755 research outputs found
From Bare Metal to Virtual: Lessons Learned when a Supercomputing Institute Deploys its First Cloud
As primary provider for research computing services at the University of
Minnesota, the Minnesota Supercomputing Institute (MSI) has long been
responsible for serving the needs of a user-base numbering in the thousands.
In recent years, MSI---like many other HPC centers---has observed a growing
need for self-service, on-demand, data-intensive research, as well as the
emergence of many new controlled-access datasets for research purposes. In
light of this, MSI constructed a new on-premise cloud service, named Stratus,
which is architected from the ground up to easily satisfy data-use agreements
and fill four gaps left by traditional HPC. The resulting OpenStack cloud,
constructed from HPC-specific compute nodes and backed by Ceph storage, is
designed to fully comply with controls set forth by the NIH Genomic Data
Sharing Policy.
Herein, we present twelve lessons learned during the ambitious sprint to take
Stratus from inception and into production in less than 18 months. Important,
and often overlooked, components of this timeline included the development of
new leadership roles, staff and user training, and user support documentation.
Along the way, the lessons learned extended well beyond the technical
challenges often associated with acquiring, configuring, and maintaining
large-scale systems.Comment: 8 pages, 5 figures, PEARC '18: Practice and Experience in Advanced
Research Computing, July 22--26, 2018, Pittsburgh, PA, US
On the Efficient Calculation of a Linear Combination of Chi-Square Random Variables with an Application in Counting String Vacua
Linear combinations of chi square random variables occur in a wide range of
fields. Unfortunately, a closed, analytic expression for the pdf is not yet
known. As a first result of this work, an explicit analytic expression for the
density of the sum of two gamma random variables is derived. Then a
computationally efficient algorithm to numerically calculate the linear
combination of chi square random variables is developed. An explicit expression
for the error bound is obtained. The proposed technique is shown to be
computationally efficient, i.e. only polynomial in growth in the number of
terms compared to the exponential growth of most other methods. It provides a
vast improvement in accuracy and shows only logarithmic growth in the required
precision. In addition, it is applicable to a much greater number of terms and
currently the only way of computing the distribution for hundreds of terms. As
an application, the exponential dependence of the eigenvalue fluctuation
probability of a random matrix model for 4d supergravity with N scalar fields
is found to be of the asymptotic form exp(-0.35N).Comment: 21 pages, 19 figures. 3rd versio
Learning like human annotators: Cyberbullying detection in lengthy social media sessions
The inherent characteristic of cyberbullying of being a recurrent attitude calls for the investigation of the problem by looking at social media sessions as a whole, beyond just isolated social media posts. However, the lengthy nature of social media sessions challenges the applicability and performance of session-based cyberbullying detection models. This is especially true when one aims to use state-of-the-art Transformer-based pre-trained language models, which only take inputs of a limited length. In this paper, we address this limitation of transformer models by proposing a conceptually intuitive framework called LS-CB, which enables cyberbullying detection from lengthy social media sessions. LS-CB relies on the intuition that we can effectively aggregate the predictions made by transformer models on smaller sliding windows extracted from lengthy social media sessions, leading to an overall improved performance. Our extensive experiments with six transformer models on two session-based datasets show that LS-CB consistently outperforms three types of competitive baselines including state-of-the-art cyberbullying detection models. In addition, we conduct a set of qualitative analyses to validate the hypotheses that cyberbullying incidents can be detected through aggregated analysis of smaller chunks derived from lengthy social media sessions (H1), and that cyberbullying incidents can occur at different points of the session (H2), hence positing that frequently used text truncation strategies are suboptimal compared to relying on holistic views of sessions. Our research in turn opens an avenue for fine-grained cyberbullying detection within sessions in future work
A Web-based multimedia collaboratory. Empirical work studies in film archives
This report represents the latest study in the activity on Ecological Information Systems conducted in the Center for Human Machine Interaction situated at Ris National Laboratory and the University of Aarhus. The purpose of this activity is to give a description of the characteristics of work domains that will serve to outline the general context of concern to design of collaboratories. In addition, a set of preliminary implications for the design of a collaboratory are derived from the cognitive work analysis. To anticipate, further research on this approach to the design of collaboratories will show how the preceding analysis is likely to lead to a novel theoretical framework, called Ecological Collaborative Information Systems (ECIS), required for the design of collaboratories. The intention is to illustrate how the general principles of ECIS can be instantiated to develop a concrete design product: A crossdisciplinary and cross-cultural collaboratory to support customer service and professional research in archives. A web based Collaboratory Numerous valuable historic and cultural films and their sources are scattered in various national archives. Knowledge and usage of the multinational film material are severely impeded by access problems. To fully exploit the cultural film heritage internationally, a high degree of cross-disciplinary and international collaboration among professionals working with the film media is required. The Collaboratory for Annotation, Indexing and Retrieval of Digitized Historical Archive Material (Collate) is intended to foster and support collaboration on research, cultural mediation and preservation of films through a distributed multimedia repository. The collaboratory will provide webbased tools and interfac..
A Comparison of Astronaut Near-Earth Object Missions
NASA intends to send astronauts to a near Earth object (NEO) in or around 2025. This
is expected to involve a six month mission with a few weeks stay-time at the NEO. Problems
with this concept include lack of abort modes, vulnerability to solar flares, and lack of
resupply opportunities. Studies by the authors (the Asteroid Mining Group) and a recent
workshop at JPL organized by the Keck Institute opens the door to an alternative that
addresses these problems and creates additional opportunities. Both groups investigated the
feasibility of bringing one of more small NEOs into Earth or Lunar orbit. Particularly for
High Earth Orbits (HEO) or High Lunar Orbits (HLO), this appears feasible with near-term
technology, especially high-propellant-velocity, low-thrust solar electric propulsion (SEP) inspace
vehicles. This paper compares the currently planned mission with an alternative:
bringing one or more NEOs into HEO or HLO using SEP and lunar gravity assist. An
astronaut mission to the NEO is then similar to a mission to the Moon without a landing.
Trip times are measured in days, the NEO can be used for solar flare protection for most of
the mission, and resupply within a few days is practical. Furthermore, materials derived
from the NEO, e.g., propellant, water, radiation shielding, metals, silicon, and others, are
available for projects in cis-lunar space, including satellite refueling, habitats, and space
solar power. The alternative mission also develops much of the technology, experience, and
infrastructure needed to protect Earth from potentially hazardous NEOs. As an outcome of
these studies we are proposing a process whereby early missions can lead to large-scale
industrialization of cis-lunar space based on solar energy and asteroidal resources
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