Bounded Model Checking of Concurrent Data Types on Relaxed Memory Models: A Case Study

Many multithreaded programs employ concurrent data types to safely share data among threads. However, highly-concurrent algorithms for even seemingly simple data types are difficult to implement correctly, especially when considering the relaxed memory ordering models commonly employed by today’s multiprocessors. The formal verification of such implementations is challenging as well because the high degree of concurrency leads to a large number of possible executions. In this case study, we develop a SAT-based bounded verification method and apply it to a representative example, a well-known two-lock concurrent queue algorithm. We first formulate a correctness criterion that specifically targets failures caused by concurrency; it demands that all concurrent executions be observationally equivalent to some serial execution. Next, we define a relaxed memory model that conservatively approximates several common shared-memory multiprocessors. Using commit point specifications, a suite of finite symbolic tests, a prototype encoder, and a standard SAT solver, we successfully identify two failures of a naive implementation that can be observed only under relaxed memory models. We eliminate these failures by inserting appropriate memory ordering fences into the code. The experiments confirm that our approach provides a valuable aid for desigining and implementing concurrent data types

Community participation in the control of trachoma in Gazankulu

Groups of villagers, the care groups, are involved in prevention and treatment of trachoma within their own communities. The effect of the scheme on standards of hygiene and prevalence of trachoma has been evaluated by randomised cluster sampling methods. The number of households who were digging refuse pits, acquired individual face cloths and were aware of the role of good hygiene in the prevention of trachoma exceeded significantly those in (control) villages without a care group, in contrast the acquisition of pit latrines showed an insignificant increase. The prevalence and intensity of active trachoma was found to be significantly reduced as a result of the intervention of the care groups. This scheme has been totally integrated into the primary health care system of the area.

Trachoma in South Africa

Trachoma remains the most common cause of preventable blindness in certain areas of the northern Transvaal region of South Africa. Results of epidemiological studies in the area indicate that trachoma is a familial disease with young children acting as the main source of infection within the family. Elderly women who have lived in these areas for long periods of time are at greater risk of blindness and impaired vision from the disease. Genital tract carriage of Chlamydia trachomatis is relatively infrequent in these trachoma-endemic areas and no evidence of eye-to-eye transmission of oculo-genital serotypes of C. trachomatis could be demonstrated.

Haplotype Inference in Complex Pedigrees

Abstract. Despite the desirable information contained in complex pedigree datasets, analysis methods struggle to efficiently process these datasets. The attractiveness of pedigree data sets is their power for detecting rare variants, particularly in comparison with studies of unrelated individuals. In addition, rather than assuming individuals in a study are unrelated, knowledge of their relationships can avoid spurious results due to confounding population structure effects. However, a major challenge for the applicability of pedigree methods is the ability handle complex pedigrees, having multiple founding lineages, inbreeding, and half-sibling relationships. A key ingredient in association studies is imputation and inference of haplotypes from genotype data. Existing haplotype inference methods either do not efficiently scales to complex pedigrees or their accuracy is limited. In this paper, we present algorithms for efficient haplotype inference and imputation in complex pedigrees. Our method, PhyloPed, leverages the perfect phylogeny model, resulting in an efficient method with high accuracy. In addition, PhyloPed effectively combines the founder haplotype information from different lineages and is immune to inaccuracies in prior information about the founders.

The case for thermalization as a contributor to the [C ii] deficit

The [C ii] deficit, which describes the observed decrease in the ratio of [C ii] 158 μm emission to continuum infrared emission in galaxies with high star formation surface densities, places a significant challenge to the interpretation of [C ii] detections from across the observable universe. In an attempt to further decode the cause of the [C ii] deficit, the [C ii] and dust continuum emission from 18 Local Volume galaxies has been split based on conditions within the interstellar medium where it originated. This is completed using the Key Insights in Nearby Galaxies: a Far-Infrared Survey with Herschel (KINGFISH) and Beyond the Peak (BtP) surveys and the wide-range of wavelength information, from UV to far-infrared emission lines, available for a selection of star-forming regions within these samples. By comparing these subdivided [C ii] emissions to isolated infrared emission and other properties, we find that the thermalization (collisional de-excitation) of the [C ii] line in H ii regions plays a significant role in the deficit observed in our sample. © 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]