. Mars exploration rovers currently use Xilinx-Space-grade FPGA devices for image processing, pyrotechnic operation control and obstacle avoidance. The hardware resource consumption for the architecture has been synthesized considering Xilinx Virtex7 FPGA as the target device.
Q-learning is one of the model-free reinforcement directed learning strategies which uses temporal differences to estimate the performances of state-action pairs called Q values. A simple implementation of Q-learning algorithm can be done using a Q table memory to store and update the Q values. However, with an increase in state space data due to a complex environment, and with an increase in possible number of actions an agent can perform, Q table reaches its space limit and would be difficult to scale well. Q-learning with neural networks eliminates the use of Q table by approximating the Q function using neural networks.
Autonomous agents need to develop cognitive properties and become self-adaptive to be deployable in any environment. Reinforcement learning with Q-learning have been very efficient in solving such problems. However, embedded systems like space rovers and autonomous robots rarely implement such techniques due to the constraints faced like processing power, chip area, convergence rate and cost of the chip. These problems present a need for a portable, low power, area efficient hardware accelerator to accelerate the process of such learning.
This problem is targeted by implementing a hardware schematic architecture for Q-learning using Artificial Neural networks. This architecture exploits the massive parallelism provided by neural network with a dedicated fine grain parallelism provided by a Field Programmable Gate Array (FPGA) thereby processing the Q values at a high throughput. Mars exploration rovers currently use Xilinx-Space-grade FPGA devices for image processing, pyrotechnic operation control and obstacle avoidance. The hardware resource consumption for the architecture has been synthesized considering Xilinx Virtex7 FPGA as the target device.
ContributorsGankidi, Pranay Reddy (Author) / Thangavelautham, Jekanthan (Thesis advisor) / Ren, Fengbo (Committee member) / Seo, Jae-Sun (Committee member) / Arizona State University (Publisher)
Created2016
Description
Computer vision is becoming an essential component of embedded system applications such as smartphones, wearables, autonomous systems and internet-of-things (IoT). These applications are generally deployed into environments with limited energy, memory bandwidth and computational resources. This trend is driving the development of energy-effi cient image processing solutions from sensing to computation. In this thesis, diff erent alternatives are explored to implement energy-efficient computer vision systems. First, I present a fi eld programmable gate array (FPGA) implementation of an adaptive subsampling algorithm for region-of-interest (ROI) -based object tracking. By implementing the computationally intensive sections of this algorithm on an FPGA, I aim to offl oad computing resources from energy-ineffi cient graphics processing units (GPUs) and/or general-purpose central processing units (CPUs). I also present a working system executing this algorithm in near real-time latency implemented on a standalone embedded device. Secondly, I present a neural network-based pipeline to improve the performance of event-based cameras in non-ideal optical conditions. Event-based cameras or dynamic vision sensors (DVS) are bio-inspired sensors that measure logarithmic per-pixel brightness changes in a scene. Their advantages include high dynamic range, low latency and ultra-low power when compared to standard frame-based cameras. Several tasks have been proposed to take advantage of these novel sensors but they rely on perfectly calibrated optical lenses that are in-focus. In this work I propose a methodto reconstruct events captured with an out-of-focus event-camera so they can be fed into an intensity reconstruction task. The network is trained with a dataset generated by simulating defocus blur in sequences from object tracking datasets such as LaSOT and OTB100. I also test the generalization performance of this network in scenes captured with a DAVIS event-based sensor equipped with an out-of-focus lens.
ContributorsTorres Muro, Victor Isaac (Author) / Jayasuriya, Suren (Thesis advisor) / Spanias, Andreas (Committee member) / Seo, Jae-Sun (Committee member) / Arizona State University (Publisher)
Created2022