Sharif Digital Repository

Although the accuracy of MEMS gyroscopes has been extremely improved, in some aspects, such as stability of bias, they still suffer from some big error sources, like run-to-run bias, which determines the sensor price but is not negligible even inexpensive sensors. Due to the fact that run-to-run bias is a kind of stochastic parameter, it has to be measured by utilizing online methods. Utilizing a novel, fast and efficient vision-based rotation estimation algorithm for ground vehicles, we have developed a visual gyroscope that is used in our sensor fusion system, in order to estimate run-to-run bias of the MEMS gyroscope, accurately. Comparing with similar approaches that use GPS, odometer,... 

For many years, computer designers benefitted from Moore's law and Dennard scaling to significantly improve the speed of single-core processors. The failure of Dennard scaling pushed the computer industry toward homogenous multicore processors for the performance improvement to continue without significant increase in power consumption. Unfortunately, even homogeneous multicore processors cannot offer the level of energy efficiency required to operate all the cores at the same time in today's and especially tomorrow's technologies. As a result of lack of energy efficiency, not all the cores in a multicore processor can be functional at the same time. This phenomenon is referred to as dark... 

Many applications, including big-data server applications, frequently encounter data misses. Consequently, they lose significant performance potential. Fortunately, data accesses of many of these applications follow temporal correlations, which means data accesses repeat over time. Temporal correlations occur because applications usually consist of loops, and hence, the sequence of instructions that constitute the body of a loop repeats many times, leading to data access repetition. Temporal data prefetchers take advantage of temporal correlation to predict and prefetch future memory accesses. In this chapter, we introduce the concept of temporal prefetching and present two instances of... 

Many applications extensively use data objects with a regular and fixed layout, which leads to the recurrence of access patterns over memory regions. Spatial data prefetching techniques exploit this phenomenon to prefetch future memory references and hide their long latency. Spatial prefetchers are particularly of interest because they usually only need a small storage budget. In this chapter, we introduce the concept of spatial prefetching and present two instances of spatial data prefetchers, SMS and VLDP. © 2021 Elsevier Inc  

Many applications, including big-data server applications, frequently encounter data misses. Consequently, they lose significant performance potential. Fortunately, data accesses of many of these applications follow temporal correlations, which means data accesses repeat over time. Temporal correlations occur because applications usually consist of loops, and hence, the sequence of instructions that constitute the body of a loop repeats many times, leading to data access repetition. Temporal data prefetchers take advantage of temporal correlation to predict and prefetch future memory accesses. In this chapter, we introduce the concept of temporal prefetching and present two instances of... 

Many applications extensively use data objects with a regular and fixed layout, which leads to the recurrence of access patterns over memory regions. Spatial data prefetching techniques exploit this phenomenon to prefetch future memory references and hide their long latency. Spatial prefetchers are particularly of interest because they usually only need a small storage budget. In this chapter, we introduce the concept of spatial prefetching and present two instances of spatial data prefetchers, SMS and VLDP. © 2022 Elsevier Inc  

Knowing the exact position and rotation is a crucial necessity for the navigation of autonomous robots. Even in outdoor environments GPS signals are not always accessible for estimating online rotation and position of robots. Also inertial aided navigation methods have their own defects such as the drift of gyroscope or inaccuracy of accelerometer in agile motions and environmental sensitivity of compass. In this article, we have introduced a novel online visual gyroscope that can estimate the rotation of a moving car with analyzing the images of a monocular camera installed on it. Our real time visual gyroscope utilizes an efficient method of rotation estimation between each pair of camera... 

Side Channel Analysis (SCA) are still harmful threats against security of embedded systems. Due to the fact that every kind of SCA attack or countermeasure against it needs to be implemented before evaluation, a huge amount of time and cost of this process is paid for providing high resolution measurement tools, calibrating them and also implementation of proposed design on ASIC or target platform. In this paper, we have introduced a novel simulation platform for evaluation of power based SCA attacks and countermeasures. We have used Synopsys power analysis tools in order to simulate a processor and implement a successful Differential Power Analysis (DPA) attack on it. Then we focused on the... 

Chip multiprocessors (CMPs) require a low-latency interconnect fabric network-on-chip (NoC) to minimize processor stall time on instruction and data accesses that are serviced by the last-level cache (LLC). While packet-switched mesh interconnects sacrifice performance of many-core processors due to NoC-induced delays, existing circuit-switched interconnects do not offer lower network delays as they cannot hide the time it takes to set up a circuit. To address this problem, this work introduces CIMA - a hybrid circuit-switched and packet-switched mesh-based interconnection network that affords low LLC access delays at a small area cost. CIMA uses virtual cut-through (VCT) switching for short... 

Server workloads benefit from execution on many-core processors due to their massive request-level parallelism. A key characteristic of server workloads is the large instruction footprints. While a shared last-level cache (LLC) captures the footprints, it necessitates a low-latency network-on-chip (NOC) to minimize the core stall time on accesses serviced by the LLC. As strict quality-of-service requirements preclude the use of lean cores in server processors, we observe that even state-of-the-art single-cycle multi-hop NOCs are far from ideal because they impose significant NOC-induced delays on the LLC access latency, and diminish performance. Most of the NOC delay is due to per-hop... 

Instruction cache misses are a significant source of performance degradation in server workloads because of their large instruction footprints and complex control flow. Due to the importance of reducing the number of instruction cache misses, there has been a myriad of proposals for hardware instruction prefetchers in the past two decades. While effectual, state-of-the-art hardware instruction prefetchers either impose considerable storage overhead or require significant changes in the frontend of a processor. Unlike hardware instruction prefetchers, code-layout optimization techniques profile a program and then reorder the code layout of the program to increase spatial locality, and hence,... 

The frontend stalls caused by instruction and BTB misses are a significant source of performance degradation in server processors. Prefetchers are commonly employed to mitigate frontend bottleneck. However, next-line prefetchers, which are available in server processors, are incapable of eliminating a considerable number of L1 instruction misses. Temporal instruction prefetchers, on the other hand, effectively remove most of the instruction and BTB misses but impose significant area overhead. Recently, an old idea of using BTB-directed instruction prefetching is revived to address the limitations of temporal instruction prefetchers. While this approach leads to prefetchers with low area... 

In many sensor fusion algorithms, the vision based RANdom Sample Consensus (RANSAC) method is used for estimating motion parameters for autonomous robots. Usually such algorithms estimate both translation and rotation parameters together which makes them inefficient solutions for merely rotation estimation purposes. This paper presents a novel 3-point RANSAC algorithm for estimating only the rotation parameters between two camera frames which can be utilized as a high rate source of information for a camera-IMU sensor fusion system. The main advantage of our proposed approach is that it performs less computations and requires fewer iterations for achieving the best result. Despite many... 

Data prefetching, i.e., the act of predicting an application's future memory accesses and fetching those that are not in the on-chip caches, is a well-known and widely used approach to hide the long latency of memory accesses. The fruitfulness of data prefetching is evident to both industry and academy: Nowadays, almost every high-performance processor incorporates a few data prefetchers for capturing various access patterns of applications; besides, there is a myriad of proposals for data prefetching in the research literature, where each proposal enhances the efficiency of prefetching in a specific way. In this survey, we evaluate the effectiveness of data prefetching in the context of... 

Applications extensively use data objects with a regular and fixed layout, which leads to the recurrence of access patterns over memory regions. Spatial data prefetching techniques exploit this phenomenon to prefetch future memory references and hide the long latency of DRAM accesses. While state-of-the-art spatial data prefetchers are effective at reducing the number of data misses, we observe that there is still significant room for improvement. To select an access pattern for prefetching, existing spatial prefetchers associate observed access patterns to either a short event with a high probability of recurrence or a long event with a low probability of recurrence. Consequently, the...