Reducing memory requirements for large size LBM simulations on GPUs

The scientific community in its never-ending road of larger and more efficient computational resources is in need of more efficient implementations that can adapt efficiently on the current parallel platforms. Graphics processing units are an appropriate platform that cover some of these demands. This architecture presents a high performance with a reduced cost and an efficient power consumption. However, the memory capacity in these devices is reduced and so expensive memory transfers are necessary to deal with big problems. Today, the lattice-Boltzmann method (LBM) has positioned as an efficient approach for Computational Fluid Dynamics simulations. Despite this method is particularly amenable to be efficiently parallelized, it is in need of a considerable memory capacity, which is the consequence of a dramatic fall in performance when dealing with large simulations. In this work, we propose some initiatives to minimize such demand of memory, which allows us to execute bigger simulations on the same platform without additional memory transfers, keeping a high performance. In particular, we present 2 new implementations, LBM-Ghost and LBM-Swap, which are deeply analyzed, presenting the pros and cons of each of them.This project was funded by the Spanish Ministry of Economy and Competitiveness (MINECO): BCAM Severo Ochoa accreditation SEV-2013-0323, MTM2013-40824, Computación de Altas Prestaciones VII TIN2015-65316-P, by the Basque Excellence Research Center (BERC 2014-2017) pro- gram by the Basque Government, and by the Departament d' Innovació, Universitats i Empresa de la Generalitat de Catalunya, under project MPEXPAR: Models de Programació i Entorns d' Execució Paral·lels (2014-SGR-1051). We also thank the support of the computing facilities of Extremadura Research Centre for Advanced Technologies (CETA-CIEMAT) and NVIDIA GPU Research Center program for the provided resources, as well as the support of NVIDIA through the BSC/UPC NVIDIA GPU Center of Excellence.Peer ReviewedPostprint (author's final draft

Book Reviews

Book Review

How Mistimed and Unwanted Pregnancies Affect Timing of Antenatal Care Initiation in three Districts in Tanzania

Early antenatal care (ANC) initiation is a doorway to early detection and management of potential complications associated with pregnancy. Although the literature reports various factors associated with ANC initiation such as parity and age, pregnancy intentions is yet to be recognized as a possible predictor of timing of ANC initiation. Data originate from a cross-sectional household survey on health behaviour and service utilization patterns. The survey was conducted in 2011 in Rufiji, Kilombero and Ulanga districts in Tanzania on 910 women of reproductive age who had given birth in the past two years. ANC initiation was considered to be early only if it occurred in the first trimester of pregnancy gestation. A recently completed pregnancy was defined as mistimed if a woman wanted it later, and if she did not want it at all the pregnancy was termed as unwanted. Chisquare was used to test for associations and multinomial logistic regression was conducted to examine how mistimed and unwanted pregnancies affect timing of ANC initiation. Although 49.3% of the women intended to become pregnant, 50.7% (34.9% mistimed and 15.8% unwanted) became pregnant unintentionally. While ANC initiation in the 1st trimester was 18.5%, so was 71.7% and 9.9% in the 2nd and 3rd trimesters respectively. Multivariate analysis revealed that ANC initiation in the 2nd trimester was 1.68 (95% CI 1.10‒2.58) and 2.00 (95% CI 1.05‒3.82) times more likely for mistimed and unwanted pregnancies respectively compared to intended pregnancies. These estimates rose to 2.81 (95% CI 1.41‒5.59) and 4.10 (95% CI 1.68‒10.00) respectively in the 3rd trimester. We controlled for gravidity, age, education, household wealth, marital status, religion, district of residence and travel time to a health facility. Late ANC initiation is a significant maternal and child health consequence of mistimed and unwanted pregnancies in Tanzania. Women should be empowered to delay or avoid pregnancies whenever they need to do so. Appropriate counseling to women, especially those who happen to conceive unintentionally is needed to minimize the possibility of delaying ANC initiation.\u

Indwelling catheter vs intermittent catheterization: is there a difference in UTI susceptibility?

BACKGROUND Patients with neurogenic lower urinary tract dysfunction (NLUTD) often rely on some type of catheterization for bladder emptying. Intermittent catheterization (IC) is considered the gold standard and is preferred over continuous catheterization, since it is considered to cause fewer urinary tract infections (UTIs) than indwelling catheterization. The main objective of our study was to describe UTI prevalence (at visit) and incidence (within the last 12 months) and urine culture characteristics between patients using an indwelling catheter versus (vs) those performing IC. METHODS In this cross-sectional study, we prospectively evaluated from 02/2020 to 01/2021 patients with NLUTD undergoing urine cultures for prophylactic reasons or due to UTI symptoms. At visit, all patients underwent a standardized interview on current UTI symptoms as well as UTI history and antibiotic consumption within the past year. Patients using an indwelling catheter (n = 206) or IC (n = 299) were included in the analysis. The main outcome was between-group differences regarding UTI characteristics. RESULTS Patients using an indwelling catheter were older (indwelling catheter vs IC: median 66 (Q1-Q3: 55-77) vs 55 (42-67) years of age) and showed a higher Charlson comorbidity index (indwelling catheter vs IC: median 4 (Q1-Q3: 2-6) vs 2 (1-4) (both p < 0·001). A total of 40 patients from both groups were diagnosed with a UTI at visit (indwelling catheters vs IC: 8% (16/206) vs 8% (24/299); p = 0·782), and the number of UTIs within the past 12 months was not significantly different between groups. Overall, Escherichia coli (21%), Enterococcus faecalis (17%), and Klebsiella spp. (12%) were the most frequently detected bacteria. CONCLUSIONS In this cohort of patients with NLUTD, we did not find relevant differences in UTI frequency between groups. These results suggest that UTI-related concerns should not be given undue emphasis when counseling patients for catheter-related bladder emptying methods

A Mechanism-Based Explanation of the Institutionalization of Semantic Technologies in the Financial Industry

Part 3: Creating Value through ApplicationsInternational audienceThis paper explains how the financial industry is solving its data, risk management, and associated vocabulary problems using semantic technologies. The paper is the first to examine this phenomenon and to identify the social and institutional mechanisms being applied to socially construct a standard common vocabulary using ontology-based models. This standardized ontology-based common vocabulary will underpin the design of next generation of semantically-enabled information systems (IS) for the financial industry. The mechanisms that are helping institutionalize this common vocabulary are identified using a longitudinal case study, whose embedded units of analysis focus on central agents of change—the Enterprise Data Management Council and the Object Management Group. All this has important implications for society, as it is intended that semantically-enabled IS will, for example, provide stakeholders, such as regulators, with better transparency over systemic risks to national and international financial systems, thereby mitigating or avoiding future financial crises

Numerical Hermitian Yang-Mills Connections and Vector Bundle Stability in Heterotic Theories

A numerical algorithm is presented for explicitly computing the gauge connection on slope-stable holomorphic vector bundles on Calabi-Yau manifolds. To illustrate this algorithm, we calculate the connections on stable monad bundles defined on the K3 twofold and Quintic threefold. An error measure is introduced to determine how closely our algorithmic connection approximates a solution to the Hermitian Yang-Mills equations. We then extend our results by investigating the behavior of non slope-stable bundles. In a variety of examples, it is shown that the failure of these bundles to satisfy the Hermitian Yang-Mills equations, including field-strength singularities, can be accurately reproduced numerically. These results make it possible to numerically determine whether or not a vector bundle is slope-stable, thus providing an important new tool in the exploration of heterotic vacua.Comment: 52 pages, 15 figures. LaTex formatting of figures corrected in version 2

Temporal development of unfavourable urodynamic parameters during the first year after spinal cord injury

Objectives: To describe the temporal development of and risk factors for the occurrence of unfavourable urodynamic parameters during the first year after spinal cord injury (SCI). Patients and methods: This population-based longitudinal study used data from 97 adult patients with a single-event traumatic or ischaemic SCI who underwent video-urodynamic investigation (UDI) at a university SCI centre. The first occurrences of unfavourable urodynamic parameters (detrusor overactivity combined with detrusor sphincter dyssynergia [DO-DSD], maximum storage detrusor pressure ≥40 cmH2 O, bladder compliance <20 mL/cmH2 O, vesico-ureteric reflux [VUR] and any unfavourable parameter [composite outcome]) were evaluated using time-to-event analysis. Results: The majority of the population (87/97 [90%]) had at least one unfavourable urodynamic parameter. Most unfavourable urodynamic parameters were initially identified during the 1- or 3-month UDI, including 92% of the DO-DSD (78/85), 82% of the maximum storage pressure ≥40 cmH2 O (31/38), and 100% of the VUR (seven of seven) observations. No low bladder compliance was observed. The risk of DO-DSD was elevated in patients with thoracic SCI compared to those with lumbar SCI (adjusted hazard ratio [aHR] 2.38, 95% confidence interval [CI] 1.16-4.89). Risk of maximum storage detrusor pressure ≥40 cmH2 O was higher in males than females (aHR 8.33, 95% CI 2.51-27.66), in patients with a cervical SCI compared to those with lumbar SCI (aHR 14.89, 95% CI 3.28-67.55), and in patients with AIS Grade B or C compared to AIS Grade D SCI (aHR 6.17, 95% CI 1.78-21.39). No risk factors were identified for the composite outcome of any unfavourable urodynamic parameter. Conclusions: The first UDI should take place within 3 months after SCI as to facilitate early diagnosis of unfavourable urodynamic parameters and timely treatment. Neuro-urological guidelines and individualised management strategies for patients with SCI may be strengthened by considering sex and SCI characteristics in the scheduling of UDIs. Keywords: #Urology; longitudinal studies; spinal cord injuries; survival analysis; urinary bladder, neurogenic; urinary bladder, overactive; urodynamic

Numerical Hermitian Yang-Mills Connections and Kahler Cone Substructure

We further develop the numerical algorithm for computing the gauge connection of slope-stable holomorphic vector bundles on Calabi-Yau manifolds. In particular, recent work on the generalized Donaldson algorithm is extended to bundles with Kahler cone substructure on manifolds with h^{1,1}>1. Since the computation depends only on a one-dimensional ray in the Kahler moduli space, it can probe slope-stability regardless of the size of h^{1,1}. Suitably normalized error measures are introduced to quantitatively compare results for different directions in Kahler moduli space. A significantly improved numerical integration procedure based on adaptive refinements is described and implemented. Finally, an efficient numerical check is proposed for determining whether or not a vector bundle is slope-stable without computing its full connection.Comment: 38 pages, 10 figure