• Source: Model of computation

In computer science, and more specifically in computability theory and computational complexity theory, a model of computation is a model which describes how an output of a mathematical function is computed given an input. A model describes how units of computations, memories, and communications are organized. The computational complexity of an algorithm can be measured given a model of computation. Using a model allows studying the performance of algorithms independently of the variations that are specific to particular implementations and specific technology.




Models


Models of computation can be classified into three categories: sequential models, functional models, and concurrent models.




= Sequential models

=
Sequential models include:

Finite state machines
Post machines (Post–Turing machines and tag machines).
Pushdown automata
Register machines
Random-access machines
Turing machines
Decision tree model




= Functional models

=
Functional models include:

Abstract rewriting systems
Combinatory logic
General recursive functions
Lambda calculus




= Concurrent models

=
Concurrent models include:

Actor model
Cellular automaton
Interaction nets
Kahn process networks
Logic gates and digital circuits
Petri nets
Process calculus
Synchronous Data Flow
Some of these models have both deterministic and nondeterministic variants. Nondeterministic models correspond to limits of certain sequences of finite computers, but do not correspond to any subset of finite computers; they are used in the study of computational complexity of algorithms.
Models differ in their expressive power; for example, each function that can be computed by a Finite state machine can also be computed by a Turing machine, but not vice versa.




Uses


In the field of runtime analysis of algorithms, it is common to specify a computational model in terms of primitive operations allowed which have unit cost, or simply unit-cost operations. A commonly used example is the random-access machine, which has unit cost for read and write access to all of its memory cells. In this respect, it differs from the above-mentioned Turing machine model.




See also


Stack machine (0-operand machine)
Accumulator machine (1-operand machine)
Register machine (2,3,... operand machine)
Random-access machine
Abstract machine
Cell-probe model
Robertson–Webb query model
Chomsky hierarchy
Turing completeness




References






Further reading


Fernández, Maribel (2009). Models of Computation: An Introduction to Computability Theory. Undergraduate Topics in Computer Science. Springer. ISBN 978-1-84882-433-1.
Savage, John E. (1998). Models Of Computation: Exploring the Power of Computing. Addison-Wesley. ISBN 978-0201895391.

Kata Kunci Pencarian:

• Teori komputasi
• Mesin Turing
• James Joseph Heckman
• Jaringan saraf tiruan
• Relasi finiter
• Model komputasi saraf
• Penalaran abduktif
• Astronomi Babilonia
• Mesin finite-state
• Ponsel cerdas
• Model of computation
• Computational model
• Theory of computation
• Computational complexity
• Nondeterministic Turing machine
• Computation
• Actor model
• Real computation
• Computational neuroscience
• Computability