10,745 research outputs found
A Cost-based Optimizer for Gradient Descent Optimization
As the use of machine learning (ML) permeates into diverse application
domains, there is an urgent need to support a declarative framework for ML.
Ideally, a user will specify an ML task in a high-level and easy-to-use
language and the framework will invoke the appropriate algorithms and system
configurations to execute it. An important observation towards designing such a
framework is that many ML tasks can be expressed as mathematical optimization
problems, which take a specific form. Furthermore, these optimization problems
can be efficiently solved using variations of the gradient descent (GD)
algorithm. Thus, to decouple a user specification of an ML task from its
execution, a key component is a GD optimizer. We propose a cost-based GD
optimizer that selects the best GD plan for a given ML task. To build our
optimizer, we introduce a set of abstract operators for expressing GD
algorithms and propose a novel approach to estimate the number of iterations a
GD algorithm requires to converge. Extensive experiments on real and synthetic
datasets show that our optimizer not only chooses the best GD plan but also
allows for optimizations that achieve orders of magnitude performance speed-up.Comment: Accepted at SIGMOD 201
Neo: A Learned Query Optimizer
Query optimization is one of the most challenging problems in database
systems. Despite the progress made over the past decades, query optimizers
remain extremely complex components that require a great deal of hand-tuning
for specific workloads and datasets. Motivated by this shortcoming and inspired
by recent advances in applying machine learning to data management challenges,
we introduce Neo (Neural Optimizer), a novel learning-based query optimizer
that relies on deep neural networks to generate query executions plans. Neo
bootstraps its query optimization model from existing optimizers and continues
to learn from incoming queries, building upon its successes and learning from
its failures. Furthermore, Neo naturally adapts to underlying data patterns and
is robust to estimation errors. Experimental results demonstrate that Neo, even
when bootstrapped from a simple optimizer like PostgreSQL, can learn a model
that offers similar performance to state-of-the-art commercial optimizers, and
in some cases even surpass them
Blow-up profile of rotating 2D focusing Bose gases
We consider the Gross-Pitaevskii equation describing an attractive Bose gas
trapped to a quasi 2D layer by means of a purely harmonic potential, and which
rotates at a fixed speed of rotation . First we study the behavior of
the ground state when the coupling constant approaches , the critical
strength of the cubic nonlinearity for the focusing nonlinear Schr{\"o}dinger
equation. We prove that blow-up always happens at the center of the trap, with
the blow-up profile given by the Gagliardo-Nirenberg solution. In particular,
the blow-up scenario is independent of , to leading order. This
generalizes results obtained by Guo and Seiringer (Lett. Math. Phys., 2014,
vol. 104, p. 141--156) in the non-rotating case. In a second part we consider
the many-particle Hamiltonian for bosons, interacting with a potential
rescaled in the mean-field manner w\int\_{\mathbb{R}^2} w(x) dx = 1\beta < 1/2a\_N \to a\_*N \to \infty$
A Multi Hidden Recurrent Neural Network with a Modified Grey Wolf Optimizer
Identifying university students' weaknesses results in better learning and
can function as an early warning system to enable students to improve. However,
the satisfaction level of existing systems is not promising. New and dynamic
hybrid systems are needed to imitate this mechanism. A hybrid system (a
modified Recurrent Neural Network with an adapted Grey Wolf Optimizer) is used
to forecast students' outcomes. This proposed system would improve instruction
by the faculty and enhance the students' learning experiences. The results show
that a modified recurrent neural network with an adapted Grey Wolf Optimizer
has the best accuracy when compared with other models.Comment: 34 pages, published in PLoS ON
Systems and controls laboratory
Advanced aerospace systems and control including thrust modulation, optimizer research, fluidic devices, hydraulic jet valves, and related researc
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