595 research outputs found

    Processor Allocation for Optimistic Parallelization of Irregular Programs

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    Optimistic parallelization is a promising approach for the parallelization of irregular algorithms: potentially interfering tasks are launched dynamically, and the runtime system detects conflicts between concurrent activities, aborting and rolling back conflicting tasks. However, parallelism in irregular algorithms is very complex. In a regular algorithm like dense matrix multiplication, the amount of parallelism can usually be expressed as a function of the problem size, so it is reasonably straightforward to determine how many processors should be allocated to execute a regular algorithm of a certain size (this is called the processor allocation problem). In contrast, parallelism in irregular algorithms can be a function of input parameters, and the amount of parallelism can vary dramatically during the execution of the irregular algorithm. Therefore, the processor allocation problem for irregular algorithms is very difficult. In this paper, we describe the first systematic strategy for addressing this problem. Our approach is based on a construct called the conflict graph, which (i) provides insight into the amount of parallelism that can be extracted from an irregular algorithm, and (ii) can be used to address the processor allocation problem for irregular algorithms. We show that this problem is related to a generalization of the unfriendly seating problem and, by extending Tur\'an's theorem, we obtain a worst-case class of problems for optimistic parallelization, which we use to derive a lower bound on the exploitable parallelism. Finally, using some theoretically derived properties and some experimental facts, we design a quick and stable control strategy for solving the processor allocation problem heuristically.Comment: 12 pages, 3 figures, extended version of SPAA 2011 brief announcemen

    Metabolic syndrome in rural Australia:An opportunity for primary health care

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    Objective: To measure the impact of a 6-month home-based behaviour change intervention on reducing the risk of chronic disease as determined by metabolic syndrome status and cardiovascular risk score, and discuss implications for primary care in rural areas. Design: A two-arm randomised controlled trial of rural adults. Setting: The rural town of Albany in the Great Southern region of Western Australia. Participants: Participants (n = 401) aged 50-69 years who were classified with or at risk of metabolic syndrome and randomly assigned to intervention (n = 201) or waitlisted control (n = 200) group. Interventions: A 6-month intervention program incorporating goal setting, self-monitoring and feedback, with motivational interviewing was conducted. Main outcome measures: Change in metabolic syndrome status and cardiovascular risk. Results: Significant improvements in metabolic syndrome status and cardiovascular disease risk score (−0.82) were observed for the intervention group relative to control group from baseline to post-test. Conclusion: This home-based physical activity and nutrition intervention reduced participants' risk of experiencing a cardiovascular event in the next 5 years by 1%. Incorporating such prevention orientated approaches in primary care might assist in reducing the burden of long-term chronic diseases. However, for realistic application in this setting, hurdles such as current national health billing system and availability of resources will need to be considered

    The symmetric-Toeplitz linear system problem in parallel

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    [EN] Many algorithms exist that exploit the special structure of Toeplitz matrices for solving linear systems. Nevertheless, these algorithms are difficult to parallelize due to its lower computational cost and the great dependency of the operations involved that produces a great communication cost. The foundation of the parallel algorithm presented in this paper consists of transforming the Toeplitz matrix into a another structured matrix called Cauchy¿like. The particular properties of Cauchy¿like matrices are exploited in order to obtain two levels of parallelism that makes possible to highly reduce the execution time. The experimental results were obtained in a cluster of PC¿s.Supported by Spanish MCYT and FEDER under Grant TIC 2003-08238-C02-02Alonso-Jordá, P.; Vidal Maciá, AM. (2005). The symmetric-Toeplitz linear system problem in parallel. Computational Science -- ICCS 2005,Pt 1, Proceedings. 3514:220-228. https://doi.org/10.1007/11428831_28S2202283514Sweet, D.R.: The use of linear-time systolic algorithms for the solution of toeplitz problems. k Technical Report JCU-CS-91/1, Department of Computer Science, James Cook University, Tue, 23 April 1996 15, 17, 55 GMT (1991)Evans, D.J., Oka, G.: Parallel solution of symmetric positive definite Toeplitz systems. Parallel Algorithms and Applications 12, 297–303 (1998)Gohberg, I., Koltracht, I., Averbuch, A., Shoham, B.: Timing analysis of a parallel algorithm for Toeplitz matrices on a MIMD parallel machine. Parallel Computing 17, 563–577 (1991)Gallivan, K., Thirumalai, S., Dooren, P.V.: On solving block toeplitz systems using a block schur algorithm. In: Proceedings of the 23rd International Conference on Parallel Processing, Boca Raton, FL, USA, vol. 3, pp. 274–281. CRC Press, Boca Raton (1994)Thirumalai, S.: High performance algorithms to solve Toeplitz and block Toeplitz systems. Ph.d. th., Grad. College of the U. of Illinois at Urbana–Champaign (1996)Alonso, P., Badía, J.M., Vidal, A.M.: Parallel algorithms for the solution of toeplitz systems of linear equations. In: Wyrzykowski, R., Dongarra, J., Paprzycki, M., Waśniewski, J. (eds.) PPAM 2004. LNCS, vol. 3019, pp. 969–976. Springer, Heidelberg (2004)Anderson, E., et al.: LAPACK Users’ Guide. SIAM, Philadelphia (1995)Blackford, L., et al.: ScaLAPACK Users’ Guide. SIAM, Philadelphia (1997)Alonso, P., Badía, J.M., González, A., Vidal, A.M.: Parallel design of multichannel inverse filters for audio reproduction. In: Parallel and Distributed Computing and Systems, IASTED, Marina del Rey, CA, USA, vol. II, pp. 719–724 (2003)Loan, C.V.: Computational Frameworks for the Fast Fourier Transform. SIAM Press, Philadelphia (1992)Heinig, G.: Inversion of generalized Cauchy matrices and other classes of structured matrices. Linear Algebra and Signal Proc., IMA, Math. Appl. 69, 95–114 (1994)Gohberg, I., Kailath, T., Olshevsky, V.: Fast Gaussian elimination with partial pivoting for matrices with displacement structure. Mathematics of Computation 64, 1557–1576 (1995)Alonso, P., Vidal, A.M.: An efficient and stable parallel solution for symmetric toeplitz linear systems. TR DSIC-II/2005, DSIC–Univ. Polit. Valencia (2005)Kailath, T., Sayed, A.H.: Displacement structure: Theory and applications. SIAM Review 37, 297–386 (1995

    Quality learning and teaching is vital for equipping the health promotion workforce to address complex public health challenges.

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    [Extract] Changes in global morbidity and mortality, and widening health inequities are occurring at unprecedented levels due to significant public health challenges.1 The impact of issues such as climate change and COVID-19 on population health and healthcare systems has been significant,2-4 highlighting the need for greater emphasis on disease prevention and people-centred, community-based health promotion initiatives.5 Health promotion academics play an important role in training the health promotion workforce, which is a vital component of the public health response to these global challenges

    Re-Focusing - Building a Future for Entrepreneurial Education & Learning

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    The field of entrepreneurship has struggled with fundamental questions concerning the subject’s nature and purpose. To whom and to what means are educational and training agendas ultimately directed? Such questions have become of central importance to policy makers, practitioners and academics alike. There are suggestions that university business schools should engage more critically with the lived experiences of practising entrepreneurs through alternative pedagogical approaches and methods, seeking to account for and highlighting the social, political and moral aspects of entrepreneurial practice. In the UK, where funding in higher education has become increasingly dependent on student fees, there are renewed pressures to educate students for entrepreneurial practice as opposed to educating them about the nature and effects of entrepreneurship. Government and EU policies are calling on business schools to develop and enhance entrepreneurial growth and skill sets, to make their education and training programmes more proactive in providing innovative educational practices which help and facilitate life experiences and experiential learning. This paper makes the case for critical frameworks to be applied so that complex social processes become a source of learning for educators and entrepreneurs and so that innovative pedagogical approaches can be developed in terms both of context (curriculum design) and process (delivery methods)

    Temperature Dependence of Ion Irradiation Induced Amorphization of Zirconolite

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    Zirconolite is one of the major host phases for actinides in various wasteforms for immobilizing high level radioactive waste (HLW). Over time, zirconolite's crystalline matrix is damaged by {alpha}-particles and energetic recoil nuclei recoil resulting from {alpha}-decay events. The cumulative damage caused by these particles results in amorphization. Data from natural zirconolites suggest that radiation damage anneals over geologic time and is dependant on the thermal history of the material. Proposed HLW containment strategies rely on both a suitable wasteform and geologic isolation. Depending on the waste loading, depth of burial, and the repository-specific geothermal gradient, burial could result in a wasteform being exposed to temperatures of between 100--450 C. Consequently, it is important to assess the effect of temperature on radiation damage in synthetic zirconolite. Zirconolite containing wasteforms are likely to be hot pressed at or below 1,473 K (1,200 C) and/or sintered at or below 1,623 K (1,350 C). Zirconolite fabricated at temperatures below 1,523 K (1,250 C) contains many stacking faults. As there have been various attempts to link radiation resistance to structure, the authors decided it was also pertinent to assess the role of stacking faults in radiation resistance. In this study, they simulate {alpha}-decay damage in two zirconolite samples by irradiating them with 1.5 MeV Kr{sup +} ions using the High Voltage Electron Microscope-Tandem User Facility (HTUF) at Argonne National Laboratory (ANL) and measure the critical dose for amorphization (D{sub c}) at several temperatures between 20 and 773 K. One of the samples has a high degree of crystallographic perfection, the other contains many stacking faults on the unit cell scale. Previous authors proposed a model for estimating the activation energy of self annealing in zirconolite and for predicting the critical dose for amorphization at any temperature. The authors discuss their results and earlier published data in relation to that model
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