11874775
Microarchitecture Level Interconnect Modeling Considering Layout Optimization
— In this paper, we study microarchitecture-level interconnect modeling for power and performance. Considering structural interconnects, layer assignment, and concurrent repeater and Flip-Flop (FF) insertion, we develop cycle-accurate microarchitecture-level power and throughput simulation and obtain an accurate modeling of interconnects at the early design stage. Experiment show that the simulation reduces over-estimation by up to 2.24X compared to the conventional power estimation based on purely stochastic interconnects and fixed switching factor. Furthermore, we optimize throughput with consideration of FF insertion for interconnects and floorplanning optimization. We show that throughput is not always higher for an increased clock frequency, and there exists an optimal clock frequency to maximize throughput for a given microarchitecture and given floorplan. In addition, floorplan optimized for IPC (instructions per cycle)-critical interconnects has little on the total interconnect length but improves throughput by 23.49%. As FF insertion becomes necessary to achieve the clock frequency specified by ITRS, we conclude that the traditional design flow optimizing IPC and clock frequency separately is no longer valid, and coupled microarchitecture and layout optimization may improve both power efficiency and throughput.
9509924
Microarchitecture-level leakage reduction with data retention
In this paper, we study microarchitecture-level leakage energy reduction by power gating. We consider the virtual power/ground rails clamp (VRC) and multithreshold CMOS (MTCMOS) techniques and apply VRC to memory-based units for data retention and MTCMOS to the other units. We propose a systematic methodology for leakage reduction at the microarchitecture level, in which profiling of idle period distribution and ideal power gating analysis are used to select a target component for realistic power gating. We show that the ideal leakage energy reduction can be up to 30% of the total energy for the modern high-performance very long instruction word processors we study and that the secondary level (L2) cache contributes most to the reduction. We further improve the existing adaptive cache decay method for leakage reduction by using VRC for data retention and name it VRC decay . Applied to L2 cache, the VRC decay, on average, increases performance by 5.6% and reduces system energy by 24.1%, compared to the adaptive cache decay without data retention.
1018288
Coupled Power and Thermal Simulation with Active Cooling
Power is rapidly becoming the primary design constraint for systems ranging from server computers to handhelds. In this paper we study microarchitecture-level coupled power and thermal simulation considering dynamic and leakage power models with temperature and voltage scaling. We develop an accurate temperature-dependent leakage power model and efficient temperature calculation, and show that leakage energy can be different by up to 10X for temperatures between 35°C and 110°C. Given the growing significance of leakage power and its sensitive dependence on temperature, no power simulation without considering dynamic temperature calculation is accurate. Furthermore, we discuss the thermal runaway induced by the interdependence between leakage power and temperature, and show that in the near future thermal runaway could be a severe problem. We also study the microarchitecture level coupled power and thermal management by novel active cooling techniques that reduce packaging thermal resistance. We show that the direct water-spray cooling technique reduces thermal resistance from 0.8°C/W for conventional packaging to 0.05°C/W, and increases system maximum clock by up to 2.44X under the same thermal constraints.
17606652
Solving the Chan-Vese Model by a Multiphase Level Set Algorithm Based on the Topological Derivative
In this work, we specifically solve the Chan-Vese active contour model by multiphase level set methods. We first develop a fast algorithm based on calculating the variational energy of the Chan-Vese model without the length term. We check whether the energy decreases or not when we move a point to another segmented region. Then we draw a connection between this algorithm and the topological derivative, a concept emerged from the shape optimization field. Furthermore, to include the length term of the Chan-Vese model, we apply a preprocessing step on the image by using nonlinear diffusion. We show numerical experiments to demonstrate the efficiency and the robustness of our algorithm.
14821600
Comparing presentation summaries: slides vs. reading vs. listening
As more audio and video technical presentations go online, it becomes imperative to give users effective summarization and skimming tools so that they can find the presentation they want and browse through it quickly. In a previous study, we reported three automated methods for generating audio-video summaries and a user evaluation of those methods. An open question remained about how well various text/image only techniques will compare to the audio-video summarizations. This study attempts to fill that gap.
This paper reports a user study that compares four possible ways of allowing a user to skim a presentation: 1) PowerPoint slides used by the speaker during the presentation, 2) the text transcript created by professional transcribers from the presentation, 3) the transcript with important points highlighted by the speaker, and 4) a audio-video summary created by the speaker. Results show that although some text-only conditions can match the audio-video summary, users have a marginal preference for audio-video (ANOVA f=3.067, p=0.087). Furthermore, different styles of slide-authoring (e.g., detailed vs. big-points only) can have a big impact on their effectiveness as summaries, raising a dilemma for some speakers in authoring for on-demand previewing versus that for live audiences.
5542322
Rendering with concentric mosaics
An image based system and process for rendering novel views of a real or synthesized 3D scene based on a series of concentric mosaics depicting the scene. In one embodiment, each concentric mosaic represents a collection of consecutive slit images of the surrounding 3D scene taken from a different viewpoint tangent to a circle on a plane within the scene. Novel views from viewpoints within circular regions of the aforementioned circle plane defined by the concentric mosaics are rendered using these concentric mosaics. Specifically, a slit image can be identified by a ray originating at its viewpoint on the circle plane and extending toward the longitudinal midline of the slit image. Each of the rays associated with the slit images needed to construct a novel view will either coincide with one of the rays associated with a previously captured slit image, or it will pass between two of the concentric circles on the circle plane. If it coincides, then the previously captured slit image associated with the coinciding ray can be used directly to construct part of the novel view. If the ray passes between two of the concentric circles of the plane, then the needed slit image is interpolated using the two previously captured slit images associated with the rays originating from the adjacent concentric circles that are parallel to the non-coinciding ray. If the objects in the 3D scene are close to the camera, depth correction is applied to reduce image distortion for pixels located above and below the circle plane. In another embodiment, a single camera is used to capture a sequence of images. Each image includes image data that has a ray direction associated therewith. To render an image at a novel viewpoint, multiple ray directions from the novel viewpoint are chosen. Image data is combined from the sequence of images by selecting image data that has a ray direction substantially aligning with the ray direction from the novel viewpoint.
14096392
Mapping DAG-based applications to multiclusters with background workload
Before an application modelled as a directed acyclic graph (DAG) is executed on a heterogeneous system, a DAG mapping policy is often enacted. After mapping, the tasks (in the DAG-based application) to be executed at each computational resource are determined. The tasks are then sent to the corresponding resources, where they are orchestrated in the pre-designed pattern to complete the work. Most DAG mapping policies in the literature assume that each computational resource is a processing node of a single processor, i.e. the tasks mapped to a resource are to be run in sequence. Our studies demonstrate that if the resource is actually a cluster with multiple processing nodes, this assumption will cause a mis-perception in the tasks' execution time and execution order. This will disturb the pre-designed cooperation among tasks so that the expected performance cannot be achieved. In this paper, a DAG mapping algorithm is presented for multicluster architectures. Each constituent cluster in the multicluster is shared by background workload (from other users) and has its own independent local scheduler. The multicluster DAG mapping policy is based on theoretical analysis and its performance is evaluated through extensive experimental studies. The results show that compared with conventional DAG mapping policies, the new scheme that we present can significantly improve the scheduling performance of a DAG-based application in terms of the schedule length.
1023314
An Investigation into the Application of Different Performance Prediction Methods to Distributed Enterprise Applications
Response time predictions for workload on new server architectures can enhance Service Level Agreement–based resource management. This paper evaluates two performance prediction methods using a distributed enterprise application benchmark. The historical method makes predictions by extrapolating from previously gathered performance data, while the layered queuing method makes predictions by solving layered queuing networks. The methods are evaluated in terms of: the systems that can be modelled; the metrics that can be predicted; the ease with which the models can be created and the level of expertise required; the overheads of recalibrating a model; and the delay when evaluating a prediction. The paper also investigates how a prediction-enhanced resource management algorithm can be tuned so as to compensate for predictive inaccuracy and balance the costs of SLA violations and server usage.