Publications

General-purpose processors, while tremendously versatile, pay a huge cost for their flexibility by wasting over 99% of the energy in programmability overheads. We observe that reducing this waste requires tuning data storage and compute structures and their connectivity to the data-flow and data-locality patterns in the algorithms. Hence, by backing off from full programmability and instead targeting key data-flow patterns used in a domain, we can create efficient engines that can be programmed and reused across a wide range of applications within that domain. We present the Convolution Engine (CE)---a programmable processor specialized for the convolution-like data-flow prevalent in computational photography, computer vision, and video processing. The CE achieves energy efficiency by capturing data-reuse patterns, eliminating data transfer overheads, and enabling a large number of operations per memory access. We demonstrate that the CE is within a factor of 2--3× of the energy and area efficiency of custom units optimized for a single kernel. The CE improves energy and area efficiency by 8--15× over data-parallel Single Instruction Multiple Data (SIMD) engines for most image processing applications.<!-- END_PAGE_1 -->

Objectives This study aims to examine the prevalence of comparisons of surgery to drug regimens, the strength of evidence of such comparisons and whether surgery or the drug intervention was favoured. Design Systematic review of systematic reviews (umbrella review). Data sources Cochrane Database of Systematic Reviews. Eligibility criteria Systematic reviews attempt to compare surgical to drug interventions. Data extraction We extracted whether the review found any randomised controlled trials (RCTs) for eligible comparisons. Individual trial results were extracted directly from the systematic review. Synthesis The outcomes of each meta-analysis were resynthesised into random-effects meta-analyses. Egger’s test and excess significance were assessed. Results Overall, 188 systematic reviews intended to compare surgery versus drugs. Only 41 included data from at least one RCT (total, 165 RCTs) and covered a total of 103 different outcomes of various comparisons of surgery versus drugs. A GRADE assessment was performed by the Cochrane reviewers for 87 (83%) outcomes in the reviews, indicating the strength of evidence was high in 4 outcomes (4%), moderate in 22 (21%), low in 27 (26%) and very low in 33 (32%). Based on 95% CIs, the surgical intervention was favoured in 38/103 (37%), and the drugs were favoured in 13/103 (13%) outcomes. Of the outcomes with high GRADE rating, only one showed conclusive superiority in our reanalysis (sphincterotomy was better than medical therapy for anal fissure). Of the 22 outcomes with moderate GRADE rating, 6 (27%) were inconclusive, 14 (64%) were in favour of surgery and 2 (9%) were in favour of drugs. There was no evidence of excess significance. Conclusions Though the relative merits of surgical versus drug interventions are important to know for many diseases, high strength randomised evidence is rare. More randomised trials comparing surgery to drug interventions are needed.

Background— A nutrient-wide approach may be useful to comprehensively test and validate associations between nutrients (derived from foods and supplements) and blood pressure (BP) in an unbiased manner. Methods and Results— Data from 4680 participants aged 40 to 59 years in the cross-sectional International Study of Macro/Micronutrients and Blood Pressure (INTERMAP) were stratified randomly into training and testing sets. US National Health and Nutrition Examination Survey (NHANES) four cross-sectional cohorts (1999–2000, 2001–2002, 2003–2004, 2005–2006) were used for external validation. We performed multiple linear regression analyses associating each of 82 nutrients and 3 urine electrolytes with systolic and diastolic BP in the INTERMAP training set. Significant findings were validated in the INTERMAP testing set and further in the NHANES cohorts (false discovery rate <5% in training, P <0.05 for internal and external validation). Among the validated nutrients, alcohol and urinary sodium-to-potassium ratio were directly associated with systolic BP, and dietary phosphorus, magnesium, iron, thiamin, folacin, and riboflavin were inversely associated with systolic BP. In addition, dietary folacin and riboflavin were inversely associated with diastolic BP. The absolute effect sizes in the validation data (NHANES) ranged from 0.97 mm Hg lower systolic BP (phosphorus) to 0.39 mm Hg lower systolic BP (thiamin) per 1-SD difference in nutrient variable. Inclusion of nutrient intake from supplements in addition to foods gave similar results for some nutrients, though it attenuated the associations of folacin, thiamin, and riboflavin intake with BP. Conclusions— We identified significant inverse associations between B vitamins and BP, relationships hitherto poorly investigated. Our analyses represent a systematic unbiased approach to the evaluation and validation of nutrient-BP associations.

Today's rising power densities have been widely cited as the foremost challenge to continued CMOS scaling. In fact, the current power crisis is reminiscent of the final days previous technologies, such as the once popular bipolar and NMOS technologies and even vacuum tubes. How CMOS technology will respond to the current power challenge to extend CMOS scaling to sub-90nm technology is an important question for designer and CAD tool developers alike. With aggressive scaling a number of new challenges have arisen, such as leakage control, heat removal and power supply distribution, that need to be addressed using new design techniques in conjunction with new CAD solutions.This panel brings together experts in circuit design and CAD tool development to discuss the current status of low-power design and provide opinions on what new EDA capabilities are most important in the power-constrained design era. For instance, how will power be distributed in a robust fashion in sub-90nm ICs, and what are the critical EDA analysis and optimization capabilities? What are the best techniques for leakage reduction, not only in standby modes, but also in the active mode? And how far will voltage scaling take us in attacking the dynamic power consumption issue? What will a power-centric design flow look like and how will it change the way we design ICs? The objective of the panel is to explore these issues and formulate a list of critical issues that need to be addressed by the EDA community to enable successful scaling of CMOS into the sub-90nm era.

Abstract Collections of meta‐analyses assembled in meta‐epidemiological studies are used to study associations of trial characteristics with intervention effect estimates. However, methods and findings are not consistent across studies. To combine data from 10 meta‐epidemiological studies into a single database, and derive a harmonized dataset without overlap between meta‐analyses. The database design allowed trials to be contained in different meta‐analyses, multiple meta‐analyses in systematic reviews, overlapping meta‐analyses between systematic reviews, and multiple references to the same trial or review. Unique identifiers were assigned to each reference and used to identify duplicate trials. Sets of meta‐analyses with overlapping trials were identified and duplicates removed. Overlapping trials were used to examine agreement between assessments of trial characteristics. The combined database contained 427 reviews, 454 meta‐analyses and 4874 trial results. Of these, 258 meta‐analyses were unique, while for 196 at least one trial overlapped with another meta‐analysis. Median kappa statistics for reliability of assessments were 0.60 for sequence generation, 0.58 for allocation concealment and 0.87 for blinding. Based on inspection of sets of overlapping meta‐analyses, 91 meta‐analyses containing 1344 trial results were removed. Additionally, 24 duplicated trial results were removed from 16 meta‐analyses, to derive a final database containing 363 meta‐analyses and 3477 unique trial results. The final database will be used to examine the combined evidence on sources of bias in randomized controlled trials. The strategy used to remove overlap between meta‐analyses may be of use for future empirical research. Copyright © 2010 John Wiley & Sons, Ltd.

Power consumption has become a major constraint in the design of processors today. To optimize a processor for energy-efficiency requires an examination of energy-performance trade-offs in all aspects of the processor design space, including both architectural and circuit design choices. In this paper, we apply an integrated architecture-circuit optimization framework to map out energy-performance trade-offs of several different high-level processor architectures. We show how the joint architecture-circuit space provides a trade-off range of approximately 6.5x in performance for 4x energy, and we identify the optimal architectures for different design objectives. We then show that many of the designs in this space come at very high marginal costs. Our results show that, for a large range of design objectives, voltage scaling is effective in efficiently trading off performance and energy, and that the choice of optimal architecture and circuits does not change much during voltage scaling. Finally, we show that with only two designs--a dual-issue in-order design and a dual-issue out-of-order design, both properly optimized-a large part of the energy-performance trade-off space can be covered within 3% of the optimal energy-efficiency.