867 research outputs found
Gradient-based Inference for Networks with Output Constraints
Practitioners apply neural networks to increasingly complex problems in
natural language processing, such as syntactic parsing and semantic role
labeling that have rich output structures. Many such structured-prediction
problems require deterministic constraints on the output values; for example,
in sequence-to-sequence syntactic parsing, we require that the sequential
outputs encode valid trees. While hidden units might capture such properties,
the network is not always able to learn such constraints from the training data
alone, and practitioners must then resort to post-processing. In this paper, we
present an inference method for neural networks that enforces deterministic
constraints on outputs without performing rule-based post-processing or
expensive discrete search. Instead, in the spirit of gradient-based training,
we enforce constraints with gradient-based inference (GBI): for each input at
test-time, we nudge continuous model weights until the network's unconstrained
inference procedure generates an output that satisfies the constraints. We
study the efficacy of GBI on three tasks with hard constraints: semantic role
labeling, syntactic parsing, and sequence transduction. In each case, the
algorithm not only satisfies constraints but improves accuracy, even when the
underlying network is state-of-the-art.Comment: AAAI 201
Recommended from our members
Evaluating Value-Graph Translation Validation for LLVM
Translation validators are static analyzers that attempt to verify that program transformations preserve semantics. Normalizing trans- lation validators do so by trying to match the value-graphs of an original function and its transformed counterpart. In this paper, we present the design of such a validator for LLVM’s intra-procedural optimizations, a design that does not require any instrumentation of the optimizer, nor any rewriting of the source code to compile, and needs to run only once to validate a pipeline of optimizations. We present the results of our preliminary experiments on a set of bench- marks that include GCC, a perl interpreter, SQLite3, and other C programs.Engineering and Applied Science
Thermalizing a telescope in Antarctica: Analysis of ASTEP observations
The installation and operation of a telescope in Antarctica represent
particular challenges, in particular the requirement to operate at extremely
cold temperatures, to cope with rapid temperature fluctuations and to prevent
frosting. Heating of electronic subsystems is a necessity, but solutions must
be found to avoid the turbulence induced by temperature fluctua- tions on the
optical paths. ASTEP 400 is a 40 cm Newton telescope installed at the Concordia
station, Dome C since 2010 for photometric observations of fields of stars and
their exoplanets. While the telescope is designed to spread star light on
several pixels to maximize photometric stability, we show that it is
nonetheless sensitive to the extreme variations of the seeing at the ground
level (between about 0.1 and 5 arcsec) and to temperature fluctuations between
--30 degrees C and --80 degrees C. We analyze both day-time and night-time
observations and obtain the magnitude of the seeing caused by the mirrors, dome
and camera. The most important effect arises from the heating of the primary
mirror which gives rise to a mirror seeing of 0.23 arcsec K--1 . We propose
solutions to mitigate these effects.Comment: Appears in Astronomical Notes / Astronomische Nachrichten, Wiley-VCH
Verlag, 2015, pp.1-2
Genomic Diversity of the Ostreid Herpesvirus Type 1 Across Time and Location and Among Host Species
The mechanisms underlying virus emergence are rarely well understood, making the appearance of outbreaks largely unpredictable. This is particularly true for pathogens with low per-site mutation rates, such as DNA viruses, that do not exhibit a large amount of evolutionary change among genetic sequences sampled at different time points. However, whole-genome sequencing can reveal the accumulation of novel genetic variation between samples, promising to render most, if not all, microbial pathogens measurably evolving and suitable for analytical techniques derived from population genetic theory. Here, we aim to assess the measurability of evolution on epidemiological time scales of the Ostreid herpesvirus 1 (OsHV-1), a double stranded DNA virus of which a new variant, OsHV-1 μVar, emerged in France in 2008, spreading across Europe and causing dramatic economic and ecological damage. We performed phylogenetic analyses of heterochronous (n = 21) OsHV-1 genomes sampled worldwide. Results show sufficient temporal signal in the viral sequences to proceed with phylogenetic molecular clock analyses and they indicate that the genetic diversity seen in these OsHV-1 isolates has arisen within the past three decades. OsHV-1 samples from France and New Zealand did not cluster together suggesting a spatial structuration of the viral populations. The genome-wide study of simple and complex polymorphisms shows that specific genomic regions are deleted in several isolates or accumulate a high number of substitutions. These contrasting and non-random patterns of polymorphism suggest that some genomic regions are affected by strong selective pressures. Interestingly, we also found variant genotypes within all infected individuals. Altogether, these results provide baseline evidence that whole genome sequencing could be used to study population dynamic processes of OsHV-1, and more broadly herpesviruses
Superconducting routing platform for large-scale integration of quantum technologies
To reach large-scale quantum computing, three-dimensional integration of
scalable qubit arrays and their control electronics in multi-chip assemblies is
promising. Within these assemblies, the use of superconducting
interconnections, as routing layers, offers interesting perspective in terms of
(1) thermal management to protect the qubits from control electronics
self-heating, (2) passive device performance with significant increase of
quality factors and (3) density rise of low and high frequency signals thanks
to minimal dispersion. We report on the fabrication, using 200 mm silicon wafer
technologies, of a multi-layer routing platform designed for the hybridization
of spin qubit and control electronics chips. A routing level couples the qubits
and the control circuits through one layer of Al0.995Cu0.005 and
superconducting layers of TiN, Nb or NbN, connected between them by W-based
vias. Wafer-level parametric tests at 300 K validate the yield of these
technologies and low temperature electrical measurements in cryostat are used
to extract the superconducting properties of the routing layers. Preliminary
low temperature radio-frequency characterizations of superconducting passive
elements, embedded in these routing levels, are presented
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