9,229 research outputs found
Deploying Jupyter Notebooks at scale on XSEDE resources for Science Gateways and workshops
Jupyter Notebooks have become a mainstream tool for interactive computing in
every field of science. Jupyter Notebooks are suitable as companion
applications for Science Gateways, providing more flexibility and
post-processing capability to the users. Moreover they are often used in
training events and workshops to provide immediate access to a pre-configured
interactive computing environment. The Jupyter team released the JupyterHub web
application to provide a platform where multiple users can login and access a
Jupyter Notebook environment. When the number of users and memory requirements
are low, it is easy to setup JupyterHub on a single server. However, setup
becomes more complicated when we need to serve Jupyter Notebooks at scale to
tens or hundreds of users. In this paper we will present three strategies for
deploying JupyterHub at scale on XSEDE resources. All options share the
deployment of JupyterHub on a Virtual Machine on XSEDE Jetstream. In the first
scenario, JupyterHub connects to a supercomputer and launches a single node job
on behalf of each user and proxies back the Notebook from the computing node
back to the user's browser. In the second scenario, implemented in the context
of a XSEDE consultation for the IRIS consortium for Seismology, we deploy
Docker in Swarm mode to coordinate many XSEDE Jetstream virtual machines to
provide Notebooks with persistent storage and quota. In the last scenario we
install the Kubernetes containers orchestration framework on Jetstream to
provide a fault-tolerant JupyterHub deployment with a distributed filesystem
and capability to scale to thousands of users. In the conclusion section we
provide a link to step-by-step tutorials complete with all the necessary
commands and configuration files to replicate these deployments.Comment: 7 pages, 3 figures, PEARC '18: Practice and Experience in Advanced
Research Computing, July 22--26, 2018, Pittsburgh, PA, US
A-infinity algebra of an elliptic curve and Eisenstein series
We compute explicitly the A-infinity structure on the Ext-algebra of the
collection , where is a line bundle of degree 1 on an
elliptic curve . The answer involves higher derivatives of Eisenstein
series.Comment: 13 pages, 3 figures; v3: added remark on the limit at the cus
Canonical decomposition of linear differential operators with selected differential Galois groups
We revisit an order-six linear differential operator having a solution which
is a diagonal of a rational function of three variables. Its exterior square
has a rational solution, indicating that it has a selected differential Galois
group, and is actually homomorphic to its adjoint. We obtain the two
corresponding intertwiners giving this homomorphism to the adjoint. We show
that these intertwiners are also homomorphic to their adjoint and have a simple
decomposition, already underlined in a previous paper, in terms of order-two
self-adjoint operators. From these results, we deduce a new form of
decomposition of operators for this selected order-six linear differential
operator in terms of three order-two self-adjoint operators. We then generalize
the previous decomposition to decompositions in terms of an arbitrary number of
self-adjoint operators of the same parity order. This yields an infinite family
of linear differential operators homomorphic to their adjoint, and, thus, with
a selected differential Galois group. We show that the equivalence of such
operators is compatible with these canonical decompositions. The rational
solutions of the symmetric, or exterior, squares of these selected operators
are, noticeably, seen to depend only on the rightmost self-adjoint operator in
the decomposition. These results, and tools, are applied on operators of large
orders. For instance, it is seen that a large set of (quite massive) operators,
associated with reflexive 4-polytopes defining Calabi-Yau 3-folds, obtained
recently by P. Lairez, correspond to a particular form of the decomposition
detailed in this paper.Comment: 40 page
Lateral-directional control of the x-15 airplane
Lateral directional control and stability characteristics of X-15 aircraf
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
Globally nilpotent differential operators and the square Ising model
We recall various multiple integrals related to the isotropic square Ising
model, and corresponding, respectively, to the n-particle contributions of the
magnetic susceptibility, to the (lattice) form factors, to the two-point
correlation functions and to their lambda-extensions. These integrals are
holonomic and even G-functions: they satisfy Fuchsian linear differential
equations with polynomial coefficients and have some arithmetic properties. We
recall the explicit forms, found in previous work, of these Fuchsian equations.
These differential operators are very selected Fuchsian linear differential
operators, and their remarkable properties have a deep geometrical origin: they
are all globally nilpotent, or, sometimes, even have zero p-curvature. Focusing
on the factorised parts of all these operators, we find out that the global
nilpotence of the factors corresponds to a set of selected structures of
algebraic geometry: elliptic curves, modular curves, and even a remarkable
weight-1 modular form emerging in the three-particle contribution
of the magnetic susceptibility of the square Ising model. In the case where we
do not have G-functions, but Hamburger functions (one irregular singularity at
0 or ) that correspond to the confluence of singularities in the
scaling limit, the p-curvature is also found to verify new structures
associated with simple deformations of the nilpotent property.Comment: 55 page
Electroencephalography (EEG) in Head Injuries
Clinical electroencephalography has gained remarkably in popularity during the past twenty years. Correspondingly we find it with more frequency in medico-legal problems, particularly the ones pertaining to head injuries
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