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Análise do consumo de energia em STMs e uma plataforma de simulação multiprocessada com abstração híbrida; Power consumption analysis of STMs and a hybrid abstraction simulation platform

João Batista Corrêa Gomes Moreira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 26/10/2010 PT
Relevância na Pesquisa
27.95%
O surgimento das novas arquiteturas multiprocessadas introduziu novos desafios ao desenvolvimento de software. Dentre estes desafios está a dificuldade de realizar a sincronização adequada entre os fluxos de execução. Para solucionar este problema, novos mecanismos de sincronização com abstrações mais simplificadas tem sido propostos. Seguindo esta corrente, as Memórias Transacionais surgem como uma promissora alternativa aos mecanismos de sincronização tradicionais. Por se tratar de uma alternativa recentemente proposta, pouco se conhece a respeito dos efeitos no consumo de energia devido ao uso de Memórias Transacionais. Este trabalho apresenta um estudo comparativo entre os consumos de energia observados na execução do benchmark STAMP com usos de um sistema STM (Memória Transacional em Software) e de sincronização baseada em locks. Os resultados obtidos demonstram que a STM apresentou um desempenho inferior aos locks no que diz respeito ao consumo de energia, apresentando um consumo médio três vezes maior. Também foi avaliada a influência das penalidades decorrentes do uso de locks no consumo de energia, mostrando que, em sistemas cujo custo de falha na aquisição de um lock supera dez mil ciclos, a aplicação de STMs passa a ser uma abordagem competitiva. Durante os testes com Memórias Transacionais tornou-se clara a necessidade de ferramentas de simulação que possibilitam projetos de hardware e testes de software de forma mais ágil. Este trabalho descreve a implementação de uma plataforma de simulação para estimar o consumo de energia com abstração híbrida obtida a partir da integração de processadores funcionais que são gerados através da linguagem ArchC com a plataforma MPARM (que possui precisão de ciclos). Esta implementação atingiu ganhos de desempenho médios de até 2.1 vezes...

Sequence tagged microsatellite profiling (STMP): improved isolation of DNA sequence flanking target SSRs

Hayden, M. J.; Good, G.; Sharp, P. J.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em 01/12/2002 EN
Relevância na Pesquisa
17.74%
Sequence tagged microsatellite profiling (STMP) enables the rapid development of large numbers of co-dominant DNA markers, known as sequence tagged microsatellites (STMs). Each STM is amplified by PCR using a single primer specific to the conserved DNA sequence flanking the microsatellite repeat in combination with a universal primer that anchors to the 5′-ends of the microsatellites. It is also possible to convert STMs into conventional microsatellite, or simple sequence repeat (SSR), markers that are amplified using a pair of primers flanking the repeat sequence. Here, we describe a modification of the STMP procedure to significantly improve the capacity to convert STMs into conventional SSRs and, therefore, facilitate the development of highly specific DNA markers for purposes such as marker-assisted breeding. The usefulness of this technique was demonstrated in bread wheat.

Transcranial magnetic stimulation: a new tool in the fight against depression

Grunhaus, Leon; Dannon, Pinhas N.; Gershon, Ari A.
Fonte: Les Laboratoires Servier Publicador: Les Laboratoires Servier
Tipo: Artigo de Revista Científica
Publicado em /03/2002 EN
Relevância na Pesquisa
17.4%
Since its introduction to the clinical realm in 1985, transcranial magnetic stimulation (TMS) has rapidly developed into a tool for exploring central nervous system function in both health and disease. The antidepressant effects of TMS were initially observed in 1993. Since then, a solid body of evidence has accumulated suggesting antidepressant effects for both slow TMS (sTMS) and repetitive TMS (rTMS). This review is divided into four parts. First, it addresses the basic concepts governing TMS, and then, second, it discusses the technical parameters involved in administering TMS. Knowledge of these parameters is necessary for understanding how TMS is administered, and how manipulation of the technique impacts on the results obtained. Third, we review the most relevant studies on the antidepressant effects of sTMS and rTMS published to date. Finally, we discuss cortical excitability and how the understanding of this basic neurophysiological function of cortical neurons can be used for monitoring the effects of TMS. In our discussion, we conclude that the time has arrived for TMS to be offered to depressed patients as a treatment.

Dissociating the role of prefrontal and premotor cortices in controlling inhibitory mechanisms during motor preparation

Duque, Julie; Labruna, Ludovica; Verset, Sophie; Olivier, Etienne; Ivry, Richard B.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 18/01/2012 EN
Relevância na Pesquisa
17.4%
Top-down control processes are critical to select goal-directed actions in flexible environments. In humans, these processes include two inhibitory mechanisms that operate during response selection: one is involved in solving a competition between different response options, the other ensures that a selected response is initiated timely. Here, we evaluated the role of dorsal premotor cortex (PMd) and lateral prefrontal cortex (LPF) of healthy subjects in these two forms of inhibition by using an innovative transcranial magnetic stimulation (TMS) protocol combining repetitive TMS (rTMS) over PMd or LPF and a single pulse TMS (sTMS) over primary motor cortex (M1). sTMS over M1 allowed us to assess inhibitory changes in corticospinal excitability, while rTMS was used to produce transient disruption of PMd or LPF. We found that rTMS over LPF reduces inhibition associated with competition resolution whereas rTMS over PMd decreases inhibition associated with response impulse control. These results emphasize the dissociable contributions of these two frontal regions to inhibitory control during motor preparation. The association of LPF with competition resolution is consistent with the role of this area in relatively abstract aspects of control related to goal maintenance...

A case of a CD56-expressing ectomesenchymal chondromyxoid tumor of the tongue: potential diagnostic usefulness of commonly available CD56 over CD57

Tajima, Shogo; Koda, Kenji
Fonte: e-Century Publishing Corporation Publicador: e-Century Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 01/03/2015 EN
Relevância na Pesquisa
17.74%
Ectomesenchymal chondromyxoid tumors (ECTs) are rare. Only approximately 55 cases have been reported in the English literature. Distinguishing ECTs from soft tissue myoepithelioma (STM) is often difficult owing to morphological and immunohistochemical similarities. Here, we present a case of an ECT arising from the anterior dorsum of the tongue in a 24-year-old woman. Grossly, the tumor was soft, had a myxoid appearance, and measured 8 × 7 × 7 mm. Microscopically, it was well-demarcated, lacked a fibrous capsule, and predominantly consisted of short, spindle to ovoid cells in a myxoid background. Vimentin, glial fibrillary acidic protein (GFAP), and S-100 protein were strongly positive on immunohistochemical analysis. While CD56 was moderately immunopositive, cytokeratin (AE1/AE3) and alpha-smooth muscle actin (αSMA) showed focal weak positivity. Thus, the immunohistochemical findings suggested a diverse immunophenotype, indicating mesenchymal (vimentin and αSMA positive), neurogenic (S100, GFAP, and CD56 positive), and epithelial differentiation (cytokeratin positive). This reflected the fact that ECTs probably arise from uncommitted ectomesenchymal cells that have the potential for multilineage differentiation. The immunohistochemical staining pattern observed for ECTs slightly differs from that of STMs. Strongly positive staining for GFAP and weakly positive staining for cytokeratin are observed in ECTs...

Snapshot Isolation for Software Transactional Memory

Felber, Pascal ; Fetzer, Christof ; Riegel, Torvald
Fonte: ACM SIGPLAN Workshop on Transactional Computing Publicador: ACM SIGPLAN Workshop on Transactional Computing
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
17.74%
Software transactional memory (STM) has been proposed to simplify the development and to increase the scalability of concurrent programs. One problem of existing STMs is that of having long-running read transactions co-exist with shorter update transactions. This problem is of practical importance and has so far not been addressed by other papers in this domain. We approach this problem by investigating the performance of a STM using snapshot isolation and a novel lazy multi-version snapshot algorithm to decrease the validation costs - which can increase quadratically with the number of objects read in STMs with invisible reads. Our measurements demonstrate that snapshot isolation can increase throughput for workloads with long transactions. In comparison to other STMs with invisible reads, we can reduce the validation costs by using our lazy consistent snapshot algorithm.

What Really Makes Transactions Faster?

Dice, David ; Shavit, Nir
Fonte: ACM SIGPLAN Workshop on Transactional Computing Publicador: ACM SIGPLAN Workshop on Transactional Computing
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
17.95%
There has been a flurry of recent work on the design of high performance software and hybrid hardware/software transactional memories (STMs and HyTMs). This paper reexamines the design decisions behind several of these state-of-the-art algorithms, adopting some ideas, rejecting others, all in an attempt to make STMs faster. The results of our evaluation led us to the design of a transactional locking (TL) algorithm which we believe to be the simplest, most flexible, and best performing STM/HyTM to date. It combines seamlessly with hardware transactions and with any system’s memory life-cycle, making it an ideal candidate for multi-language deployment today, long before hardware transactional support becomes commonly available. Most important of all however were the results we derived from a comprehensive comparison of the performance of non-blocking, lock-based, and Hybrid STM algorithms versus fine-grained hand-crafted ones. Contrary to our intuitions, concurrent code generated in a mechanical fashion using our TL algorithm and several other STMs, scaled better than the hand-crafted fine-grained lock-based and lock-free data structures, even though their throughput was lower. We found that it was the lower latency of the hand-crafted data structures that made them faster than STMs...

Efficient Nonblocking Software Transactional Memory

Marathe, Virendra Jayant (1977 - ); Moir, Mark
Fonte: University of Rochester. Computer Science Department. Publicador: University of Rochester. Computer Science Department.
Tipo: Relatório
ENG
Relevância na Pesquisa
18.09%
The current state of the art seems to favour blocking software transactional memory (STM) implementations over nonblocking ones, and a common belief is that nonblocking STMs fundamentally cannot be made to perform as well as blocking ones. But this belief is based on experience, intuition, and anecdote, not on rigorous analysis. We believe there is still plenty of room for improvement in the performance of nonblocking STMs and that, regardless of performance, blocking is unacceptable in some contexts. It is therefore important to continue improving nonblocking STMs, both as a goal in its own right, as well as to inform research aimed at determining whether a fundamental gap exists between blocking and nonblocking STMs. We describe a novel nonblocking copyback mechanism for a word-based software transactional memory (STM), which closely follows simple and efficient blocking mechanisms in the common case. Previous nonblocking copyback mechanisms impose significant overhead on the common case. Our performance experiments show that this approach yields significant performance improvement over the previous best nonblocking word-based STM. Our design approach can be applied to some other blocking STMs to achieve nonblocking counterparts that perform similarly in the common case.

Enhancing the performance and usability of software transactional memory

Marathe, Virendra Jayant (1977 - ); Scott, Michael L. (1959 - )
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xx, 232 leaves
ENG
Relevância na Pesquisa
18.42%
Thesis (Ph. D.)--University of Rochester. Dept. of Computer Science, 2008.; The computing industry is at the brink of a “concurrency revolution”. Mainstream microprocessor vendors have started manufacturing multicore chips. Low end desktops and laptops are already turning into parallel machines. Soon, every programmer will have to write parallel programs to leverage the processing horsepower of multicore chips. However, parallel programming is known to be hard; at the current state-of-the-art, it is effectively limited to (rare) experts. One of the key challenges in parallel programming is correct data sharing among concurrent computations. The traditional solution of lock-based mutual exclusion is known to have several significant drawbacks, such as deadlock, lack of composability, intolerance to arbitrary delays, etc.Transactional Memory (TM) is a new technology that promises to alleviate these problems, significantly simplifying parallel programming. One of the key properties of early software runtimes for TM (STMs) was that they were nonblocking, i.e. arbitrary delays in some transactions in the system would not interfere with forward progress of other transactions. Nonblocking STMs avoid some severe problems such as delays due to preemption...

Development of sequence tagged microsatellites (STMs) for the barley scald pathogen Rhynchosporium secalis

Keiper, F.; Hayden, M.; Wallwork, H.
Fonte: Blackwell Publishing Ltd Publicador: Blackwell Publishing Ltd
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
27.95%
A rapid and cost efficient technique was developed and used to generate 168 sequence tagged microsatellites (STMs) in the barley scald pathogen Rhynchosporium secalis. Sixty-two STMs, amplifying 66 loci, revealed a high level of polymorphism among a diverse set of 16 Australian isolates. Each locus revealed two to nine alleles (average 4 ± 1.82), and a gene diversity measure of 0.54 was obtained. This technique not only halved the cost of marker development compared to traditional methods, but substantially reduced the cost of performing fluorescence-based microsatellite assays. These STMs provide a powerful tool for genetic studies in R. secalis.; Felicity J. Keiper, Matthew J. Hayden and Hugh Wallwork; The definitive version is available at www.blackwell-synergy.com

Development and genetic mapping of sequence-tagged microsatellites (STMs) in bread wheat (Triticum aestivum L.)

Hayden, Matthew James; Stephenson, P.; Logojan, A. M.; Khatkar, D.; Rogers, C.; Elsden, Joanne Catherine; Koebner, Robert Max David; Snape, J. W.; Sharp, P. J.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2006 EN
Relevância na Pesquisa
27.95%
The density of SSRs on the published genetic map of bread wheat (Triticum aestivum L.) has steadily increased over the last few years. This has improved the efficiency of marker-assisted breeding and certain types of genetic research by providing more choice in the quality of SSRs and a greater chance of finding polymorphic markers in any cross for a chromosomal region of interest. Increased SSR density on the published wheat genetic map will further enhance breeding and research efforts. Here, sequence-tagged microsatellite profiling (STMP) is demonstrated as a rapid technique for the economical development of anonymous genomic SSRs to increase marker density on the wheat genetic map. A total of 684 polymorphic sequence-tagged microsatellites (STMs) were developed, and 380 were genetically mapped in three mapping populations, with 296 being mapped in the International Triticeae Mapping Initiative W7984 × Opata85 recombinant inbred cross. Across the three populations, a total of 479 STM loci were mapped. Several technological advantages of STMs over conventional SSRs were also observed. These include reduced marker deployment costs for fluorescent-based SSR analysis, and increased genotyping throughput by more efficient electrophoretic separation of STMs and a high amenability to multiplex PCR.; M. J. Hayden...

Sequence tagged microsatellites for the Xgwm533 locus provide new diagnostic markers to select for the presence of stem rust resistance gene Sr2 in bread wheat (Triticum aestivum L.)

Hayden, M.; Kuchel, H.; Chalmers, K.
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
17.4%
The stem rust resistance gene Sr2 has provided durable broad-spectrum, adult-plant resistance to the fungal pathogen Puccinia graminis Pers. f. sp. tritici throughout wheat-growing regions of the world for more than 50 years. The ability to select for Sr2 in wheat breeding programs was recently improved by the identification of a tightly linked microsatellite marker gwm533. This marker typically amplifies a 120-bp polymerase chain reaction fragment from wheat lines carrying Sr2. In instances where the 120-bp fragment is not associated with the presence of Sr2, DNA sequence analysis has shown that a second allele was amplified, differing in the structure of the microsatellite repeat. To discriminate this allelic homoplasy (alleles identical in size, but not identical by descent), sequence-tagged microsatellites (STM) markers were developed for the Xgwm533 locus. These markers were shown to be diagnostic for the presence of Sr2 in a wide range of germplasm, representative of all major wheat varieties historically grown in Australia. The STMs will be particularly useful for marker-assisted selection in Southern Australian breeding programs, where the use of the marker gwm533 is often precluded by the presence of the non-Sr2- associated 120-bp allele in the pedigree of current breeding germplasm. The STMs also revealed a high incidence of previously undetected allelic homoplasy at the Xgwm533 locus and may have broader utility in genetic research and breeding...

Sequence tagged microsatellite profiling (STMP): improved isolation of DNA sequence flanking target SSRs

Hayden, Matthew James; Good, G.; Sharp, P. J.
Fonte: Oxford University Press Publicador: Oxford University Press
Tipo: Artigo de Revista Científica
Publicado em //2002 EN
Relevância na Pesquisa
17.74%
Sequence tagged microsatellite profiling (STMP) enables the rapid development of large numbers of co-dominant DNA markers, known as sequence tagged microsatellites (STMs). Each STM is amplified by PCR using a single primer specific to the conserved DNA sequence flanking the microsatellite repeat in combination with a universal primer that anchors to the 5'-ends of the microsatellites. It is also possible to convert STMs into conventional microsatellite, or simple sequence repeat (SSR), markers that are amplified using a pair of primers flanking the repeat sequence. Here, we describe a modification of the STMP procedure to significantly improve the capacity to convert STMs into conventional SSRs and, therefore, facilitate the development of highly specific DNA markers for purposes such as marker-assisted breeding. The usefulness of this technique was demonstrated in bread wheat.; M. J. Hayden, G. Good and P. J. Sharp

Analise das proporções verticais dos tecidos moles faciais. Estudo cefalometrico pre e pro-operatorio de pacientes submetidos ao retroposicionamento mandibular

Jose Rodrigues Laureano Filho
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 20/01/1999 PT
Relevância na Pesquisa
18.09%
O presente estudo avaliou as alterações do perfil do tecido mole facial em pacientes com prognatismo mandibular submetido a recuo, utilizando para isto a análise cefalométrica de proporções verticais dos tecidos moles faciais, descrita por EPKER & FISH (1986). Foram confeccionados cefalogramas sobre as telerradiografias tomadas em norma lateral pré-operatória e pós-operatória, no mínimo de seis meses, de 10 pacientes submetidos a este tipo de procedimento cirúrgico- ortognático. Os resultados mostraram uma diminuição estatisticamente significante em duas proporções (G-Sn:Sn-Me' e Sn-Stms:Stms-Me) entre os traçados pré e pós-operatório. Já a razão Sn-Li:Li-Me', apesar de apresentar-se reduzida após a cirurgia, não foi estatisticamente significante. A distância interlabial (Stms-Stmi) se manteve dentre os padrões normais descritos por EPKER & FISH (1986), tanto no pré como no pós-operatório.; The present study evaluated the alteration of fa.cial soft tis sue in patients who underwent surgical correction of mandibular prognathism. Cephalometric analysis based on vertical proportions in facial soft tissues described by EPKER & FISH (1986) was perfomed. Cephalograms were made in pre-op and pos-op (with a minimum six months follow up) lateral cephalometric X-rays in tem patients with set back mandibular surgery.Results showed a decreased significant difIerence in two proportions (G-Srz:Sn-Me' e Sn-Stms:Stins-Me ') between the pre-operative and post-operative cephalometrics traces. The ratio Sn-Li:Li-Me " despite showed decreased after surgery...

Estudo cefalometrico radiografico das alterações faciais das maloclusões de classe II e classe III, empregando a analise de Epker & Fish

Rosangela Damis Rodrigues
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/02/2001 PT
Relevância na Pesquisa
18.34%
O presente trabalho constou de uma amostra de 120 telerradiografias de indivíduos leucodermas, de ambos os sexos e com idade média de 27,4 anos. Esta amostra foi dividida segundo o tipo de deformidade dento-esquelético-facial, em quatro grupos de 30 Classe II esquelética por retrognatismo mandibular, 30 Classe II esquelética por prognatismo maxilar, 30 Classe III esquelética por prognatismo mandibular e 30 Classe lII por retrognatismo maxilar. As alterações faciais decorrentes da deformidade apresentada foram avaliadas empregando-se a análise de EPKER & FISH (1986). Após a avaliação dos resultados, parece-nos válido concluir que: 1Quanto aos grupos: no grupo Classe II por prognatismo maxilar, a medida Sbn perp LS apresentou-se mais protruída, enquanto que no grupo Classe II por retrognatismo mandibular as medidas Sbn perp LI e Sbn perp Me' encontram se mais retruídas, confirmando, na face, as características esqueléticas no sentido antero-posterior; a altura do terço inferior da face (G-Sn:Sn-Me') apresentou-se maior no grupo Classe III por retrognatismo maxilar do que no Classe III por prognatismo mandibular; no grupo Classe III por retrognatismo maxilar, a medida Sbn perp LS mostrou-se significantemente mais retruída do que o Classe III por prognatismo mandibular...

Discordant expression and variable numbers of neighboring GGA- and GAA-rich triplet repeats in the 3' untranslated regions of two groups of messenger RNAs encoded by the rat polymeric immunoglobulin receptor gene.

Koch, K S; Gleiberman, A S; Aoki, T; Leffert, H L; Feren, A; Jones, A L; Fodor, E J
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 11/04/1995 EN
Relevância na Pesquisa
17.95%
An unusual S1-nuclease sensitive microsatellite (STMS) has been found in the single copy, rat polymeric immunoglobulin receptor gene (PIGR) terminal exon. In Fisher rats, elements within or beyond the STMS are expressed variably in the 3' untranslated regions (3'UTRs) of two 'Groups' of PIGR-encoded hepatic mRNAs (pIg-R) during liver regeneration. STMS elements include neighboring constant regions (a 60-bp d[GA]-rich tract with a chi-like octamer, followed by 15 tandem d[GGA] repeats) that merge directly with 36 or 39 tandem d[GAA] repeats (Fisher or Wistar strains, respectively) interrupted by d[AA] between their 5th-6th repeat units. The Wistar STMS is flanked upstream by two regions of nearly contiguous d[CA] or d[CT] repeats in the 3' end of intron 8; and downstream, by a 283 bp 'unit' containing several inversions at its 5' end, and two polyadenylation signals at its 3' end. The 283 nt unit is expressed in Group 1 pIg-R mRNAs; but it is absent in the Group 2 family so that their GAA repeats merge with their poly A tails. In contrast to genomic sequence, GGA triplet repeats are amplified (n > or = 24-26), whereas GAA triplet repeats are truncated variably (n < or = 9-37) and expressed uninterruptedly in both mRNA Groups. These results suggest that 3' end processing of the rat PIGR gene may involve misalignment...

Memory Abstractions for Data Transactions

Herman, Nathaniel
Fonte: Harvard University Publicador: Harvard University
Tipo: Thesis or Dissertation; text Formato: application/pdf
EN
Relevância na Pesquisa
17.4%
This thesis presents STO, a software transactional memory (STM) based not on low-level reads and writes on memory, but on datatypes—arrays, lists, queues, hash tables, and so forth—that explicitly support transactional operations. Conventional STMs allow programmers to write concurrent code in much the same way as sequential code—thereby more easily taking advantage of multiple CPU cores. However, these conventional STMs track every memory word accessed during a transaction, so even simple operations can perform many more memory accesses for synchronization than is strictly required for transactional correctness. Our insight is that concurrent data structures can generate fewer superfluous accesses, and use more efficient concurrency protocols, when transaction bookkeeping tracks high-level operations like “insert node into tree.” We test our ideas on the STAMP benchmark suite for STM applications, on a high-performance in-memory database, and on a previously single-threaded program that we extend to multithreaded operation. We find that datatypes can support transactional operations without too much trouble; that relatively naive users can build simple transaction support into their own data structures; and that our typed STM can outperform and outscale conventional...

On the Cost of Concurrency in Transactional Memory

Kuznetsov, Petr; Ravi, Srivatsan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
17.74%
The crux of software transactional memory (STM) is to combine an easy-to-use programming interface with an efficient utilization of the concurrent-computing abilities provided by modern machines. But does this combination come with an inherent cost? We evaluate the cost of concurrency by measuring the amount of expensive synchronization that must be employed in an STM implementation that ensures positive concurrency, i.e., allows for concurrent transaction processing in some executions. We focus on two popular progress conditions that provide positive concurrency: progressiveness and permissiveness. We show that in permissive STMs, providing a very high degree of concurrency, a transaction performs a linear number of expensive synchronization patterns with respect to its read-set size. In contrast, progressive STMs provide a very small degree of concurrency but, as we demonstrate, can be implemented using at most one expensive synchronization pattern per transaction. However, we show that even in progressive STMs, a transaction has to "protect" (e.g., by using locks or strong synchronization primitives) a linear amount of data with respect to its write-set size. Our results suggest that looking for high degrees of concurrency in STM implementations may bring a considerable synchronization cost.

Multiversion Conflict Notion for Transactional Memory Systems

Kumar, Priyanka; Peri, Sathya
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
17.95%
In recent years, Software Transactional Memory systems (STMs) have garnered significant interest as an elegant alternative for addressing concurrency issues in memory. STM systems take optimistic approach. Multiple transactions are allowed to execute concurrently. On completion, each transaction is validated and if any inconsistency is observed it is aborted. Otherwise it is allowed to commit. In databases a class of histories called as conflict-serializability (CSR) based on the notion of conflicts have been identified, whose membership can be efficiently verified. As a result, CSR is the commonly used correctness criterion in databases. Similarly, using the notion of conflicts, a correctness criterion, conflict-opacity (co-opacity) which is a sub-class of can be designed whose membership can be verified in polynomial time. Using the verification mechanism, an efficient STM implementation can be designed that is permissive w.r.t co-opacity. By storing multiple versions for each transaction object, multi-version STMs provide more concurrency than single-version STMs. But the main drawback of co-opacity is that it does not admit histories that are uses multiple versions. This has motivated us to develop a new conflict notions for multi-version STMs. In this paper...

Habilidades especializadas do tênis: um estudo de intervenção na iniciação esportiva com crianças escolares; Tennis specialized skills: a beginning sport intervention study with school children

Píffero, Constance Muller; Valentini, Nadia Cristina
Fonte: Universidade de São Paulo. Escola de Educação Física e Esporte Publicador: Universidade de São Paulo. Escola de Educação Física e Esporte
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; ; Formato: application/pdf
Publicado em 01/06/2010 POR
Relevância na Pesquisa
17.74%
O objetivo desta pesquisa, de delineamento quase-experimental e correlacional, foi verificar a influência de um Programa de Iniciação ao Tênis (PIT) com duas abordagens, Clássica (AC) e de Contexto Motivacional para a Maestria (AM), no desempenho de habilidades motoras especializadas do Tênis (HMET) e investigar as associações entre o desenvolvimento das habilidades especializadas e as fundamentais. Participaram do estudo 61 crianças (29 meninas e 32 meninos), com idades de seis a 12 anos (M = 9,4), sendo 30 crianças da AC e 31 crianças da AM. Para as avaliações das crianças foram utilizados o Test of Gross Motor Development-2 (TGMD-2) e o instrumento de Habilidades Motoras Especializadas do Tênis (HMET). O PIT foi desenvolvido em 26 semanas, implementando, para a AM os pressupostos da estrutura TARGET e do Sport Education Model e para a AC os modelos clássicos de aprendizagem do Tênis. Os resultados indicaram que 1) mudanças positivas e significantes (p < 0,01) nas HMET para todas as crianças; 2) interação não significante da faixa etária (p = 0,519) e do gênero (p = 0,24) nas HMET; 3) associação restrita a locomoção no pós teste entre habilidades especializadas e fundamentais para o grupo da maestria. A implementação de um Programa de Iniciação ao Tênis...