uu.seUppsala universitets publikasjoner
Endre søk
Begrens søket
1234567 101 - 150 of 2118
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 101.
    Abenius, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Johansson, Christer
    Modeling of inhomogeneous waveguides using hybrid methods2005Manuskript (preprint) (Annet vitenskapelig)
  • 102.
    Abenius, Erik
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Strand, Bo
    Solving inverse electromagnetic problems using FDTD and gradient-based minimization2006Inngår i: International Journal for Numerical Methods in Engineering, ISSN 0029-5981, E-ISSN 1097-0207, Vol. 68, s. 650-673Artikkel i tidsskrift (Fagfellevurdert)
  • 103. Abenius, Erik
    et al.
    Strand, Bo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Alestra, Stephane
    Inverse Electromagnetic Scattering Using the Finite-Difference Time-Domain Method2000Inngår i: Proc. Millennium Conference on Antennas and Propagation, Noordwijk, The Netherlands: ESA Publications , 2000, s. 4-Konferansepaper (Fagfellevurdert)
  • 104. Aceto, Luca
    et al.
    Longo, GiuseppeVictor, BjörnUppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    The difference between concurrent and sequential computation2003Collection/Antologi (Annet (populærvitenskap, debatt, mm))
  • 105. Aceto, Luca
    et al.
    Victor, BjörnUppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    EXPRESS'00: 7th International Workshop on Expressiveness in Concurrency2000Konferanseproceedings (Annet vitenskapelig)
  • 106. Adawi, Tom
    et al.
    Berglund, Anders
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi.
    Ingerman, Åke
    Booth, Shirley
    On context in phenomenographic research on understanding heat and temperate2002Inngår i: EARLI, Bi-annual Symposium, Fribourg, Switzerland, 2002Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Starting from an empirical study of lay adults' understanding of heatand temperature, we distinguish between different meanings of "context" inphenomenographic research. To confuse the variation in ways of experiencingthe context(s) of the study with the variation in ways of experiencing thephenomenon of study is to risk losing fundamental insights. We discuss contextas experienced and as interwoven with the experience of the phenomenon, andanalyse its significance in two dimensions: (1) the stage of the research project:formulating the question, collecting data, analysing data and deploying results;and (2) "who is experiencing" the context: the individual, the collective, or theresearcher. The arguments are illustrated from the empirical study.

  • 107.
    Aftab, Obaid
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Cancerfarmakologi och beräkningsmedicin.
    Fryknäs, Mårten
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Cancerfarmakologi och beräkningsmedicin.
    Hassan, Saadia
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Cancerfarmakologi och beräkningsmedicin.
    Nygren, Peter
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för radiologi, onkologi och strålningsvetenskap, Enheten för onkologi.
    Larsson, Rolf
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Cancerfarmakologi och beräkningsmedicin.
    Hammerling, Ulf
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Cancerfarmakologi och beräkningsmedicin.
    Gustafsson, Mats
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Medicinska fakulteten, Institutionen för medicinska vetenskaper, Cancerfarmakologi och beräkningsmedicin.
    Label free quantification of time evolving morphologies using time-lapse video microscopy enables identity control of cell lines and discovery of chemically induced differential activity in iso-genic cell line pairs2015Inngår i: Chemometrics and Intelligent Laboratory Systems, ISSN 0169-7439, E-ISSN 1873-3239, Vol. 141, s. 24-32Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Label free time-lapse video microscopy based monitoring of time evolving cell population morphology has potential to offer a simple and cost effective method for identity control of cell lines. Such morphology monitoring also has potential to offer discovery of chemically induced differential changes between pairs of cell lines of interest, for example where one in a pair of cell lines is normal/sensitive and the other malignant/resistant. A new simple algorithm, pixel histogram hierarchy comparison (PHHC), for comparison of time evolving morphologies (TEM) in phase contrast time-lapse microscopy movies was applied to a set of 10 different cell lines and three different iso-genic colon cancer cell line pairs, each pair being genetically identical except for a single mutation. PHHC quantifies differences in morphology by comparing pixel histogram intensities at six different resolutions. Unsupervised clustering and machine learning based classification methods were found to accurately identify cell lines, including their respective iso-genic variants, through time-evolving morphology. Using this experimental setting, drugs with differential activity in iso-genic cell line pairs were likewise identified. Thus, this is a cost effective and expedient alternative to conventional molecular profiling techniques and might be useful as part of the quality control in research incorporating cell line models, e.g. in any cell/tumor biology or toxicology project involving drug/agent differential activity in pairs of cell line models.

  • 108.
    Ahani, Ghafour
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Yuan, Di
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    BS-assisted Task Offloading for D2D Networks with Presence of User Mobility2019Inngår i: 2019 IEEE 89TH VEHICULAR TECHNOLOGY CONFERENCE (VTC2019-SPRING), IEEE , 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Task offloading is a key component in mobile edge computing. Offloading a task to a remote server takes communication and networking resources. An alternative is device-to-device (D2D) offloading, where a task of a device is offloaded to some device having computational resource available. The latter requires that the devices are within the range of each other, first for task collection, and later for result gathering. Hence, in mobility scenarios, the performance of D2D offloading will suffer if the contact rates between the devices are low. We enhance the setup to base station (BS) assisted D2D offloading, namely, a BS can act as a relay for task distribution or result collection. However, this would imply additional consumption of wireless resources. The associated cost and the improvement in completion time of task offloading compose a fundamental trade-off. For the resulting optimization problem, we mathematically prove the complexity, and propose an algorithm using Lagrangian duality. The simulation results demonstrate not only that the algorithm has close-to-optimal performance, but also provide structural insights of the optimal trade-off.

  • 109.
    Ahlberg, Daniel
    et al.
    Stockholm Univ, Dept Math, S-10691 Stockholm, Sweden.
    Deijfen, Maria
    Stockholm Univ, Dept Math, S-10691 Stockholm, Sweden.
    Janson, Svante
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Matematiska institutionen, Analys och sannolikhetsteori.
    Competing first passage percolation on random graphs with finite variance degrees2019Inngår i: Random structures & algorithms (Print), ISSN 1042-9832, E-ISSN 1098-2418, Vol. 55, nr 3, s. 545-559Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We study the growth of two competing infection types on graphs generated by the configuration model with a given degree sequence. Starting from two vertices chosen uniformly at random, the infection types spread via the edges in the graph in that an uninfected vertex becomes type 1 (2) infected at rate lambda(1) (lambda(2)) times the number of nearest neighbors of type 1 (2). Assuming (essentially) that the degree of a randomly chosen vertex has finite second moment, we show that if lambda(1) = lambda(2), then the fraction of vertices that are ultimately infected by type 1 converges to a continuous random variable V is an element of (0,1), as the number of vertices tends to infinity. Both infection types hence occupy a positive (random) fraction of the vertices. If lambda(1) not equal lambda(2), on the other hand, then the type with the larger intensity occupies all but a vanishing fraction of the vertices. Our results apply also to a uniformly chosen simple graph with the given degree sequence.

  • 110. Ahlberg, Ragnar
    et al.
    Gustafsson, Bertil
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    A note on parallel algorithms for partial differential equations1984Inngår i: Parallel Computing: 83, Amsterdam, The Netherlands: Elsevier Science , 1984, s. 93-98Konferansepaper (Fagfellevurdert)
  • 111.
    Ahlberg, Sofia
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Språkvetenskapliga fakulteten, Engelska institutionen. Uppsala Univ, Uppsala, Sweden.
    Unthought: The power of the cognitive nonconscious2018Inngår i: Studia Neophilologica, ISSN 0039-3274, E-ISSN 1651-2308, Vol. 90, nr 2, s. 273-274Artikkel, omtale (Annet vitenskapelig)
  • 112.
    Al Nahas, Beshr
    et al.
    Swedish Institute of Computer Science.
    Duquennoy, Simon
    Swedish Institute of Computer Science.
    Iyer, Venkatraman
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Voigt, Thiemo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Low-Power Listening Goes Multi-Channel2014Inngår i: 2014 IEEE INTERNATIONAL CONFERENCE ON DISTRIBUTED COMPUTING IN SENSOR SYSTEMS (IEEE DCOSS 2014), 2014, s. 2-9Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Exploiting multiple radio channels for communicationhas been long known as a practical way to mitigateinterference in wireless settings. In Wireless Sensor Networks,however, multichannel solutions have not reached their fullpotential: the MAC layers included in TinyOS or the ContikiOS for example are mostly single-channel. The literature offersa number of interesting solutions, but experimental results wereoften too few to build confidence. We propose a practical extensionof low-power listening, MiCMAC, that performs channel hopping,operates in a distributed way, and is independent of upper layersof the protocol stack. The above properties make it easy todeploy in a variety of scenarios, without any extra configuration/scheduling/channelselection hassle. We implement our solutionin Contiki and evaluate it in a 97-node testbed while runninga complete, out-of-the-box low-power IPv6 communication stack(UDP/RPL/6LoWPAN). Our experimental results demonstrateincreased resilience to emulated WiFi interference (e.g., data yieldkept above 90% when ContikiMAC drops in the 40% range). In noiseless environments, MiCMAC keeps the overhead low incomparison to ContikiMAC, achieving performance as high as 99% data yield along with sub-percent duty cycle and sub-secondlatency for a 1-minute inter-packet interval data collection.

  • 113.
    Alaya, Cheikh Faouzi
    et al.
    Uppsala universitet, Humanistisk-samhällsvetenskapliga vetenskapsområdet, Samhällsvetenskapliga fakulteten, Institutionen för informationsvetenskap.
    Cramariuc, Bogdan
    Reynaud, Carole
    Quinghong, Meng
    Dragos-Adrian, Badea
    Hnich, Brahim
    Gabbouj, Moncef
    Kerminen, Petteri
    Makinen, Timo
    MUVIS: A System for Content-Based Indexing and Retrieval in Large Image1999Inngår i: Proceedings of the Conference on Storage and Retrieval for Image and Video Databases VII, SPIE PRESS, USA , 1999, Vol. 3656, nr VII, s. 98-106Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Until recently, collections of digital images were stored in classical databases and indexed by keywords entered by a human operator. This is not longer practical, due to the growing size of these collections. Moreover, the keywords associated with an ima

  • 114.
    Aldmour, Ismat
    et al.
    Al Baha University, Saudi Arabia.
    Nylén, Aletta
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Impact of cultural and language background on learning Computer Science concepts2014Inngår i: Proc. 2nd International Conference on Learning and Teaching in Computing and Engineering, Los Alamitos, CA: IEEE Computer Society, 2014, s. 37-40Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Computer science terminology is generally based on words that have a related original meaning in English and rooted in western tradition. Hence, students from other cultures and students that are not native English speakers, will not be helped by language and culture in understanding computer science concepts. In this work, the authors review the interrelationship between language, cultural background, and the learning of computer science. A comparative study is under preparation in which this relationship is to be examined. The study will compare the intuitive understanding of computer science concepts between Saudi student groups of different English language proficiency levels and of different maturity levels. A test has been designed in order to reveal differences in the perception of computer science concepts that can be attributed to such background differences. The study will serve as a starting point for further work on how computer science education can be enhanced for students that are non-native English speakers.

  • 115. Alexander, Perry
    et al.
    Flener, PierreUppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Datalogi. CSD.
    Special Issue on ASE'002003Collection/Antologi (Annet vitenskapelig)
  • 116. Alexander, Sylvia
    et al.
    Amillo, June
    Roger, Boyle
    Martyn, Clark
    Daniels, Mats
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Datorteknik.
    Laxer, Cary
    Loose, Ken
    Case studies in admission to and early performance in computer science degrees2003Inngår i: ACM SIGCSE Bulletin, ISSN 0097-8418, Vol. 35, nr 4, s. 149-153Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Changing conditions for teaching increase our motivation to understand the teaching and learning process. First time investigators of educational settings often feel uncertain about what aspects are involved and how to design a meaningful investigation. This paper develops and describes an applied research model with the ob jective of providing computer science (CS) academics of with a structured overview of the inter-disciplinary research components of CS education research.

    The paper argues that adopting such a model has the potential to enhance the maturity, significance and applicability of CS education research studies by placing them in a more complete research context. This helps to make the outcomes more readily transportable to other teaching and learning situations.

    One aim of publicizing the model is to help inspire the growing numbers of people who are becoming interested in CS education research. In addition we hope to simplify the task of gaining a rapid understanding of the research design issues and options that are typically involved.

  • 117.
    Alghamdi, Fayiq
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi. Al-Baha University .
    Why Computer Science teachers in Saudi Arabia Learn on Their Own: Impulse for Self-Directed Professional Development in CS teachingManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The research investigates the self-directed learning of CS teaching among Computer Science (CS) teachers in Saudi Arabia schools as a way of their professional development. The researchers developed a questionnaire with a 42-items inspiring from the previous literature and the purpose of the research question: How CS teachers were influenced by self-directed professional development in CS teaching? The questionnaires evaluated by the virtual honesty, Factor analysis and Alpha-Cronbach. Then, it distributed to 16 education offices and responses were received from 352 participants. The data shows that CS female teachers are more engaged in self-directed learning than CS male teachers. Also, the participants agreed on the total of average scores of the survey on learners’ self-directedness in the workplaces and self- reflection, planning, reasons and professional development for CS teachers. The recommendation made supported the CS teaching internet material recourses and make them easy and accessibility for all CS teachers community.

  • 118.
    Alghamdi, Fayiq
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Nylén, Aletta
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Pears, Arnold
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Changing the Educational Epistemologies of Computer Science Teachers: A Case Study of the Kingdom of Saudi Arabia2018Inngår i: 2018 IEEE Frontiers in Education Conference (FIE), Piscataway, NJ: IEEE, 2018Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper explores the attitudes of Computer Sci- ence (CS) teachers in the Kingdom of Saudi Arabia (KSA) who are confronted by the Saudi Teaching Competencies Standards (STCS). The STCS is a response to a substantial need to develop both subject-specific pedagogical ability as well as teachers subject area knowledge. The Ministry of Education in the KSA is encouraging teachers to improve their practices to achieve the new quality requirements for education. This paper presents the results of an investigation of CS teachers’ views on educational belief changes in the KSA schools. The paper addresses how and why CS teachers adopt new educational beliefs in their teaching. The paper presents the results of the investigation of the CS teachers views on educational belief changes in the KSA schools and the STCS policy document guidelines. Research in the area of changing educational epistemology in teaching CS identifies six factors that influence teachers, these are personal pedagogical beliefs, peer learning, curriculum, self-directed learning, student feedback and the STCS. A mixed method study approach was adopted in this work. Content analysis has been applied to the interview transcript and thematic coding analysis to the government policy document (STCS). The results provide a valuable case study in the KSA and emphasize the weak relationship between educational epistemology change and the STCS norms. The findings show that the STCS should provide stronger guidance for CS teachers to keep changing beliefs in teaching CS. The STCS should offer supporting official resources to CS teachers to help them in changing their beliefs in regard to teaching CS.

  • 119.
    Alghamdi, Fayiq
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Nylén, Aletta
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Pears, Arnold
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Teachers’ Awards - an Incentive for Pedagogical Development in Saudi Arabia2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This work-in-progress paper presents a study on

    how K-12 Computer Science teachers in Saudi Arabia have

    changed their pedagogy as a result of engaging in one year of

    professional development leading up to applying for a teacher’s

    award. The results are based on thematic analysis of fourteen

    interviews with teachers that have been awarded either the

    ’Education Excellence Award’ or the ’Microsoft Expert in Education’.

    The study focuses on how preparing for and getting

    the teaching award has influenced them focusing on changes

    in their pedagogical development and subsequent practices. The

    work provides an in-depth description of several aspects of

    the Saudi Arabian teaching culture. It explores and discusses

    the affordances of mechanisms used to strengthen pedagogical

    competence in a teacher community, paying extra attention to

    awards. This study identifies four main factors that motivate

    teachers to engage in pedagogical development in teaching

    Computer Science. The research suggests that awards can be an

    efficient motivator in establishing a culture of excellence among

    Computer Science teachers.

  • 120.
    Alghamdi, Fayiq
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Pears, Arnold
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Nylén, Aletta
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Computer science teachers perspectives on competencies: A case study in the Kingdom of Saudi Arabia2018Inngår i: Informatics in Schools. Fundamentals of Computer Science and Software Engineering, Springer, 2018, s. 129-140Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The Kingdom of Saudi Arabia (KSA) has recently adopted the Saudi Teaching Competencies Standard (STCS). This paper tries to answer how these competencies are achieved, how they are maintained, and what support exists to support teaching CS competently in the KSA. This paper presents the results of an investigation of teacher awareness of, and attitudes to, the STCS in the Kingdom. Through the study reported here, we address an urgent need in the Kingdom to understand teacher preparedness in terms of CS teaching competencies. The study draws on interviews with ten CS teachers in five different cities in the KSA. A thematic coding analysis approach was used. This study explores the CS teaching competencies held by teachers in three areas of CS teaching, focusing on connection to society, professional practice and professional development. The results of the study highlight the CS teaching competencies that CS teachers feel they currently grasp well in the KSA. By enhancing awareness of what teachers currently do well we contribute to the adjustment and improvement of the STCS and help to build a program which addresses the current in-service training needs of CS teachers. The outcomes also help to raise awareness of the challenges of implementing the Computer Education curriculum in KSA schools.

  • 121.
    Alhalaweh, Amjad
    et al.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Alzghoul, Ahmad
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Kaialy, Waseem
    Mahlin, Denny
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Bergström, Christel A. S.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Computational predictions of glass-forming ability and crystallization tendency of drug molecules2014Inngår i: Molecular Pharmaceutics, ISSN 1543-8384, E-ISSN 1543-8392, Vol. 11, nr 9, s. 3123-3132Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Amorphization is an attractive formulation technique for drugs suffering from poor aqueous solubility as a result of their high lattice energy. Computational models that can predict the material properties associated with amorphization, such as glass-forming ability (GFA) and crystallization behavior in the dry state, would be a time-saving, cost-effective, and material-sparing approach compared to traditional experimental procedures. This article presents predictive models of these properties developed using support vector machine (SVM) algorithm. The GFA and crystallization tendency were investigated by melt-quenching 131 drug molecules in situ using differential scanning calorimetry. The SVM algorithm was used to develop computational models based on calculated molecular descriptors. The analyses confirmed the previously suggested cutoff molecular weight (MW) of 300 for glass-formers, and also clarified the extent to which MW can be used to predict the GFA of compounds with MW < 300. The topological equivalent of Grav3_3D, which is related to molecular size and shape, was a better descriptor than MW for GFA; it was able to accurately predict 86% of the data set regardless of MW. The potential for crystallization was predicted using molecular descriptors reflecting Hückel pi atomic charges and the number of hydrogen bond acceptors. The models developed could be used in the early drug development stage to indicate whether amorphization would be a suitable formulation strategy for improving the dissolution and/or apparent solubility of poorly soluble compounds.

  • 122.
    Alipour, Mehdi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Carlson, Trevor E.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Maximizing limited resources: A limit-based study and taxonomy of out-of-order commit2019Inngår i: Journal of Signal Processing Systems, ISSN 1939-8018, E-ISSN 1939-8115, Vol. 91, nr 3-4, s. 379-397Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Out-of-order execution is essential for high performance, general-purpose computation, as it can find and execute useful work instead of stalling. However, it is typically limited by the requirement of visibly sequential, atomic instruction executionin other words, in-order instruction commit. While in-order commit has a number of advantages, such as providing precise interrupts and avoiding complications with the memory consistency model, it requires the core to hold on to resources (reorder buffer entries, load/store queue entries, physical registers) until they are released in program order. In contrast, out-of-order commit can release some resources much earlier, yielding improved performance and/or lower resource requirements. Non-speculative out-of-order commit is limited in terms of correctness by the conditions described in the work of Bell and Lipasti (2004). In this paper we revisit out-of-order commit by examining the potential performance benefits of lifting these conditions one by one and in combination, for both non-speculative and speculative out-of-order commit. While correctly handling recovery for all out-of-order commit conditions currently requires complex tracking and expensive checkpointing, this work aims to demonstrate the potential for selective, speculative out-of-order commit using an oracle implementation without speculative rollback costs. Through this analysis of the potential of out-of-order commit, we learn that: a) there is significant untapped potential for aggressive variants of out-of-order commit; b) it is important to optimize the out-of-order commit depth for a balanced design, as smaller cores benefit from reduced depth while larger cores continue to benefit from deeper designs; c) the focus on implementing only a subset of the out-of-order commit conditions could lead to efficient implementations; d) the benefits of out-of-order commit increases with higher memory latency and in conjunction with prefetching; e) out-of-order commit exposes additional parallelism in the memory hierarchy.

  • 123.
    Alipour, Mehdi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Carlson, Trevor E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    A Taxonomy of Out-of-Order Instruction Commit2017Inngår i: 2017 Ieee International Symposium On Performance Analysis Of Systems And Software (Ispass), Los Alamitos: IEEE Computer Society, 2017, s. 135-136Konferansepaper (Fagfellevurdert)
    Abstract [en]

    While in-order instruction commit has its advantages, such as providing precise interrupts and avoiding complications with the memory consistency model, it requires the core to hold on to resources (reorder buffer entries, load/store queue entries, registers) until they are released in program order. In contrast, out-of-order commit releases resources much earlier, yielding improved performance without the need for additional hardware resources. In this paper, we revisit out-of-order commit from a different perspective, not by proposing another hardware technique, but by introducing a taxonomy and evaluating three different micro-architectures that have this technique enabled. We show how smaller processors can benefit from simple out-oforder commit strategies, but that larger, aggressive cores require more aggressive strategies to improve performance.

  • 124.
    Alipour, Mehdi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Carlson, Trevor E.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Exploring the performance limits of out-of-order commit2017Inngår i: Proc. 14th Computing Frontiers Conference, New York: ACM Press, 2017, s. 211-220Konferansepaper (Fagfellevurdert)
  • 125.
    Alipour, Mehdi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kumar, Rakesh
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Delay and Bypass: Ready and Criticality Aware Instruction Scheduling in Out-of-Order Processors2020Inngår i: The 26th IEEE International Symposium on High-Performance Computer Architecture (HPCA) / [ed] IEEE, 2020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Flexible instruction scheduling is essential for performance in out-of-order processors. This is typically achieved by using CAM-based Instruction Queues (IQs) that provide complete flexibility in choosing ready instructions for execution, but at the cost of significant scheduling energy.

    In this work we seek to reduce the instruction scheduling energy by reducing the depth and width of the IQ. We do so by classifying instructions based on their readiness and criticality, and using this information to bypass the IQ for instructions that will not benefit from its expensive scheduling structures and delay instructions that will not harm performance. Combined, these approaches allow us to offload a significant portion of the instructions from the IQ to much cheaper FIFO-based scheduling structures without hurting performance. As a result we can reduce the IQ depth and width by half, thereby saving energy.

    Our design, Delay and Bypass (DNB), is the first design to explicitly address both readiness and criticality to reduce scheduling energy. By handling both classes we are able to achieve 95% of the baseline out-of-order performance while only using 33% of the scheduling energy. This represents a significant improvement over previous designs which addressed only criticality or readiness (91%/89% performance at 74%/53% energy).

  • 126.
    Alipour, Mehdi
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kumar, Rakesh
    Norwegian Univ Sci & Technol, Dept Comp Sci, Trondheim, Norway.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    FIFOrder MicroArchitecture: Ready-Aware Instruction Scheduling for OoO Processors2019Inngår i: 2019 Design, Automation & Test in Europe Conference & Exhibition (DATE), IEEE, 2019, s. 716-721Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The number of instructions a processor's instruction queue can examine (depth) and the number it can issue together (width) determine its ability to take advantage of the ILP in an application. Unfortunately, increasing either the width or depth of the instruction queue is very costly due to the content-addressable logic needed to wakeup and select instructions out-of-order. This work makes the observation that a large number of instructions have both operands ready at dispatch, and therefore do not benefit from out-of-order scheduling. We leverage this to place such ready-at-dispatch instructions in separate, simpler, in-order FIFO queues for scheduling. With such additional queues, we can reduce the size and width of the expensive out-of-order instruction queue, without reducing the processor's overall issue width and depth. Our design, FIFOrder, is able to steer more than 60% of instructions to the cheaper FIFO queues, providing a 50% energy savings over a traditional out-of-order instruction queue design, while delivering 8% higher performance.

  • 127.
    Alves, Ricardo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datorteknik. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Leveraging Existing Microarchitectural Structures to Improve First-Level Caching Efficiency2019Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Low-latency data access is essential for performance. To achieve this, processors use fast first-level caches combined with out-of-order execution, to decrease and hide memory access latency respectively. While these approaches are effective for performance, they cost significant energy, leading to the development of many techniques that require designers to trade-off performance and efficiency.

    Way-prediction and filter caches are two of the most common strategies for improving first-level cache energy efficiency while still minimizing latency. They both have compromises as way-prediction trades off some latency for better energy efficiency, while filter caches trade off some energy efficiency for lower latency. However, these strategies are not mutually exclusive. By borrowing elements from both, and taking into account SRAM memory layout limitations, we proposed a novel MRU-L0 cache that mitigates many of their shortcomings while preserving their benefits. Moreover, while first-level caches are tightly integrated into the cpu pipeline, existing work on these techniques largely ignores the impact they have on instruction scheduling. We show that the variable hit latency introduced by way-misspredictions causes instruction replays of load dependent instruction chains, which hurts performance and efficiency. We study this effect and propose a variable latency cache-hit instruction scheduler, that identifies potential misschedulings, reduces instruction replays, reduces negative performance impact, and further improves cache energy efficiency.

    Modern pipelines also employ sophisticated execution strategies to hide memory latency and improve performance. While their primary use is for performance and correctness, they require intermediate storage that can be used as a cache as well. In this work we demonstrate how the store-buffer, paired with the memory dependency predictor, can be used to efficiently cache dirty data; and how the physical register file, paired with a value predictor, can be used to efficiently cache clean data. These strategies not only improve both performance and energy, but do so with no additional storage and minimal additional complexity, since they recycle existing cpu structures to detect reuse, memory ordering violations, and misspeculations.

    Delarbeid
    1. Addressing energy challenges in filter caches
    Åpne denne publikasjonen i ny fane eller vindu >>Addressing energy challenges in filter caches
    2017 (engelsk)Inngår i: Proc. 29th International Symposium on Computer Architecture and High Performance Computing, IEEE Computer Society, 2017, s. 49-56Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Filter caches and way-predictors are common approaches to improve the efficiency and/or performance of first-level caches. Filter caches use a small L0 to provide more efficient and faster access to a small subset of the data, and work well for programs with high locality. Way-predictors improve efficiency by accessing only the way predicted, which alleviates the need to read all ways in parallel without increasing latency, but hurts performance due to mispredictions.In this work we examine how SRAM layout constraints (h-trees and data mapping inside the cache) affect way-predictors and filter caches. We show that accessing the smaller L0 array can be significantly more energy efficient than attempting to read fewer ways from a larger L1 cache; and that the main source of energy inefficiency in filter caches comes from L0 and L1 misses. We propose a filter cache optimization that shares the tag array between the L0 and the L1, which incurs the overhead of reading the larger tag array on every access, but in return allows us to directly access the correct L1 way on each L0 miss. This optimization does not add any extra latency and counter-intuitively, improves the filter caches overall energy efficiency beyond that of the way-predictor.By combining the low power benefits of a physically smaller L0 with the reduction in miss energy by reading L1 tags upfront in parallel with L0 data, we show that the optimized filter cache reduces the dynamic cache energy compared to a traditional filter cache by 26% while providing the same performance advantage. Compared to a way-predictor, the optimized cache improves performance by 6% and energy by 2%.

    sted, utgiver, år, opplag, sider
    IEEE Computer Society, 2017
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-334221 (URN)10.1109/SBAC-PAD.2017.14 (DOI)000426895600007 ()978-1-5090-1233-6 (ISBN)
    Konferanse
    29th International Symposium on Computer Architecture and High Performance Computing SBAC-PAD, 2017, October 17–20, Campinas, Brazil.
    Tilgjengelig fra: 2017-11-09 Laget: 2017-11-21 Sist oppdatert: 2019-05-22bibliografisk kontrollert
    2. Dynamically Disabling Way-prediction to Reduce Instruction Replay
    Åpne denne publikasjonen i ny fane eller vindu >>Dynamically Disabling Way-prediction to Reduce Instruction Replay
    2018 (engelsk)Inngår i: 2018 IEEE 36th International Conference on Computer Design (ICCD), IEEE, 2018, s. 140-143Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Way-predictors have long been used to reduce dynamic cache energy without the performance loss of serial caches. However, they produce variable-latency hits, as incorrect predictions increase load-to-use latency. While the performance impact of these extra cycles has been well-studied, the need to replay subsequent instructions in the pipeline due to the load latency increase has been ignored. In this work we show that way-predictors pay a significant performance penalty beyond previously studied effects due to instruction replays caused by mispredictions. To address this, we propose a solution that learns the confidence of the way prediction and dynamically disables it when it is likely to mispredict and cause replays. This allows us to reduce cache latency (when we can trust the way-prediction) while still avoiding the need to replay instructions in the pipeline (by avoiding way-mispredictions). Standard way-predictors degrade IPC by 6.9% vs. a parallel cache due to 10% of the instructions being replayed (worst case 42.3%). While our solution decreases way-prediction accuracy by turning off the way-predictor in some cases when it would have been correct, it delivers higher performance than a standard way-predictor. Our confidence-based way-predictor degrades IPC by only 4.4% by replaying just 5.6% of the instructions (worse case 16.3%). This reduces the way-predictor cache energy overhead compared to serial access cache, from 8.5% to 3.7% on average and on the worst case, from 33.8% to 9.5%.

    sted, utgiver, år, opplag, sider
    IEEE, 2018
    Serie
    Proceedings IEEE International Conference on Computer Design, ISSN 1063-6404, E-ISSN 2576-6996
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-361215 (URN)10.1109/ICCD.2018.00029 (DOI)000458293200018 ()978-1-5386-8477-1 (ISBN)
    Konferanse
    IEEE 36th International Conference on Computer Design (ICCD), October 7–10, 2018, Orlando, FL, USA
    Tilgjengelig fra: 2018-09-21 Laget: 2018-09-21 Sist oppdatert: 2019-05-22bibliografisk kontrollert
    3. Minimizing Replay under Way-Prediction
    Åpne denne publikasjonen i ny fane eller vindu >>Minimizing Replay under Way-Prediction
    2019 (engelsk)Rapport (Annet vitenskapelig)
    Abstract [en]

    Way-predictors are effective at reducing dynamic cache energy by reducing the number of ways accessed, but introduce additional latency for incorrect way-predictions. While previous work has studied the impact of the increased latency for incorrect way-predictions, we show that the latency variability has a far greater effect as it forces replay of in-flight instructions on an incorrect way-prediction. To address the problem, we propose a solution that learns the confidence of the way-prediction and dynamically disables it when it is likely to mispredict. We further improve this approach by biasing the confidence to reduce latency variability further at the cost of reduced way-predictions. Our results show that instruction replay in a way-predictor reduces IPC by 6.9% due to 10% of the instructions being replayed. Our confidence-based way-predictor degrades IPC by only 2.9% by replaying just 3.4% of the instructions, reducing way-predictor cache energy overhead (compared to serial access cache) from 8.5% to 1.9%.

    Serie
    Technical report / Department of Information Technology, Uppsala University, ISSN 1404-3203 ; 2019-003
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-383596 (URN)
    Tilgjengelig fra: 2019-05-17 Laget: 2019-05-17 Sist oppdatert: 2019-07-03bibliografisk kontrollert
    4. Filter caching for free: The untapped potential of the store-buffer
    Åpne denne publikasjonen i ny fane eller vindu >>Filter caching for free: The untapped potential of the store-buffer
    2019 (engelsk)Inngår i: Proc. 46th International Symposium on Computer Architecture, New York: ACM Press, 2019, s. 436-448Konferansepaper, Publicerat paper (Fagfellevurdert)
    Abstract [en]

    Modern processors contain store-buffers to allow stores to retire under a miss, thus hiding store-miss latency. The store-buffer needs to be large (for performance) and searched on every load (for correctness), thereby making it a costly structure in both area and energy. Yet on every load, the store-buffer is probed in parallel with the L1 and TLB, with no concern for the store-buffer's intrinsic hit rate or whether a store-buffer hit can be predicted to save energy by disabling the L1 and TLB probes.

    In this work we cache data that have been written back to memory in a unified store-queue/buffer/cache, and predict hits to avoid L1/TLB probes and save energy. By dynamically adjusting the allocation of entries between the store-queue/buffer/cache, we can achieve nearly optimal reuse, without causing stalls. We are able to do this efficiently and cheaply by recognizing key properties of stores: free caching (since they must be written into the store-buffer for correctness we need no additional data movement), cheap coherence (since we only need to track state changes of the local, dirty data in the store-buffer), and free and accurate hit prediction (since the memory dependence predictor already does this for scheduling).

    As a result, we are able to increase the store-buffer hit rate and reduce store-buffer/TLB/L1 dynamic energy by 11.8% (up to 26.4%) on SPEC2006 without hurting performance (average IPC improvements of 1.5%, up to 4.7%).The cost for these improvements is a 0.2% increase in L1 cache capacity (1 bit per line) and one additional tail pointer in the store-buffer.

    sted, utgiver, år, opplag, sider
    New York: ACM Press, 2019
    HSV kategori
    Identifikatorer
    urn:nbn:se:uu:diva-383473 (URN)10.1145/3307650.3322269 (DOI)978-1-4503-6669-4 (ISBN)
    Konferanse
    ISCA 2019, June 22–26, Phoenix, AZ
    Forskningsfinansiär
    Knut and Alice Wallenberg FoundationEU, Horizon 2020, 715283EU, Horizon 2020, 801051Swedish Foundation for Strategic Research , SM17-0064
    Tilgjengelig fra: 2019-06-22 Laget: 2019-05-16 Sist oppdatert: 2019-07-03bibliografisk kontrollert
    5.
    Posten ble ikke funnet. Det kan skyldes at posten ikke lenger er tilgjengelig eller det er feil id i adressefeltet.
  • 128.
    Alves, Ricardo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Dynamically Disabling Way-prediction to Reduce Instruction Replay2018Inngår i: 2018 IEEE 36th International Conference on Computer Design (ICCD), IEEE, 2018, s. 140-143Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Way-predictors have long been used to reduce dynamic cache energy without the performance loss of serial caches. However, they produce variable-latency hits, as incorrect predictions increase load-to-use latency. While the performance impact of these extra cycles has been well-studied, the need to replay subsequent instructions in the pipeline due to the load latency increase has been ignored. In this work we show that way-predictors pay a significant performance penalty beyond previously studied effects due to instruction replays caused by mispredictions. To address this, we propose a solution that learns the confidence of the way prediction and dynamically disables it when it is likely to mispredict and cause replays. This allows us to reduce cache latency (when we can trust the way-prediction) while still avoiding the need to replay instructions in the pipeline (by avoiding way-mispredictions). Standard way-predictors degrade IPC by 6.9% vs. a parallel cache due to 10% of the instructions being replayed (worst case 42.3%). While our solution decreases way-prediction accuracy by turning off the way-predictor in some cases when it would have been correct, it delivers higher performance than a standard way-predictor. Our confidence-based way-predictor degrades IPC by only 4.4% by replaying just 5.6% of the instructions (worse case 16.3%). This reduces the way-predictor cache energy overhead compared to serial access cache, from 8.5% to 3.7% on average and on the worst case, from 33.8% to 9.5%.

  • 129.
    Alves, Ricardo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Minimizing Replay under Way-Prediction2019Rapport (Annet vitenskapelig)
    Abstract [en]

    Way-predictors are effective at reducing dynamic cache energy by reducing the number of ways accessed, but introduce additional latency for incorrect way-predictions. While previous work has studied the impact of the increased latency for incorrect way-predictions, we show that the latency variability has a far greater effect as it forces replay of in-flight instructions on an incorrect way-prediction. To address the problem, we propose a solution that learns the confidence of the way-prediction and dynamically disables it when it is likely to mispredict. We further improve this approach by biasing the confidence to reduce latency variability further at the cost of reduced way-predictions. Our results show that instruction replay in a way-predictor reduces IPC by 6.9% due to 10% of the instructions being replayed. Our confidence-based way-predictor degrades IPC by only 2.9% by replaying just 3.4% of the instructions, reducing way-predictor cache energy overhead (compared to serial access cache) from 8.5% to 1.9%.

  • 130.
    Alves, Ricardo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Nikoleris, Nikos
    ARM Res, Lund, Sweden.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Addressing energy challenges in filter caches2017Inngår i: Proc. 29th International Symposium on Computer Architecture and High Performance Computing, IEEE Computer Society, 2017, s. 49-56Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Filter caches and way-predictors are common approaches to improve the efficiency and/or performance of first-level caches. Filter caches use a small L0 to provide more efficient and faster access to a small subset of the data, and work well for programs with high locality. Way-predictors improve efficiency by accessing only the way predicted, which alleviates the need to read all ways in parallel without increasing latency, but hurts performance due to mispredictions.In this work we examine how SRAM layout constraints (h-trees and data mapping inside the cache) affect way-predictors and filter caches. We show that accessing the smaller L0 array can be significantly more energy efficient than attempting to read fewer ways from a larger L1 cache; and that the main source of energy inefficiency in filter caches comes from L0 and L1 misses. We propose a filter cache optimization that shares the tag array between the L0 and the L1, which incurs the overhead of reading the larger tag array on every access, but in return allows us to directly access the correct L1 way on each L0 miss. This optimization does not add any extra latency and counter-intuitively, improves the filter caches overall energy efficiency beyond that of the way-predictor.By combining the low power benefits of a physically smaller L0 with the reduction in miss energy by reading L1 tags upfront in parallel with L0 data, we show that the optimized filter cache reduces the dynamic cache energy compared to a traditional filter cache by 26% while providing the same performance advantage. Compared to a way-predictor, the optimized cache improves performance by 6% and energy by 2%.

  • 131.
    Alves, Ricardo
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Ros, Alberto
    Black-Schaffer, David
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Kaxiras, Stefanos
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorarkitektur och datorkommunikation.
    Filter caching for free: The untapped potential of the store-buffer2019Inngår i: Proc. 46th International Symposium on Computer Architecture, New York: ACM Press, 2019, s. 436-448Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Modern processors contain store-buffers to allow stores to retire under a miss, thus hiding store-miss latency. The store-buffer needs to be large (for performance) and searched on every load (for correctness), thereby making it a costly structure in both area and energy. Yet on every load, the store-buffer is probed in parallel with the L1 and TLB, with no concern for the store-buffer's intrinsic hit rate or whether a store-buffer hit can be predicted to save energy by disabling the L1 and TLB probes.

    In this work we cache data that have been written back to memory in a unified store-queue/buffer/cache, and predict hits to avoid L1/TLB probes and save energy. By dynamically adjusting the allocation of entries between the store-queue/buffer/cache, we can achieve nearly optimal reuse, without causing stalls. We are able to do this efficiently and cheaply by recognizing key properties of stores: free caching (since they must be written into the store-buffer for correctness we need no additional data movement), cheap coherence (since we only need to track state changes of the local, dirty data in the store-buffer), and free and accurate hit prediction (since the memory dependence predictor already does this for scheduling).

    As a result, we are able to increase the store-buffer hit rate and reduce store-buffer/TLB/L1 dynamic energy by 11.8% (up to 26.4%) on SPEC2006 without hurting performance (average IPC improvements of 1.5%, up to 4.7%).The cost for these improvements is a 0.2% increase in L1 cache capacity (1 bit per line) and one additional tail pointer in the store-buffer.

  • 132.
    Alzghoul, Ahmad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Alhalaweh, Amjad
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Mahlin, Denny
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Bergström, Christel A. S.
    Uppsala universitet, Medicinska och farmaceutiska vetenskapsområdet, Farmaceutiska fakulteten, Institutionen för farmaci.
    Experimental and Computational Prediction of Glass Transition Temperature of Drugs2014Inngår i: JOURNAL OF CHEMICAL INFORMATION AND MODELING, ISSN 1549-9596, Vol. 54, nr 12, s. 3396-3403Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Glass transition temperature (T-g) is an important inherent property of an amorphous solid material which is usually determined experimentally. In this study, the relation between T-g and melting temperature (T-m) was evaluated using a data set of 71 structurally diverse druglike compounds. Further, in silico models for prediction of T-g were developed based on calculated molecular descriptors and linear (multilinear regression, partial least-squares, principal component regression) and nonlinear (neural network, support vector regression) modeling techniques. The models based on T-m predicted T-g with an RMSE of 19.5 K for the test set. Among the five computational models developed herein the support vector regression gave the best result with RMSE of 18.7 K for the test set using only four chemical descriptors. Hence, two different models that predict T-g of drug-like molecules with high accuracy were developed. If T-m is available, a simple linear regression can be used to predict T-g. However, the results also suggest that support vector regression and calculated molecular descriptors can predict T-g with equal accuracy, already before compound synthesis.

  • 133.
    Alzghoul, Ahmad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Backe, Björn
    Löfstrand, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Byström, Arne
    Liljedahl, Bengt
    Comparing a knowledge-based and a data-driven method in querying data streams for system fault detection: A hydraulic drive system application2014Inngår i: Computers in industry (Print), ISSN 0166-3615, E-ISSN 1872-6194, Vol. 65, nr 8, s. 1126-1135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The field of fault detection and diagnosis has been the subject of considerable interest in industry. Fault detection may increase the availability of products, thereby improving their quality. Fault detection and diagnosis methods can be classified in three categories: data-driven, analytically based, and knowledge-based methods.

    In this work, we investigated the ability and the performance of applying two fault detection methods to query data streams produced from hydraulic drive systems. A knowledge-based method was compared to a data-driven method. A fault detection system based on a data stream management system (DSMS) was developed in order to test and compare the two methods using data from real hydraulic drive systems.

    The knowledge-based method was based on causal models (fault trees), and principal component analysis (PCA) was used to build the data-driven model. The performance of the methods in terms of accuracy and speed, was examined using normal and physically simulated fault data. The results show that both methods generate queries fast enough to query the data streams online, with a similar level of fault detection accuracy. The industrial applications of both methods include monitoring of individual industrial mechanical systems as well as fleets of such systems. One can conclude that both methods may be used to increase industrial system availability.

  • 134.
    Alzghoul, Ahmad
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Löfstrand, Magnus
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Addressing concept drift to improve system availability by updating one-class data-driven models2015Inngår i: Evolving Systems, ISSN 1868-6478, E-ISSN 1868-6486, Vol. 6, nr 3, s. 187-198Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Data-driven models have been used to detect system faults, thereby increasing industrial system availability. The ability to search data streams while dealing with concept drift are challenges for data-driven models. The objective of this work is to demonstrate a general method to manage concept drift when using one-class data-driven models. The method has been used to develop an automatically retrained and updated polygon-based model. In this paper, the available industrial data allowed for use of one-class data-driven models, and the polygon-based model was selected because it has previously been successful. Possible scenarios that allow one-class data-driven models to be retrained or updated were identified. Based on the identified scenarios, a method to automatically update a polygon-based model online is proposed. The method has been tested and verified using data collected from a Bosch Rexroth Mellansel AB hydraulic drive system. Data representing relevant faults was inserted into the data set in close collaboration with engineers from the company. The results show that the developed polygon-based model method was able to address the concept drift issue and was able to significantly improve the classification accuracy compared to the static polygon-based model. Thereby, the model could significantly improve industrial system availability when applied in the relevant production process. This paper shows that the developed polygon-based model requires small memory space while its updating procedure is simple and fast. Finally, the identified scenarios may be helpful as input for supporting other one-class data-driven models to cope with concept drift, thus increasing the generalizability of the results.

  • 135.
    Amadini, Roberto
    et al.
    University of Melbourne, Melbourne, Australia.
    Flener, Pierre
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Pearson, Justin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Scott, Joseph D.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Stuckey, Peter J.
    University of Melbourne, Melbourne, Australia.
    Tack, Guido
    Monash University, Melbourne, Australia.
    MiniZinc with strings2017Inngår i: Logic-Based Program Synthesis and Transformation, Springer, 2017, s. 59-75Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Strings are extensively used in modern programming languages and constraints over strings of unknown length occur in a wide range of real-world applications such as software analysis and verification, testing, model checking, and web security. Nevertheless, practically no constraint programming solver natively supports string constraints. We introduce string variables and a suitable set of string constraints as builtin features of the MiniZinc modelling language. Furthermore, we define an interpreter for converting a MiniZinc model with strings into a FlatZinc instance relying only on integer variables. This conversion is obtained via rewrite rules, and does not require any extension of the existing FlatZinc specification. This provides a user-friendly interface for modelling combinatorial problems with strings, and enables both string and non-string solvers to actually solve such problems.

  • 136.
    Amnell, Tobias
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Fersman, Elena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Mokrushin, Leonid
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Pettersson, Paul
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    Yi, Wang
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik.
    TIMES: A Tool for Modelling and Implementation of Embedded Systems2002Inngår i: Tools and Algorithms for the Construction and Analysis of Systems: TACAS 2002, Berlin: Springer-Verlag , 2002, s. 460-464Konferansepaper (Fagfellevurdert)
  • 137.
    Amnell, Tobias
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. DoCS.
    Fersman, Elena
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. DoCS.
    Mokrushin, Leonid
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. DoCS.
    Pettersson, Paul
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. DoCS.
    Yi, Wang
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. DoCS.
    TIMES: a Tool for Schedulability Analysis and Code Generation of Real-Time Systems2003Inngår i: Proceedings of the International Conference of Formal Modeling and Analysis of Timed Systems, 2003Konferansepaper (Fagfellevurdert)
    Abstract [en]

    TIMES is a tool suite designed mainly for symbolic schedulability analysis and synthesis of executable code with predictable behaviours for real-time systems. Given a system design model consisting of

    (1) a set of application tasks whose executions may be required to meet mixed timing, precedence, and resource constraints,

    (2) a network of timed automata describing the task arrival patterns and

    (3) a preemptive or non-preemptive scheduling policy,

    TIMES will generate a scheduler, and calculate the worst case response times for the tasks. The design model may be further validated using a model checker e.g. UPPAAL and then compiled to executable C-code using the TIMES compiler. In this paper, we present the design and main features of TIMES including a summary of theoretical results behind the tool. TIMES can be downloaded at www.timestool.com.

  • 138.
    Amoignon, Olivier
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Moving mesh adaptation scheme for aerodynamic shape optimization2006Rapport (Annet vitenskapelig)
  • 139.
    Amoignon, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Berggren, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Adjoint of a median-dual finite-volume scheme: Application to transonic aerodynamic shape optimization2006Rapport (Annet vitenskapelig)
  • 140.
    Amoignon, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Berggren, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Discrete adjoint-based shape optimization for an edge-based finite-volume solver2003Inngår i: Computational Fluid and Solid Mechanics: 2003, Elsevier Science , 2003, s. 2190-2193Konferansepaper (Fagfellevurdert)
  • 141.
    Amoignon, Olivier
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Pralits, Jan
    Hanifi, Ardeshir
    Berggren, Martin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för teknisk databehandling. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Numerisk analys.
    Henningson, Dan
    Shape optimization for delay of laminar-turbulent transition2006Inngår i: AIAA Journal, ISSN 0001-1452, E-ISSN 1533-385X, Vol. 44, s. 1009-1024Artikkel i tidsskrift (Fagfellevurdert)
  • 142.
    An, Jie
    et al.
    Tongji Univ, Sch Software Engn, Shanghai, Peoples R China.
    Zhan, Naijun
    Chinese Acad Sci, Inst Software, State Key Lab Comp Sci, Beijing, Peoples R China;Uni CAS, Beijing, Peoples R China.
    Li, Xiaoshan
    Univ Macau, Fac Sci & Technol, Macau, Peoples R China.
    Zhang, Miaomiao
    Tongji Univ, Sch Software Engn, Shanghai, Peoples R China.
    Wang, Yi
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datorteknik. Uppsala Univ, Dept Informat Technol, Uppsala, Sweden.
    Model Checking Bounded Continuous-time Extended Linear Duration Invariants2018Inngår i: HSCC 2018: Proceedings of the 21st International Conference on Hybrid Systems: Computation and Control (HSCC), ASSOC COMPUTING MACHINERY , 2018, s. 81-90Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Extended Linear Duration Invariants (ELDI), an important subset of Duration Calculus, extends well-studied Linear Duration Invariants with logical connectives and the chop modality. It is known that the model checking problem of ELDI is undecidable with both the standard continuous-time and discrete-time semantics [12, 13], but it turns out to be decidable if only bounded execution fragments of timed automata are concerned in the context of the discrete-time semantics [36]. In this paper, we prove that this problem is still decidable in the continuous-time semantics, although it is well-known that model-checking Duration Calculus with the continuous-time semantics is much more complicated than the one with the discrete-time semantics. This is achieved by reduction to the validity of Quantified Linear Real Arithmetic (QLRA). Some examples are provided to illustrate the efficiency of our approach.

  • 143.
    Anderson, Kevin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Naturresurser och hållbar utveckling. Univ Manchester, Sch Engn, Tyndall Ctr Climate Change Res, Manchester M13 9PL, Lancs, England.
    Wrong tool for the job: Debating the bedrock of climate-change mitigation scenarios2019Inngår i: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 573, nr 7774, s. 348-348Artikkel i tidsskrift (Annet vitenskapelig)
  • 144.
    Andersson, Arne
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Holmström, Jim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Willman, Mattias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    An Auction Mechanism for Polynomial-time Execution with Combinatorial Constraints2005Inngår i: Proc. 7th International Conference on E-Commerce Technology, Piscataway, NJ: IEEE , 2005, s. 17-24Konferansepaper (Fagfellevurdert)
  • 145.
    Andersson, Arne
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Datalogi. Datalogi.
    Tenhunen, Mattias
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi. Teknisk-naturvetenskapliga fakulteten, Biologiska sektionen, Institutionen för ekologi och evolution, Datalogi. Datalogi.
    Ygge, Fredrik
    Integer Programming for Combinatorial Auction Winner Determination.2000Inngår i: Proc. of the Fourth International Conference on Multiagent Systems (ICMAS-00), 2000Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Combinatorial auctions are important as they enable bidders to place bids on combinations of items; compared to other auction mechanisms, they often increase the efficiency of the auction, while keeping risks for bidders low. However, the determination of an optimal winner combination in combinatorial auctions is a complex computational problem.

    In this paper we (i) compare recent algorithms for winner determination to traditional algorithms, (ii) present and benchmark a mixed integer progra mming approach to the problem, which enables very general auctions to be treated efficiently by standard integer programming algorithms (and hereby also by commercially available software), and (iii) discuss the impact of the probability distributions chosen for benchmarking.

  • 146.
    Andersson, Arne
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Thorup, Mikkel
    Dynamic Ordered Sets with Exponential Search Trees2007Inngår i: Journal of the ACM, ISSN 0004-5411, E-ISSN 1557-735X, Vol. 54, nr 3, s. 1236460-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We introduce exponential search trees as a novel technique for converting static polynomial space search structures for ordered sets into fully-dynamic linear space data structures. This leads to an optimal bound of O(log n/log log n) for searching and updating a dynamic set X of n integer keys in linear space. Searching X for an integer y means finding the maximum key in X which is smaller than or equal to y. This problem is equivalent to the standard text book problem of maintaining an ordered set. The best previous deterministic linear space bound was O(log n/log log n) due to Fredman and Willard from STOC 1990. No better deterministic search bound was known using polynomial space. We also get the following worst-case linear space trade-offs between the number n, the word length W, and the maximal key U < 2W: O(min log log n + log n/logW, log log n log log U/log log log U). These trade-offs are, however, not likely to be optimal. Our results are generalized to finger searching and string searching, providing optimal results for both in terms of n.

  • 147.
    Andersson, Arne
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Wilenius, Jim
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    A New Analysis of Revenue in the Combinatorial and Simultaneous Auction2009Rapport (Annet vitenskapelig)
    Abstract [en]

    We prove that in many cases, a first-price sealed-bid combinatorial auction gives higher expected revenue than a sealed-bid simultaneous auction. This is the first theoretical evidence that combinatorial auctions indeed generate higher revenue, which has been a common belief for decades.

    We use a model with many bidders and items, where bidders are of two types: (i) single-bidders interested in only one item and (ii) synergy-bidders, each interested in one random combination of items. We provide an upper bound on the expected revenue for simultaneous auctions and a lower bound on combinatorial auctions. Our bounds are parameterized on the number of bidders and items, combination size, and synergy.

    We derive an asymptotic result, proving that as the number of bidders approach infinity, expected revenue of the combinatorial auction will be higher than that of the simultaneous auction. We also provide concrete examples where the combinatorial auction is revenue-superior.

  • 148.
    Andrejev, Andrej
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Avdelningen för datalogi.
    Semantic Web Queries over Scientific Data2016Doktoravhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    Semantic Web and Linked Open Data provide a potential platform for interoperability of scientific data, offering a flexible model for providing machine-readable and queryable metadata. However, RDF and SPARQL gained limited adoption within the scientific community, mainly due to the lack of support for managing massive numeric data, along with certain other important features – such as extensibility with user-defined functions, query modularity, and integration with existing environments and workflows.

    We present the design, implementation and evaluation of Scientific SPARQL – a language for querying data and metadata combined, represented using the RDF graph model extended with numeric multidimensional arrays as node values – RDF with Arrays. The techniques used to store RDF with Arrays in a scalable way and process Scientific SPARQL queries and updates are implemented in our prototype software – Scientific SPARQL Database Manager, SSDM, and its integrations with data storage systems and computational frameworks. This includes scalable storage solutions for numeric multidimensional arrays and an efficient implementation of array operations. The arrays can be physically stored in a variety of external storage systems, including files, relational databases, and specialized array data stores, using our Array Storage Extensibility Interface. Whenever possible SSDM accumulates array operations and accesses array contents in a lazy fashion.

    In scientific applications numeric computations are often used for filtering or post-processing the retrieved data, which can be expressed in a functional way. Scientific SPARQL allows expressing common query sub-tasks with functions defined as parameterized queries. This becomes especially useful along with functional language abstractions such as lexical closures and second-order functions, e.g. array mappers.

    Existing computational libraries can be interfaced and invoked from Scientific SPARQL queries as foreign functions. Cost estimates and alternative evaluation directions may be specified, aiding the construction of better execution plans. Costly array processing, e.g. filtering and aggregation, is thus preformed on the server, saving the amount of communication. Furthermore, common supported operations are delegated to the array storage back-ends, according to their capabilities. Both expressivity and performance of Scientific SPARQL are evaluated on a real-world example, and further performance tests are run using our mini-benchmark for array queries.

  • 149.
    Andrejev, Andrej
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    He, Xueming
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Scientific data as RDF with arrays: Tight integration of SciSPARQL queries into MATLAB2014Inngår i: Proc. ISWC 2014 Posters & Demonstrations Track, RWTH Aachen University , 2014, s. 221-224Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present an integrated solution for storing and querying scientific data and metadata, using MATLAB envi ronment as client front-end and our prototype DBMS on the server. We use RDF for experiment metadata, and numeric arrays for the rest. Our extension of SPARQL supports array operations and extensibility with foreign functions.

  • 150.
    Andrejev, Andrej
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Risch, Tore
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Matematisk-datavetenskapliga sektionen, Institutionen för informationsteknologi, Datalogi.
    Scientific SPARQL: Semantic web queries over scientific data2012Inngår i: Proc. 28th International Conference on Data Engineering Workshops, IEEE Computer Society, 2012, s. 5-10Konferansepaper (Fagfellevurdert)
1234567 101 - 150 of 2118
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf