1,876,212 research outputs found
Dynamic Sampling from a Discrete Probability Distribution with a Known Distribution of Rates
In this paper, we consider a number of efficient data structures for the
problem of sampling from a dynamically changing discrete probability
distribution, where some prior information is known on the distribution of the
rates, in particular the maximum and minimum rate, and where the number of
possible outcomes N is large.
We consider three basic data structures, the Acceptance-Rejection method, the
Complete Binary Tree and the Alias Method. These can be used as building blocks
in a multi-level data structure, where at each of the levels, one of the basic
data structures can be used.
Depending on assumptions on the distribution of the rates of outcomes,
different combinations of the basic structures can be used. We prove that for
particular data structures the expected time of sampling and update is
constant, when the rates follow a non-decreasing distribution, log-uniform
distribution or an inverse polynomial distribution, and show that for any
distribution, an expected time of sampling and update of
is possible, where is the
maximum rate and the minimum rate.
We also present an experimental verification, highlighting the limits given
by the constraints of a real-life setting
Geocoded data structures and their applications to Earth science investigations
A geocoded data structure is a means for digitally representing a geographically referenced map or image. The characteristics of representative cellular, linked, and hybrid geocoded data structures are reviewed. The data processing requirements of Earth science projects at the Goddard Space Flight Center and the basic tools of geographic data processing are described. Specific ways that new geocoded data structures can be used to adapt these tools to scientists' needs are presented. These include: expanding analysis and modeling capabilities; simplifying the merging of data sets from diverse sources; and saving computer storage space
Maximum Likelihood Estimation with Emphasis on Aircraft Flight Data
Accurate modeling of flexible space structures is an important field that is currently under investigation. Parameter estimation, using methods such as maximum likelihood, is one of the ways that the model can be improved. The maximum likelihood estimator has been used to extract stability and control derivatives from flight data for many years. Most of the literature on aircraft estimation concentrates on new developments and applications, assuming familiarity with basic estimation concepts. Some of these basic concepts are presented. The maximum likelihood estimator and the aircraft equations of motion that the estimator uses are briefly discussed. The basic concepts of minimization and estimation are examined for a simple computed aircraft example. The cost functions that are to be minimized during estimation are defined and discussed. Graphic representations of the cost functions are given to help illustrate the minimization process. Finally, the basic concepts are generalized, and estimation from flight data is discussed. Specific examples of estimation of structural dynamics are included. Some of the major conclusions for the computed example are also developed for the analysis of flight data
Programming an interpreter using molecular dynamics
PGA (ProGram Algebra) is an algebra of programs which concerns programs in
their simplest form: sequences of instructions. Molecular dynamics is a simple
model of computation developed in the setting of PGA, which bears on the use of
dynamic data structures in programming. We consider the programming of an
interpreter for a program notation that is close to existing assembly languages
using PGA with the primitives of molecular dynamics as basic instructions. It
happens that, although primarily meant for explaining programming language
features relating to the use of dynamic data structures, the collection of
primitives of molecular dynamics in itself is suited to our programming wants.Comment: 27 page
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