Halting Problem
The problem of determining if a program halts or doesn't halt on
a particular input. This is an incomputable problem.
Halting Set
The recursively enumerable set of Gödel numbers that
correspond to programs that halt if given their own Gödel
number as input.
Hebbian Learning
A rule that specifies that the strength of a synapse between two
neurons should be proportional to the product of the activations
of the two neurons.
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Hénon Map
A chaotic system (defined by the two equations x(t+1) = a
- x(t)^2 + b y(t) and y(t+1) = x(t)) that has a fractal
strange attractor and operates in discrete time.
Hidden Layer
In a feedforward or recurrent neural network, a layer
of neurons that is neither the input layer nor the output layer
but is physically between the two.
Hill-Climbing
One of the simplest search methods that attempts to find a
local maximum by moving in an uphill direction. It is related
to steepest ascent. Hill-climbing may use gradient
information, or random sampling of nearby points, in order to
estimate the uphill direction.
Holism
The idea that ``the whole is greater than the sum of the parts.''
Holism is credible on the basis of emergence alone, since
reductionism and bottom-up descriptions of nature often fail
to predict complex higher-level patterns. See also top-down.
Hopfield Network
A type of feedback neural network that is often used as an
associative memory or as a solution to a combinatorial
optimization problem.
