4,958 research outputs found
Price Jump Prediction in Limit Order Book
A limit order book provides information on available limit order prices and
their volumes. Based on these quantities, we give an empirical result on the
relationship between the bid-ask liquidity balance and trade sign and we show
that liquidity balance on best bid/best ask is quite informative for predicting
the future market order's direction. Moreover, we define price jump as a sell
(buy) market order arrival which is executed at a price which is smaller
(larger) than the best bid (best ask) price at the moment just after the
precedent market order arrival. Features are then extracted related to limit
order volumes, limit order price gaps, market order information and limit order
event information. Logistic regression is applied to predict the price jump
from the limit order book's feature. LASSO logistic regression is introduced to
help us make variable selection from which we are capable to highlight the
importance of different features in predicting the future price jump. In order
to get rid of the intraday data seasonality, the analysis is based on two
separated datasets: morning dataset and afternoon dataset. Based on an analysis
on forty largest French stocks of CAC40, we find that trade sign and market
order size as well as the liquidity on the best bid (best ask) are consistently
informative for predicting the incoming price jump.Comment: 16 page
Exponential Weight Functions for Quasi-Proportional Auctions
In quasi-proportional auctions, the allocation is shared among bidders in
proportion to their weighted bids. The auctioneer selects a bid weight
function, and bidders know the weight function when they bid. In this note, we
analyze how weight functions that are exponential in the bid affect bidder
behavior. We show that exponential weight functions have a pure-strategy Nash
equilibrium, we characterize bids at an equilibrium, and we compare it to an
equilibrium for power weight functions.Comment: 16 pages, 16 figure
Revenue-Maximizing Mechanism Design for Quasi-Proportional Auctions
In quasi-proportional auctions, each bidder receives a fraction of the
allocation equal to the weight of their bid divided by the sum of weights of
all bids, where each bid's weight is determined by a weight function. We study
the relationship between the weight function, bidders' private values, number
of bidders, and the seller's revenue in equilibrium. It has been shown that if
one bidder has a much higher private value than the others, then a nearly flat
weight function maximizes revenue. Essentially, threatening the bidder who has
the highest valuation with having to share the allocation maximizes the
revenue. We show that as bidder private values approach parity, steeper weight
functions maximize revenue by making the quasi-proportional auction more like a
winner-take-all auction. We also show that steeper weight functions maximize
revenue as the number of bidders increases. For flatter weight functions, there
is known to be a unique pure-strategy Nash equilibrium. We show that a
pure-strategy Nash equilibrium also exists for steeper weight functions, and we
give lower bounds for bids at an equilibrium. For a special case that includes
the two-bidder auction, we show that the pure-strategy Nash equilibrium is
unique, and we show how to compute the revenue at equilibrium. We also show
that selecting a weight function based on private value ratios and number of
bidders is necessary for a quasi-proportional auction to produce more revenue
than a second-price auction
Beverage Bloggers: A Developing Relationship Between Wine Blogger Expertise and Twitter Followers
This pilot study examines how beverage bloggers’ beverage experience and certified wine knowledge influences their wine destination recommendations on Twitter. Microblogging a wine destination through Twitter is explored in this study. In the context of social media, the role of Twitter as a microblog in promoting wine destinations is specifically examined. The present study examines the food and beverage experience and wine credentials of bloggers through survey and correlations of their wine destination recommendations, travel habits and geographic home. This exploratory study finds that different levels of wine credentials have an influence on blogger\u27s recommendation of both international and domestic wine destinations. The analysis shows that the increasing number of wine credentials possessed by a blogger influences the number of followers they have on Twitter
Integrated RF-photonic Filters via Photonic-Phononic Emit-Receive Operations
The creation of high-performance narrowband filters is of great interest for
many RF-signal processing applications. To this end, numerous schemes for
electronic, MEMS-based, and microwave photonic filters have been demonstrated.
Filtering schemes based on microwave photonic systems offer superior
flexibility and tunability to traditional RF filters. However, these
optical-based filters are typically limited to GHz-widths and often have large
RF insertion losses, posing challenges for integration into high-fidelity
radiofrequency circuits. In this article, we demonstrate a novel type of
microwave filter that combines the attractive features of microwave photonic
filters with high-Q phononic signal processing using a photonic-phononic
emit-receive process. Through this process, a RF signal encoded on a guided
optical wave is transduced onto a GHz-frequency acoustic wave, where it may be
filtered through shaping of acoustic transfer functions before being re-encoded
onto a spatially separate optical probe. This emit-receive functionality,
realized in an integrated silicon waveguide, produces MHz-bandwidth band-pass
filtering while supporting low RF insertion losses necessary for high dynamic
range in a microwave photonic link. We also demonstrate record-high internal
efficiency for emit-receive operations of this type, and show that the
emit-receive operation is uniquely suitable for the creation of serial filter
banks with minimal loss of fidelity. This photonic-phononic emitter-receiver
represents a new method for low-distortion signal-processing in an integrated
all-silicon device
Consistent Bounded-Asynchronous Parameter Servers for Distributed ML
In distributed ML applications, shared parameters are usually replicated
among computing nodes to minimize network overhead. Therefore, proper
consistency model must be carefully chosen to ensure algorithm's correctness
and provide high throughput. Existing consistency models used in
general-purpose databases and modern distributed ML systems are either too
loose to guarantee correctness of the ML algorithms or too strict and thus fail
to fully exploit the computing power of the underlying distributed system.
Many ML algorithms fall into the category of \emph{iterative convergent
algorithms} which start from a randomly chosen initial point and converge to
optima by repeating iteratively a set of procedures. We've found that many such
algorithms are to a bounded amount of inconsistency and still converge
correctly. This property allows distributed ML to relax strict consistency
models to improve system performance while theoretically guarantees algorithmic
correctness. In this paper, we present several relaxed consistency models for
asynchronous parallel computation and theoretically prove their algorithmic
correctness. The proposed consistency models are implemented in a distributed
parameter server and evaluated in the context of a popular ML application:
topic modeling.Comment: Corrected Titl
State Space LSTM Models with Particle MCMC Inference
Long Short-Term Memory (LSTM) is one of the most powerful sequence models.
Despite the strong performance, however, it lacks the nice interpretability as
in state space models. In this paper, we present a way to combine the best of
both worlds by introducing State Space LSTM (SSL) models that generalizes the
earlier work \cite{zaheer2017latent} of combining topic models with LSTM.
However, unlike \cite{zaheer2017latent}, we do not make any factorization
assumptions in our inference algorithm. We present an efficient sampler based
on sequential Monte Carlo (SMC) method that draws from the joint posterior
directly. Experimental results confirms the superiority and stability of this
SMC inference algorithm on a variety of domains
A silicon Brillouin laser
Brillouin laser oscillators offer powerful and flexible dynamics as the basis
for mode-locked lasers, microwave oscillators, and optical gyroscopes in a
variety of optical systems. However, Brillouin interactions are exceedingly
weak in conventional silicon photonic waveguides, stifling progress towards
silicon-based Brillouin lasers. The recent advent of hybrid photonic-phononic
waveguides has revealed Brillouin interactions to be one of the strongest and
most tailorable nonlinearities in silicon. Here, we harness these engineered
nonlinearities to demonstrate Brillouin lasing in silicon. Moreover, we show
that this silicon-based Brillouin laser enters an intriguing regime of
dynamics, in which optical self-oscillation produces phonon linewidth
narrowing. Our results provide a platform to develop a range of applications
for monolithic integration within silicon photonic circuits.Comment: Updated after publication on June 8, 201
Primitives for Dynamic Big Model Parallelism
When training large machine learning models with many variables or
parameters, a single machine is often inadequate since the model may be too
large to fit in memory, while training can take a long time even with
stochastic updates. A natural recourse is to turn to distributed cluster
computing, in order to harness additional memory and processors. However,
naive, unstructured parallelization of ML algorithms can make inefficient use
of distributed memory, while failing to obtain proportional convergence
speedups - or can even result in divergence. We develop a framework of
primitives for dynamic model-parallelism, STRADS, in order to explore
partitioning and update scheduling of model variables in distributed ML
algorithms - thus improving their memory efficiency while presenting new
opportunities to speed up convergence without compromising inference
correctness. We demonstrate the efficacy of model-parallel algorithms
implemented in STRADS versus popular implementations for Topic Modeling, Matrix
Factorization and Lasso
Supervised Dimensionality Reduction for Big Data
To solve key biomedical problems, experimentalists now routinely measure
millions or billions of features (dimensions) per sample, with the hope that
data science techniques will be able to build accurate data-driven inferences.
Because sample sizes are typically orders of magnitude smaller than the
dimensionality of these data, valid inferences require finding a
low-dimensional representation that preserves the discriminating information
(e.g., whether the individual suffers from a particular disease). Existing
linear and nonlinear dimensionality reduction methods either are not
supervised, scale poorly to operate in big data regimes, lack theoretical
guarantees, or are "black-box" methods unsuitable for many applications. We
introduce "Linear Optimal Low-rank" projection (LOL), which extends principle
components analysis by incorporating, rather than ignoring, class labels, and
facilitates straightforward generalizations. We prove, and substantiate with
both synthetic and real data benchmarks, that LOL leads to an improved data
representation for subsequent classification, while maintaining computational
efficiency and scalability. Using multiple brain imaging datasets consisting of
>150 million features, and several genomics datasets with >500,000 features,
LOL achieves achieves state-of-the-art classification accuracy, while only
requiring a few minutes on a standard desktop computer.Comment: 6 figure
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