Clarifying and compiling C/C++ concurrency: from C++11 to POWER

The upcoming C and C++ revised standards add concurrency to the languages, for the first time, in the form of a subtle *relaxed memory model* (the *C++11 model*). This aims to permit compiler optimisation and to accommodate the differing relaxed-memory behaviours of mainstream multiprocessors, combining simple semantics for most code with high-performance *low-level atomics* for concurrency libraries. In this paper, we first establish two simpler but provably equivalent models for C++11, one for the full language and another for the subset without consume operations. Subsetting further to the fragment without low-level atomics, we identify a subtlety arising from atomic initialisation and prove that, under an additional condition, the model is equivalent to sequential consistency for race-free programs

Exploring Student Understanding of the Connections Between Music and Literacy

It has been found that music training improves attention and recall of memory, two skills that are linked to literacy. Music is also strongly correlated with phonological and phonemic awareness. More research is needed to pinpoint therapy methods that integrate music and are Evidence- Based Practices. The purpose of this project was to discover the extent to which aspiring speech language pathologists are aware that musical experiences aid learning and literacy by conducting a survey of undergraduate speech-language pathology and audiology students at The University of Akron. For the methods of this survey, twenty-eight participants completed a survey that was approximately fifteen minutes long. Two sections- “Background Questions” and “Literacy-Based Questions”- were included in the survey. The project was mixed methods, with some questions being likert scale and others being qualitative short- answer prompts. methods, discussion, etc. After the data was collected and the results were analyzed, one overall theme was noted by the researchers: students are somewhat knowledgeable about the neurological connections between music and literacy, and when asked, students can think of ways to apply music to therapy. However, when asked to discuss music integration in therapy or music appreciation in general, students are more inclined to first view music as a calming, engaging sensory activity, rather than a potential therapy aide

WILL FARMERS USE SAFER PESTICIDES?

Virtually all technology adoption studies are conducted ex post, yet policy makers often need to assess the likely level of adoption before the technology is introduced. This study uses data from a contingent valuation survey of Michigan corn growers to assess what factors would influence the adoption of two safer corn herbicides, one that is not carcinogenic and one that does not leach. Results indicate that price, risk perception, and sources of pest control information are all important. This suggests that public policies designed to change perceptions and improve information dissemination may encourage voluntary use of more environmentally friendly technologies.atrazine, cancer risk, contingent valuation, herbicides, nitrate leaching, public policy, technology adoption, Crop Production/Industries,

Molecular Aspects of H. pylori-Related MALT Lymphoma

Helicobacter pylori-related extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue is a paradigm for malignancy arising in an inflammatory background. While the diagnosis of H. pylori gastritis is often straightforward, distinction between severe gastritis and early lymphoma can be difficult and requires careful assessment of clinical findings in addition to histological features and immunohistochemical results. A number of cytogenetic abnormalities have been discovered in H. pylori-related lymphomas and several have clinical importance, related to the responsiveness of lymphoma to H. pylori eradication therapy, but routine molecular studies are not widely utilized. While molecular methods may be used in equivocal cases, a trial of conservative therapy is warranted given the propensity for these lymphomas to regress with eradication of the organism. Once therapy is initiated, care must be taken to avoid a premature assignment of disease refractoriness because complete response can take several months to more than a year. Cases truly refractory to H. pylori eradication therapy may be treated with adjuvant chemoradiation with a high response rate

Synchronising C/C++ and POWER

Shared memory concurrency relies on synchronisation primitives: compare-and-swap, load-reserve/store-conditional (aka LL/SC), language-level mutexes, and so on. In a sequentially consistent setting, or even in the TSO setting of x86 and Sparc, these have well-understood semantics. But in the very relaxed settings of IBM®, POWER®, ARM, or C/C++, it remains surprisingly unclear exactly what the programmer can depend on. This paper studies relaxed-memory synchronisation. On the hardware side, we give a clear semantic characterisation of the load-reserve/store-conditional primitives as provided by POWER multiprocessors, for the first time since they were introduced 20 years ago; we cover their interaction with relaxed loads, stores, barriers, and dependencies. Our model, while not officially sanctioned by the vendor, is validated by extensive testing, comparing actual implementation behaviour against an oracle generated from the model, and by detailed discussion with IBM staff. We believe the ARM semantics to be similar. On the software side, we prove sound a proposed compilation scheme of the C/C++ synchronisation constructs to POWER, including C/C++ spinlock mutexes, fences, and read-modify-write operations, together with the simpler atomic operations for which soundness is already known from our previous work; this is a first step in verifying concurrent algorithms that use load-reserve/store-conditional with respect to a realistic semantics. We also build confidence in the C/C++ model in its own terms, fixing some omissions and contributing to the C standards committee adoption of the C++11 concurrency model

A Verified Type System for CakeML

CakeML is a dialect of the (strongly typed) ML family of programming languages, designed to play a central role in high-assurance software systems. To date, the main artefact supporting this is a verified compiler from CakeML source code to x86-64 machine code. The verification effort addresses each phase of compilation from parsing through to code generation and garbage collection. In this paper, we focus on the type system: its declarative speci- fication, type soundness theorem, and the soundness and completeness of an implementation of type inference – all formally veri- fied in the HOL4 proof assistant. Each of these aspects of a type system is important in any design and implementation of a typed functional programming language. They allow the programmer to soundly employ (informal) type-based reasoning, and the compiler to apply optimisations that assume type-correctness. So naturally, their verification is a critical part of a verified compiler

Mathematizing C++ concurrency

Shared-memory concurrency in C and C++ is pervasive in systems programming, but has long been poorly defined. This motivated an ongoing shared effort by the standards committees to specify concurrent behaviour in the next versions of both languages. They aim to provide strong guarantees for race-free programs, together with new (but subtle) relaxed-memory atomic primitives for high-performance concurrent code. However, the current draft standards, while the result of careful deliberation, are not yet clear and rigorous definitions, and harbour substantial problems in their details. In this paper we establish a mathematical (yet readable) semantics for C++ concurrency. We aim to capture the intent of the current (`Final Committee') Draft as closely as possible, but discuss changes that fix many of its problems. We prove that a proposed x86 implementation of the concurrency primitives is correct with respect to the x86-TSO model, and describe our Cppmem tool for exploring the semantics of examples, using code generated from our Isabelle/HOL definitions. Having already motivated changes to the draft standard, this work will aid discussion of any further changes, provide a correctness condition for compilers, and give a much-needed basis for analysis and verification of concurrent C and C++ programs

Emergency Department Medical Directors’ Knowledge of Medicare Payment Policies for Inpatient Admissions

Introduction: The policies governing Medicare reimbursement for inpatient admissions affect admission status for older adults. These rules strongly influence the willingness of hospital providers to accept patients from the emergency department. We contend that emergency physicians have limited knowledge of these rules, and that knowledge is tied to how EM medical directors would manage patients in hypothetical cases designed to be inappropriate for admission under current Medicare guidelines. Methods: We administered an online survey to emergency department medical directors presenting two hypothetical cases designed to miss one or both of the Medicare severity of illness and intensity of service criteria. The cases also raised issues of 30-day readmissions penalties and condition at presentation vs. admission. We asked Respondents questions about the applicability of Medicare rules to the cases, how they would manage the patients, and what case management resources they use or could use in managing these patients. Results: Sixty-two medical directors of the 1,460 reached via the Medical Directors listserv completed the survey. Overall, knowledge of Medicare admissions guidelines was limited, with the average respondent answering 56.3% (S.D. 13.1) of questions correctly. We found no correlation between two kinds of Medicare knowledge, that of of the intensity of service/severity of illness rules, and knowledge of the rules governing 30-day readmissions. Physicians with greater knowledge were less likely to recommend inpatient admissions that Medicare guidelines would consider inappropriate. They were also more likely to recommend skilled nursing placement over inpatient admission in a hypothetical case that would qualify for skilled nursing, but not inpatient care(p=0.02). Conclusion: Knowledge of Medicare admission and readmission rules among emergency department medical directors is limited, and stronger knowledge is associated with more likely recommendations for appropriate care, and may be associated with a reduction in social admissions. This pilot study successfully identified targets for further inquiry including the role of case management in preventing social admissions for injured older adults and the identification of predictors of EM physician awareness of Medicare inpatient payment policies.Master of Public Healt