141 research outputs found
uFLIP: Understanding Flash IO Patterns
Does the advent of flash devices constitute a radical change for secondary
storage? How should database systems adapt to this new form of secondary
storage? Before we can answer these questions, we need to fully understand the
performance characteristics of flash devices. More specifically, we want to
establish what kind of IOs should be favored (or avoided) when designing
algorithms and architectures for flash-based systems. In this paper, we focus
on flash IO patterns, that capture relevant distribution of IOs in time and
space, and our goal is to quantify their performance. We define uFLIP, a
benchmark for measuring the response time of flash IO patterns. We also present
a benchmarking methodology which takes into account the particular
characteristics of flash devices. Finally, we present the results obtained by
measuring eleven flash devices, and derive a set of design hints that should
drive the development of flash-based systems on current devices.Comment: CIDR 200
ViRMA: Virtual Reality Multimedia Analytics at LSC 2021
In this paper we describe the first iteration of the ViRMA prototype system, a novel approach to multimedia analysis in virtual reality and inspired by the M3 data model. We intend to evaluate our approach via the Lifelog Search Challenge (LSC) to serve as a benchmark against other multimedia analytics systems
Scalability of the NV-tree: Three Experiments
International audienceThe NV-tree is a scalable approximate high-dimensional indexing method specifically designed for large-scale visual instance search. In this paper, we report on three experiments designed to evaluate the performance of the NV-tree. Two of these experiments embed standard benchmarks within collections of up to 28.5 billion features, representing the largest single-server collection ever reported in the literature. The results show that indeed the NV-tree performs very well for visual instance search applications over large-scale collections
Elastic Collision Based Dynamic Partitioning Scheme for Hybrid Simulations
The scattering-adapted flexible inner region ensemble separator (SAFIRES) is
a partitioning scheme designed to divide a simulation cell into two regions to
be treated with different computational methodologies. SAFIRES prevents
particles from crossing between regions and resolves boundary events through
elastic collisions of the particles mediated by the boundary, conserving energy
and momenta. A multiple-time-step propagation algorithm is introduced where the
time step is scaled automatically to identify the moment a collision occurs. If
the length of the time step is kept constant, the new propagator reduces to a
regular algorithm for Langevin dynamics, and to the velocity Verlet algorithm
for classical dynamics if the friction coefficient is set to zero. SAFIRES
constitutes the exact limit of the premise behind boundary-based methods such
as FIRES, BEST, and BCC which take advantage of the indistinguishability of
molecules on opposite sides of the separator. It gives correct average ensemble
statistics despite the introduction of an ensemble separator. SAFIRES is tested
in simulations where the molecules on the two sides are treated in the same
way, for a Lennard-Jones (LJ) liquid and a LJ liquid in contact with a surface,
as well as for liquid modelling simulations using the TIP4P force field.
Simulations using SAFIRES are shown to reproduce the unconstrained reference
simulations without significant deviations.Comment: To be submitted to Journal of Chemical Theory and Computatio
Smart Contract Upgradeability on the Ethereum Blockchain Platform: An Exploratory Study
Context: Smart contracts are computerized self-executing contracts that
contain clauses, which are enforced once certain conditions are met. Smart
contracts are immutable by design and cannot be modified once deployed, which
ensures trustlessness. Despite smart contracts' immutability benefits,
upgrading contract code is still necessary for bug fixes and potential feature
improvements. In the past few years, the smart contract community introduced
several practices for upgrading smart contracts. Upgradeable contracts are
smart contracts that exhibit these practices and are designed with
upgradeability in mind. During the upgrade process, a new smart contract
version is deployed with the desired modification, and subsequent user requests
will be forwarded to the latest version (upgraded contract). Nevertheless,
little is known about the characteristics of the upgrading practices, how
developers apply them, and how upgrading impacts contract usage.
Objectives: This paper aims to characterize smart contract upgrading patterns
and analyze their prevalence based on the deployed contracts that exhibit these
patterns. Furthermore, we intend to investigate the reasons why developers
upgrade contracts (e.g., introduce features, fix vulnerabilities) and how
upgrades affect the adoption and life span of a contract in practice.
Method: We collect deployed smart contracts metadata and source codes to
identify contracts that exhibit certain upgrade patterns (upgradeable
contracts) based on a set of policies. Then we trace smart contract versions
for each upgradable contract and identify the changes in contract versions
using similarity and vulnerabilities detection tools. Finally, we plan to
analyze the impact of upgrading on contract usage based on the number of
transactions received and the lifetime of the contract version
- …