271 research outputs found
Characterization of TLB and page allocation behavior on modern processors
No full textVirtual memory support is prevalent in most modern processors and is facilitated through Translation Lookaside Buffers (TLBs) which play a major role in the overall system performance. TLB misses are costly since they require multiple high latency memory references to walk the page table and locate the desired Virtual Page Number (VPN) - Physical Page Number (PPN) mapping. This study improves TLB hit rates by taking advantage of any contiguity present in the pages allocated by the Operating System (OS). By contiguity we refer to cases where consecutive VPNs are mapped to consecutive PPNs. Traditionally, OSs use large or superpages to collapse hundreds of such contiguous entries, thereby using one TLB entry to represent them rather than hundreds of entries they would normally require. Unfortunately due to implementation complexities superpaging has not been universally successful in reducing TLB pressure. We show, however, that even without explicit superpaging, various OS virtual memory allocation activities lead to intermediate levels of contiguity that may be exploited to coalesce TLB entries and significantly improve hit rates. We verify the presence of contiguity by running benchmarks on a real system and checking the page allocations of the OS. The OS page allocation schemes depend on memory pressure and memory defragmentation daemons. Further, we find an average contiguity of 30 pages over all the benchmarks and configurations with superpaging turned on and about 10 with superpaging turned off. To verify the performance of a Coalesced TLB we have implemented a fully associative TLB with variable size and Least Recently Used (LRU) replacement policy. Our results show an average hit rate improvement of 25% by adding an 8-16 entry fully associative Coalesced TLB. The Coalesced TLB further needs no complex hardware to implement, hence providing to a low cost means to reduce miss rates.M.S.Includes bibliographical referencesby Viswanathan Vaidyanatha
Sustainable product and market development for subsistence marketplaces: Creating educational initiatives in radically different contexts
No full textDeveloping products and business processes to serve subsistence marketplaces (or the roughly 4 billion poor around the world referred to as the bottom of the pyramid) is a significant challenge for businesses. Despite the importance of subsistence marketplaces, most product development educational curricula have been focused on relatively resource-rich and literate consumers and markets. We teach an innovative year-long product development course which includes an international immersion experience and which covers a broad spectrum of learning from understanding poverty, to consumer behavior, to product development and engineering design specifically for subsistence consumers. This unique course represents a pioneering effort to focus attention and create knowledge about product development, marketing, management, and engineering practices for subsistence marketplaces. Our two-semester course sequence for graduate-level students in a variety of business and engineering disciplines and industrial design combines in-class pedagogy with experiential learning and results in useful and marketable product concepts and prototypes. Working on projects with multinational companies or startups, students identify an opportunity of general need, conduct field market research to better understand subsistence consumer needs and contexts through an international immersion experience, develop a product concept, convert the concept to a workable prototype, and develop a manufacturing plan, marketing strategy, and overall business plan for the product. Overlaying the content found in a typical new product development lab course we develop a contextual understanding of subsistence marketplaces, setting the stage for new product development. A central aspect of the learning experience is travel to subsistence markets for actual immersion in the context and to conduct market research. Our course is at the confluence of two of the most important issues facing humanity, subsistence and sustainability. Lessons learned here can also be extended to other radically different contexts, such as future scenarios involving severe energy shortages or climate change consequences. Such educational initiatives provide challenging learning experiences in preparing students for the unique demands of the 21st century. © 2011 Product Development and Management Association.APPLE LE, 1988, J PROD INNOVAT MANAG, V5, P70, DOI 10.1111-1540-5885.510070; ASHBY M, 2003, MATER TODAY, V6, P24, DOI 10.1016-S1369-7021(03)01223-9; Cardozo RN, 2002, J PROD INNOVAT MANAG, V19, P4, DOI 10.1016-S0737-6782(01)00116-3; CHICK A, 1997, J SUSTAINABLE PRODUC, V1, P53; Donaldson KM, 2006, RES ENG DES, V17, P135, DOI 10.1007-s00163-006-0017-3; Ehrenreich B., 2002, NICKEL DIMED; Eppinger S.D., 2002, DESIGN MANAGEMENT J, V13, P58; GESCHKA H, 1986, J PROD INNOVAT MANAG, V3, P48, DOI 10.1016-0737-6782(86)90043-3; GREEN M, 2006, P ASME DES ENG TECHN; HAMMOND A. L., 2007, INNOVATIONS, V2, P147, DOI [10.1162-itgg.2007.2.1-2.147, DOI 10.1162-ITGG.2007.2.1-2.147]; HANNUKAINEN P, 2006, P ASME DES ENG TECHN; Hargadon A, 2000, HARVARD BUS REV, V78, P157; HAUSER JR, 1988, HARVARD BUS REV, V66, P63; HERSTATT C, 1992, J PROD INNOVAT MANAG, V9, P213, DOI 10.1016-0737-6782(92)90031-7; HORAN J, 2004, ONE PAGE BUSINESS PL; Murcott S., 2007, J INT DEV, V19, P123, DOI 10.1002-jid.1353; Prahalad CK, 2002, HARVARD BUS REV, V80, P48; PRAHALAD CK, 2005, FORT BOTT PYR ER POV; PUGH P, 1991, TOTAL DESIGN INTEGRA; Rodriguez J, 2006, INTERACT COMPUT, V18, P956, DOI 10.1016-j.intcom.2006.05.007; Sahlman WA, 1997, HARVARD BUS REV, V75, P98; Schumacher Ernest F., 1973, SMALL IS BEAUTIFUL E; *SME, 2003, PLAST INJ MOLD; *SME, 2004, FUND MAN PROC SAMPL; Sridharan S, 2008, J CONSUM MARK, V25, P455, DOI 10.1108-07363760810915671; Stone R. B., 2000, Design Studies, V21, DOI 10.1016-S0142-694X(99)00003-4; TAGUCHI J, 1990, HARVARD BUS REV, V68, P65; Tybout JR, 2000, J ECON LIT, V38, P11, DOI 10.1257-jel.38.1.11; Ulrich K., 2007, PRODUCT DESIGN DEV; Viswanathan M, 2005, J MARKETING, V69, P15, DOI 10.1509-jmkg.69.1.15.55507; Viswanathan M., 2009, IVEY BUSINESS J MAR; Viswanathan M, 2009, J MACROMARKETING, V29, P406, DOI 10.1177-0276146709345620; Viswanathan M, 2008, EDUC ASIA PAC REG-IS, V12, P1, DOI 10.1007-978-1-4020-5769-4; Viswanathan M., 2007, PRODUCT MARKET DEV S, P1; Viswanathan M., 2007, PRODUCT MARKET DEV S, P212
Algorithmic advances in dynamic analysis for detecting concurrency bugs
Get PDFConcurrency is an indispensable programming paradigm and multi-threaded programs form the bedrock of most modern software applications. Multi-threaded programs, however, are also the most tricky to get right. Despite rigorous in-house testing, concurrency issues like data races, race conditions, deadlocks and atomicity violations incessantly find there way into production-level software. In the past, errors arising due to complex concurrency bugs in software have led to catastrophic loss of human lives and money. Tackling concurrency bugs, and in particular, efficiently detecting such bugs, has, therefore, been the center of attention in computer science research for several decades now.
Dynamic analysis techniques, in particular, have emerged as the de facto standard for detecting concurrency bugs. Such techniques, examine execution traces of programs, with an aim to detect concurrency bugs at runtime. This thesis advances the state-of-the art in dynamic analysis for detecting concurrency bugs. We propose several algorithms for improving the precision, recall and efficiency of existing techniques for dynamically detecting concurrency bugs like data races and atomicity violations. We also investigate several complexity-theoretic questions establishing precise complexity bounds on several questions arising in dynamic concurrency bug detection.
We first consider the problem of detecting data races dynamically. Most popular techniques for dynamic race detection are either based on a principle of lockset violations, or on the happens-before partial order. While these techniques are usually employed at runtime, for detecting data races on-the-fly, there are many scenarios when executions can be, or need to be analyzed for concurrency bugs in an offline setting. Since executions can be extremely large, they are often stored in a compressed format to ease their warehousing. In this thesis, we study the problem of detecting data races when the analysis needs to be performed over an execution that has been compressed using a grammar-based compression scheme. We show how to detect data races efficiently in such a setting, without needing to decompress the (potentially) exponentially succinct compressed format.
We next study the problem of dynamic race prediction, which asks if one can infer the presence of data races beyond those present in a single trace observed by monitoring a program while it is executing. Existing race detectors report false alarms, miss a lot of real races, or do not scale beyond small execution traces. We propose several algorithms that offer a good balance of scalability and predictive power, while being sound (no false positives). We also study the problem from a complexity-theoretic point of view and identify upper and lower bounds, both in the general setting and in settings when the observed execution trace satisfies special properties.
Next, we consider the problem of dynamically detecting atomicity violations. This thesis proposes a linear time vector-clock algorithm for a well-studied notion of atomicity, called conflict serializability, for which the only known algorithms ran in cubic time.
The algorithms proposed in this thesis have been implemented and evaluated against large benchmark suites to evaluate their effectiveness. The techniques developed in this thesis are backed by strong theoretical foundations that ensure that our algorithms are scalable, sound and have high predictive power, making them applicable for analyzing modern software systems.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-12-01The student, Umang Mathur, accepted the attached license on 2021-07-16 at 17:21.The student, Umang Mathur, submitted this Dissertation for approval on 2021-07-16 at 17:26.This Dissertation was approved for publication on 2021-07-19 at 11:23.DSpace SAF Submission Ingestion Package generated from Vireo submission #16995 on 2022-04-06 at 17:16:10Made available in DSpace on 2022-04-29T21:41:39Z (GMT). No. of bitstreams: 2
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Outside the fold conversion, modernity, and belief
No full text"Outside the Fold is a radical reexamination of religious conversion. Gauri Viswanathan skillfully argues that conversion is an interpretive act that belongs in the realm of cultural criticism. To that end, this work examines key moments in colonial and postcolonial history to show how conversion questions the limitations of secular ideologies, particularly the discourse of rights central to both the British empire and the British nation-state. Implicit in such questioning is an attempt to construct an alternative epistemological and ethical foundation of national community. Viswanathan grounds her study in an examination of two stimultaneous and, she asserts, linked events: the legal emancipation of religious minorities in England and the acculturation of colonial subjects to British rule. The author views these two apparently disparate events as part of a common pattern of national consolidation that produced the English state. She seeks to explain why resistance, in both cases, frequently took the form of religious conversion, especially to "minority" or alternative religions. Confronting the general characterization of conversion as assimilative and annihilating of identity, Viswanathan demonstrates that a willful change of religion can be seen instead as an act of opposition. Outside the Fold concludes that, as a form of cultural crossing, conversion comes to represent a vital release into difference.""Through the figure of the convert, Viswanathan addresses the vexing question of the role of belief and minority discourse in modern society. She establishes new points of contact between the convert as religious dissenter and as colonial subject. This convergence provides a transcultural perspective not otherwise visible in literary and historical texts. It allows for radically new readings of significant figures as diverse as John Henry Newman, Pandita Ramabai, Annie Besant, and B. R. Ambedkar, as well as close studies of court cases, census reports, and popular English fiction. These varying texts illuminate the means by which discourses of religious identity are produced, contained, or opposed by the languages of law, reason, and classificatory knowledge. Outside the Fold is a challenging, provocative contribution to the multidisciplinary field of cultural studies. Book jacket."--BOOK JACKE
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Built-in-self-test and foreground calibration of SAR ADCs
Get PDFThis thesis explores the scope of ‘Built-in-Self-Test’(BIST) schemes to reduce the time cost complexity associated with the production tests for static linearity errors in Successive Approximation (SAR) ADCs. In this regard, an on-chip implementation of the ‘Stimulus Based Error Identification and Removal’ (SEIR) method [1] is sought to be pursued. As an extension, it is proposed that the estimated ADC non-linearities may then be suitably calibrated to achieve higher resolution. A brief review of the testing and calibration algorithm is undertaken. Further, this work elaborates on the design of a prototype front-end test generator and a buffer interface to calibrate a 10MHz 14 bit redundant SAR ADC in the TSMC 180nm process. Simulation results validating the circuit implementation of the integrated front-end system have been presented.Electrical and Computer Engineerin
REANALYSIS OF THE EMISSION SPECTRUM OF IN FOREIGN GASES
No full textA. L. Guy, K.S. Viswanathan, A. Sur, and J. Tellinghuisen, Chem. Phys. Lett. 73, 582 (1980). H. Hemmati and G. J. Collins, Chem. Phys. Lett. 67, 5 (1979). P. Venkateswarlu, Phys. Rev. 81. 821 (1951). R. D. Verma, Proc. Ind. Acad. Sci. 48A, 197 (1958). K.S. Viswanathan, A. Sur, and J. Tellinghuisen, J. Mol. Spectrosc. (in press).Author Institution:The emission spectrum of in foreign gases is studied as a function of pressure, temperature, end isotopic species, using a tesla discharge as Evidence is found for at least 12 of the 18 ion-pair states arising from , of which (2g) appears to be the lowest. The pressure- and temperature-dependent spectra support the suggestion that both the 3400-A system and a broad band near 5000 A originate from this state. High-resolution spectra show discrete structure in electronic bands at 2380 A, 2770 A, and 2880 A, in addition to the well-known F-X (2700 A), D-A(3400 A), and E-B (4300 A) systems. The 2380 system originates from a state near and terminates on the X state near v = 50. The 2770 system, which was previously as terminating on the X or B state, is now found to involve the A() The 2880 system terminates on a weakly bound lower slate which probably dissociates to ground-stale atoms. Work is continuing on the other electronic bands of the emission spectrum, most of which appear to be diffuse
Adaptive transmit power control based on signal strength and frame loss measurements for WLANs:
No full textIn the past few years, we witnessed a rapid penetration of Wireless Local Area Networks (WLANs) into the home and enterprise. Emerging technology such as the IEEE 802.11n radio, which is getting increasingly affordable, makes delivering multimedia content over
wireless networks possible and this would drive the technology further into our daily life. As the number of available wireless channels in the unlicensed spectrum is limited (3 non-overlapping channels in 2.4GHz unlicensed band and up to 24 non-overlapping channels in 5GHz unlicensed band), they have to be shared by multiple WLANs consisting of Access Points (APs) and STAtions (STAs). In a Multi-Dwelling Unit (MDU) WLAN deployment, e.g. in an apartment building or hotel, transmissions in overlapping cells tend to interfere with each other. This will adversely impact the aggregate wireless network throughput and thus the quality of experience for applications such as multimedia streaming. Hence there is a need for automatic and adaptive resource management strategy to ensure a good overall network performance.
In this thesis we propose an adaptive per-link Transmit Power Control (TPC) solution for WLANs. TPC can reduce interference, increase channel reuse, and eventually increase the overall capacity in dense 802.11 wireless networks. However intelligent algorithms are
required to adapt transmit power in a practical and distributed way to achieve improvement in performance. It becomes more challenging given different types of interference (cooperative and non-cooperative) in the unlicensed band as well as the hidden node problem. From a detailed study of the previous efforts at power control, we observe that in order to make better decisions on transmit power; an AP needs to actively monitor several factors. Hence we develop a TPC algorithm based on both link margin estimation as well as frame loss rate measurement. Compared to previous solutions that adapt the transmit power based on measurement of a single parameter (either received signal strength or frame loss rate), the proposed power control mechanism can diagnose and take remedial action for hidden nodes and channel access asymmetry problems manifesting as frame losses. It is adaptive to mobility, complementary to any rate control algorithm and can also be incrementally deployed amidst non-cooperative nodes. We have implemented the algorithm as an application running on Atheros chipset-based 802.11n APs, taking practical system-level limitations into account. The proposed solution achieves significant transmit power reduction at the APs (to as low as 60% of the maximum power) for STAs as far as 70ft and over ∼60% increase in total network throughput through interference mitigation.M.S.Includes bibliographical references (p. 47-48)by Hariharasudhan Viswanatha
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Global Factor Returns
Get PDFThe 86 of 97 McLean and Pontiff (2016) factors that can be readily tested internationally deliver higher returns in Developed ex US and yet higher returns in Emerging Markets than in the United States. An equally weighted portfolio of these factors is highly significant in each region and such portfolios in Developed ex US and Emerging Markets earn a significant alpha on their US counterpart. In no region are these factors adequately explained by current models that attempt to explain factor excess returns. These factors are driven by the underlying characteristics as opposed to loadings on risk factors demonstrating that these factors are anomalies, not priced risks. However, there is some evidence that the premia on these anomalies and the characteristics’ ability to predict return are declining over time
Evolution and Current Trends in Bleomycin Therapy for Lymphangiomas: A Comprehensive Review and Future Directions
No full textBackground: Lymphangiomas are rare congenital malformations that and pose a specific challenge in the pediatric age group and require effective therapeutic intervention. In our systematic review we look at how bleomycin therapy for lymphangiomas has evolved across the five decades from (1977-2024). Methods: We conducted a systematic literature review of 127 studies, via a comprehensive search of a plethora of databases including PubMed/MEDLINE, Embase, and Cochrane Library. This analysis of studies allowed us to chart the gradual transition from surgery being the mainstay of treatment to bleomycin becoming a preferred treatment modality. Results: Analysis of our observations showed that our current success rates for bleomycin therapy range from 60-88%, with huge age dependent variations in the treatment responses. Protocol refinement has led to a significant improvement in standardization of therapy. Optimal concentration of 1 IU/mL with maximum cumulative therapy dose of 15 IU/kg are the established standards now. Conclusions: Recent advances in molecular pathophysiology have yielded promising results from combination therapy approaches which suggests new avenues for more efficacious
treatment methods. We propose structured evidence based recommendations which emphasise the standardisation of protocols whilst incorporating personalized therapy based on lesion morphology and patient characteristics
Publishing in wireless and wireline environments
No full textPublishing is a spontaneous and periodic broadcasting of information by a server. This dissertation shows how publishing can be efficiently used in both low bandwidth wireless networks and high bandwidth wireline networks. The first part of this dissertation deals with publishing in wireless networks. The solutions that we propose for wireless environments are motivated by the two most important resource constraints in such environments: limited power at the clients and scarce network bandwidth.
In a wireless environment it is crucial for the server to publish a directory along with the data. This enables battery powered clients to selectively download only relevant pieces of data, thereby saving significant power. However, publishing a directory leaves less bandwidth for the data itself. Thus, there is a need for efficient multiplexing of the directory along with the data in order to remove as little bandwidth as possible and simultaneously offer efficient solutions for power conservation at the clients. Such techniques are provided in this dissertation for both primary and secondary indexes. In addition, we also provide some hashing based solutions. This dissertation analytically demonstrates that the proposed techniques result in power and bandwidth conservation. Further on, we propose techniques for adaptive publishing when data items are accessed with different frequencies. Finally, we propose a general architecture for future wireless information systems. In wireline networks we focus on efficient utilization of network bandwidth. This dissertation proposes a new technique for providing key multimedia services like the Video On Demand service. It also provides analytical results demonstrating the benefits of this technique along with an implementation of its prototype on Ethernet LAN.Technical report lcsr-tr-24
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