Non-Reversible Parallel Tempering: a Scalable Highly Parallel MCMC Scheme

Parallel tempering (PT) methods are a popular class of Markov chain Monte Carlo schemes used to sample complex high-dimensional probability distributions. They rely on a collection of $N$ interacting auxiliary chains targeting tempered versions of the target distribution to improve the exploration of the state-space. We provide here a new perspective on these highly parallel algorithms and their tuning by identifying and formalizing a sharp divide in the behaviour and performance of reversible versus non-reversible PT schemes. We show theoretically and empirically that a class of non-reversible PT methods dominates its reversible counterparts and identify distinct scaling limits for the non-reversible and reversible schemes, the former being a piecewise-deterministic Markov process and the latter a diffusion. These results are exploited to identify the optimal annealing schedule for non-reversible PT and to develop an iterative scheme approximating this schedule. We provide a wide range of numerical examples supporting our theoretical and methodological contributions. The proposed methodology is applicable to sample from a distribution $\pi$ with a density $L$ with respect to a reference distribution $\pi_0$ and compute the normalizing constant. A typical use case is when $\pi_0$ is a prior distribution, $L$ a likelihood function and $\pi$ the corresponding posterior.Comment: 74 pages, 30 figures. The method is implemented in an open source probabilistic programming available at https://github.com/UBC-Stat-ML/blangSD

Impact of information technology in trade facilitation on small and medium-sized enterprises in Bangladesh

This paper focuses specifically on one particular aspect of trade facilitation in the context of Bangladesh, i.e., impact on SMEs of IT in trade facilitation. It is hoped that the policy recommendations offered in this paper will be useful in furthering the cause of SME internationalization in Bangladesh.Trade Facilitation, Bangladesh, SMEs, Information Technology

Impact of the Global Economic Crisis on the Employment and Labour Market of Bangladesh A Preliminary Assessment

ILOs initiative to assess the impact of the financial crisis on employment and labour market of South Asian economies and develop alternative policy responses to mitigate the adverse social effects of the crisis on the world of work, especially the vulnerable groups, is timely and addresses a key emerging concern. The Bangladesh country study is part of this South Asia wide study, and the Centre for Policy Dialogue (CPD) has been entrusted with carrying out this part of the regional study. The study will be carried out in two phases : a rapid assessment study to be followed by a more indepth study of the impact of recession on the labour market of Bangladesh which will focus on required policy responses.Bangladesh, Global Economic Crisis, Employement, Labour Market

Studies in Trade and Investment: The Development Impact of Information Technology in Trade Facilitation

In Bangladesh, SMEs are very important players in the economy. About 90 per cent of all industrial units in Bangladesh are SMEs, which generate some 25 per cent of the gross domestic product (GDP), employ about 31 million people and provide 75 per cent of household income. There is no denying that SMEs act as the driver of the economy and are very important for national economic and social development. They serve as employers creating new jobs and providers of products for daily needs. They also act as stewards over employees and the community. However, SMEs in developing and least developed countries face considerable barriers in running their businesses and are often constrained financially and technologically. This includes inadequate and/or complex sets of policies by the respective governments. Such impediments largely contribute to the under-involvement of SMEs in international markets. This is where the nature and extent of SME participation in the global trading system needs to be highlighted. Trade facilitation is thus a crucial factor in providing SMEs with access to global markets.Trade facilitation, ICT, IT, SMEs, international trade, Bangladesh

Impact of Information Technology in Trade Facilitation on Small and Medium-Sized Enterprises in Bangladesh

F10, F13, F15

Local Exchangeability

Exchangeability---in which the distribution of an infinite sequence is invariant to reorderings of its elements---implies the existence of a simple conditional independence structure that may be leveraged in the design of probabilistic models, efficient inference algorithms, and randomization-based testing procedures. In practice, however, this assumption is too strong an idealization; the distribution typically fails to be exactly invariant to permutations and de Finetti's representation theory does not apply. Thus there is the need for a distributional assumption that is both weak enough to hold in practice, and strong enough to guarantee a useful underlying representation. We introduce a relaxed notion of local exchangeability---where swapping data associated with nearby covariates causes a bounded change in the distribution. We prove that locally exchangeable processes correspond to independent observations from an underlying measure-valued stochastic process. We thereby show that de Finetti's theorem is robust to perturbation and provide further justification for the Bayesian modelling approach. Using this probabilistic result, we develop three novel statistical procedures for (1) estimating the underlying process via local empirical measures, (2) testing via local randomization, and (3) estimating the canonical premetric of local exchangeability. These three procedures extend the applicability of previous exchangeability-based methods without sacrificing rigorous statistical guarantees. The paper concludes with examples of popular statistical models that exhibit local exchangeability

Business Competitiveness Environment In Bangladesh (2005): Domestic Perceptions And Global Comparison

Business Competitiveness Environment, Business, Competitiveness Environment, Bangladesh

Business Competitiveness Environment In Bangladesh (2005) - Domestic Perceptions And Global Comparison

Although it is true that a liberal trade and investment policy is essential for attracting higher level of private investment, it is not a sufficient factor. Many developing countries (DCs) and least developed countries (LDCs) which have opened up their economies to a large extent and have in general put in place market friendly policies, but did not succeed in their bid to have significant foreign investment flow. The reason why broad macroeconomic policies, even when these appear to be liberal, do not get translated into favourable micro decisions by entrepreneurs is something that needs to be closely looked into. Policymakers in DCs and LDCs do not give as much attention to these missing links as they generally tend to give to putting the macro-framework right. Major objectives of this paper are to assess the competitiveness environment in Bangladesh by identifying the key bottlenecks and impediments which constrain proper functioning of the business sector, and also to come up with a set of policy recommendations to help policymakers and stakeholders prioritise the areas for improving economic governance in the country through focused initiative. The paper also attempts to situate Bangladesh in terms of growth and business competitiveness performance in the context of other countries, globally, for the year 2005 as compared to 2004.Bangladesh, Business Competetiveness

Posterior Microphthalmos Pigmentary Retinopathy Syndrome

Purpose: To report a case of a rare disease entity Posterior Microphthalmos Pigmentary Retinopathy Syndrome (PMPRS) in a 47-year-old female with a brief review of literature. Case Report: A 47-year-old woman presented with a history of defective vision with an associated difficulty in night vision. Clinical workup was done, which included a thorough ocular examination showing diffuse pigmentary mottling of fundus, ocular biometry showing short axial length with normal anterior segment dimensions, electroretinography showing extinguished response, optical coherence tomography showing foveoschisis, and ultrasonography showing thickened sclera–choroidal complex. Findings were consistent with those reported by other authors with PMPRS. Conclusion: Posterior microphthalmia with or without other ocular and systemic associations should be suspected in cases with high hyperopia. It is mandatory to carefully examine the patient at presentation and close follow-ups are needed to maintain visual function