221 research outputs found
Tutorial: Are You My Neighbor?: Bringing Order to Neighbor Computing Problems
Finding nearest neighbors is an important topic that has attracted much attention over the years and has applications in many fields, such as market basket analysis, plagiarism and anomaly detection, community detection, ligand-based virtual screening, etc. As data are easier and easier to collect, finding neighbors has become a potential bottleneck in analysis pipelines. Performing pairwise comparisons given the massive datasets of today is no longer feasible. The high computational complexity of the task has led researchers to develop approximate methods, which find many but not all of the nearest neighbors. Yet, for some types of data, efficient exact solutions have been found by carefully partitioning or filtering the search space in a way that avoids most unnecessary comparisons.In recent years, there have been several fundamental advances in our ability to efficiently identify appropriate neighbors, especially in non-traditional data, such as graphs or document collections. In this tutorial, we provide an in-depth overview of recent methods for finding (nearest) neighbors, focusing on the intuition behind choices made in the design of those algorithms and on the utility of the methods in real-world applications. Our tutorial aims to provide a unifying view of neighbor computing problems, spanning from numerical data to graph data, from categorical data to sequential data, and related application scenarios. For each type of data, we will review the current state-of-the-art approaches used to identify neighbors and discuss how neighbor search methods are used to solve important problems
Conversion Prediction Using Multi-task Conditional Attention Networks to Support the Creation of Effective Ad Creative
Accurately predicting conversions in advertisements is generally a
challenging task, because such conversions do not occur frequently. In this
paper, we propose a new framework to support creating high-performing ad
creatives, including the accurate prediction of ad creative text conversions
before delivering to the consumer. The proposed framework includes three key
ideas: multi-task learning, conditional attention, and attention highlighting.
Multi-task learning is an idea for improving the prediction accuracy of
conversion, which predicts clicks and conversions simultaneously, to solve the
difficulty of data imbalance. Furthermore, conditional attention focuses
attention of each ad creative with the consideration of its genre and target
gender, thus improving conversion prediction accuracy. Attention highlighting
visualizes important words and/or phrases based on conditional attention. We
evaluated the proposed framework with actual delivery history data (14,000
creatives displayed more than a certain number of times from Gunosy Inc.), and
confirmed that these ideas improve the prediction performance of conversions,
and visualize noteworthy words according to the creatives' attributes.Comment: 9 pages, 6 figures. Accepted at The 25th ACM SIGKDD Conference on
Knowledge Discovery and Data Mining (KDD 2019) as an applied data science
pape
Network Density of States
Spectral analysis connects graph structure to the eigenvalues and
eigenvectors of associated matrices. Much of spectral graph theory descends
directly from spectral geometry, the study of differentiable manifolds through
the spectra of associated differential operators. But the translation from
spectral geometry to spectral graph theory has largely focused on results
involving only a few extreme eigenvalues and their associated eigenvalues.
Unlike in geometry, the study of graphs through the overall distribution of
eigenvalues - the spectral density - is largely limited to simple random graph
models. The interior of the spectrum of real-world graphs remains largely
unexplored, difficult to compute and to interpret.
In this paper, we delve into the heart of spectral densities of real-world
graphs. We borrow tools developed in condensed matter physics, and add novel
adaptations to handle the spectral signatures of common graph motifs. The
resulting methods are highly efficient, as we illustrate by computing spectral
densities for graphs with over a billion edges on a single compute node. Beyond
providing visually compelling fingerprints of graphs, we show how the
estimation of spectral densities facilitates the computation of many common
centrality measures, and use spectral densities to estimate meaningful
information about graph structure that cannot be inferred from the extremal
eigenpairs alone.Comment: 10 pages, 7 figure
Pb-Hash: Partitioned b-bit Hashing
Many hashing algorithms including minwise hashing (MinHash), one permutation
hashing (OPH), and consistent weighted sampling (CWS) generate integers of
bits. With hashes for each data vector, the storage would be
bits; and when used for large-scale learning, the model size would be
, which can be expensive. A standard strategy is to use only the
lowest bits out of the bits and somewhat increase , the number of
hashes. In this study, we propose to re-use the hashes by partitioning the
bits into chunks, e.g., . Correspondingly, the model size
becomes , which can be substantially smaller than the
original .
Our theoretical analysis reveals that by partitioning the hash values into
chunks, the accuracy would drop. In other words, using chunks of
bits would not be as accurate as directly using bits. This is due to the
correlation from re-using the same hash. On the other hand, our analysis also
shows that the accuracy would not drop much for (e.g.,) . In some
regions, Pb-Hash still works well even for much larger than 4. We expect
Pb-Hash would be a good addition to the family of hashing methods/applications
and benefit industrial practitioners.
We verify the effectiveness of Pb-Hash in machine learning tasks, for linear
SVM models as well as deep learning models. Since the hashed data are
essentially categorical (ID) features, we follow the standard practice of using
embedding tables for each hash. With Pb-Hash, we need to design an effective
strategy to combine embeddings. Our study provides an empirical evaluation
on four pooling schemes: concatenation, max pooling, mean pooling, and product
pooling. There is no definite answer which pooling would be always better and
we leave that for future study
Topic-enhanced memory networks for personalised point-of-interest recommendation
Point-of-Interest (POI) recommender systems play a vital role in people's
lives by recommending unexplored POIs to users and have drawn extensive
attention from both academia and industry. Despite their value, however, they
still suffer from the challenges of capturing complicated user preferences and
fine-grained user-POI relationship for spatio-temporal sensitive POI
recommendation. Existing recommendation algorithms, including both shallow and
deep approaches, usually embed the visiting records of a user into a single
latent vector to model user preferences: this has limited power of
representation and interpretability. In this paper, we propose a novel
topic-enhanced memory network (TEMN), a deep architecture to integrate the
topic model and memory network capitalising on the strengths of both the global
structure of latent patterns and local neighbourhood-based features in a
nonlinear fashion. We further incorporate a geographical module to exploit
user-specific spatial preference and POI-specific spatial influence to enhance
recommendations. The proposed unified hybrid model is widely applicable to
various POI recommendation scenarios. Extensive experiments on real-world
WeChat datasets demonstrate its effectiveness (improvement ratio of 3.25% and
29.95% for context-aware and sequential recommendation, respectively). Also,
qualitative analysis of the attention weights and topic modeling provides
insight into the model's recommendation process and results.China Scholarship Council and Cambridge Trus
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