1856152
Understanding the energy efficiency of simultaneous multithreading
Simultaneous multithreading (SMT) has proven to be an effective method of increasing the performance of microprocessors by extracting additional instruction-level parallelism from multiple threads. In current microprocessor designs, power-efficiency is of critical importance, and we present modeling extensions to an architectural simulator to allow us to study the power-performance efficiency of SMT. After a thorough design space exploration we find that SMT can provide a performance speedup of nearly 20% for a wide range of applications with a power overhead of roughly 24%. Thus, SMT can provide a substantial benefit for energy-efficiency metrics such as ED/sup 2/. We also explore the underlying reasons for the power uplift, analyze the impact of leakage-sensitive process technologies, and discuss our model validation strategy.
7167027
Power and thermal effects of SRAM vs. latch-mux design styles and clock gating choices
This paper studies the impact on energy efficiency and thermal behavior of design style and clock-gating style in queue and array structures. These structures are major sources of power dissipation, and both design styles and various clock gating schemes can be found in modern, high-performance processors. Although some work in the circuits domain has explored these issues from a power perspective, thermal treatments are less common, and we are not aware of any work in the architecture domain. We study both SRAM and latch and multiplexer ("latch-mux") designs and their associated clock-gating options. Using circuit-level simulations of both design styles, we derive power-dissipation ratios which are then used in cycle-level power/performance/thermal simulations. We find that even though the "unconstrained" power of SRAM designs is always better than latch-mux designs, latch-mux designs dissipate less power in practice when a structure's average occupancy is low but access rate is high, especially when "stall gating" is used to minimize switching power. We also find that latch-mux designs with stall gating are especially promising from a thermal perspective, because they exhibit lower power density than SRAM designs. Overall, when combined with implementation and verification challenges for SRAMs, latch-mux designs with stall gating appear especially promising for designs with thermal constraints. This paper also shows the importance of considering the interaction between architectural and circuit design choices when performing early-stage design exploration.
2533092
State-preserving vs. non-state-preserving leakage control in caches
This paper compares the effectiveness of state-preserving and non-state-preserving techniques for leakage control in caches by comparing drowsy cache and gated-V/sub ss/ for data caches using 70nm technology parameters. To perform the comparison, we introduce "HotLeakage", a new architectural model for subthreshold and gate leakage that explicitly models the effects of temperature, voltage, and parameter variations, and has the ability to recalculate leakage currents dynamically as temperature and voltage change at runtime due to operating conditions, DVS techniques, etc. By comparing drowsy-cache and gated-V/sub ss/ at different L2 latencies and different gate oxide thickness values, we are able to identify a range of operating parameters at which gated-V/sub ss/ is more energy efficient than drowsy-cache, even though gated-V/sub ss/ does not preserve data in cache lines that have been deactivated. We are also able to show potential further benefits of gated-V/sub ss/ if an effective dynamic adaptation technique can be found. These results debunk a fairly widespread belief that state-preserving techniques are inherently superior to non-state-preserving techniques.
8401209
Optimal Traffic-Oblivious Energy-Aware Routing for Multihop Wireless Networks
Energy efficiency is an important issue in multihop wireless networks with energy concerns. Usually it is achieved with accurate knowledge of the traffic pattern and/or the current network information such as the remaining energy level. We investigate the problem of designing a routing scheme to minimize the maximum energy utilization of a multihop wireless network with weak assumption of the traffic pattern and without ongoing collection of network information. We develop polynomial size LP models to design such a routing scheme. We discuss generalizations of the LP models to various radio transmission models. In an interference-limited scenario, we show how to guarantee schedulability of the oblivious routing. We present an extension to consider lossy links. We also discuss implementation issues. The LP models achieve performance close to what an oracle can achieve in the performance study. The results for multihop wireless networks with a single sink are especially good. We make a first stride in designing a traffic-oblivious energy-aware routing framework in multihop wireless networks.
11857431
Implementation of single precision floating point square root on FPGAs
The square root operation is hard to implement on FPGAs because of the complexity of the algorithms. In this paper, we present a non-restoring square root algorithm and two very simple single precision floating point square root implementations based on the algorithm on FPGAs. One is low-cost iterative implementation that uses a traditional adder/subtracter. The operation latency is 25 clock cycles and the issue rate is 24 clock cycles. The other is high-throughput pipelined implementation that uses multiple adder/subtracters. The operation latency is 15 clock cycles and the issue rate is one clock cycle. It means that the pipelined implementation is capable of accepting a square root instruction on every clock cycle.
12892539
Experimental analysis of mode switching techniques in pen-based user interfaces
Inking and gesturing are two central tasks in pen-based user interfaces. Switching between modes for entry of uninterpreted ink and entry of gestures is required by many pen-based user interfaces. Without an appropriate mode switching technique, pen-based interactions in such situations may be inefficient and cumbersome. In this paper, we investigate five techniques for switching between ink and gesture modes in pen interfaces, including a pen-pressure based mode switching technique that allows implicit mode transition. A quantitative experimental study was conducted to evaluate the performance of these techniques. The results suggest that pressing a button with the non-preferred hand offers the fastest performance, while the technique of holding the pen still is significantly slower and more prone to error than the other techniques. Pressure, while promising, did not perform as well as the non-preferred hand button with our current implementation.
3052468
Performance Modeling and Analysis for Resource Scheduling in Data Grids
Data Grids normally deal with large data-intensive problems on geographically distributed resources; yet, most current research on performance evaluation of resource scheduling in Data Grids is based on simulation techniques, which can only consider a limited range of scenarios. In this paper, we propose a formal framework via Stochastic Petri Nets to deal with this problem. Within this framework, we model and analyze the performance of resource scheduling in Data Grids, allowing for a wide variety of job and data scheduling algorithms. As a result of our research, we can investigate more scenarios with multiple input parameters. Moreover, we can evaluate the combined effectiveness of job and data scheduling algorithms, rather than study them separately.
8805137
Classification of Text Documents
The exponential growth of the internet has led to a great deal of interest in developing useful and efficient tools and software to assist users in searching the Web. Document retrieval, categorization, routing and filtering can all be formulated as classification problems. However, the complexity of natural languages and the extremely high dimensionality of the feature space of documents have made this classification problem very difficult. We investigate four different methods for document classification: the naive Bayes classifier, the nearest neighbour classifier, decision trees and a subspace method. These were applied to seven-class Yahoo news groups (business, entertainment, health, international, politics, sports and technology) individually and in combination. We studied three classifier combination approaches: simple voting, dynamic classifier selection and adaptive classifier combination. Our experimental results indicate that the naive Bayes classifier and the subspace method outperform the other two classifiers on our data sets. Combinations of multiple classifiers did not always improve the classification accuracy compared to the best individual classifier. Among the three different combination approaches, our adaptive classifier combination method introduced here performed the best. The best classification accuracy that we are able to achieve on this seven-class problem is approximately 83%, which is comparable to the performance of other similar studies. However, the classification problem considered here is more difficult because the pattern classes used in our experiments have a large overlap of words in their corresponding documents.