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A Framework for Globally Optimizing Mixed-Integer Signomial Programs
Mixed-integer signomial optimization problems have broad applicability in engineering. Extending the Global Mixed-Integer Quadratic Optimizer, GloMIQO (Misener, Floudas in J. Glob. Optim., 2012. doi:10.1007/s10898-012-9874-7), this manuscript documents a computational framework for deterministically addressing mixed-integer signomial optimization problems to ε-global optimality. This framework generalizes the GloMIQO strategies of (1) reformulating user input, (2) detecting special mathematical structure, and (3) globally optimizing the mixed-integer nonconvex program. Novel contributions of this paper include: flattening an expression tree towards term-based data structures; introducing additional nonconvex terms to interlink expressions; integrating a dynamic implementation of the reformulation-linearization technique into the branch-and-cut tree; designing term-based underestimators that specialize relaxation strategies according to variable bounds in the current tree node. Computational results are presented along with comparison of the computational framework to several state-of-the-art solvers. © 2013 Springer Science+Business Media New York
Fast and automated oscillation frequency extraction using Bayesian multi-modality
Since the advent of CoRoT, and NASA Kepler and K2, the number of low- and
intermediate-mass stars classified as pulsators has increased very rapidly with
time, now accounting for several targets. With the recent launch of NASA
TESS space mission, we have confirmed our entrance to the era of all-sky
observations of oscillating stars. TESS is currently releasing good quality
datasets that already allow for the characterization and identification of
individual oscillation modes even from single 27-days shots on some stars. When
ESA PLATO will become operative by the next decade, we will face the
observation of several more hundred thousands stars where identifying
individual oscillation modes will be possible. However, estimating the
individual frequency, amplitude, and lifetime of the oscillation modes is not
an easy task. This is because solar-like oscillations and especially their
evolved version, the red giant branch (RGB) oscillations, can vary
significantly from one star to another depending on its specific stage of the
evolution, mass, effective temperature, metallicity, as well as on its level of
rotation and magnetism. In this perspective I will present a novel, fast, and
powerful way to derive individual oscillation mode frequencies by building on
previous results obtained with \diamonds. I will show that the oscillation
frequencies obtained with this new approach can reach precisions of about 0.1 %
and accuracies of about 0.01 % when compared to published literature values for
the RGB star KIC~12008916.Comment: 10 pages, 2 figures, accepted for publication in Frontiers in
Astronomy and Space Sciences. Invited contribution for the research topic
"The Future of Asteroseismology
Maiter: An Asynchronous Graph Processing Framework for Delta-based Accumulative Iterative Computation
Myriad of graph-based algorithms in machine learning and data mining require
parsing relational data iteratively. These algorithms are implemented in a
large-scale distributed environment in order to scale to massive data sets. To
accelerate these large-scale graph-based iterative computations, we propose
delta-based accumulative iterative computation (DAIC). Different from
traditional iterative computations, which iteratively update the result based
on the result from the previous iteration, DAIC updates the result by
accumulating the "changes" between iterations. By DAIC, we can process only the
"changes" to avoid the negligible updates. Furthermore, we can perform DAIC
asynchronously to bypass the high-cost synchronous barriers in heterogeneous
distributed environments. Based on the DAIC model, we design and implement an
asynchronous graph processing framework, Maiter. We evaluate Maiter on local
cluster as well as on Amazon EC2 Cloud. The results show that Maiter achieves
as much as 60x speedup over Hadoop and outperforms other state-of-the-art
frameworks.Comment: ScienceCloud 2012, TKDE 201
Cross-border cooperation: the meaning of cognitive and normative expectations for the emergence of Global research and development cooperation
Drawing on Niklas Luhmann's theory of social systems, we analyse the importance of different styles of expectation (cognitive and normative) for global research and development. In our study, we find that contrary to Luhmann's prediction in 1971, the normative expectation style still plays a vital role for the cooperative deals under examination. The second result of our study is that non-state mechanismus such as reputation, resource-dependency and trust are highly important for the stabilization of normative expectations in global business transactions. The role of the state-based legal system is reduced to stabilizing few, albeit crucial, normative expectations. --
A Survey of Symbolic Execution Techniques
Many security and software testing applications require checking whether
certain properties of a program hold for any possible usage scenario. For
instance, a tool for identifying software vulnerabilities may need to rule out
the existence of any backdoor to bypass a program's authentication. One
approach would be to test the program using different, possibly random inputs.
As the backdoor may only be hit for very specific program workloads, automated
exploration of the space of possible inputs is of the essence. Symbolic
execution provides an elegant solution to the problem, by systematically
exploring many possible execution paths at the same time without necessarily
requiring concrete inputs. Rather than taking on fully specified input values,
the technique abstractly represents them as symbols, resorting to constraint
solvers to construct actual instances that would cause property violations.
Symbolic execution has been incubated in dozens of tools developed over the
last four decades, leading to major practical breakthroughs in a number of
prominent software reliability applications. The goal of this survey is to
provide an overview of the main ideas, challenges, and solutions developed in
the area, distilling them for a broad audience.
The present survey has been accepted for publication at ACM Computing
Surveys. If you are considering citing this survey, we would appreciate if you
could use the following BibTeX entry: http://goo.gl/Hf5FvcComment: This is the authors pre-print copy. If you are considering citing
this survey, we would appreciate if you could use the following BibTeX entry:
http://goo.gl/Hf5Fv
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