5,901 research outputs found
Darwinian Data Structure Selection
Data structure selection and tuning is laborious but can vastly improve an
application's performance and memory footprint. Some data structures share a
common interface and enjoy multiple implementations. We call them Darwinian
Data Structures (DDS), since we can subject their implementations to survival
of the fittest. We introduce ARTEMIS a multi-objective, cloud-based
search-based optimisation framework that automatically finds optimal, tuned DDS
modulo a test suite, then changes an application to use that DDS. ARTEMIS
achieves substantial performance improvements for \emph{every} project in
Java projects from DaCapo benchmark, popular projects and uniformly
sampled projects from GitHub. For execution time, CPU usage, and memory
consumption, ARTEMIS finds at least one solution that improves \emph{all}
measures for () of the projects. The median improvement across
the best solutions is , , for runtime, memory and CPU
usage.
These aggregate results understate ARTEMIS's potential impact. Some of the
benchmarks it improves are libraries or utility functions. Two examples are
gson, a ubiquitous Java serialization framework, and xalan, Apache's XML
transformation tool. ARTEMIS improves gson by \%, and for
memory, runtime, and CPU; ARTEMIS improves xalan's memory consumption by
\%. \emph{Every} client of these projects will benefit from these
performance improvements.Comment: 11 page
Parametric ordering of complex systems
Cellular automata (CA) dynamics are ordered in terms of two global
parameters, computable {\sl a priori} from the description of rules. While one
of them (activity) has been used before, the second one is new; it estimates
the average sensitivity of rules to small configurational changes. For two
well-known families of rules, the Wolfram complexity Classes cluster
satisfactorily. The observed simultaneous occurrence of sharp and smooth
transitions from ordered to disordered dynamics in CA can be explained with the
two-parameter diagram
The short-time Dynamics of the Critical Potts Model
The universal behaviour of the short-time dynamics of the three state Potts
model in two dimensions at criticality is investigated with Monte Carlo
methods. The initial increase of the order is observed. The new dynamic
exponent as well as exponent and are determined. The
measurements are carried out in the very beginning of the time evolution. The
spatial correlation length is found to be very short compared with the lattice
size.Comment: 6 pages, 3 figure
Models for Monolayers Adsorbed on a Square Substrate
Motivated by recent experimental studies of Hg and Pb monolayers on Cu(001)
we introduce a zero temperature model of a monolayer adsorbed on a square
substrate. Lennard-Jones potentials are used to describe the interaction
between pairs of adlayer-adlayer and adlayer-substrate atoms. We study a
special case in which the monolayer atoms form a perfect square structure and
the lattice constant, position and orientation with respect to the substrate
can vary to minimize the energy. We introduce a rule based on the Farey tree
construction to generate systematically the most energetically favored phases
and use it to calculate the phase diagram in this model.Comment: 14 pages, Table (included), Two Figures (available upon request).
SU-92-150
Determination of the Critical Point and Exponents from short-time Dynamics
The dynamic process for the two dimensional three state Potts model in the
critical domain is simulated by the Monte Carlo method. It is shown that the
critical point can rigorously be located from the universal short-time
behaviour. This makes it possible to investigate critical dynamics
independently of the equilibrium state. From the power law behaviour of the
magnetization the exponents and are determined.Comment: 6 pages, 4 figure
Conformal Dimension of the Brownian Graph
Conformal dimension of a metric space , denoted by , is the
infimum of the Hausdorff dimension among all its quasisymmetric images. If
conformal dimension of is equal to its Hausdorff dimension, is said to
be minimal for conformal dimension. In this paper we show that the graph of the
one dimensional Brownian motion is almost surely minimal for conformal
dimension. We also give many other examples of minimal sets for conformal
dimension, which we call Bedford-McMullen type sets. In particular we show that
Bedford-McMullen self-affine sets with uniform fibers are minimal for conformal
dimension. The main technique in the proofs is the construction of ``rich
families of minimal sets of conformal dimension one''. The latter concept is
quantified using Fuglede's modulus of measures.Comment: 42 pages, 6 figure
On computability of equilibrium states
Equilibrium states are natural dynamical analogs of Gibbs states in
thermodynamic formalism. This paper is devoted to the study of their
computability in the sense of Computable Analysis. We show that the unique
equilibrium state associated to a pair of a computable, topologically exact,
distance-expanding, open map and a computable H\"older
continuous potential is always
computable. Furthermore, the Hausdorff dimension of the Julia set and the
equilibrium state for the geometric potential of a computable hyperbolic
rational map are computable. On the other hand, we introduce a mechanism to
establish non-uniqueness of equilibrium states. We also present some computable
dynamical systems whose equilibrium states are all non-computable.Comment: 41 pages. Reformatted, polished, typos corrected, Theorems D and E
reformulated with Section 6 adjusted accordingl
Universality and Scaling in Short-time Critical Dynamics
Numerically we simulate the short-time behaviour of the critical dynamics for
the two dimensional Ising model and Potts model with an initial state of very
high temperature and small magnetization. Critical initial increase of the
magnetization is observed. The new dynamic critical exponent as well
as the exponents and are determined from the power law
behaviour of the magnetization, auto-correlation and the second moment.
Furthermore the calculation has been carried out with both Heat-bath and
Metropolis algorithms. All the results are consistent and therefore
universality and scaling are confirmed.Comment: 14 pages, 14 figure
Critical Behaviour of the 3D XY-Model: A Monte Carlo Study
We present the results of a study of the three-dimensional -model on a
simple cubic lattice using the single cluster updating algorithm combined with
improved estimators. We have measured the susceptibility and the correlation
length for various couplings in the high temperature phase on lattices of size
up to . At the transition temperature we studied the fourth-order
cumulant and other cumulant-like quantities on lattices of size up to .
From our numerical data we obtain for the critical coupling
\coup_c=0.45420(2), and for the static critical exponents and .Comment: 24 pages (4 PS-Figures Not included, Revtex 3.O file), report No.:
CERN-TH.6885/93, KL-TH-93/1
Physico-chemical foundations underpinning microarray and next-generation sequencing experiments
Hybridization of nucleic acids on solid surfaces is a key process involved in high-throughput technologies such as microarrays and, in some cases, next-generation sequencing (NGS). A physical understanding of the hybridization process helps to determine the accuracy of these technologies. The goal of a widespread research program is to develop reliable transformations between the raw signals reported by the technologies and individual molecular concentrations from an ensemble of nucleic acids. This research has inputs from many areas, from bioinformatics and biostatistics, to theoretical and experimental biochemistry and biophysics, to computer simulations. A group of leading researchers met in Ploen Germany in 2011 to discuss present knowledge and limitations of our physico-chemical understanding of high-throughput nucleic acid technologies. This meeting inspired us to write this summary, which provides an overview of the state-of-the-art approaches based on physico-chemical foundation to modeling of the nucleic acids hybridization process on solid surfaces. In addition, practical application of current knowledge is emphasized
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