1,424 results on '"Consistency model"'
Search Results
2. Full‐dose whole‐body PET synthesis from low‐dose PET using high‐efficiency denoising diffusion probabilistic model: PET consistency model.
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Pan, Shaoyan, Abouei, Elham, Peng, Junbo, Qian, Joshua, Wynne, Jacob F, Wang, Tonghe, Chang, Chih‐Wei, Roper, Justin, Nye, Jonathon A, Mao, Hui, and Yang, Xiaofeng
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POSITRON emission tomography , *TRANSFORMER models , *RANDOM noise theory , *RADIATION doses , *CLINICAL medicine , *RADIOACTIVE tracers , *RADIATION exposure - Abstract
Purpose: Positron Emission Tomography (PET) has been a commonly used imaging modality in broad clinical applications. One of the most important tradeoffs in PET imaging is between image quality and radiation dose: high image quality comes with high radiation exposure. Improving image quality is desirable for all clinical applications while minimizing radiation exposure is needed to reduce risk to patients. Methods: We introduce PET Consistency Model (PET‐CM), an efficient diffusion‐based method for generating high‐quality full‐dose PET images from low‐dose PET images. It employs a two‐step process, adding Gaussian noise to full‐dose PET images in the forward diffusion, and then denoising them using a PET Shifted‐window Vision Transformer (PET‐VIT) network in the reverse diffusion. The PET‐VIT network learns a consistency function that enables direct denoising of Gaussian noise into clean full‐dose PET images. PET‐CM achieves state‐of‐the‐art image quality while requiring significantly less computation time than other methods. Evaluation with normalized mean absolute error (NMAE), peak signal‐to‐noise ratio (PSNR), multi‐scale structure similarity index (SSIM), normalized cross‐correlation (NCC), and clinical evaluation including Human Ranking Score (HRS) and Standardized Uptake Value (SUV) Error analysis shows its superiority in synthesizing full‐dose PET images from low‐dose inputs. Results: In experiments comparing eighth‐dose to full‐dose images, PET‐CM demonstrated impressive performance with NMAE of 1.278 ± 0.122%, PSNR of 33.783 ± 0.824 dB, SSIM of 0.964 ± 0.009, NCC of 0.968 ± 0.011, HRS of 4.543, and SUV Error of 0.255 ± 0.318%, with an average generation time of 62 s per patient. This is a significant improvement compared to the state‐of‐the‐art diffusion‐based model with PET‐CM reaching this result 12× faster. Similarly, in the quarter‐dose to full‐dose image experiments, PET‐CM delivered competitive outcomes, achieving an NMAE of 0.973 ± 0.066%, PSNR of 36.172 ± 0.801 dB, SSIM of 0.984 ± 0.004, NCC of 0.990 ± 0.005, HRS of 4.428, and SUV Error of 0.151 ± 0.192% using the same generation process, which underlining its high quantitative and clinical precision in both denoising scenario. Conclusions: We propose PET‐CM, the first efficient diffusion‐model‐based method, for estimating full‐dose PET images from low‐dose images. PET‐CM provides comparable quality to the state‐of‐the‐art diffusion model with higher efficiency. By utilizing this approach, it becomes possible to maintain high‐quality PET images suitable for clinical use while mitigating the risks associated with radiation. The code is availble at https://github.com/shaoyanpan/Full‐dose‐Whole‐body‐PET‐Synthesis‐from‐Low‐dose‐PET‐Using‐Consistency‐Model. [ABSTRACT FROM AUTHOR]
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- 2024
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3. Designing the replication layer of a general-purpose datacenter key-value store
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Gavrielatos, Vasilis, Nagarajan, Vijayanand, and Grot, Boris
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key-value store ,KVS ,consistency model ,performance maximization ,Release consistency - Abstract
Online services and cloud applications such as graph applications, messaging systems, coordination services, HPC applications, social networks and deep learning rely on key-value stores (KVSes), in order to reliably store and quickly retrieve data. KVSes are NoSQL Databases with a read/write/read-modify-write API. KVSes replicate their dataset in a few servers, such that the KVS can continue operating in the presence of faults (availability). To allow programmers to reason about replication, KVSes specify a set of rules (consistency), which are enforced through the use of replication protocols. These rules must be intuitive to facilitate programmer productivity (programmability). A general-purpose KVS must maximize the number of operations executed per unit of time within a predetermined latency (performance) without compromising on consistency, availability or programmability. However, all three of these guarantees are at odds with performance. In this thesis, we explore the design of the replication layer of a general-purpose KVS, which is responsible for navigating this trade-off, by specifying and enforcing the consistency and availability guarantees of the KVS. We start the exploration by observing that modern, server-grade hardware with manycore servers and RDMA-capable networks, challenges conventional wisdom in protocol design. In order to investigate the impact of these advances on protocols and their design, we first create an informal taxonomy of strongly-consistent replication protocols. We focus on strong consistency semantics because they are necessary for a general-purpose KVS and they are at odds with performance. Based on this taxonomy we carefully select 10 protocols for analysis. Secondly, we present Odyssey, a frame-work tailored towards protocol implementation for multi-threaded, RDMA-enabled, in-memory, replicated KVSes. Using Odyssey, we characterize the design space of strongly-consistent replication protocols, by building, evaluating and comparing the 10 protocols. Our evaluation demonstrates that some of the protocols that were efficient in yesterday's hardware are not so today because they cannot take advantage of the abundant parallelism and fast networking present in modern hardware. Conversely, some protocols that were inefficient in yesterday's hardware are very attractive today. We distil our findings in a concise set of general guidelines and recommendations for protocol selection and design in the era of modern hardware. The second step of our exploration focuses on the tension between consistency and performance. The problem is that expensive strongly-consistent primitives are necessary to achieve synchronization, but in typical applications only a small fraction of accesses is actually used for synchronization. To navigate this trade-off, we advocate the adoption of Release Consistency (RC) for KVSes. We argue that RC's one-sided barriers are ideal for capturing the ordering relationship between synchronization and non-synchronization accesses while enabling high performance. We present Kite, a general-purpose, replicated KVS that enforces RC through a novel fast/slow path mechanism that leverages the absence of failures in the typical case to maximize performance, while relying on the slow path for progress. In ad dition, Kite leverages our study of replication protocols to select the most suitable protocols for its primitives and is implemented over Odyssey to make the most out of modern hardware. Finally, Kite does not compromise on consistency, availability or programmability, as it provides sufficient primitives to implement any algorithm (consistency), does not interrupt its operation on a failure (availability), and offers the RC API that programmers are already familiar with (programmability).
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- 2021
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4. Evaluación del Modelode Consistencia de Grawe en población mexicana.
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Cárdenas-López, Georgina, Chicchi-Giglioli, Irene Alice, Durón-Figueroa, Raúl, Reyes, Fabiola, Carrasco-Ribelles, Lucia A., and Alcañiz-Raya, Mariano
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MEXICANS , *BASIC needs , *MENTAL illness , *SOCIAL problems , *SELF-esteem - Abstract
Mental disorders represent one of the leading social problems in the world, revolving around several theoretical models to support integrative interventions. Grawe's Consistency Model states that four basic psychological needs must be satisfied to maintain mental health. These needs refer to attachment, self-esteem, control or self-efficacy, and decreased pain and increased pleasure. Although some studies have analyzed the relationship between these constructs, few studies focused on evaluating Grawe's model. Objective. The present study aimed to evaluate the relationship between the four basic psychological needs in the Mexican population. Sixty-one participants: 29 men and 31 women, were administered a series of scales measuring the abovementioned four constructs. Results. Results showed significant correlations in the different scales and subscales. Discussion. The present study allowed a greater understanding of the basic psychological needs raised in Grawe's model in the Mexican population; however, the study had some limitations and cautionary aspects for future studies. [ABSTRACT FROM AUTHOR]
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- 2023
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5. Revisit Raft Consistency Protocol on Private Blockchain System in High Network Latency
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Cao, Ning, Jiang, Dianheng, Liu, Yang, Zhou, Yulan, Du, Haiwen, Qiao, Xueming, Xia, Yingxue, Zhu, Dongjie, Yu, Fang, Bi, Wenbin, Filipe, Joaquim, Editorial Board Member, Ghosh, Ashish, Editorial Board Member, Prates, Raquel Oliveira, Editorial Board Member, Zhou, Lizhu, Editorial Board Member, Sun, Xingming, editor, Zhang, Xiaorui, editor, Xia, Zhihua, editor, and Bertino, Elisa, editor
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- 2021
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6. Locality and Singularity for Store-Atomic Memory Models
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Derevenetc, Egor, Meyer, Roland, Schweizer, Sebastian, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, El Abbadi, Amr, editor, and Garbinato, Benoît, editor
- Published
- 2017
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7. Realizing Highly-Available, Scalable, and Protocol-Independent vSDN Slicing With a Distributed Network Hypervisor System
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Huibai Huang, Bin Niu, Shaofei Tang, Shengru Li, Sicheng Zhao, Kai Han, and Zuqing Zhu
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Software-defined networking (SDN) ,network virtualization ,distributed network hypervisor ,consistency model ,protocol-oblivious forwarding (POF) ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 - Abstract
In this paper, we design and implement a distributed network virtualization hypervisor (NVH) system, namely, DPVisor, which can provide superior network programmability based on protocol-oblivious forwarding to realize highly-available, scalable, and protocol-independent virtual software-defined network slicing. The experimental comparisons indicate that DPVisor achieves comparable performance as ONVisor (i.e., an OpenFlow-based ONOS benchmark), in terms of the message processing latency, message processing throughput, and failure recovery time. Moreover, to optimize the performance of the distributed NVH systems, we carefully adjust the consistency model used in the state synchronization of NVH instances and propose a local cache-based scheme to balance the tradeoff between the consistency and availability of network status. Our experimental results confirm that the message processing throughput of the distributed NVH systems can be greatly improved (i.e., for both DPVisor and ONVisor), while the data consistency among NVH instances is still maintained well.
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- 2018
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8. Simulation and Invariance for Weak Consistency
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Alglave, Jade, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, and Rival, Xavier, editor
- Published
- 2016
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9. Transaction Chopping for Parallel Snapshot Isolation
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Cerone, Andrea, Gotsman, Alexey, Yang, Hongseok, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Weikum, Gerhard, Series editor, and Moses, Yoram, editor
- Published
- 2015
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10. Distributed Data Persistency
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Apostolos Kokolis, Benjamin Reidys, Antonis Psistakis, Jian Huang, and Josep Torrellas
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Data consistency ,Computer science ,business.industry ,Distributed computing ,Consistency model ,Fault tolerance ,Data loss ,Durability ,Data recovery ,Consistency (database systems) ,Hardware and Architecture ,Electrical and Electronic Engineering ,business ,Auxiliary memory ,Software - Abstract
Distributed applications such as key-value stores and databases avoid frequent writes to secondary storage devices to minimize performance degradation. They provide fault tolerance by replicating variables in the memories of different nodes, and using data consistency protocols to ensure consistency across replicas. Unfortunately, the reduced data durability guarantees provided can cause data loss or slow data recovery. In this environment, non-volatile memory (NVM) offers the ability to attain both high performance and data durability in distributed applications. However, it is unclear how to tie NVM memory persistency models to the existing data consistency frameworks, and what are the durability guarantees that the combination will offer to distributed applications. In this paper, we propose the concept of Distributed Data Persistency (DDP) model, which is the binding of the memory persistency model with the data consistency model in a distributed system. We reason about the interaction between consistency and persistency by using the concepts of Visibility Point and Durability Point. We design low-latency distributed protocols for DDP models that combine five consistency models with five persistency models. For the resulting DDP models, we investigate the trade-offs between performance, durability, and intuition provided to the programmer.
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- 2022
11. Evaluation of Labeling Strategies for Rotating Maps
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Gemsa, Andreas, Nöllenburg, Martin, Rutter, Ignaz, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Kobsa, Alfred, editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Weikum, Gerhard, editor, Gudmundsson, Joachim, editor, and Katajainen, Jyrki, editor
- Published
- 2014
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12. CAP Theorem: Revision of Its Related Consistency Models.
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Muñoz-Escoí, Francesc D, Juan-Marín, Rubén de, García-Escrivá, José-Ramón, Mendívil, J R González de, and Bernabéu-Aubán, José M
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CAP theorem (Distributed computer systems) , *CONSISTENCY models (Computers) , *CLOUD computing , *TECHNOLOGY convergence , *COMPUTER simulation - Abstract
The CAP theorem states that only two of these properties can be simultaneously guaranteed in a distributed service: (i) consistency, (ii) availability and (iii) network partition tolerance. This theorem was stated and proved assuming that 'consistency' refers to atomic consistency. However, multiple consistency models exist and atomic consistency is located at the strongest edge of that spectrum. Many distributed services deployed in cloud platforms should be highly available and scalable. Network partitions may arise in those deployments and should be tolerated. One way of dealing with CAP constraints consists in relaxing consistency. Therefore, it is interesting to explore the set of consistency models not supported in an available and partition-tolerant service (CAP-constrained models). Other weaker consistency models could be maintained when scalable services are deployed in partitionable systems (CAP-free models). Three contributions arise: (i) multiple other CAP-constrained models are identified, (ii) a borderline between CAP-constrained and CAP-free models is set and (iii) a hierarchy of consistency models depending on their strength and convergence is built. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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13. Modeling Geometric Design Consistency and Road Safety for Two-Lane Rural Highways in the West Bank, Palestine.
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Al-Sahili, Khaled and Dwaikat, Mohammed
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ROAD construction , *GEOMETRIC modeling , *ROAD safety measures , *TRAFFIC flow , *INFORMATION superhighway , *AUTOMOBILE speed - Abstract
This study investigates the effect of geometric design consistency on road safety in the West Bank. Studies have shown that operating speed, vehicle stability, alignment indices, and driver's workload are the common consistency measures that might affect safety. A total of 118-km two-lane rural highways in the West Bank, Palestine, were studied based on limitations of available data. Comprehensive geometric and operating data for the selected highways obtained from field survey, maps, and official sources were used to investigate the effect of design consistency measures on road safety. Crashes for years 2008–2012, totaling 263, were used for model development using the generalized linear regression approach. Tested models were statistically significant at 95%, and adopted models showed acceptable levels of goodness of fit. The recommended model performed well across additional highway sections, additional years of data, validation of algorithm, and "%error" with a high linear correlation. The study adds to the evidence that several geometric design consistency measures contribute to roadway safety. The significant measures for the two-lane rural highways in the West Bank were segment length, traffic volume, difference between operating and design speeds, absolute difference in the 85th percentile speeds between successive design elements, and the ratio of individual curve radius to the average radius. The practical implication of this study, in addition to being able to predict crashes based on the recommended measures, highway designers should pay careful attention to inconsistent designs of two-lane rural highways to reduce their crash frequency. [ABSTRACT FROM AUTHOR]
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- 2019
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14. A Survey on NoSQL Stores.
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DAVOUDIAN, ALI, LIU CHEN, and MENGCHI LIU
- Abstract
Recent demands for storing and querying big data have revealed various shortcomings of traditional relational database systems. This, in turn, has led to the emergence of a new kind of complementary nonrelational data store, named as NoSQL. This survey mainly aims at elucidating the design decisions of NoSQL stores with regard to the four nonorthogonal design principles of distributed database systems: data model, consistency model, data partitioning, and the CAP theorem. For each principle, its available strategies and corresponding features, strengths, and drawbacks are explained. Furthermore, various implementations of each strategy are exemplified and crystallized through a collection of representative academic and industrial NoSQL technologies. Finally, we disclose some existing challenges in developing effective NoSQL stores, which need attention of the research community, application designers, and architects. [ABSTRACT FROM AUTHOR]
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- 2019
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15. 5 种常用敷料预防高危风险患者压疮的 网状 Meta 分析.
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黄锐娜, 黄锐佳, 邱文波, 陈旭珊, 魏 宁, 王小俊, 王海焦, and 吴小婉
- Abstract
Copyright of Chinese Medical Equipment Journal is the property of Chinese Medical Equipment Journal Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
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- 2019
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16. Consistency Model
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Sakr, Sherif, editor and Zomaya, Albert Y., editor
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- 2019
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17. Corporate Consistency and the Regulations of the Corporate Governance System
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Ryszard Kamiński and Michał Flieger
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corporate consistency ,consistency concept ,platforms of consistency ,consistency model ,corporate governance ,UE regulations ,Law - Abstract
Corporate governance involves not only working out the relationship between a company and its shareholders, but also a search for consistency on a daily basis. When consistency is achieved, the shareholders’ satisfaction is higher and relations improve. Consistency is a prerequisite for a company’s effectiveness and efficiency, and it is the board’s task to make a corporation consistent. The first part of the paper introduces M. Flieger’s concept of corporate consistency, where platforms of consistency are introduced and the consistency model is proposed. This is the first time that such an introduction has been made, and this may lead to further discussion and research. The author points out that managers are rarely aware of the consistency problem, and there are no tools which enable a consistent system to be worked out. This makes the concept of corporate consistency worth investigating. In the second part of the paper, R. Kaminski focuses on the development of the European Union and Polish regulations, which were introduced as a consequence of the changing conditions in company activity. This section determines the content and sequence of the main issues discussed in the article. These include: the characteristics of the concept of a corporate governance system, the presentation of changes in regulations regarding a corporate governance system in the EU and the presentation of Polish regulations on corporate governance. The primary sources used in the work were literature and the rules and standards (mandatory and optional) on corporate governance. Both authors used descriptive analysis and the comparative method.
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- 2017
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18. Quality-of-Service for Consistency of Data Geo-replication in Cloud Computing
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Esteves, Sérgio, Silva, João, Veiga, Luís, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Kaklamanis, Christos, editor, Papatheodorou, Theodore, editor, and Spirakis, Paul G., editor
- Published
- 2012
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19. Eventually Consistent Transactions
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Burckhardt, Sebastian, Leijen, Daan, Fähndrich, Manuel, Sagiv, Mooly, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, and Seidl, Helmut, editor
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- 2012
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20. PCCM-GAN: Photographic Text-to-Image Generation with Pyramid Contrastive Consistency Model
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Shu Zhan, Jiajia Xu, Zhongjian Qi, Jun Sun, and Jinzhao Qian
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0209 industrial biotechnology ,Image generation ,Computer science ,business.industry ,Cognitive Neuroscience ,ComputingMethodologies_IMAGEPROCESSINGANDCOMPUTERVISION ,Consistency model ,Pattern recognition ,02 engineering and technology ,Attention model ,Computer Science Applications ,Semantic consistency ,020901 industrial engineering & automation ,Artificial Intelligence ,0202 electrical engineering, electronic engineering, information engineering ,Leverage (statistics) ,020201 artificial intelligence & image processing ,Attentional network ,Pyramid (image processing) ,Artificial intelligence ,business ,Generator (mathematics) - Abstract
Synthesizing photographic images from given text descriptions is a challenging problem. Although previous many studies have made significant progress on the visual quality of the generated images by using the multi-stage and attentional network, they ignore the interrelationships between the images generated by the generator in each stage and simply leverage the attention mechanism. In this paper, the Photographic Text-to-Image Generation with Pyramid Contrastive Consistency Model (PCCM-GAN) is proposed to generate photographic images. PCCM-GAN introduces two modules: a Pyramid Contrastive Consistency Model (PCCM) and a stack attention model (Stack-Attn). Based on generated images from the different stages, PCCM is proposed to compute a contrastive loss for training the generator. Stack-Attn concentrates on generating images with more details and better semantic consistency by stacking the global–local attention mechanism. And visual inspection of the inner product of PCCM and Stack-Attn is also performed to validate their effectiveness. Extensive experiments and ablation studies on the CUB and MS-COCO datasets prove the superiority of the proposed method.
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- 2021
21. Analysis of Handling Processes of Record Versions in NoSQL Databases
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Yu. A. Grigorev
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NoSQL database ,record versions ,vector clock ,consistency model ,confidence interval ,Computer engineering. Computer hardware ,TK7885-7895 ,Mechanics of engineering. Applied mechanics ,TA349-359 - Abstract
This article investigates the handling processes versions of a record in NoSQL databases. The goal of this work is to develop a model, which enables users both to handle record versions and work with a record simultaneously. This model allows us to estimate both a time distribution for users to handle record versions and a distribution of the count of record versions. With eventual consistency (W=R=1) there is a possibility for several users to update any record simultaneously. In this case, several versions of records with the same key will be stored in database. When reading, the user obtains all versions, handles them, and saves a new version, while older versions are deleted. According to the model, the user’s time for handling the record versions consists of two parts: random handling time of each version and random deliberation time for handling a result. Record saving time and records deleting time are much less than handling time, so, they are ignored in the model. The paper offers two model variants. According to the first variant, client's handling time of one record version is calculated as the sum of random handling times of one version based on the count of record versions. This variant ignores explicitly the fact that handling time of record versions may depend on the update count, performed by the other users between the sequential updates of the record by the current client. So there is the second variant, which takes this feature into consideration. The developed models were implemented in the GPSS environment. The model experiments with different counts of clients and different ratio between one record handling time and results deliberation time were conducted. The analysis showed that despite the resemblance of model variants, a difference in change nature between average values of record versions count and handling time is significant. In the second variant dependences of the average count of record versions in database and its right bound of the confidence interval on the average deliberation time have a pronounced maximum. In the same variant an average handling time of record versions practically does not depend on the average deliberation time, but the right bound of the confidence interval of this time has a pronounced minimum.
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- 2015
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22. Consistency Models for Replicated Data
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Fekete, Alan D., Ramamritham, Krithi, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Doug, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Charron-Bost, Bernadette, editor, Pedone, Fernando, editor, and Schiper, André, editor
- Published
- 2010
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23. EVENTUAL CONSISTENCY: ORIGIN AND SUPPORT.
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MUÑOZ-ESCOÍ, Francesc D., GARCÍA-ESCRIVÁ, José-Ramón, SENDRA-ROIG, Juan Salvador, BERNABÉU-AUBÁN, José M., and GONZÁLEZ DE MENDÍVIL, José Ramón
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COMPUTER networks ,DATA replication ,CONVERGENCE (Telecommunication) ,CAP theorem (Distributed computer systems) ,ONLINE data processing - Abstract
Eventual consistency is demanded nowadays in geo-replicated services that need to be highly scalable and available. According to the CAP constraints, when network partitions may arise, a distributed service should choose between be- ing strongly consistent or being highly available. Since scalable services should be available, a relaxed consistency (while the network is partitioned) is the preferred choice. Eventual consistency is not a common data-centric consistency model, but only a state convergence condition to be added to a relaxed consistency model. There are still several aspects of eventual consistency that have not been analysed in depth in previous works: 1. which are the oldest replication proposals providing eventual consistency, 2. which replica consistency models provide the best basis for building eventually consistent services, 3. which mechanisms should be considered for implementing an eventually consistent service, and 4. which are the best com- binations of those mechanisms for achieving different concrete goals. This paper provides some notes on these important topics. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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24. A thermodynamic consistent rate-dependent elastoplastic-damage model.
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Ganjiani, Mehdi
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ELASTOPLASTICITY , *THERMODYNAMIC control , *CONTINUUM damage mechanics , *FINITE element method , *ALGORITHMS - Abstract
In this article, a rate-dependent elastoplastic-damage constitutive model considering the effect of strain rate has been developed. The derivation of this model has been established based on the irreversible thermodynamics with internal variables within the fundamentals of Continuum damage mechanics (CDM). For investigating the rate effect, an additional power function dependent on the effective strain rate has been involved in the plastic dissipation function (dynamic plastic yield surface). The damage has been assumed as a tensor-type variable and based on the energy equivalence hypothesis, the damage evolution has been developed. The proposed constitutive model has been implemented into user-defined subroutines UMAT and VUMAT in the finite-element program ABAQUS/(Standard and Explicit). For this purpose, the implicit and explicit stress integration algorithms of the model have been explained. The model has been validated by comparing the predicted results with experimental data conducted on Al2024-T3. These experiments are including the tensile and double-notched tests. Furthermore, the numerical results have been compared with some data available in the literature. The numerical examples show the excellent correlation between experiments and simulations for stress (or force) and damage results. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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25. Revising 1-Copy Equivalence in Replicated Databases with Snapshot Isolation
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Muñoz-Escoí, Francesc D., Bernabé-Gisbert, Josep M., de Juan-Marín, Ruben, Armendáriz-Íñigo, Jose Enrique, González De Mendívil, Jose Ramon, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Meersman, Robert, editor, Dillon, Tharam, editor, and Herrero, Pilar, editor
- Published
- 2009
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26. RMOST: A Shared Memory Model for Online Steering
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Lorenz, Daniel, Buchholz, Peter, Uebing, Christian, Walkowiak, Wolfgang, Wismüller, Roland, Hutchison, editor, Kanade, editor, Kittler, editor, Kleinberg, editor, Mattern, editor, Mitchell, editor, Naor, editor, Nierstrasz, editor, Pandu Rangan, editor, Steffen, editor, Sudan, editor, Terzopoulos, editor, Tygar, editor, Vardi, editor, Weikum, editor, Bubak, Marian, editor, van Albada, Geert Dick, editor, Dongarra, Jack, editor, and Sloot, Peter M. A., editor
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- 2008
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27. On-Chip COMA Cache-Coherence Protocol for Microgrids of Microthreaded Cores
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Zhang, Li, Jesshope, Chris, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Bougé, Luc, editor, Forsell, Martti, editor, Träff, Jesper Larsson, editor, Streit, Achim, editor, Ziegler, Wolfgang, editor, Alexander, Michael, editor, and Childs, Stephen, editor
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- 2008
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28. Armed Cats
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Richard Grisenthwaite, Luc Maranget, Will Deacon, Jade Alglave, Antoine Hacquard, ARM Ltd [Cambridge] (ARM), University College of London [London] (UCL), Ecole Pour l'Informatique et les Techniques Avancées (EPITA), Langages de programmation : systèmes de types, concurrence, preuve de programme (CAMBIUM), Collège de France (CdF (institution))-Inria de Paris, and Institut National de Recherche en Informatique et en Automatique (Inria)-Institut National de Recherche en Informatique et en Automatique (Inria)
- Subjects
[INFO.INFO-PL]Computer Science [cs]/Programming Languages [cs.PL] ,Computer science ,Programming language ,Process (engineering) ,Suite ,Concurrency ,Consistency model ,020207 software engineering ,02 engineering and technology ,computer.software_genre ,ARM architecture ,020204 information systems ,0202 electrical engineering, electronic engineering, information engineering ,x86 ,computer ,Software - Abstract
We report on the process for formal concurrency modelling at Arm. An initial formal consistency model of the Arm achitecture, written in the cat language, was published and upstreamed to the herd+diy tool suite in 2017. Since then, we have extended the original model with extra features, for example, mixed-size accesses, and produced two provably equivalent alternative formulations. In this article, we present a comprehensive review of work done at Arm on the consistency model. Along the way, we also show that our principle for handling mixed-size accesses applies to x86: We confirm this via vast experimental campaigns. We also show that our alternative formulations are applicable to any model phrased in a style similar to the one chosen by Arm.
- Published
- 2021
29. Checking Interaction Consistency in MARMOT Component Refinements
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Choi, Yunja, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Rangan, C. Pandu, editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Doug, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, van Leeuwen, Jan, editor, Italiano, Giuseppe F., editor, van der Hoek, Wiebe, editor, Meinel, Christoph, editor, Sack, Harald, editor, and Plášil, František, editor
- Published
- 2007
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30. Fast and Generalized Polynomial Time Memory Consistency Verification
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Roy, Amitabha, Zeisset, Stephan, Fleckenstein, Charles J., Huang, John C., Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Ball, Thomas, editor, and Jones, Robert B., editor
- Published
- 2006
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31. Multi-version Coherence Protocol for Replicated Shared Objects
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Brzeziński, Jerzy, Kobusiński, Jacek, Wawrzyniak, Dariusz, Hutchison, David, Series editor, Kanade, Takeo, Series editor, Kittler, Josef, Series editor, Kleinberg, Jon M., Series editor, Mattern, Friedemann, Series editor, Mitchell, John C., Series editor, Naor, Moni, Series editor, Nierstrasz, Oscar, Series editor, Pandu Rangan, C., Series editor, Steffen, Bernhard, Series editor, Sudan, Madhu, Series editor, Terzopoulos, Demetri, Series editor, Tygar, Dough, Series editor, Vardi, Moshe Y., Series editor, Weikum, Gerhard, Series editor, Wyrzykowski, Roman, editor, Dongarra, Jack, editor, Meyer, Norbert, editor, and Waśniewski, Jerzy, editor
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- 2006
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32. Communication Paradigms for Distributed Network Systems
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Du, Ding-Zhu, editor, Raghavendra, Cauligi, editor, Jia, Weijia, and Zhou, Wanlei
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- 2005
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33. Safety of a Server-Based Version Vector Protocol Implementing Session Guarantees
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Brzeziński, Jerzy, Sobaniec, Cezary, Wawrzyniak, Dariusz, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Sunderam, Vaidy S., editor, van Albada, Geert Dick, editor, Sloot, Peter M. A., editor, and Dongarra, Jack, editor
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- 2005
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34. Reconfigurable Object Consistency Model for Distributed Shared Memory
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Pousa, Christiane V., Góes, Luís F. W., Martins, Carlos A. P. S., Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Pan, Yi, editor, Chen, Daoxu, editor, Guo, Minyi, editor, Cao, Jiannong, editor, and Dongarra, Jack, editor
- Published
- 2005
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35. Dynamic Adaptation for Grid Computing
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Buisson, Jérémy, André, Françoise, Pazat, Jean-Louis, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Sloot, Peter M. A., editor, Hoekstra, Alfons G., editor, Priol, Thierry, editor, Reinefeld, Alexander, editor, and Bubak, Marian, editor
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- 2005
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36. Pastis: A Highly-Scalable Multi-user Peer-to-Peer File System
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Busca, Jean-Michel, Picconi, Fabio, Sens, Pierre, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Cunha, José C., editor, and Medeiros, Pedro D., editor
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- 2005
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37. Analyzing Convergence in Consistency Models for Distributed Objects
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Torres-Rojas, Francisco J., Meneses, Esteban, and Higashino, Teruo, editor
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- 2005
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38. A Generic and Flexible Model for Replica Consistency Management
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Ferdean, Corina, Makpangou, Mesaac, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Ghosh, R. K., editor, and Mohanty, Hrushikesha, editor
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- 2005
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39. A Study on the Consistency of Features for On-Line Signature Verification
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Lei, Hansheng, Govindaraju, Venu, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Fred, Ana, editor, Caelli, Terry M., editor, Duin, Robert P. W., editor, Campilho, Aurélio C., editor, and de Ridder, Dick, editor
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- 2004
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40. Decoupled Interconnection of Distributed Memory Models
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Jiménez, Ernesto, Fernández, Antonio, Cholvi, Vicente, Hutchison, David, editor, Kanade, Takeo, editor, Kittler, Josef, editor, Kleinberg, Jon M., editor, Mattern, Friedemann, editor, Mitchell, John C., editor, Naor, Moni, editor, Nierstrasz, Oscar, editor, Pandu Rangan, C., editor, Steffen, Bernhard, editor, Sudan, Madhu, editor, Terzopoulos, Demetri, editor, Tygar, Dough, editor, Vardi, Moshe Y., editor, Weikum, Gerhard, editor, Papatriantafilou, Marina, editor, and Hunel, Philippe, editor
- Published
- 2004
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41. Modeling and Testing Legacy Data Consistency Requirements
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Nytun, Jan Pettersen, Jensen, Christian S., Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Stevens, Perdita, editor, Whittle, Jon, editor, and Booch, Grady, editor
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- 2003
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42. Distributed Versioning: Consistent Replication for Scaling Back-End Databases of Dynamic ContentWeb Sites
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Amza, Cristiana, Cox, Alan L., Zwaenepoel, Willy, Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Endler, Markus, editor, and Schmidt, Douglas, editor
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- 2003
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43. Consistency Requirements of Peterson’s Algorithm for Mutual Exclusion of n Processes in a Distributed Shared Memory System
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Brzeziński, Jerzy, Wawrzyniak, Dariusz, Goos, Gerhard, editor, Hartmanis, Juris, editor, van Leeuwen, Jan, editor, Wyrzykowski, Roman, editor, Dongarra, Jack, editor, Paprzycki, Marcin, editor, and Waśniewski, Jerzy, editor
- Published
- 2002
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44. A User-Centred Consistency Model in Real-Time Collaborative Editing Systems
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Xue, Liyin, Orgun, Mehmet, Zhang, Kang, Goos, G., editor, Hartmanis, J., editor, van Leeuwen, J., editor, Plaice, John, editor, Kropf, Peter G., editor, Schulthess, Peter, editor, and Slonim, Jacob, editor
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- 2002
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45. Systems-on-Chip with Strong Ordering
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Mikko H. Lipasti and Sooraj Puthoor
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010302 applied physics ,Sequential consistency ,Computer science ,Consistency model ,02 engineering and technology ,Lockstep ,Parallel computing ,01 natural sciences ,020202 computer hardware & architecture ,Hardware and Architecture ,Memory ordering ,0103 physical sciences ,0202 electrical engineering, electronic engineering, information engineering ,Memory model ,Baseline (configuration management) ,Implementation ,Software ,Information Systems - Abstract
Sequential consistency (SC) is the most intuitive memory consistency model and the easiest for programmers and hardware designers to reason about. However, the strict memory ordering restrictions imposed by SC make it less attractive from a performance standpoint. Additionally, prior high-performance SC implementations required complex hardware structures to support speculation and recovery. In this article, we introduce the lockstep SC consistency model (LSC), a new memory model based on SC but carefully defined to accommodate the data parallel lockstep execution paradigm of GPUs. We also describe an efficient LSC implementation for an APU system-on-chip (SoC) and show that our implementation performs close to the baseline relaxed model. Evaluation of our implementation shows that the geometric mean performance cost for lockstep SC is just 0.76% for GPU execution and 6.11% for the entire APU SoC compared to a baseline with a weaker memory consistency model. Adoption of LSC in future APU and SoC designs will reduce the burden on programmers trying to write correct parallel programs, while also simplifying the implementation and verification of systems with heterogeneous processing elements and complex memory hierarchies. 1
- Published
- 2021
46. Strong and Efficient Consistency with Consistency-aware Durability
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Andrea C. Arpaci-Dusseau, Remzi H. Arpaci-Dusseau, Ramnatthan Alagappan, and Aishwarya Ganesan
- Subjects
Property (programming) ,Computer science ,Distributed computing ,Strong consistency ,Consistency model ,020206 networking & telecommunications ,CAD ,02 engineering and technology ,Replication (computing) ,Consistency (database systems) ,Hardware and Architecture ,020204 information systems ,Distributed data store ,0202 electrical engineering, electronic engineering, information engineering ,Throughput (business) - Abstract
We introduce consistency-aware durability or C ad , a new approach to durability in distributed storage that enables strong consistency while delivering high performance. We demonstrate the efficacy of this approach by designing cross-client monotonic reads , a novel and strong consistency property that provides monotonic reads across failures and sessions in leader-based systems; such a property can be particularly beneficial in geo-distributed and edge-computing scenarios. We build O rca , a modified version of ZooKeeper that implements C ad and cross-client monotonic reads. We experimentally show that O rca provides strong consistency while closely matching the performance of weakly consistent ZooKeeper. Compared to strongly consistent ZooKeeper, O rca provides significantly higher throughput (1.8--3.3×) and notably reduces latency, sometimes by an order of magnitude in geo-distributed settings. We also implement C ad in Redis and show that the performance benefits are similar to that of C ad ’s implementation in ZooKeeper.
- Published
- 2021
47. Foundations of empirical memory consistency testing
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Esin Tureci, Tyler Sorensen, Margaret Martonosi, and Jake Kirkham
- Subjects
Software portability ,Consistency (database systems) ,Unit testing ,Computer engineering ,Computer science ,Interface (Java) ,Test suite ,Consistency model ,Memory model ,Safety, Risk, Reliability and Quality ,Conformance testing ,Software - Abstract
Modern memory consistency models are complex, and it is difficult to reason about the relaxed behaviors that current systems allow. Programming languages, such as C and OpenCL, offer a memory model interface that developers can use to safely write concurrent applications. This abstraction provides functional portability across any platform that implements the interface, regardless of differences in the underlying systems. This powerful abstraction hinges on the ability of the system to correctly implement the interface. Many techniques for memory consistency model validation use empirical testing, which has been effective at uncovering undocumented behaviors and even finding bugs in trusted compilation schemes. Memory model testing consists of small concurrent unit tests called “litmus tests”. In these tests, certain observations, including potential bugs , are exceedingly rare, as they may only be triggered by precise interleaving of system steps in a complex processor, which is probabilistic in nature. Thus, each test must be run many times in order to provide a high level of confidence in its coverage. In this work, we rigorously investigate empirical memory model testing. In particular, we propose methodologies for navigating complex stressing routines and analyzing large numbers of testing observations. Using these insights, we can more efficiently tune stressing parameters, which can lead to higher confidence results at a faster rate. We emphasize the need for such approaches by performing a meta-study of prior work, which reveals results with low reproducibility and inefficient use of testing time. Our investigation is presented alongside empirical data. We believe that OpenCL targeting GPUs is a pragmatic choice in this domain as there exists a variety of different platforms to test, from large HPC servers to power-efficient edge devices. The tests presented in the work span 3 GPUs from 3 different vendors. We show that our methodologies are applicable across the GPUs, despite significant variances in the results. Concretely, our results show: lossless speedups of more than 5× in tuning using data peeking; a definition of portable stressing parameters which loses only 12% efficiency when generalized across our domain; a priority order of litmus tests for tuning. We stress test a conformance test suite for the OpenCL 2.0 memory model and discover a bug in Intel’s compiler. Our methods are evaluated on the other two GPUs using mutation testing. We end with recommendations for official memory model conformance tests.
- Published
- 2020
48. Two Layers Distributed Shared Memory
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Baiardi, F., Guerri, D., Mori, P., Moroni, L., Ricci1, L., Goos, G., editor, Hartmanis, J., editor, van Leeuwen, J., editor, Hertzberger, Bob, editor, Hoekstra, Alfons, editor, and Williams, Roy, editor
- Published
- 2001
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49. Hive: Implementing a Virtual Distributed Shared Memory in Java
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Baiardi, Fabrizio, Dobloni, Gianmarco, Mori, Paolo, Ricci, Laura, Kacsuk, Peter, editor, and Kotsis, Gabriele, editor
- Published
- 2000
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50. A Hybrid Static-Dynamic Classification for Dual-Consistency Cache Coherence.
- Author
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Ros, Alberto and Jimborean, Alexandra
- Subjects
- *
CACHE memory , *PERFORMANCE of multiprocessors , *RUN time systems (Computer science) , *COMPILERS (Computer programs) , *PARALLEL processing - Abstract
Traditional cache coherence protocols manage all memory accesses equally and ensure the strongest memory model, namely, sequential consistency. Recent cache coherence protocols based on self-invalidation advocate for the model sequential consistency for data-race-free, which enables powerful optimizations for race-free code. However, for racy code these cache coherence protocols provide sub-optimal performance compared to traditional protocols. This paper proposes SPEL++, a dual-consistency cache coherence protocol that supports two execution modes: a traditional sequential-consistent protocol and a protocol that provides weak consistency (or sequential consistency for data-race-free). SPEL++ exploits a static-dynamic hybrid classification of memory accesses based on (i) a compile-time identification of extended data-race-free code regions for OpenMP applications and (ii) a runtime classification of accesses based on the operating system's memory page management. By executing racy code under the sequential-consistent protocol and race-free code under the cache coherence protocol that provides sequential consistency for data-race-free, the end result is an efficient execution of the applications while still providing sequential consistency. Compared to a traditional protocol, we show improvements in performance from 19 to 38 percent and reductions in energy consumption from 47 to 53 percent, on average for different benchmark suites, on a 64-core chip multiprocessor. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
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