• 제목/요약/키워드: Time predictability

검색결과 219건 처리시간 0.027초

Exploiting Standard Deviation of CPI to Evaluate Architectural Time-Predictability

  • Zhang, Wei;Ding, Yiqiang
    • Journal of Computing Science and Engineering
    • /
    • 제8권1호
    • /
    • pp.34-42
    • /
    • 2014
  • Time-predictability of computing is critical for hard real-time and safety-critical systems. However, currently there is no metric available to quantitatively evaluate time-predictability, a feature crucial to the design of time-predictable processors. This paper first proposes the concept of architectural time-predictability, which separates the time variation due to hardware architectural/microarchitectural design from that due to software. We then propose the standard deviation of clock cycles per instruction (CPI), a new metric, to measure architectural time-predictability. Our experiments confirm that the standard deviation of CPI is an effective metric to evaluate and compare architectural time-predictability for different processors.

Time-Predictable Java Dynamic Compilation on Multicore Processors

  • Sun, Yu;Zhang, Wei
    • Journal of Computing Science and Engineering
    • /
    • 제6권1호
    • /
    • pp.26-38
    • /
    • 2012
  • Java has been increasingly used in programming for real-time systems. However, some of Java's features such as automatic memory management and dynamic compilation are harmful to time predictability. If these problems are not solved properly then it can fundamentally limit the usage of Java for real-time systems, especially for hard real-time systems that require very high time predictability. In this paper, we propose to exploit multicore computing in order to reduce the timing unpredictability that is caused by dynamic compilation and adaptive optimization. Our goal is to retain high performance comparable to that of traditional dynamic compilation, while at the same time, obtain better time predictability for Java virtual machine (JVM). We have studied pre-compilation techniques to utilize another core more efficiently, preoptimization on another core (PoAC) scheme to replace the adaptive optimization system (AOS) in Jikes JVM and the counter based optimization (CBO). Our evaluation reveals that the proposed approaches are able to attain high performance while greatly reducing the variation of the execution time for Java applications.

Scratchpad Memory Architectures and Allocation Algorithms for Hard Real-Time Multicore Processors

  • Liu, Yu;Zhang, Wei
    • Journal of Computing Science and Engineering
    • /
    • 제9권2호
    • /
    • pp.51-72
    • /
    • 2015
  • Time predictability is crucial in hard real-time and safety-critical systems. Cache memories, while useful for improving the average-case memory performance, are not time predictable, especially when they are shared in multicore processors. To achieve time predictability while minimizing the impact on performance, this paper explores several time-predictable scratch-pad memory (SPM) based architectures for multicore processors. To support these architectures, we propose the dynamic memory objects allocation based partition, the static allocation based partition, and the static allocation based priority L2 SPM strategy to retain the characteristic of time predictability while attempting to maximize the performance and energy efficiency. The SPM based multicore architectural design and the related allocation methods thus form a comprehensive solution to hard real-time multicore based computing. Our experimental results indicate the strengths and weaknesses of each proposed architecture and the allocation method, which offers interesting on-chip memory design options to enable multicore platforms for hard real-time systems.

CReMeS: A CORBA COmpliant Reflective Memory based Real-time Communication Service

  • Chung, Sun-Tae
    • 한국통신학회논문지
    • /
    • 제25권10B호
    • /
    • pp.1675-1689
    • /
    • 2000
  • We present CReMeS a CORBA-compliant design and implementation of a new real-time communication service. It provides for efficient predictable and scalable communication between information producers and consumers. The CReMeS architecture is based on MidART's Real-Time Channel-based Reflective Memory (RT-CRM) abstraction. This architecture supports the separation of QoS specification between producer and consumer of data and employs a user-level scheduling scheme for communicating real-time tasks. These help us achieve end-to-end predictability and allows our service to scale. The CReMeS architecture provides a CORBA interface to applications and demands no changes to the ORB layer and the language mapping layer. Thus it can run on non real-time Off-The-Shelf ORBs enables applications on these ORBs to have scalable and end-to-end predictable asynchronous communication facility. In addition an application designer can select whether to use an out-of-band channel or the ORB GIOP/IIOP for data communication. This permits a trade-off between performance predictability and reliability. Experimental results demonstrate that our architecture can achieve better performance and predictability than a real-time implementation of the CORBA Even Service when the out-of-band channel is employed for data communication it delivers better predictability with comparable performance when the ORB GIOP/IIOP is used.

  • PDF

기상연구소 3개월 예측시스템의 예측성 평가 (Predictability of the Seasonal Simulation by the METRI 3-month Prediction System)

  • 변영화;송지혜;박수희;임한철
    • 대기
    • /
    • 제17권1호
    • /
    • pp.27-44
    • /
    • 2007
  • The purpose of this study is to investigate predictability of the seasonal simulation by the METRI (Meteorological Research Institute) AGCM (Atmospheric General Circulation Model), which is a long-term prediction model for the METRI 3-month prediction system. We examine the performance skill of climate simulation and predictability by the analysis of variance of the METRI AGCM, focusing on the precipitation, 850 hPa temperature, and 500 hPa geopotential height. According to the result, the METRI AGCM shows systematic errors with seasonal march, and represents large errors over the equatorial region, compared to the observation. Also, the response of the METRI AGCM by the variation of the sea surface temperature is obvious for the wintertime and springtime. However, the METRI AGCM does not show the significant ENSO-related signal in autumn. In case of prediction over the east Asian region, errors between the prediction results and the observation are not quite large with the lead-time. However, in the predictability assessment using the analysis of variance method, longer lead-time makes the prediction better, and the predictability becomes better in the springtime.

부사 및 부사구의 의미적 예측가능성과 피치액센트 실현의 상관관계 (Correlation between sematic predictability and pitch-accent realization)

  • 조상현;이주경
    • 대한음성학회:학술대회논문집
    • /
    • 대한음성학회 2007년도 한국음성과학회 공동학술대회 발표논문집
    • /
    • pp.281-284
    • /
    • 2007
  • This experimental study aims to find out the correlation between semantic predictability and pitch-accent realization. For the experiment, we classified the predictability into three degrees: unpredictable, implicitly predictable, and explicitly predictable. And then each degree divided into to two subcatergories: one is adverbs/adverbial phrases of time or place and the other one is not time or place adverbs/adverbial phrases. The materials used in the experiment were 9 sentences for the each subcategory. One male and one female English native speakers participated in this experiment. Their reading speeches were recorded on Digital Audio Tape. Their speech data were analyzed by using Pitchworks program. The results of this experiment show pitch accented ratio is somewhat in inverse proportion to the degree of predictability.

  • PDF

마이크로 유전알고리즘을 이용한 적운물리과정 모수 최적화에 따른 여름철 강수예측성능 개선 (The Improvement of Summer Season Precipitation Predictability by Optimizing the Parameters in Cumulus Parameterization Using Micro-Genetic Algorithm)

  • 장지연;이용희;최현주
    • 대기
    • /
    • 제30권4호
    • /
    • pp.335-346
    • /
    • 2020
  • Three free parameters included in a cumulus parameterization are optimized by using micro-genetic algorithm for three precipitation cases occurred in the Korea Peninsula during the summer season in order to reduce biases in a regional model associated with the uncertainties of the parameters and thus to improve the predictability of precipitation. The first parameter is the one that determines the threshold in convective trigger condition. The second parameter is the one that determines boundary layer forcing in convective closure. Finally, the third parameter is the one used in calculating conversion parameter determining the fraction of condensate converted to convective precipitation. Optimized parameters reduce the occurrence of convections by suppressing the trigger of convection. The reduced convection occurrence decreases light precipitation but increases heavy precipitation. The sensitivity experiments are conducted to examine the effects of the optimized parameters on the predictability of precipitation. The predictability of precipitation is the best when the three optimized parameters are applied to the parameterization at the same time. The first parameter most dominantly affects the predictability of precipitation. Short-range forecasts for July 2018 are also conducted to statistically assess the precipitation predictability. It is found that the predictability of precipitation is consistently improved with the optimized parameters.

S2S 멀티 모델 앙상블을 이용한 북극 해빙 면적의 예측성 (Predictability of the Arctic Sea Ice Extent from S2S Multi Model Ensemble)

  • 박진경;강현석;현유경
    • 대기
    • /
    • 제28권1호
    • /
    • pp.15-24
    • /
    • 2018
  • Sea ice plays an important role in modulating surface conditions at high and mid-latitudes. It reacts rapidly to climate change, therefore, it is a good indicator for capturing these changes from the Arctic climate. While many models have been used to study the predictability of climate variables, their performance in predicting sea ice was not well assessed. This study examines the predictability of the Arctic sea ice extent from ensemble prediction systems. The analysis is focused on verification of predictability in each model compared to the observation and prediction in particular, on lead time in Sub-seasonal to Seasonal (S2S) scales. The S2S database now provides quasi-real time ensemble forecasts and hindcasts up to about 60 days from 11 centers: BoM, CMA, ECCC, ECMWF, HMCR, ISAC-CNR, JMA, KMA, Meteo France, NCEP and UKMO. For multi model comparison, only models coupled with sea ice model were selected. Predictability is quantified by the climatology, bias, trends and correlation skill score computed from hindcasts over the period 1999 to 2009. Most of models are able to reproduce characteristics of the sea ice, but they have bias with seasonal dependence and lead time. All models show decreasing sea ice extent trends with a maximum magnitude in warm season. The Arctic sea ice extent can be skillfully predicted up 6 weeks ahead in S2S scales. But trend-independent skill is small and statistically significant for lead time over 6 weeks only in summer.

Two-Level Scratchpad Memory Architectures to Achieve Time Predictability and High Performance

  • Liu, Yu;Zhang, Wei
    • Journal of Computing Science and Engineering
    • /
    • 제8권4호
    • /
    • pp.215-227
    • /
    • 2014
  • In modern computer architectures, caches are widely used to shorten the gap between processor speed and memory access time. However, caches are time-unpredictable, and thus can significantly increase the complexity of worst-case execution time (WCET) analysis, which is crucial for real-time systems. This paper proposes a time-predictable two-level scratchpad-based architecture and an ILP-based static memory objects assignment algorithm to support real-time computing. Moreover, to exploit the load/store latencies that are known statically in this architecture, we study a Scratch-pad Sensitive Scheduling method to further improve the performance. Our experimental results indicate that the performance and energy consumption of the two-level scratchpad-based architecture are superior to the similar cache based architecture for most of the benchmarks we studied.

인터넷을 통한 원격제어기의 임의 시간지연의 예측가능성에 대한 연구 (A Study on the Predictability of Random Time Delay of Telecontroller via Internet)

  • 심현승;허경무;김장기
    • 제어로봇시스템학회논문지
    • /
    • 제7권10호
    • /
    • pp.849-858
    • /
    • 2001
  • One of the important problems which should be solved in the telecontroller control is the time delay problem. In this paper, we propose a method of solving a random time delay problem using QoS(quality of service), and we show not only how to solve an unpredictable time delay problem but also how to compute a maximum time delay that could satisfy a basic assumption of many telecontroller methods. Using our proposed method, it is find that we can offer more stable time delay in telecontroller than using TCP and UDP.

  • PDF