A.B. Gebregiorgis
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An Area and Energy Efficient Arithmetic Unit for Stacked Machine Learning Models
Mo Model Mo Problems, Like... Hardware Design Problems
Machine learning on edge devices performs crucial identification or prediction tasks while limiting the amount of data that needs to be transmitted to more centralized computing nodes. However, strict area and energy requirements necessitate specialized hardware developed for the requirements of the device and model. This thesis is concerned with developing an area and energy arithmetic unit as part of the implementation of a stacked machine learning model in embedded automotive devices. The model in question was previously designed to perform lifetime prediction with the goal of improving the reliability of semiconductor devices used in various automotive applications.
This thesis aims to achieve area and energy efficiency by exploiting the commonalities in the arithmetic operations of several of the internal learners of the stacked machine learning model. The use of a weighted figure of merit, taking into account area, energy and delay, allow for simple comparisons of designs at any operation frequency and easy insight into the changes in the merit of designs if device requirements were to change. A sweep of the percentage of multiplications in the workload also gave insight into how design choices may change due to future redesigns of the stacked machine learning model.
It was found that the MAC, multiply, divide and accumulate operations of the internal learners can best be supported by one arithmetic unit containing a "Reduced Area" parallel multiplier (still taking up most of the area), a small, dedicated accumulator and invariant integer division using the multiplier. It was also found that the ability to reconfigure the multiplier for different levels of bit-precision does not yield performance improvement for the expected precision distribution. ...
This thesis aims to achieve area and energy efficiency by exploiting the commonalities in the arithmetic operations of several of the internal learners of the stacked machine learning model. The use of a weighted figure of merit, taking into account area, energy and delay, allow for simple comparisons of designs at any operation frequency and easy insight into the changes in the merit of designs if device requirements were to change. A sweep of the percentage of multiplications in the workload also gave insight into how design choices may change due to future redesigns of the stacked machine learning model.
It was found that the MAC, multiply, divide and accumulate operations of the internal learners can best be supported by one arithmetic unit containing a "Reduced Area" parallel multiplier (still taking up most of the area), a small, dedicated accumulator and invariant integer division using the multiplier. It was also found that the ability to reconfigure the multiplier for different levels of bit-precision does not yield performance improvement for the expected precision distribution. ...
Machine learning on edge devices performs crucial identification or prediction tasks while limiting the amount of data that needs to be transmitted to more centralized computing nodes. However, strict area and energy requirements necessitate specialized hardware developed for the requirements of the device and model. This thesis is concerned with developing an area and energy arithmetic unit as part of the implementation of a stacked machine learning model in embedded automotive devices. The model in question was previously designed to perform lifetime prediction with the goal of improving the reliability of semiconductor devices used in various automotive applications.
This thesis aims to achieve area and energy efficiency by exploiting the commonalities in the arithmetic operations of several of the internal learners of the stacked machine learning model. The use of a weighted figure of merit, taking into account area, energy and delay, allow for simple comparisons of designs at any operation frequency and easy insight into the changes in the merit of designs if device requirements were to change. A sweep of the percentage of multiplications in the workload also gave insight into how design choices may change due to future redesigns of the stacked machine learning model.
It was found that the MAC, multiply, divide and accumulate operations of the internal learners can best be supported by one arithmetic unit containing a "Reduced Area" parallel multiplier (still taking up most of the area), a small, dedicated accumulator and invariant integer division using the multiplier. It was also found that the ability to reconfigure the multiplier for different levels of bit-precision does not yield performance improvement for the expected precision distribution.
This thesis aims to achieve area and energy efficiency by exploiting the commonalities in the arithmetic operations of several of the internal learners of the stacked machine learning model. The use of a weighted figure of merit, taking into account area, energy and delay, allow for simple comparisons of designs at any operation frequency and easy insight into the changes in the merit of designs if device requirements were to change. A sweep of the percentage of multiplications in the workload also gave insight into how design choices may change due to future redesigns of the stacked machine learning model.
It was found that the MAC, multiply, divide and accumulate operations of the internal learners can best be supported by one arithmetic unit containing a "Reduced Area" parallel multiplier (still taking up most of the area), a small, dedicated accumulator and invariant integer division using the multiplier. It was also found that the ability to reconfigure the multiplier for different levels of bit-precision does not yield performance improvement for the expected precision distribution.
Benchmarking and Algorithm Optimization for SENeCA
A RISC-V-based Neuromorphic Processor
With recent breakthroughs in AI (Artificial Intelligence) technology, the impact of AI on society can be felt in various fields. The market for AI software, for example, reached a valuation of \$62 billion in 2022. A growing number of new computer architectures specialized in running these AI software were also developed. At first they were run on conventional CPUs (Central Processing Unit) and GPUs (Graphical Processing Units), but then more specialized hardware emerged, such as the TPU (Tensor Processing Unit). However, since algorithms in these AI software are generally data-intensive, the power consumption became a problem. Therefore, as many of these algorithms were based on biological neural networks, there is a growing interest to develop hardware similarly based on principles found these networks as well to replicate their efficiency. This new architecture is known as neuromorphic architecture.
However, a new architecture does not come without challenges. As a nascent and fragmented field, neuromorphic computing in general lacks a standardized benchmarking suite or methodology. In other, more mature fields, benchmarks are a standard way of evaluating the performance of different designs objectively and fairly. This thesis aims to propose and demonstrate a benchmarking methodology and implementation flow for neuromorphic processors. This methodology aims to measure the important performance metrics for a neuromorphic processor, both on the small scale of individual synaptic operations, and the large scale of performing an actual workload. The chosen workload is a keyword spotting program based on a simple DNN architecture, which detects a specific phrase in an audio recording. This workload was chosen due to its potential application in an environment where energy is limited, such as an embedded device.
The neuromorphic processor that is the target of this benchmarking is SENeCA (short for Scalable Energy-efficient Neuromorphic Computer Architecture), a flexible and scalable design developed at IMEC The Netherlands. To implement the keyword spotting program on SENeCA, the keyword spotting program was rewritten and parsed. Since no physical chip implementation of SENeCA exists at the time of writing, the program was run on SENeCA using a HDL simulator. The execution time of the program is measured in detail, taking into account not only the total time, but also the time required to complete the specific stages of program. Afterwards, the power consumption of SENeCA during the execution of the program was measured using a power estimation software, both for the entire chip and its individual components. This is done both in average mode, obtaining the average power consumption over the total execution time, and in time-based mode, providing insight to the peak power and fluctuations over time. Then, the energy to solution is calculated using the execution time and power consumption. This process is done in multiple iterations, with a specific optimization done each iteration using SENeCA's accelerators. This provides insight into the impact of each optimization to power consumption and performance. Finally, a measurement of the energy consumption of SENeCA per individual synaptic operations is also done, allowing estimates of the energy consumption of future implementations. ...
However, a new architecture does not come without challenges. As a nascent and fragmented field, neuromorphic computing in general lacks a standardized benchmarking suite or methodology. In other, more mature fields, benchmarks are a standard way of evaluating the performance of different designs objectively and fairly. This thesis aims to propose and demonstrate a benchmarking methodology and implementation flow for neuromorphic processors. This methodology aims to measure the important performance metrics for a neuromorphic processor, both on the small scale of individual synaptic operations, and the large scale of performing an actual workload. The chosen workload is a keyword spotting program based on a simple DNN architecture, which detects a specific phrase in an audio recording. This workload was chosen due to its potential application in an environment where energy is limited, such as an embedded device.
The neuromorphic processor that is the target of this benchmarking is SENeCA (short for Scalable Energy-efficient Neuromorphic Computer Architecture), a flexible and scalable design developed at IMEC The Netherlands. To implement the keyword spotting program on SENeCA, the keyword spotting program was rewritten and parsed. Since no physical chip implementation of SENeCA exists at the time of writing, the program was run on SENeCA using a HDL simulator. The execution time of the program is measured in detail, taking into account not only the total time, but also the time required to complete the specific stages of program. Afterwards, the power consumption of SENeCA during the execution of the program was measured using a power estimation software, both for the entire chip and its individual components. This is done both in average mode, obtaining the average power consumption over the total execution time, and in time-based mode, providing insight to the peak power and fluctuations over time. Then, the energy to solution is calculated using the execution time and power consumption. This process is done in multiple iterations, with a specific optimization done each iteration using SENeCA's accelerators. This provides insight into the impact of each optimization to power consumption and performance. Finally, a measurement of the energy consumption of SENeCA per individual synaptic operations is also done, allowing estimates of the energy consumption of future implementations. ...
With recent breakthroughs in AI (Artificial Intelligence) technology, the impact of AI on society can be felt in various fields. The market for AI software, for example, reached a valuation of \$62 billion in 2022. A growing number of new computer architectures specialized in running these AI software were also developed. At first they were run on conventional CPUs (Central Processing Unit) and GPUs (Graphical Processing Units), but then more specialized hardware emerged, such as the TPU (Tensor Processing Unit). However, since algorithms in these AI software are generally data-intensive, the power consumption became a problem. Therefore, as many of these algorithms were based on biological neural networks, there is a growing interest to develop hardware similarly based on principles found these networks as well to replicate their efficiency. This new architecture is known as neuromorphic architecture.
However, a new architecture does not come without challenges. As a nascent and fragmented field, neuromorphic computing in general lacks a standardized benchmarking suite or methodology. In other, more mature fields, benchmarks are a standard way of evaluating the performance of different designs objectively and fairly. This thesis aims to propose and demonstrate a benchmarking methodology and implementation flow for neuromorphic processors. This methodology aims to measure the important performance metrics for a neuromorphic processor, both on the small scale of individual synaptic operations, and the large scale of performing an actual workload. The chosen workload is a keyword spotting program based on a simple DNN architecture, which detects a specific phrase in an audio recording. This workload was chosen due to its potential application in an environment where energy is limited, such as an embedded device.
The neuromorphic processor that is the target of this benchmarking is SENeCA (short for Scalable Energy-efficient Neuromorphic Computer Architecture), a flexible and scalable design developed at IMEC The Netherlands. To implement the keyword spotting program on SENeCA, the keyword spotting program was rewritten and parsed. Since no physical chip implementation of SENeCA exists at the time of writing, the program was run on SENeCA using a HDL simulator. The execution time of the program is measured in detail, taking into account not only the total time, but also the time required to complete the specific stages of program. Afterwards, the power consumption of SENeCA during the execution of the program was measured using a power estimation software, both for the entire chip and its individual components. This is done both in average mode, obtaining the average power consumption over the total execution time, and in time-based mode, providing insight to the peak power and fluctuations over time. Then, the energy to solution is calculated using the execution time and power consumption. This process is done in multiple iterations, with a specific optimization done each iteration using SENeCA's accelerators. This provides insight into the impact of each optimization to power consumption and performance. Finally, a measurement of the energy consumption of SENeCA per individual synaptic operations is also done, allowing estimates of the energy consumption of future implementations.
However, a new architecture does not come without challenges. As a nascent and fragmented field, neuromorphic computing in general lacks a standardized benchmarking suite or methodology. In other, more mature fields, benchmarks are a standard way of evaluating the performance of different designs objectively and fairly. This thesis aims to propose and demonstrate a benchmarking methodology and implementation flow for neuromorphic processors. This methodology aims to measure the important performance metrics for a neuromorphic processor, both on the small scale of individual synaptic operations, and the large scale of performing an actual workload. The chosen workload is a keyword spotting program based on a simple DNN architecture, which detects a specific phrase in an audio recording. This workload was chosen due to its potential application in an environment where energy is limited, such as an embedded device.
The neuromorphic processor that is the target of this benchmarking is SENeCA (short for Scalable Energy-efficient Neuromorphic Computer Architecture), a flexible and scalable design developed at IMEC The Netherlands. To implement the keyword spotting program on SENeCA, the keyword spotting program was rewritten and parsed. Since no physical chip implementation of SENeCA exists at the time of writing, the program was run on SENeCA using a HDL simulator. The execution time of the program is measured in detail, taking into account not only the total time, but also the time required to complete the specific stages of program. Afterwards, the power consumption of SENeCA during the execution of the program was measured using a power estimation software, both for the entire chip and its individual components. This is done both in average mode, obtaining the average power consumption over the total execution time, and in time-based mode, providing insight to the peak power and fluctuations over time. Then, the energy to solution is calculated using the execution time and power consumption. This process is done in multiple iterations, with a specific optimization done each iteration using SENeCA's accelerators. This provides insight into the impact of each optimization to power consumption and performance. Finally, a measurement of the energy consumption of SENeCA per individual synaptic operations is also done, allowing estimates of the energy consumption of future implementations.
Master thesis
(2021)
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A. Zografou, S. Hamdioui, R.K. Bishnoi, A.B. Gebregiorgis, T.G.R.M. van Leuken
Computation-In-Memory (CIM) employing Resistive-RAM
(RRAM)-based crossbar arrays is a promising solution to implement Neural Networks (NNs) on hardware, such that they are efficient with respect to consumption of energy, memory, computational resources, and computation time. In this respect, Binary NNs (BNNs), where the weights obtain single binary values, are inherently suitable for cost-effective CIM-based NN implementations. However, RRAM devices, due to variability and reliability issues, restrict the applicability of CIM-based NN. To address this issue and towards a low-cost NN hardware realization, in this thesis, we: a) thoroughly investigate the impact of RRAM faults on the inference accuracy of RRAM-based BNNs, and b) propose three complementary fault-tolerance techniques to mitigate the impact of RRAM faults on the BNN's accuracy. These techniques are namely: a) a fault-tolerant activation function, b) a redundancy and weight range adjustment scheme and c) a retraining technique. Evaluation results compiled on the MNIST, Fashion-MNIST, and CIFAR-10 datasets demonstrate that the proposed techniques can improve the inference accuracy in the presence of RRAM faults by up to 20%, 40%, and 80%, respectively. Moreover, comparisons with certain related state-of-the-art fault-tolerance frameworks indicate that the proposed techniques yield competitive results. ...
(RRAM)-based crossbar arrays is a promising solution to implement Neural Networks (NNs) on hardware, such that they are efficient with respect to consumption of energy, memory, computational resources, and computation time. In this respect, Binary NNs (BNNs), where the weights obtain single binary values, are inherently suitable for cost-effective CIM-based NN implementations. However, RRAM devices, due to variability and reliability issues, restrict the applicability of CIM-based NN. To address this issue and towards a low-cost NN hardware realization, in this thesis, we: a) thoroughly investigate the impact of RRAM faults on the inference accuracy of RRAM-based BNNs, and b) propose three complementary fault-tolerance techniques to mitigate the impact of RRAM faults on the BNN's accuracy. These techniques are namely: a) a fault-tolerant activation function, b) a redundancy and weight range adjustment scheme and c) a retraining technique. Evaluation results compiled on the MNIST, Fashion-MNIST, and CIFAR-10 datasets demonstrate that the proposed techniques can improve the inference accuracy in the presence of RRAM faults by up to 20%, 40%, and 80%, respectively. Moreover, comparisons with certain related state-of-the-art fault-tolerance frameworks indicate that the proposed techniques yield competitive results. ...
Computation-In-Memory (CIM) employing Resistive-RAM
(RRAM)-based crossbar arrays is a promising solution to implement Neural Networks (NNs) on hardware, such that they are efficient with respect to consumption of energy, memory, computational resources, and computation time. In this respect, Binary NNs (BNNs), where the weights obtain single binary values, are inherently suitable for cost-effective CIM-based NN implementations. However, RRAM devices, due to variability and reliability issues, restrict the applicability of CIM-based NN. To address this issue and towards a low-cost NN hardware realization, in this thesis, we: a) thoroughly investigate the impact of RRAM faults on the inference accuracy of RRAM-based BNNs, and b) propose three complementary fault-tolerance techniques to mitigate the impact of RRAM faults on the BNN's accuracy. These techniques are namely: a) a fault-tolerant activation function, b) a redundancy and weight range adjustment scheme and c) a retraining technique. Evaluation results compiled on the MNIST, Fashion-MNIST, and CIFAR-10 datasets demonstrate that the proposed techniques can improve the inference accuracy in the presence of RRAM faults by up to 20%, 40%, and 80%, respectively. Moreover, comparisons with certain related state-of-the-art fault-tolerance frameworks indicate that the proposed techniques yield competitive results.
(RRAM)-based crossbar arrays is a promising solution to implement Neural Networks (NNs) on hardware, such that they are efficient with respect to consumption of energy, memory, computational resources, and computation time. In this respect, Binary NNs (BNNs), where the weights obtain single binary values, are inherently suitable for cost-effective CIM-based NN implementations. However, RRAM devices, due to variability and reliability issues, restrict the applicability of CIM-based NN. To address this issue and towards a low-cost NN hardware realization, in this thesis, we: a) thoroughly investigate the impact of RRAM faults on the inference accuracy of RRAM-based BNNs, and b) propose three complementary fault-tolerance techniques to mitigate the impact of RRAM faults on the BNN's accuracy. These techniques are namely: a) a fault-tolerant activation function, b) a redundancy and weight range adjustment scheme and c) a retraining technique. Evaluation results compiled on the MNIST, Fashion-MNIST, and CIFAR-10 datasets demonstrate that the proposed techniques can improve the inference accuracy in the presence of RRAM faults by up to 20%, 40%, and 80%, respectively. Moreover, comparisons with certain related state-of-the-art fault-tolerance frameworks indicate that the proposed techniques yield competitive results.