151,621 research outputs found
A Concurrent Perspective on Smart Contracts
In this paper, we explore remarkable similarities between multi-transactional
behaviors of smart contracts in cryptocurrencies such as Ethereum and classical
problems of shared-memory concurrency. We examine two real-world examples from
the Ethereum blockchain and analyzing how they are vulnerable to bugs that are
closely reminiscent to those that often occur in traditional concurrent
programs. We then elaborate on the relation between observable contract
behaviors and well-studied concurrency topics, such as atomicity, interference,
synchronization, and resource ownership. The described
contracts-as-concurrent-objects analogy provides deeper understanding of
potential threats for smart contracts, indicate better engineering practices,
and enable applications of existing state-of-the-art formal verification
techniques.Comment: 15 page
Optimal damping algorithm for unrestricted Hartree-Fock calculations
We have developed a couple of optimal damping algorithms (ODAs) for
unrestricted Hartree-Fock (UHF) calculations of open-shell molecular systems. A
series of equations were derived for both concurrent and alternate
constructions of alpha- and beta-Fock matrices in the integral-direct
self-consistent-field (SCF) procedure. Several test calculations were performed
to check the convergence behaviors. It was shown that the concurrent algorithm
provides better performance than does the alternate one.Comment: 4 color figure
Static Safety for an Actor Dedicated Process Calculus by Abstract Interpretation
The actor model eases the definition of concurrent programs with non uniform
behaviors. Static analysis of such a model was previously done in a data-flow
oriented way, with type systems. This approach was based on constraint set
resolution and was not able to deal with precise properties for communications
of behaviors. We present here a new approach, control-flow oriented, based on
the abstract interpretation framework, able to deal with communication of
behaviors. Within our new analyses, we are able to verify most of the previous
properties we observed as well as new ones, principally based on occurrence
counting
The prosocial and antisocial behavior in sport scale
This research aimed to (a) develop a measure of prosocial and antisocial behavior in sport, (b) examine its invariance across sex and sport, and (c) provide evidence for its discriminant and concurrent validity. We conducted two studies. In study 1, team sport athletes (N = 1,213) recruited from 103 teams completed questionnaires assessing demographics and prosocial and antisocial behaviors in sport. Factor analyses revealed two factors representing prosocial behavior and two factors representing antisocial behavior. The model had a very good fit to the data and showed configural, metric, and scalar invariance across sex and sport. The final scale consisted of 20 items. In Study 2, team-sport athletes (N = 106) completed the scale and measures of empathy and goal orientation. Analyses provided Support for the discriminant and concurrent validity of the scale. In conclusion, the new scale can be used to measure prosocial and antisocial behaviors in team sport
Jeeg: Temporal Constraints for the Synchronization of Concurrent Objects
We introduce Jeeg, a dialect of Java based on a declarative replacement of the synchronization mechanisms of Java that results in a complete decoupling of the 'business' and the 'synchronization' code of classes. Synchronization constraints in Jeeg are expressed in a linear temporal logic which allows to effectively limit the occurrence of the inheritance anomaly that commonly affects concurrent object oriented languages. Jeeg is inspired by the current trend in aspect oriented languages. In a Jeeg program the sequential and concurrent aspects of object behaviors are decoupled: specified separately by the programmer these are then weaved together by the Jeeg compiler
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