170,304 research outputs found
Dead code elimination based pointer analysis for multithreaded programs
This paper presents a new approach for optimizing multitheaded programs with
pointer constructs. The approach has applications in the area of certified code
(proof-carrying code) where a justification or a proof for the correctness of
each optimization is required. The optimization meant here is that of dead code
elimination.
Towards optimizing multithreaded programs the paper presents a new
operational semantics for parallel constructs like join-fork constructs,
parallel loops, and conditionally spawned threads. The paper also presents a
novel type system for flow-sensitive pointer analysis of multithreaded
programs. This type system is extended to obtain a new type system for
live-variables analysis of multithreaded programs. The live-variables type
system is extended to build the third novel type system, proposed in this
paper, which carries the optimization of dead code elimination. The
justification mentioned above takes the form of type derivation in our
approach.Comment: 19 page
The simultaneous extraction of multiple social categories from unfamiliar faces
The research was supported by an award from the Experimental Psychology Society's Small Grant scheme.Peer reviewedPostprin
Engineering a static verification tool for GPU kernels
We report on practical experiences over the last 2.5 years related to the engineering of GPUVerify, a static verification tool for OpenCL and CUDA GPU kernels, plotting the progress of GPUVerify from a prototype to a fully functional and relatively efficient analysis tool. Our hope is that this experience report will serve the verification community by helping to inform future tooling efforts. © 2014 Springer International Publishing
Thread-Modular Static Analysis for Relaxed Memory Models
We propose a memory-model-aware static program analysis method for accurately
analyzing the behavior of concurrent software running on processors with weak
consistency models such as x86-TSO, SPARC-PSO, and SPARC-RMO. At the center of
our method is a unified framework for deciding the feasibility of inter-thread
interferences to avoid propagating spurious data flows during static analysis
and thus boost the performance of the static analyzer. We formulate the
checking of interference feasibility as a set of Datalog rules which are both
efficiently solvable and general enough to capture a range of hardware-level
memory models. Compared to existing techniques, our method can significantly
reduce the number of bogus alarms as well as unsound proofs. We implemented the
method and evaluated it on a large set of multithreaded C programs. Our
experiments showthe method significantly outperforms state-of-the-art
techniques in terms of accuracy with only moderate run-time overhead.Comment: revised version of the ESEC/FSE 2017 pape
Prehypertensive blood pressures and regional cerebral blood flow independently relate to cognitive performance in midlife
Background
High blood pressure is thought to contribute to dementia in late life, but our understanding of the relationship between individual differences in blood pressure (
BP
) and cognitive functioning is incomplete. In this study, cognitive performance in nonhypertensive midlife adults was examined as a function of resting
BP
and regional cerebral blood flow (
rCBF
) responses during cognitive testing. We hypothesized that
BP
would be negatively related to cognitive performance and that cognitive performance would also be related to
rCBF
responses within areas related to
BP
control. We explored whether deficits related to systolic
BP
might be explained by
rCBF
responses to mental challenge.
Methods and Results
Healthy midlife participants (n=227) received neuropsychological testing and performed cognitive tasks in a magnetic resonance imaging scanner. A pseudocontinuous arterial spin labeling sequence assessed
rCBF
in brain areas related to
BP
in prior studies. Systolic
BP
was negatively related to 4 of 5 neuropsychological factors (standardized β>0.13): memory, working memory, executive function, and mental efficiency. The
rCBF
in 2 brain regions of interest was similarly related to memory, executive function, and working memory (standardized β>0.17); however,
rCBF
responses did not explain the relationship between resting systolic
BP
and cognitive performance.
Conclusions
Relationships at midlife between prehypertensive levels of systolic
BP
and both cognitive and brain function were modest but suggested the possible value of midlife intervention.
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Racial differences in neurocognitive outcomes post-stroke: The impact of healthcare variables
AbstractObjectives:The present study examined differences in neurocognitive outcomes among non-Hispanic Black and White stroke survivors using the NIH Toolbox-Cognition Battery (NIHTB-CB), and investigated the roles of healthcare variables in explaining racial differences in neurocognitive outcomes post-stroke.Methods:One-hundred seventy adults (91 Black; 79 White), who participated in a multisite study were included (age:M=56.4;SD=12.6; education:M=13.7;SD=2.5; 50% male; years post-stroke: 1–18; stroke type: 72% ischemic, 28% hemorrhagic). Neurocognitive function was assessed with the NIHTB-CB, using demographically corrected norms. Participants completed measures of socio-demographic characteristics, health literacy, and healthcare use and access. Stroke severity was assessed with the Modified Rankin Scale.Results:An independent samplesttest indicated Blacks showed more neurocognitive impairment (NIHTB-CB Fluid Composite T-score:M=37.63;SD=11.67) than Whites (Fluid T-score:M=42.59,SD=11.54;p=.006). This difference remained significant after adjusting for reading level (NIHTB-CB Oral Reading), and when stratified by stroke severity. Blacks also scored lower on health literacy, reported differences in insurance type, and reported decreased confidence in the doctors treating them. Multivariable models adjusting for reading level and injury severity showed that health literacy and insurance type were statistically significant predictors of the Fluid cognitive composite (p<.001 andp=.02, respectively) and significantly mediated racial differences on neurocognitive impairment.Conclusions:We replicated prior work showing that Blacks are at increased risk for poorer neurocognitive outcomes post-stroke than Whites. Health literacy and insurance type might be important modifiable factors influencing these differences. (JINS, 2017,23, 640–652)</jats:p
Modular Verification of Interrupt-Driven Software
Interrupts have been widely used in safety-critical computer systems to
handle outside stimuli and interact with the hardware, but reasoning about
interrupt-driven software remains a difficult task. Although a number of static
verification techniques have been proposed for interrupt-driven software, they
often rely on constructing a monolithic verification model. Furthermore, they
do not precisely capture the complete execution semantics of interrupts such as
nested invocations of interrupt handlers. To overcome these limitations, we
propose an abstract interpretation framework for static verification of
interrupt-driven software that first analyzes each interrupt handler in
isolation as if it were a sequential program, and then propagates the result to
other interrupt handlers. This iterative process continues until results from
all interrupt handlers reach a fixed point. Since our method never constructs
the global model, it avoids the up-front blowup in model construction that
hampers existing, non-modular, verification techniques. We have evaluated our
method on 35 interrupt-driven applications with a total of 22,541 lines of
code. Our results show the method is able to quickly and more accurately
analyze the behavior of interrupts.Comment: preprint of the ASE 2017 pape
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