In computer science, computational learning theory (or just learning theory) is a subfield of artificial intelligence devoted to studying the design and analysis of machine learning algorithms.

Overview

Theoretical results in machine learning mainly deal with a type of inductive learning called supervised learning. In supervised learning, an algorithm is given samples that are labeled in some useful way. For example, the samples might be descriptions of mushrooms, and the labels could be whether or not the mushrooms are edible. The algorithm takes these previously labeled samples and uses them to induce a classifier. This classifier is a function that assigns labels to samples, including samples that have not been seen previously by the algorithm. The goal of the supervised learning algorithm is to optimise some measure of performance such as minimising the number of mistakes made on new samples.

In addition to performance bounds, computational learning theory studies the time complexity and feasibility of learning.[ citation needed ] In computational learning theory, a computation is considered feasible if it can be done in polynomial time.[ citation needed ] There are two kinds of time complexity results:

  • Positive results – Showing that a certain class of functions is learnable in polynomial time.
  • Negative results – Showing that certain classes cannot be learned in polynomial time.

Negative results often rely on commonly believed, but yet unproven assumptions,[ citation needed ] such as:

  • Computational complexity – P ≠ NP (the P versus NP problem);
  • CryptographicOne-way functions exist.

There are several different approaches to computational learning theory. These differences are based on making assumptions about the inference principles used to generalize from limited data.[ citation needed ] This includes different definitions of probability (see frequency probability, Bayesian probability) and different assumptions on the generation of samples.[ citation needed ] The different approaches include:[ citation needed ]

  • Exact learning, proposed by Dana Angluin;
  • Probably approximately correct learning (PAC learning), proposed by Leslie Valiant;
  • VC theory, proposed by Vladimir Vapnik and Alexey Chervonenkis;
  • Bayesian inference;
  • Algorithmic learning theory, from the work of E. Mark Gold;
  • Online machine learning, from the work of Nick Littlestone.

Computational learning theory has led to several practical algorithms.[ according to whom? ] For example, PAC theory inspired boosting, VC theory led to support vector machines, and Bayesian inference led to belief networks (by Judea Pearl).

Surveys

VC dimension

    Feature selection

      Inductive inference

        Optimal O notation learning

          Negative results

            Boosting (machine learning)

              Occam Learning

              Probably approximately correct learning

                Error tolerance

                Equivalence

                • D.Haussler, M.Kearns, N.Littlestone and M. Warmuth, Equivalence of models for polynomial learnability, Proc. 1st ACM Workshop on Computational Learning Theory, (1988) 42-55.

                A description of some of these publications is given at important publications in machine learning.

                Distribution Learning Theory


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