164 research outputs found
Information-theoretic Feature Selection via Tensor Decomposition and Submodularity
Feature selection by maximizing high-order mutual information between the
selected feature vector and a target variable is the gold standard in terms of
selecting the best subset of relevant features that maximizes the performance
of prediction models. However, such an approach typically requires knowledge of
the multivariate probability distribution of all features and the target, and
involves a challenging combinatorial optimization problem. Recent work has
shown that any joint Probability Mass Function (PMF) can be represented as a
naive Bayes model, via Canonical Polyadic (tensor rank) Decomposition. In this
paper, we introduce a low-rank tensor model of the joint PMF of all variables
and indirect targeting as a way of mitigating complexity and maximizing the
classification performance for a given number of features. Through low-rank
modeling of the joint PMF, it is possible to circumvent the curse of
dimensionality by learning principal components of the joint distribution. By
indirectly aiming to predict the latent variable of the naive Bayes model
instead of the original target variable, it is possible to formulate the
feature selection problem as maximization of a monotone submodular function
subject to a cardinality constraint - which can be tackled using a greedy
algorithm that comes with performance guarantees. Numerical experiments with
several standard datasets suggest that the proposed approach compares favorably
to the state-of-art for this important problem
A decomposition method for global evaluation of Shannon entropy and local estimations of algorithmic complexity
We investigate the properties of a Block Decomposition Method (BDM), which extends the power of a Coding Theorem Method (CTM) that approximates local estimations of algorithmic complexity based on Solomonoff–Levin’s theory of algorithmic probability providing a closer connection to algorithmic complexity than previous attempts based on statistical regularities such as popular lossless compression schemes. The strategy behind BDM is to find small computer programs that produce the components of a larger, decomposed object. The set of short computer programs can then be artfully arranged in sequence so as to produce the original object. We show that the method provides efficient estimations of algorithmic complexity but that it performs like Shannon entropy when it loses accuracy. We estimate errors and study the behaviour of BDM for different boundary conditions, all of which are compared and assessed in detail. The measure may be adapted for use with more multi-dimensional objects than strings, objects such as arrays and tensors. To test the measure we demonstrate the power of CTM on low algorithmic-randomness objects that are assigned maximal entropy (e.g., π) but whose numerical approximations are closer to the theoretical low algorithmic-randomness expectation. We also test the measure on larger objects including dual, isomorphic and cospectral graphs for which we know that algorithmic randomness is low. We also release implementations of the methods in most major programming languages—Wolfram Language (Mathematica), Matlab, R, Perl, Python, Pascal, C++, and Haskell—and an online algorithmic complexity calculator.Swedish Research Council (Vetenskapsrådet
A decomposition method for global evaluation of Shannon entropy and local estimations of algorithmic complexity
We investigate the properties of a Block Decomposition Method (BDM), which extends the power of a Coding Theorem Method (CTM) that approximates local estimations of algorithmic complexity based on Solomonoff–Levin’s theory of algorithmic probability providing a closer connection to algorithmic complexity than previous attempts based on statistical regularities such as popular lossless compression schemes. The strategy behind BDM is to find small computer programs that produce the components of a larger, decomposed object. The set of short computer programs can then be artfully arranged in sequence so as to produce the original object. We show that the method provides efficient estimations of algorithmic complexity but that it performs like Shannon entropy when it loses accuracy. We estimate errors and study the behaviour of BDM for different boundary conditions, all of which are compared and assessed in detail. The measure may be adapted for use with more multi-dimensional objects than strings, objects such as arrays and tensors. To test the measure we demonstrate the power of CTM on low algorithmic-randomness objects that are assigned maximal entropy (e.g., π) but whose numerical approximations are closer to the theoretical low algorithmic-randomness expectation. We also test the measure on larger objects including dual, isomorphic and cospectral graphs for which we know that algorithmic randomness is low. We also release implementations of the methods in most major programming languages—Wolfram Language (Mathematica), Matlab, R, Perl, Python, Pascal, C++, and Haskell—and an online algorithmic complexity calculator.Swedish Research Council (Vetenskapsrådet
Nonlinear System Identification via Tensor Completion
Function approximation from input and output data pairs constitutes a
fundamental problem in supervised learning. Deep neural networks are currently
the most popular method for learning to mimic the input-output relationship of
a general nonlinear system, as they have proven to be very effective in
approximating complex highly nonlinear functions. In this work, we show that
identifying a general nonlinear function from
input-output examples can be formulated as a tensor completion problem and
under certain conditions provably correct nonlinear system identification is
possible. Specifically, we model the interactions between the input
variables and the scalar output of a system by a single -way tensor, and
setup a weighted low-rank tensor completion problem with smoothness
regularization which we tackle using a block coordinate descent algorithm. We
extend our method to the multi-output setting and the case of partially
observed data, which cannot be readily handled by neural networks. Finally, we
demonstrate the effectiveness of the approach using several regression tasks
including some standard benchmarks and a challenging student grade prediction
task.Comment: AAAI 202
Algebraic Methods in Computational Complexity
Computational Complexity is concerned with the resources that are required for algorithms to detect properties of combinatorial objects and structures. It has often proven true that the best way to argue about these combinatorial objects is by establishing a connection (perhaps approximate) to a more well-behaved algebraic setting. Indeed, many of the deepest and most powerful results in Computational Complexity rely on algebraic proof techniques. The Razborov-Smolensky polynomial-approximation method for proving constant-depth circuit lower bounds, the PCP characterization of NP, and the Agrawal-Kayal-Saxena polynomial-time primality test
are some of the most prominent examples. In some of the most exciting recent progress in Computational Complexity the algebraic theme still plays a central role. There have been significant recent advances in algebraic circuit lower bounds, and the so-called chasm at depth 4 suggests that the restricted models now being considered are not so far from ones that would lead to a general result. There have been similar successes concerning the related problems of polynomial identity testing and circuit reconstruction in the algebraic model (and these are tied to central questions regarding the power of randomness in computation). Also the areas of derandomization and coding theory have experimented important advances. The seminar aimed to capitalize on recent progress and bring together researchers who are using a diverse array of algebraic methods in a variety of settings. Researchers in these areas are relying on ever more sophisticated and specialized mathematics and the goal of the seminar was to play an important role in educating a diverse community about the latest new techniques
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