337 research outputs found
A methodology for full-system power modeling in heterogeneous data centers
The need for energy-awareness in current data centers has encouraged the use of power modeling to estimate their power consumption. However, existing models present noticeable limitations, which make them application-dependent, platform-dependent, inaccurate, or computationally complex. In this paper, we propose a platform-and application-agnostic methodology for full-system power modeling in heterogeneous data centers that overcomes those limitations. It derives a single model per platform, which works with high accuracy for heterogeneous applications with different patterns of resource usage and energy consumption, by systematically selecting a minimum set of resource usage indicators and extracting complex relations among them that capture the impact on energy consumption of all the resources in the system. We demonstrate our methodology by generating power models for heterogeneous platforms with very different power consumption profiles. Our validation experiments with real Cloud applications show that such models provide high accuracy (around 5% of average estimation error).This work is supported by the Spanish Ministry of Economy and Competitiveness under contract TIN2015-65316-P, by the Gener-
alitat de Catalunya under contract 2014-SGR-1051, and by the European Commission under FP7-SMARTCITIES-2013 contract 608679 (RenewIT) and FP7-ICT-2013-10 contracts 610874 (AS- CETiC) and 610456 (EuroServer).Peer ReviewedPostprint (author's final draft
Exactly solvable models of adaptive networks
A satisfiability (SAT-UNSAT) transition takes place for many optimization
problems when the number of constraints, graphically represented by links
between variables nodes, is brought above some threshold. If the network of
constraints is allowed to adapt by redistributing its links, the SAT-UNSAT
transition may be delayed and preceded by an intermediate phase where the
structure self-organizes to satisfy the constraints. We present an analytic
approach, based on the recently introduced cavity method for large deviations,
which exactly describes the two phase transitions delimiting this adaptive
intermediate phase. We give explicit results for random bond models subject to
the connectivity or rigidity percolation transitions, and compare them with
numerical simulations.Comment: 4 pages, 4 figure
Amorphous-amorphous transition and the two-step replica symmetry breaking phase
The nature of polyamorphism and amorphous-to-amorphous transition is
investigated by means of an exactly solvable model with quenched disorder, the
spherical s+p multi-spin interaction model. The analysis is carried out in the
framework of Replica Symmetry Breaking theory and leads to the identification
of low temperature glass phases of different kinds. Besides the usual
`one-step' solution, known to reproduce all basic properties of structural
glasses, also a physically consistent `two-step' solution arises. More
complicated phases are found as well, as temperature is further decreased,
expressing a complex variety of metastable states structures for amorphous
systems.Comment: 8 pages, 7 figures, longer version, new references adde
The cavity method for large deviations
A method is introduced for studying large deviations in the context of
statistical physics of disordered systems. The approach, based on an extension
of the cavity method to atypical realizations of the quenched disorder, allows
us to compute exponentially small probabilities (rate functions) over different
classes of random graphs. It is illustrated with two combinatorial optimization
problems, the vertex-cover and coloring problems, for which the presence of
replica symmetry breaking phases is taken into account. Applications include
the analysis of models on adaptive graph structures.Comment: 18 pages, 7 figure
Cusps and shocks in the renormalized potential of glassy random manifolds: How Functional Renormalization Group and Replica Symmetry Breaking fit together
We compute the Functional Renormalization Group (FRG) disorder- correlator
function R(v) for d-dimensional elastic manifolds pinned by a random potential
in the limit of infinite embedding space dimension N. It measures the
equilibrium response of the manifold in a quadratic potential well as the
center of the well is varied from 0 to v. We find two distinct scaling regimes:
(i) a "single shock" regime, v^2 ~ 1/L^d where L^d is the system volume and
(ii) a "thermodynamic" regime, v^2 ~ N. In regime (i) all the equivalent
replica symmetry breaking (RSB) saddle points within the Gaussian variational
approximation contribute, while in regime (ii) the effect of RSB enters only
through a single anomaly. When the RSB is continuous (e.g., for short-range
disorder, in dimension 2 <= d <= 4), we prove that regime (ii) yields the
large-N FRG function obtained previously. In that case, the disorder correlator
exhibits a cusp in both regimes, though with different amplitudes and of
different physical origin. When the RSB solution is 1-step and non- marginal
(e.g., d < 2 for SR disorder), the correlator R(v) in regime (ii) is
considerably reduced, and exhibits no cusp. Solutions of the FRG flow
corresponding to non-equilibrium states are discussed as well. In all cases the
regime (i) exhibits a cusp non-analyticity at T=0, whose form and thermal
rounding at finite T is obtained exactly and interpreted in terms of shocks.
The results are compared with previous work, and consequences for manifolds at
finite N, as well as extensions to spin glasses and related models are
discussed.Comment: v2: Note added in proo
Optical fiber tips functionalized with semiconductor photonic crystal cavities
We demonstrate a simple and rapid epoxy-based method for transferring
photonic crystal cavities to the facets of optical fibers. Passive Si cavities
were measured via fiber taper coupling as well as direct transmission from the
fiber facet. Active quantum dot containing GaAs cavities showed
photoluminescence that was collected both in free space and back through the
original fiber. Cavities maintain a high quality factor (2000-4000) in both
material systems. This new design architecture provides a practical
mechanically stable platform for the integration of photonic crystal cavities
with macroscale optics and opens the door for novel research on fiber-coupled
cavity devices.Comment: 10 pages, 5 figure
The theoretical capacity of the Parity Source Coder
The Parity Source Coder is a protocol for data compression which is based on
a set of parity checks organized in a sparse random network. We consider here
the case of memoryless unbiased binary sources. We show that the theoretical
capacity saturate the Shannon limit at large K. We also find that the first
corrections to the leading behavior are exponentially small, so that the
behavior at finite K is very close to the optimal one.Comment: Added references, minor change
Random multi-index matching problems
The multi-index matching problem (MIMP) generalizes the well known matching
problem by going from pairs to d-uplets. We use the cavity method from
statistical physics to analyze its properties when the costs of the d-uplets
are random. At low temperatures we find for d>2 a frozen glassy phase with
vanishing entropy. We also investigate some properties of small samples by
enumerating the lowest cost matchings to compare with our theoretical
predictions.Comment: 22 pages, 16 figure
The Phase Diagram of 1-in-3 Satisfiability Problem
We study the typical case properties of the 1-in-3 satisfiability problem,
the boolean satisfaction problem where a clause is satisfied by exactly one
literal, in an enlarged random ensemble parametrized by average connectivity
and probability of negation of a variable in a clause. Random 1-in-3
Satisfiability and Exact 3-Cover are special cases of this ensemble. We
interpolate between these cases from a region where satisfiability can be
typically decided for all connectivities in polynomial time to a region where
deciding satisfiability is hard, in some interval of connectivities. We derive
several rigorous results in the first region, and develop the
one-step--replica-symmetry-breaking cavity analysis in the second one. We
discuss the prediction for the transition between the almost surely satisfiable
and the almost surely unsatisfiable phase, and other structural properties of
the phase diagram, in light of cavity method results.Comment: 30 pages, 12 figure
- …