Evaluating policies for generalized bandits via a notion of duality

2000 ◽  
Vol 37 (2) ◽  
pp. 540-546 ◽  
Author(s):  
J. H. Crosbie ◽  
K. D. Glazebrook
Keyword(s):  
Index Theory ◽  
Independent Interest ◽  
Central Feature ◽  
Gittins Index ◽  
Bandit Problems ◽  
Natural Restriction ◽  
Special Cases ◽  
The One

Nash's generalization of Gittins’ classic index result to so-called generalized bandit problems (GBPs) in which returns are dependent on the states of all arms (not only the one which is pulled) has proved important for applications. The index theory for special cases of this model in which all indices are positive is straightforward. However, this is not a natural restriction in practice. An earlier proposal for the general case did not yield satisfactory index-based suboptimality bounds for policies — a central feature of classical Gittins index theory. We develop such bounds via a notion of duality for GBPs which is of independent interest. The index which emerges naturally from this analysis is the reciprocal of the one proposed by Nash.

Evaluating policies for generalized bandits via a notion of duality

2000 ◽  
Vol 37 (02) ◽  
pp. 540-546
Author(s):  
J. H. Crosbie ◽  
K. D. Glazebrook
Keyword(s):  
Index Theory ◽  
Independent Interest ◽  
Central Feature ◽  
Gittins Index ◽  
Bandit Problems ◽  
Natural Restriction ◽  
Special Cases ◽  
The One

Nash's generalization of Gittins’ classic index result to so-called generalized bandit problems (GBPs) in which returns are dependent on the states of all arms (not only the one which is pulled) has proved important for applications. The index theory for special cases of this model in which all indices are positive is straightforward. However, this is not a natural restriction in practice. An earlier proposal for the general case did not yield satisfactory index-based suboptimality bounds for policies — a central feature of classical Gittins index theory. We develop such bounds via a notion of duality for GBPs which is of independent interest. The index which emerges naturally from this analysis is the reciprocal of the one proposed by Nash.

scholarly journals Some indexable families of restless bandit problems

2006 ◽  
Vol 38 (3) ◽  
pp. 643-672 ◽  
Author(s):  
K. D. Glazebrook ◽  
D. Ruiz-Hernandez ◽  
C. Kirkbride
Keyword(s):  
Index Theory ◽  
Stochastic Scheduling ◽  
Gittins Index ◽  
Scheduling Problems ◽  
Bandit Problems ◽  
Index Policy ◽  
Restless Bandit ◽  
Machine Maintenance ◽  
State Evolution ◽  
Strong Performance

In 1988 Whittle introduced an important but intractable class of restless bandit problems which generalise the multiarmed bandit problems of Gittins by allowing state evolution for passive projects. Whittle's account deployed a Lagrangian relaxation of the optimisation problem to develop an index heuristic. Despite a developing body of evidence (both theoretical and empirical) which underscores the strong performance of Whittle's index policy, a continuing challenge to implementation is the need to establish that the competing projects all pass an indexability test. In this paper we employ Gittins' index theory to establish the indexability of (inter alia) general families of restless bandits which arise in problems of machine maintenance and stochastic scheduling problems with switching penalties. We also give formulae for the resulting Whittle indices. Numerical investigations testify to the outstandingly strong performance of the index heuristics concerned.

scholarly journals Some indexable families of restless bandit problems

2006 ◽  
Vol 38 (03) ◽  
pp. 643-672 ◽  
Author(s):  
K. D. Glazebrook ◽  
D. Ruiz-Hernandez ◽  
C. Kirkbride
Keyword(s):  
Index Theory ◽  
Stochastic Scheduling ◽  
Gittins Index ◽  
Scheduling Problems ◽  
Bandit Problems ◽  
Index Policy ◽  
Restless Bandit ◽  
Machine Maintenance ◽  
State Evolution ◽  
Strong Performance

In 1988 Whittle introduced an important but intractable class of restless bandit problems which generalise the multiarmed bandit problems of Gittins by allowing state evolution for passive projects. Whittle's account deployed a Lagrangian relaxation of the optimisation problem to develop an index heuristic. Despite a developing body of evidence (both theoretical and empirical) which underscores the strong performance of Whittle's index policy, a continuing challenge to implementation is the need to establish that the competing projects all pass an indexability test. In this paper we employ Gittins' index theory to establish the indexability of (inter alia) general families of restless bandits which arise in problems of machine maintenance and stochastic scheduling problems with switching penalties. We also give formulae for the resulting Whittle indices. Numerical investigations testify to the outstandingly strong performance of the index heuristics concerned.

scholarly journals When to Substitute a Missing Upper Lateral With a Canine: A Simplified Approach

2021 ◽  
pp. 030157422098054
Author(s):  
Renu Datta
Keyword(s):  
Anterior Segment ◽  
Specific Treatment ◽  
Simplified Approach ◽  
Special Cases ◽  
Randomized Control ◽  
The One ◽  
Individual Presentation ◽  
Available Information ◽  
Missing Tooth ◽  
Made In

Introduction: The upper lateral incisor is the most commonly missing tooth in the anterior segment. It leads to esthetic and functional imbalance for the patients. The ideal solution is the one that is most conservative and which fulfills the functional and esthetic needs of the concerned individual. Canine substitution is evolving to be the treatment of choice in most of the cases, because of its various advantages. These are special cases that need more time and effort from the clinicians due to space discrepancy in the upper and lower arches, along with the presentation of individual malocclusion. Aims and Objectives: Malocclusion occurring due to missing laterals is more complex, needing more time and effort from the clinicians because of space discrepancy, esthetic compromise, and individual presentation of the malocclusion. An attempt has been made in this article to review, evaluate, and tabulate the important factors for the convenience of clinicians. Method: All articles related to canine substitution were searched in the electronic database PubMed, and the important factors influencing the decision were reviewed. After careful evaluation, the checklist was evolved. Result: The malocclusions in which canine substitution is the treatment of choice are indicated in the tabular form for the convenience of clinicians. Specific treatment-planning considerations and biomechanics that can lead to an efficient and long-lasting result are also discussed. Conclusion: The need of the hour is an evidence-based approach, along with a well-designed prospective randomized control trial to understand the importance of each factor influencing these cases. Until that time, giving the available information in a simplified way can be a quality approach to these cases.

On transforming an index for generalised bandit problems

1995 ◽  
Vol 32 (1) ◽  
pp. 168-182 ◽  
Author(s):  
K. D. Glazebrook ◽  
S. Greatrix
Keyword(s):  
Dynamic Programming ◽  
Policy Evaluation ◽  
Gittins Index ◽  
Bandit Problem ◽  
Bandit Problems ◽  
Index Policies

Nash (1980) demonstrated that index policies are optimal for a class of generalised bandit problem. A transform of the index concerned has many of the attributes of the Gittins index. The transformed index is positive-valued, with maximal values yielding optimal actions. It may be characterised as the value of a restart problem and is hence computable via dynamic programming methodologies. The transformed index can also be used in procedures for policy evaluation.

Diverse Dimensions of the Cotard’s Syndrome - an Approach Towards a Clear Classification of the Phenomenon

2009 ◽  
Vol 24 (S1) ◽  
pp. 1-1
Author(s):  
A. Nagy ◽  
V. Voros ◽  
T. Tenyi
Keyword(s):  
Clinical Practice ◽  
Diagnostic Category ◽  
Treatment Strategies ◽  
Differential Diagnostics ◽  
Dimensional System ◽  
Central Feature ◽  
Scientific Databases ◽  
Search Terms ◽  
The One

Aim:The authors present the Cotard's syndrome, a rare psychiatric condition, pointing out the latest results in terms of psychoneurology and classification of the phenomenon. The central feature of the syndrome is a nihilistic delusion, in which the patient denies his or her own existence and that of the external world.Method:We searched electronic scientific databases using the appropriate search terms; relevant articles were carefully reviewed. We also present three cases from our clinical practice.Results:After the overview of the latest biological and neuropsychological findings, the terminology, the nosology, the classification and the differential diagnostics are discussed. To sum up with useful information for the clinical practice, the possible treatment strategies, the course and the prognosis of the disease are also presented.Conclusions:The reported cases together with the reviewed literature suggest that a dimensional system of classifying Cotard's syndrome is preferable. At the one end of the spectrum is the presence of the pure nihilistic delusions, appearing as a symptom of an underlying psychiatric or neurological condition. The full-blown, classical syndrome as a diagnostic category forms the other end of the spectrum. The presented theoretical and practical aspects give a lead on deeper understanding, easier recognition and more adequate therapy of the Cotard's syndrome.

The Maximum Claims of Gauthier's Bargainers: Are the Fixed Social Inequalities Acceptable?

Dialogue ◽  
1982 ◽  
Vol 21 (3) ◽  
pp. 411-429
Author(s):  
David Braybrooke
Keyword(s):  
Social Contract ◽  
Social Inequalities ◽  
Social Contract Theory ◽  
The Other ◽  
Relative Advantage ◽  
Central Feature ◽  
Maximum Utility ◽  
The Difference ◽  
The One ◽  
Principle Of Maximum

A central feature of David Gauthier's impressively searching version of social contract theory is the principle of maximin relative advantage. Given certain assumptions—more than he originally thought—this principle may be described as calling for maximum equal advantage, which is easier to talk about; and I shall refer to the principle under this description. Maximum equal relative advantage is equivalent to minimum equal relative concession; hence the principle of maximum equal relative advantage has a twin and mirror, the principle of minimum equal relative concession. Relative advantage and relative concession are ratios with the same denominator, the difference for a given agent between the maximum utility (umax) that she might get from the societyt o be contracted for and the minimum utility (umin) that would give her an incentive to cooperate in establishing the society and in keeping it up. The numerator for the one ratio—relative advantage—is the difference between the utility that she is actually going to gain from society (ua) and her minimum cooperative utility (umin). The numerator for the other ratio—relative concession—is the difference between her maximum utility (umax) and the utility that she is going to get (ua), in other words, the amount of utility that she foregoes in not getting her maximum.

On the Relation Between Global Modernity and Nationalism: The Crisis of Hegemony and the Rise of (Islamic) Identity in Turkey

1995 ◽  
Vol 13 ◽  
pp. 93-120 ◽  
Author(s):  
E. Fuat Keyman
Keyword(s):  
Free Market ◽  
Political Elite ◽  
Central Feature ◽  
Old Regime ◽  
Global Culture ◽  
End Of History ◽  
Global Modernity ◽  
The One ◽  
Cultural Homogenization ◽  
Made In

Turkey did not rise phoenix-like out of the ashes of the Ottoman Empire. It was ‘made’ in the image of the Kemalist elite which won the national struggle against foreign invaders and the old regime. Thereafter, the image of the country kept changing as the political elite grew and matured, and as it responded to challenges both at home and abroad. This process of ‘making’ goes on even today (Ahmad 1993, p.i).The process of contemporary globalization in its most general form involves a tension between universalism and particularism (see Robertson, 1992, pp. 8-61). On the one hand, with Francis Fukuyama’s “the end of history thesis” which suggests universalization of liberal democracy, along with the globalization of free market ideology, the dissolution of differences into sameness can be said to mark an emergence of cultural homogenization. On the other hand, it can be suggested that particularistic conflicts have begun to dictate the mode of articulation of political practices and ideological/discursive forms in global relations, which draws our attention to the tendency towards cultural heteroge-nization. Arjun Appadurai asserts in this context that “the central problem of today’s global interactions is the tension between cultural homogenization and cultural heterogenization”, or, as he puts it:the central feature of global culture today is the politics of the mutual effort of sameness and difference to cannibalize one another and thus to proclaim their successful hijacking of the twin Enlightenment ideas of the triumphantly universal and the resiliently particular (Appadurai, 1990, p. 17).

scholarly journals Code-Switching, Language Emotionality and Identity in Junot Díaz’s “Invierno”

2020 ◽  
Vol 42 (2) ◽  
pp. 99-118
Author(s):  
María Jesús Sánchez ◽  
Elisa Pérez-García
Keyword(s):  
Short Story ◽  
First Language ◽  
Code Switching ◽  
Emotional Expressions ◽  
Central Feature ◽  
Bilingual Speakers ◽  
Linguistic Activity ◽  
The Caribbean ◽  
The One ◽  
The Relationship

Code-switching (CS) is a linguistic activity typical of bilingual speakers, and thus, a central feature characterising Latino/a literature. The present study reads Junot Díaz’s “Invierno,” a short story from This Is How You Lose Her (2012), with a focus on the oral code-switches that the bilingual Latino/a characters make from English—their second language (L2)—to Spanish—their first language (L1). More specifically, it explores the relationship between CS, language emotionality and identity. The Spanish code-switches are analysed in terms of the emotionality degree they elicit and, linguistically, according to frequency and type—intersentential CS, intrasentential CS and tag-switching. The results reveal a low percentage of Spanish vocabulary, which, nevertheless, fills the story with Latino-Dominican touches and transports the reader to the Caribbean lifestyle. This is probably due to the fact that most are emotionally charged words and expressions, which supports the idea that the frequency of CS to L1 increases when talking about emotional topics with known interlocutors. Thefindings suggest that the L1 and the L2 play different roles in the characters’ lives: the former is preferred for cultural and emotional expressions and is the language the one they identify with more, while the latter is colder and more objective.

scholarly journals Deformation of finite morphisms and smoothing of ropes

2008 ◽  
Vol 144 (3) ◽  
pp. 673-688 ◽  
Author(s):  
Francisco Javier Gallego ◽  
Miguel González ◽  
Bangere P. Purnaprajna
Keyword(s):  
General Theory ◽  
Projective Space ◽  
General Result ◽  
The Other ◽  
Independent Interest ◽  
Higher Dimension ◽  
Smooth Curves ◽  
Other Hand ◽  
Finite Covers ◽  
The One

AbstractIn this paper we prove that most ropes of arbitrary multiplicity supported on smooth curves can be smoothed. By a rope being smoothable we mean that the rope is the flat limit of a family of smooth, irreducible curves. To construct a smoothing, we connect, on the one hand, deformations of a finite morphism to projective space and, on the other hand, morphisms from a rope to projective space. We also prove a general result of independent interest, namely that finite covers onto smooth irreducible curves embedded in projective space can be deformed to a family of 1:1 maps. We apply our general theory to prove the smoothing of ropes of multiplicity 3 on P1. Even though this paper focuses on ropes of dimension 1, our method yields a general approach to deal with the smoothing of ropes of higher dimension.

Sign in / Sign up

Export Citation Format

Share Document