315 research outputs found
A Unified Approach to Holomorphic Anomaly Equations and Quantum Spectral Curves
We present a unified approach to holomorphic anomaly equations and some
well-known quantum spectral curves. We develop a formalism of abstract quantum
field theory based on the diagrammatics of the Deligne-Mumford moduli spaces
and derive a quadratic recursion relation for
the abstract free energies in terms of the edge-cutting operators. This
abstract quantum field theory can be realized by various choices of a sequence
of holomorphic functions or formal power series and suitable propagators, and
the realized quantum field theory can be represented by formal Gaussian
integrals. Various applications are given.Comment: A section is adde
Efficient Algorithms for Sparse Moment Problems without Separation
We consider the sparse moment problem of learning a -spike mixture in
high-dimensional space from its noisy moment information in any dimension. We
measure the accuracy of the learned mixtures using transportation distance.
Previous algorithms either assume certain separation assumptions, use more
recovery moments, or run in (super) exponential time. Our algorithm for the
one-dimensional problem (also called the sparse Hausdorff moment problem) is a
robust version of the classic Prony's method, and our contribution mainly lies
in the analysis. We adopt a global and much tighter analysis than previous work
(which analyzes the perturbation of the intermediate results of Prony's
method). A useful technical ingredient is a connection between the linear
system defined by the Vandermonde matrix and the Schur polynomial, which allows
us to provide tight perturbation bound independent of the separation and may be
useful in other contexts. To tackle the high-dimensional problem, we first
solve the two-dimensional problem by extending the one-dimensional algorithm
and analysis to complex numbers. Our algorithm for the high-dimensional case
determines the coordinates of each spike by aligning a 1d projection of the
mixture to a random vector and a set of 2d projections of the mixture. Our
results have applications to learning topic models and Gaussian mixtures,
implying improved sample complexity results or running time over prior work
A mixed precision Jacobi method for the symmetric eigenvalue problem
The eigenvalue problem is a fundamental problem in scientific computing. In
this paper, we propose a mixed precision Jacobi method for the symmetric
eigenvalue problem. We first compute the eigenvalue decomposition of a real
symmetric matrix by an eigensolver at low precision and we obtain a
low-precision matrix of eigenvectors. Then by using the modified Gram-Schmidt
orthogonalization process to the low-precision eigenvector matrix in high
precision, a high-precision orthogonal matrix is obtained, which is used as an
initial guess for the Jacobi method. We give the rounding error analysis for
the proposed method and the quadratic convergence of the proposed method is
established under some sufficient conditions. We also present a mixed precision
one-side Jacobi method for the singular value problem and the corresponding
rounding error analysis and quadratic convergence are discussed. Numerical
experiments on CPUs and GPUs are conducted to illustrate the efficiency of the
proposed mixed precision Jacobi method over the original Jacobi method.Comment: 31 pages, 2 figure
Mantle upwelling beneath the South China Sea and links to surrounding subduction systems
© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Lin, J., Xu, Y., Sun, Z., & Zhou, Z. Mantle upwelling beneath the South China Sea and links to surrounding subduction systems. National Science Review, 6(5), (2019): 877-881, doi:10.1093/nsr/nwz123.The evolution of the South China Sea (SCS) is directly linked to the complex subduction systems of the surrounding Pacific, Philippine Sea and Indo-Australian Plates (Fig. 1a). Major advances in the last several years are providing new insights into the SCS-mantle dynamics, through regional seismic imaging of the upper mantle [1,2], unprecedented IODP drilling expeditions (349/367/368/368X) [3–5] that obtained the oceanic basement basalt samples for the first time, geochemical analyses of the SCS-mantle source compositions [6–8] and geodynamic modeling [9,10]. Furthermore, new geological mapping, seismic imaging [11,12] and IODP drilling [13,14] have revealed evidence for significantly greater magma production at the northern SCS rifted margin, in comparison to the magma-poor end-member of the Atlantic rifted margins. This paper provides a new perspective of the SCS-mantle dynamics inspired by new observations and geodynamic modeling. We first highlight new geophysical evidence for a broad region of low-seismic-velocity anomalies in the upper mantle beneath the northern SCS, abundant magmatism during continental breakup and post-seafloor spreading, and geochemical evidence for recycled oceanic components beneath the SCS. We then present new models of layered flows in the mantle beneath the SCS, revealing two modes of plate- and subduction-driven mantle upwelling, including (i) narrow centers of mantle upwelling at shallow depths induced by divergent plate motion at seafloor-spreading centers and (ii) broad zones of mantle upwelling as a result of subduction-induced mantle-return flows at greater depths. These new observations and geodynamic studies suggest strong links between mantle upwelling beneath the SCS and surrounding subducting plates.This work was supported by the National Natural Science Foundation of China (41890813, 91628301, U1606401, 41976066, 91858207 and 41706056), the Chinese Academy of Sciences (Y4SL021001, QYZDY-SSW-DQC005 and 133244KYSB20180029), the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou, GML2019ZD0205), the National Key R&D Program of China (2018YFC0309800 and 2018YFC0310100), the State Oceanic Administration (GASI-GEOGE-02) and China Ocean Mineral Resources R&D Association (DY135-S2–1-04)
A Hierarchical Framework of Cloud Resource Allocation and Power Management Using Deep Reinforcement Learning
Automatic decision-making approaches, such as reinforcement learning (RL),
have been applied to (partially) solve the resource allocation problem
adaptively in the cloud computing system. However, a complete cloud resource
allocation framework exhibits high dimensions in state and action spaces, which
prohibit the usefulness of traditional RL techniques. In addition, high power
consumption has become one of the critical concerns in design and control of
cloud computing systems, which degrades system reliability and increases
cooling cost. An effective dynamic power management (DPM) policy should
minimize power consumption while maintaining performance degradation within an
acceptable level. Thus, a joint virtual machine (VM) resource allocation and
power management framework is critical to the overall cloud computing system.
Moreover, novel solution framework is necessary to address the even higher
dimensions in state and action spaces. In this paper, we propose a novel
hierarchical framework for solving the overall resource allocation and power
management problem in cloud computing systems. The proposed hierarchical
framework comprises a global tier for VM resource allocation to the servers and
a local tier for distributed power management of local servers. The emerging
deep reinforcement learning (DRL) technique, which can deal with complicated
control problems with large state space, is adopted to solve the global tier
problem. Furthermore, an autoencoder and a novel weight sharing structure are
adopted to handle the high-dimensional state space and accelerate the
convergence speed. On the other hand, the local tier of distributed server
power managements comprises an LSTM based workload predictor and a model-free
RL based power manager, operating in a distributed manner.Comment: accepted by 37th IEEE International Conference on Distributed
Computing (ICDCS 2017
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