594 research outputs found
Operations research methods in compiler backends
Operations research can be defined as the theory of numerically
solving decision problems. In this context, dealing with optimization
problems is a central issue. Code generation is performed by the backend phase of a compiler, a program which transforms the source code of an application into optimized machine code. Basically, code generation is an optimization problem, which can be modelled in a way similar to typical problems in the area of operations research. In this article, that similarity is demonstrated by opposing integer linear programming models for problems of the operations research and of code generation. The time frame for solving the generated integer linear programs (ILPs) as a part of the compilation process is small. As a consequence, using well-structured ILP-formulations and ILP-based approximations is necessary. The second part of the paper will give a brief survey on guidelines and techniques for both issues
Halo Cores and Phase Space Densities: Observational Constraints on Dark Matter Physics and Structure Formation
We explore observed dynamical trends in a wide range of dark matter dominated
systems (about seven orders of magnitude in mass) to constrain hypothetical
dark matter candidates and scenarios of structure formation. First, we argue
that neither generic warm dark matter (collisionless or collisional) nor
self-interacting dark matter can be responsible for the observed cores on all
scales. Both scenarios predict smaller cores for higher mass systems, in
conflict with observations; some cores must instead have a dynamical origin.
Second, we show that the core phase space densities of dwarf spheroidals,
rotating dwarf and low surface brightness galaxies, and clusters of galaxies
decrease with increasing velocity dispersion like Q ~ sigma^-3 ~ M^-1, as
predicted by a simple scaling argument based on merging equilibrium systems,
over a range of about eight orders of magnitude in Q. We discuss the processes
which set the overall normalization of the observed phase density hierarchy. As
an aside, we note that the observed phase-space scaling behavior and density
profiles of dark matter halos both resemble stellar components in elliptical
galaxies, likely reflecting a similar collisionless, hierarchical origin. Thus,
dark matter halos may suffer from the same systematic departures from homology
as seen in ellipticals, possibly explaining the shallower density profiles
observed in low mass halos. Finally, we use the maximum observed phase space
density in dwarf spheroidal galaxies to fix a minimum mass for relativistically
decoupled warm dark matter candidates of roughly 700 eV for thermal fermions,
and 300 eV for degenerate fermions.Comment: Submitted to the Astrophysical Journal, LaTeX, 26 pages including 4
pages of figure
Development of Lifting-based VLSI Architectures for Two-Dimensional Discrete Wavelet Transform
Two-dimensional discrete wavelet transform (2-D DWT) has evolved as an essential
part of a modem compression system. It offers superior compression with good image
quality and overcomes disadvantage of the discrete cosine transform, which suffers
from blocks artifacts that reduces the quality of the inage. The amount of
computations involve in 2-D DWT is enormous and cannot be processed by generalpurpose
processors when real-time processing is required. Th·"efore, high speed and
low power VLSI architecture that computes 2-D DWT effectively is needed. In this
research, several VLSI architectures have been developed that meets real-time
requirements for 2-D DWT applications. This research iaitially started off by
implementing a software simulation program that decorrelates the original image and
reconstructs the original image from the decorrelated image. Then, based on the
information gained from implementing the simulation program, a new approach for
designing lifting-based VLSI architectures for 2-D forward DWT is introduced. As a
result, two high performance VLSI architectures that perform 2-D DWT for 5/3 and
9/7 filters are developed based on overlapped and nonoverlapped scan methods. Then,
the intermediate architecture is developed, which aim a·: reducing the power
consumption of the overlapped areas without using the expensive line buffer. In order
to best meet real-time applications of 2-D DWT with demanding requirements in
terms of speed and throughput parallelism is explored. The single pipelined
intermediate and overlapped architectures are extended to 2-, 3-, and 4-parallel
architectures to achieve speed factors of 2, 3, and 4, respectively. To further
demonstrate the effectiveness of the approach single and para.llel VLSI architectures
for 2-D inverse discrete wavelet transform (2-D IDWT) are developed. Furthermore,
2-D DWT memory architectures, which have been overlooked in the literature, are
also developed. Finally, to show the architectural models developed for 2-D DWT are
simple to control, the control algorithms for 4-parallel architecture based on the first
scan method is developed. To validate architectures develcped in this work five
architectures are implemented and simulated on Altera FPGA.
In compliance with the terms of the Copyright Act 1987 and the IP Policy of the
university, the copyright of this thesis has been reassigned by the author to the legal
entity of the university,
Institute of Technology PETRONAS Sdn bhd.
Due acknowledgement shall always be made of the use of any material contained
in, or derived from, this thesis
laGP: Large-Scale Spatial Modeling via Local Approximate Gaussian Processes in R
Gaussian process (GP) regression models make for powerful predictors in out of sample exercises, but cubic runtimes for dense matrix decompositions severely limit the size of data - training and testing - on which they can be deployed. That means that in computer experiment, spatial/geo-physical, and machine learning contexts, GPs no longer enjoy privileged status as data sets continue to balloon in size. We discuss an implementation of local approximate Gaussian process models, in the laGP package for R, that offers a particular sparse-matrix remedy uniquely positioned to leverage modern parallel computing architectures. The laGP approach can be seen as an update on the spatial statistical method of local kriging neighborhoods. We briefly review the method, and provide extensive illustrations of the features in the package through worked-code examples. The appendix covers custom building options for symmetric multi-processor and graphical processing units, and built-in wrapper routines that automate distribution over a simple network of workstations
Flow-of-funds analysis in the Brazilian economy (2004–2014)
This paper is applies the flow-of-funds (FOF) framework proposed by Tsujimura and Mizoshita (2004) to investigate the structure of financial system in the Brazilian economy. The study presents the compilation process of the asset–liability matrix (ALM) and then develops an ALM with six institutional sectors (households, non-financial firms, government, the rest of world, financial firms and the Central Bank of Brazil) for the years 2004 to 2014. From the Brazilian ALM, FOF indexes are calculated (the power of dispersion, the sensitivity of dispersion and the discrepancy of dispersion). For selected years, the structural decomposition of change in the discrepancy index is calculated and an additional expansion presents an ALM with four additional financial firms: three government-sponsored banks—Banco do Brasil, Caixa Econômica Federal, and Banco Nacional de Desenvolvimento Econômico e Social —and one private bank—Itaú. The role of each institutional sector in the Brazilian financial system is illustrated and the discrepancy of dispersion is highlighted with a good indicator of economic problems showing that the origin of recessions in Brazilian economy was almost in the structure of the financial system
Zonal shear and super-rotation in a magnetized spherical Couette flow experiment
We present measurements performed in a spherical shell filled with liquid
sodium, where a 74 mm-radius inner sphere is rotated while a 210 mm-radius
outer sphere is at rest. The inner sphere holds a dipolar magnetic field and
acts as a magnetic propeller when rotated. In this experimental set-up called
DTS, direct measurements of the velocity are performed by ultrasonic Doppler
velocimetry. Differences in electric potential and the induced magnetic field
are also measured to characterize the magnetohydrodynamic flow. Rotation
frequencies of the inner sphere are varied between -30 Hz and +30 Hz, the
magnetic Reynolds number based on measured sodium velocities and on the shell
radius reaching to about 33. We have investigated the mean axisymmetric part of
the flow, which consists of differential rotation. Strong super-rotation of the
fluid with respect to the rotating inner sphere is directly measured. It is
found that the organization of the mean flow does not change much throughout
the entire range of parameters covered by our experiment. The direct
measurements of zonal velocity give a nice illustration of Ferraro's law of
isorotation in the vicinity of the inner sphere where magnetic forces dominate
inertial ones. The transition from a Ferraro regime in the interior to a
geostrophic regime, where inertial forces predominate, in the outer regions has
been well documented. It takes place where the local Elsasser number is about
1. A quantitative agreement with non-linear numerical simulations is obtained
when keeping the same Elsasser number. The experiments also reveal a region
that violates Ferraro's law just above the inner sphere.Comment: Phys Rev E, in pres
Hierarchical decomposition and simulation of manufacturing cells using Ada
A useful tool in the development of flexible automation is a system description language which can generate a complete func tional description of a manufacturing cell of arbitrary complexity. We propose a description system based on the concept of hierar chical decomposition utilizing the Ada programming language in conjunction with established diagrammatical decomposition methods. The distinguishing aspect of our work is that it takes advantage of certain features of Ada (such as type checking) to create a description that can be automatically verified for con sistency Simulation is often an indispensable tool in the develop ment of manufacturing systems. We show how a simulation of the operation of the manufacturing cell can be embedded in its description. Finally, we apply the methodology to a specific instance of a manufacturing cell.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68498/2/10.1177_003754978604600402.pd
Qibolab: an open-source hybrid quantum operating system
We present Qibolab, an open-source software library for quantum hardware
control integrated with the Qibo quantum computing middleware framework.
Qibolab provides the software layer required to automatically execute
circuit-based algorithms on custom self-hosted quantum hardware platforms. We
introduce a set of objects designed to provide programmatic access to quantum
control through pulses-oriented drivers for instruments, transpilers and
optimization algorithms. Qibolab enables experimentalists and developers to
delegate all complex aspects of hardware implementation to the library so they
can standardize the deployment of quantum computing algorithms in a
hardware-agnostic way. We first describe the status of all components of the
library, then we show examples of control setup for superconducting qubits
platforms. Finally, we present successful application results related to
circuit-based algorithms.Comment: 18 pages, 10 figures, code available at
https://github.com/qiboteam/qibola
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