12737974
The Role of Top-down and Bottom-up Processes in Guiding Eye Movements during Visual Search
To investigate how top-down (TD) and bottom-up (BU) information is weighted in the guidance of human search behavior, we manipulated the proportions of BU and TD components in a saliency-based model. The model is biologically plausible and implements an artificial retina and a neuronal population code. The BU component is based on feature-contrast. The TD component is defined by a feature-template match to a stored target representation. We compared the model's behavior at different mixtures of TD and BU components to the eye movement behavior of human observers performing the identical search task. We found that a purely TD model provides a much closer match to human behavior than any mixture model using BU information. Only when biological constraints are removed (e.g., eliminating the retina) did a BU/TD mixture model begin to approximate human behavior.
15851389
Compiler-directed data cache leakage reduction
Leakage energy reduction for caches has been the target of many recent research efforts. In this work, we propose a novel compiler directed approach to reduce the data cache leakage energy by exploiting the program behavior. The proposed approach is based on the observation that only a small potion of data are active at runtime and the program spends a lot of execution time in loops, so a large portion of data cache lines, which are not accessed by the loops, can be placed into leakage control mode to reduce leakage energy consumption. The experimental results show that the proposal approach is comparable to the pure hardware based approach in reducing data cache leakage energy.
15072800
Loop-based leakage control for branch predictors
Leakage energy consumption is becoming an important design consideration with the scaling of technology. Besides caches, branch predictors are among the largest on-chip array structures and consume non-trivial leakage energy. This paper proposes two loop-based strategies to reduce the branch predictor leakage without impacting prediction accuracy, which is crucial for achieving high performance. The loop-based approaches exploit the fact that loops usually only contain a small number of instructions and hence fewer branch instructions. Consequently, all the non-active entries of branch predictors can be placed into the low leakage mode during the loop execution for leakage energy savings. Compilers can annotate this information and pass it to the processor for reducing leakage at runtime. Compared to the recently-proposed decay-based approach, our experimental results show that the loop-based approach can extract 16.2% more branch predictor idleness on average, leading to more leakage energy savings without impacting the branch prediction accuracy and performance.
15801995
Data space oriented scheduling in embedded systems
With the widespread use of embedded devices such as PDAs, printers, game machines, cellular telephones, achieving high performance demands an optimized operating system (OS) that can take full advantage of the underlying hardware components. This paper presents a locality conscious process scheduling strategy for embedded environments. The objective of our scheduling strategy is to maximize reuse in the data cache. It achieves this by restructuring the process codes based on data sharing patterns between processes.
13431767
A compiler approach for reducing data cache energy
Silicon technology advances have made it possible to pack millions of transistors --- switching at high clock speeds --- on a single chip. While these advances bring unprecedented performance to electronic products, they pose difficult power/energy consumption problems. For example, large number of transistors in dense on-chip cache memories consume significant static (leakage) power even if the cache is not used by the current computation. While previous compiler research studied code and data restructuring for improving data cache performance, to our knowledge, there is no compiler-based study that targets data cache leakage power consumption. In this paper, we present code restructuring techniques for array-based and pointer-intensive applications for reducing data cache energy consumption. The idea is to let the compiler to analyze the code and insert instructions that turn off cache lines that keep variables not used by the current computation. This turning off does not destroy contents of a cache line, and waking up the cache line incurs very little overhead. Due to data locality, we find that at a given time only a small portion of the data cache needs to be active; the remaining part can be placed into a leakage-saving mode (state); i.e., they can be turned off. Our preliminary results indicate that the proposed strategy reduces the cache energy consumption significantly. We also show that several compiler optimizations increase the effectiveness of our strategy.
8356979
Real-time Accurate Object Detection using Multiple Resolutions
We propose a multi-resolution framework inspired by human visual search for general object detection. Different resolutions are represented using a coarse-to-fine feature hierarchy. During detection, the lower resolution features are initially used to reject the majority of negative windows at relatively low cost, leaving a relatively small number of windows to be processed in higher resolutions. This enables the use of computationally more expensive higher resolution features to achieve high detection accuracy. We applied this framework on Histograms of Oriented Gradient (HOG) features for object detection. Our multi-resolution detector produced better performance for pedestrian detection than state-of-the-art methods (Dalal and Triggs, 2005), and was faster during both training and testing. Testing our method on motorbikes and cars from the VOC database revealed similar improvements in both speed and accuracy, suggesting that our approach is suitable for realtime general object detection applications.
16445226
Modal expansion of HRTFs: Continuous representation in frequency-range-angle
This paper proposes a continuous HRTF representation in both 3D spatial and frequency domains. The method is based on the acoustic reciprocity principle and a modal expansion of the wave equation solution to represent the HRTF variations with different variables in separate basis functions. The derived spatial basis modes can achieve HRTF near-field and far-field representation in one formulation. The HRTF frequency components are expanded using Fourier Spherical Bessel series for compact representation. The proposed model can be used to reconstruct HRTFs at any arbitrary position in space and at any frequency point from a finite number of measurements. Analytical simulated and measured HRTFs from a KEMAR are used to validate the model.
7006061
Iterative extrapolation algorithm for data reconstruction over sphere
Given limited or incomplete measurement data on a sphere, a new iterative algorithm is proposed on how to extrapolate signal over the whole sphere. The algorithm is based on a priori assumption that the Fourier decomposition of the signal on the sphere has finite degree of spherical harmonic coefficients, that is, the signal is mode limited. The algorithm is a simple iteration involving only the spherical harmonic decomposition. It is proven that the algorithm converges to the original signal over observation region and the convergence rate is lower bounded by the largest eigenvalue of an associated Fredholm integral equation.