456 research outputs found
Adaptive load balancing for HPC applications
No full textOne of the critical factors that affect the performance of many applications is load imbalance. Applications are increasingly becoming sophisticated and are using irregular structures and adaptive refinement techniques, resulting in load imbalance. Moreover, systems are becoming more complex. The number of cores per node is increasing substantially and nodes are becoming heterogeneous. High variability in the performance of the hardware components introduces further imbalance. Load imbalance leads to drop in system utilization and degrades the performance. To address the load imbalance problem, many HPC applications employ dynamic load balancing algorithms to redistribute the work and balance the load. Therefore, performing load balancing is necessary to achieve high performance.
Different application characteristics warrant different load balancing strategies. We need a variety of high-quality, scalable load balancing algorithms to cater to different applications. However, using an appropriate load balancer is insufficient to achieve good performance because performing load balancing incurs a cost. Moreover, due to the dynamic nature of the application, it is hard to decide when to perform load balancing. Therefore, deciding when to load balance and which strategy to use for load balancing may not be possible a priori.
With the ever increasing core counts on a node, there will be a vast amount of on-node parallelism. Due to the massive on-node parallelism, load imbalance occurring at the node level can be mitigated within the node instead of performing a global load balancing. However, having the application developer manage resources and handle dynamic imbalances is inefficient as well as is a burden on the programmer.
The focus of this dissertation is on developing scalable and adaptive techniques for handling load imbalance. The dissertation presents different load balancing algorithms for handling inter and intra-node load imbalance. It also presents an introspective run-time system, which will monitor the application and system characteristics and make load balancing decisions automatically.Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2017-02-28 without embargo termsThe student, Harshitha Menon Gopalakrishnan Menon, accepted the attached license on 2016-10-10 at 10:41.The student, Harshitha Menon Gopalakrishnan Menon, submitted this Dissertation for approval on 2016-10-10 at 11:06.This Dissertation was approved for publication on 2016-10-10 at 15:37.DSpace SAF Submission Ingestion Package generated from Vireo submission #10184 on 2017-02-28 at 14:46:33Made available in DSpace on 2017-03-01T15:46:12Z (GMT). No. of bitstreams: 3
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Previous issue date: 2016-10-1
Tettagalma Menon, new genus
No full text<i>Tettagalma</i> Menon, new genus <p> <b>Diagnosis.</b> Medium­sized (25 mm forewing length) tettigarctid; prominent costal margin; Rs with three branches; origin of MA branches proximal to nodal line; CuA strongly deflected anteriorly at nodal line; wide marginal membrane; marginal membrane bearing numerous, equidistant striae.</p> <p> <b>Etymology.</b> Genus­group name formed from a combination of <i>tetti</i> in reference to the family and <i>agalma</i> from the Greek present, gift, as the specimen was donated to the author.</p> <p> <b>Type locality and horizon.</b> Vicinity of Nova Olinda, Nova Olinda Member, Crato Formation.</p> <p> <b>Type species.</b> <i>Tettagalma striata</i> Menon new genus and species, by monotypy.</p>Published as part of <i>Menon, Federica, 2005, New record of Tettigarctidae (Insecta, Hemiptera, Cicadoidea) from the Lower Cretaceous of Brazil, pp. 53-58 in Zootaxa 1087</i> on page 54, DOI: <a href="http://zenodo.org/record/170508">10.5281/zenodo.170508</a>
Applying Graph Partitioning Methods in Measurement-based Dynamic Load Balancing
No full textLoad imbalance in an application can lead to degradation of performance and a significant drop in system utilization. Achieving the best parallel efficiency for a program requires optimal load balancing which is an NP-hard problem. This paper explores the use of graph partitioning algorithms, traditionally used for partitioning physical domains/meshes, for measurement-based dynamic load balancing of parallel applica- tions. In particular, we present repartitioning methods that consider the previous mapping to minimize dynamic migration costs. We also discuss the use of a greedy algorithm in conjunction with iterative graph partitioning algorithms to reduce the load imbalance for graphs with heavily skewed load distributions. These algorithms are implemented in a graph partitioning toolbox called SCOTCH and we use CHARM++, a migratable objects based programming model, to experiment with various load balancing scenarios. To compare with different load balancing strategies based on graph partitioners, we have implemented METIS and ZOLTAN-based load balancers in CHARM++. We demonstrate the effectiveness of the new algorithms de- veloped in SCOTCH in the context of the NAS BT solver and two micro-benchmarks. We show that SCOTCH based strategies lead to better performance compared to other existing partitioners, both in terms of the application execution time and fewer number of objects migrated.Submitted by Harshitha Menon Gopalakrishnan Menon ([email protected]) on 2015-05-05T18:51:02Z
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Previous issue date: 2015Ope
Novel Dialogue 2.3: Because I Couldn't Be a Dancer: Sigrid Nunez and Tara Menon (JP)
No full textThe brilliant New York writer Sigrid Nunez's most recent novel is What Are You Going Through; her previous one, The Friend, (2018) won the National Book Award. She speaks with Tara Menon, of the Harvard English department, and author of a terrific article about Sigrid Nunez in the Sewanee Review. The conversation ranges widely and then plunges into depths. Because life is defined by grief and mourning, so too are my novels, says Nunez. She thinks her upbringing with immigrant parents who felt adrift from their homeland and her own "failure" as a dancer (recounted in her 1995 debut novel, A Feather on the Breath of God ) are the ferment from which her vocation as a writer arose. The question of genre is tossed around: "fictional memoir" perhaps, which gets confused (insultingly, Tara thinks!) with auto-fiction. But Sigrid is fascinated by establishing a reality that is entirely made-up ("not a single friend angry!"), yet also documentary in nature. Perhaps the best tag for her work is "essay novel": that allows one to do what Javier Marias calls "literary thinking." And there's a wonderfully non-Pavlovian answer to the treat question: sometimes you can just have the whiskey
A priori and a posteriori analysis of the hybrid two-level large-eddy simulation method for high Reynolds number complex flows
No full textWe present a priori and a posteriori analysis of the assumptions and predictions of the hybrid two-level large-eddy simulation (TLS-LES) method for high Reynolds number complex flows. The TLS-LES methodology is a multi-scale framework for simulation of turbulent flows in complex configurations at practically relevant Reynolds number. It additively combines the two-level simulation (TLS) model with a conventional large-eddy simulation (LES) approach by employing a static or dynamic blending function. In the present study, first we analyze the model assumptions employed by the TLS model to obtain the small-scale solution necessary for closure of the large-scale equations. Afterward, we analyze the large-scale and small-scale solutions to assess the predictive ability of the multi-scale framework for specific turbulence physics such as role of forward and backscatter of energy and presence of co- and counter-gradient diffusion. To perform these investigations, we consider cases with increasing degree of geometrical complexity, namely, flow in a periodic channel, flow past a bump placed on the lower surface of the channel and flow past a finite-span NACA0015 airfoil
Il bene del filosofo e il limite della città. Sulla politica filosofica di Leo Strauss
No full textThe intention of this paper is to show how Leo Straussʼ mature writings respond to the twofold necessity of political philosophy: contributing, at the same time, to the good of the city and to the good of the philosophers. In the first place, it will try to prove this point by analyzing in detail the Introduction to On Tyranny (1948), which represents an essential step in order to understand the intention of the author. In the second place, it will tackle the problem of justice, that is, of natural right, by concentrating on the so called " tyrannical teaching ". This teaching is a way to present a truth which the city cannot find acceptable, that is, an unpleasant truth concerning the irresoluble problem of justice and legitimacy. In conclusion, it will point to the tension between philosophy, i.e., search for knowledge, and the city, i.e., the realm of opinion. For the philosopher, as such, has to " corrupt " the young in order to pursue his search for knowledge of the whole, or the nature of all things. Therefore, he weakens the city, since philosophizing implies unbelief in the gods of the city
Equivariant elliptic cohomology and twisted equivariant k-theory
No full textEquivariant elliptic cohomology and twisted equivariant K-theory are both related to the representations of loop groups. After making these relationships precise, we propose a map from twisted equivariant elliptic cohomology to twisted K-theory of the inertia stack using equivariant de Rham models. This proposal agrees with the Freed-Hopkins-Teleman q = 1 map from characters of representations of loop groups to distributions associated to twisted equivariant K-theory classes.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-08-01The student, Dileep Menon, accepted the attached license on 2019-05-24 at 15:54.The student, Dileep Menon, submitted this Dissertation for approval on 2019-05-24 at 16:06.This Dissertation was approved for publication on 2019-05-28 at 10:50.DSpace SAF Submission Ingestion Package generated from Vireo submission #13991 on 2019-11-26 at 13:00:58Made available in DSpace on 2019-11-26T20:49:00Z (GMT). No. of bitstreams: 4
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Previous issue date: 2019-05-28Embargo set by: Seth Robbins for item 112889
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Meta-Balancer: automated load balancing based on application behavior
No full textWith the dawn of petascale, and with exascale in the near future, it has become significantly difficult to write parallel applications that fully exploit the processing
power, and scale to large systems. Load imbalance, both computationally and communication induced, presents itself as one of the important challenges in achieving scalability and high performance. Problem sizes and system sizes have become so large that manually handling the imbalance in dynamic
applications, and finding an optimum distribution of load has become a herculean task.
Charm++~\cite provides the user with a run time system that
performs dynamic load balancing. To enable Charm++ to perform load balancing
in an efficient manner, the user takes certain decisions such as when to load
balance and which strategy to use, and informs the Charm++ run-time system of
these decisions. Many a times, taking these important decisions involve hand
tuning each application by observing various runs of the application.
In this thesis, a Meta-Balancer which relieves the user from the
effort of making the load balancing related decisions, is presented. The Meta-Balancer
is a part of the Charm++ load balancing framework. It identifies the characteristics
of the application, and based on the principle of persistence and the accrued
information, makes load balancing related decisions. We study the performance of
the Meta-Balancer in the context of leanmd mini application.
We also evaluate the Meta-Balancer in the context of micro benchmarks such as kNeighbor and jacobi2D.
We also present several new load balancing strategies, that have been
incorporated into Charm++, and study their impact on the performance of applications.
These new strategies are: 1)RefineSwapLB, which is a refinement based load balancing strategy,
2)CommAwareRefineLB, which is a communication aware refinement strategy,
3)ScotchRefineLB, which is a refinement based graph partitioning strategy using
Scotch, a graph partitioner, and 4) ZoltanLB, which is a multicast
aware load balancing strategy using Zoltan, a hypergraph partitioner.Item withdrawn by Mark Zulauf ([email protected]) on 2012-04-26T18:39:23Z
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University of Illinois Theses & Dissertations (ID: 1)
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Risk-reducing early salpingectomy and delayed oophorectomy as a two-staged alternative for primary prevention of ovarian cancer in women at increased risk: a commentary.
No full textThis is the peer reviewed version of the following article: Gaba, F. , Piek, J. , Menon, U. and Manchanda, R. (2019), Risk reducing early salpingectomy and delayed oophorectomy as a two staged alternative for primary prevention of ovarian cancer in increased risk women: a commentary. BJOG: Int J Obstet Gy. Accepted Author Manuscript. doi:10.1111/1471-0528.15651, which has been published in final form at https://doi.org/10.1111/1471-0528.15651. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Version
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