Block Iterative Eigensolvers for Sequences of Correlated Eigenvalue Problems

In Density Functional Theory simulations based on the LAPW method, each self-consistent field cycle comprises dozens of large dense generalized eigenproblems. In contrast to real-space methods, eigenpairs solving for problems at distinct cycles have either been believed to be independent or at most very loosely connected. In a recent study [7], it was demonstrated that, contrary to belief, successive eigenproblems in a sequence are strongly correlated with one another. In particular, by monitoring the subspace angles between eigenvectors of successive eigenproblems, it was shown that these angles decrease noticeably after the first few iterations and become close to collinear. This last result suggests that we can manipulate the eigenvectors, solving for a specific eigenproblem in a sequence, as an approximate solution for the following eigenproblem. In this work we present results that are in line with this intuition. We provide numerical examples where opportunely selected block iterative eigensolvers benefit from the reuse of eigenvectors by achieving a substantial speed-up. The results presented will eventually open the way to a widespread use of block iterative eigensolvers in ab initio electronic structure codes based on the LAPW approach.Comment: 12 Pages, 5 figures. Accepted for publication on Computer Physics Communication

Can we help in changing the future of Italian health care?

[The abstract of this article is not available. Here are the first sentences of the article. The full text is freely available upon registration]The retirement age of the baby boom generation is almost out-door. The proportion of ageing people will grow rapidly in the near future [1-3]. There will be fewer people to pay for the health and social care of the quickly aging population; furthermore, advancements in medical science will raise a new bar for quality in terms of the outcomes achieved in the treatment of illness [3]. An ageing population and the rising public expectations will produce an increase in costs and will impede timely access to care, thus jeopardising sustainability.The Italian National Health system is an example of a collapsing system: the ageing Italian workforce affects not only patient demographics but also the availability of clinicians. The upcoming wave of retiring health care professionals will occur in the exact moment when they will be more necessary. To overcome these challenges, our health care system will have to use its resources more effectively. Access and equity remain essential characteristics of our health care system, but are insufficient goals in terms of improving quality and achieving financial sustainability

An Optimized and Scalable Eigensolver for Sequences of Eigenvalue Problems

In many scientific applications the solution of non-linear differential equations are obtained through the set-up and solution of a number of successive eigenproblems. These eigenproblems can be regarded as a sequence whenever the solution of one problem fosters the initialization of the next. In addition, in some eigenproblem sequences there is a connection between the solutions of adjacent eigenproblems. Whenever it is possible to unravel the existence of such a connection, the eigenproblem sequence is said to be correlated. When facing with a sequence of correlated eigenproblems the current strategy amounts to solving each eigenproblem in isolation. We propose a alternative approach which exploits such correlation through the use of an eigensolver based on subspace iteration and accelerated with Chebyshev polynomials (ChFSI). The resulting eigensolver is optimized by minimizing the number of matrix-vector multiplications and parallelized using the Elemental library framework. Numerical results show that ChFSI achieves excellent scalability and is competitive with current dense linear algebra parallel eigensolvers.Comment: 23 Pages, 6 figures. First revision of an invited submission to special issue of Concurrency and Computation: Practice and Experienc

How many authors are needed to write a review?

[The abstract of this article is not available. Here are the first sentences of the article. The full text is freely available upon registration]We received with pleasure the letter of Prof. Manfredi, published in the present Reviews in Health Care issue (see pages 137-140), that underlines the problem of the proliferation of authors in HIV-related articles.This is not a new topic. In the last 40 years there has been a dramatic increase, not only in the volume of publications but also in the number of authors per article. However, after all these years, the discussion about authorship is still relevant and ongoing in biomedical literature. A variety of authorship standards exist; nonetheless, adoption of these criteria has not been universal and misconduct cases related to irresponsible authorship are still quite common, including ghostwriting, gift or honorary authorship, duplicate and redundant publication and, in some cases, the authors’ refusal to accept responsibility for their articles despite their ready acceptance of credit. Publication in biomedical literature is important because it is the major pathway by which new concepts and discoveries are disseminated amongst scientists, but it is also the only way for a researcher to survive in a competitive world as the biomedical field. “Publish or perish!” is the actual common saying in the biomedical research field

Neuroinflammation and Cerebrovascular Disease in Old Age: A Translational Medicine Perspective

The incidence of cerebrovascular disease is highest in the elderly population. However, the pathophysiological mechanisms of brain response to cerebral ischemia in old age are currently poorly understood. Ischemic changes in the commonly used young animal stroke models do not reflect the molecular changes associated with the aged brain. Neuroinflammation and oxidative stress are important pathogenic processes occurring during the acute phase of cerebral ischemia. Free radical generation is also implicated in the aging process, and the combination of these effects in elderly stroke patients could explain the higher risk of morbidity and mortality. A better understanding of stroke pathophysiology in the elderly patient would assist in the development of new therapeutic strategies for this vulnerable age group. With the increasing use of reperfusion therapies, inflammatory pathways and oxidative stress remain attractive therapeutic targets for the development of adjuvant neuroprotective agents. This paper will discuss these molecular aspects of acute stroke and senescence from a bench-to-bedside research perspective

Use of Forest Residues for Building Forest Biomass Supply Chains: Technical and Economic Analysis of the Production Process

(c) there are strong margins for economic profits at the level of each single supply basi