Editing Simulation (section)

==Computer simulation==
{{main|Computer simulation}}
A computer simulation (or "sim") is an attempt to model a real-life or hypothetical situation on a computer so that it can be studied to see how the system works. By changing variables in the simulation, [[prediction]]s may be made about the behaviour of the system. It is a tool to virtually investigate the behaviour of the system under study.<ref name="definition"/>

Computer simulation has become a useful part of [[model (abstract)|modeling]] many natural systems in [[physics]], [[chemistry]] and [[biology]],<ref>For a popular research project in the field of [[biochemistry]] where "computer simulation is particularly well suited to address these questions"[http://folding.stanford.edu/Pande/Main Folding@home – Main] {{Webarchive|url=https://web.archive.org/web/20080306100315/http://folding.stanford.edu/Pande/Main |date=6 March 2008 }}, see [[Folding@Home]].</ref> and human systems in economics and [[social science]] (e.g., [[computational sociology]]) as well as in engineering to gain insight into the operation of those systems. A good example of the usefulness of using computers to simulate can be found in the field of [[network traffic simulation]]. In such simulations, the [[model (abstract)|model]] behaviour will change each simulation according to the set of initial parameters assumed for the environment.

Traditionally, the formal modeling of systems has been via a [[mathematical model]], which attempts to find analytical solutions enabling the prediction of the behaviour of the system from a set of parameters and initial conditions. Computer simulation is often used as an adjunct to, or substitution for, modeling systems for which simple [[closed-form solution|closed form analytic solutions]] are not possible. There are many different types of computer simulation, the common feature they all share is the attempt to generate a sample of representative [[scenario]]s for a model in which a complete enumeration of all possible states would be prohibitive or impossible.

Several software packages exist for running computer-based simulation modeling (e.g. [[Monte Carlo method|Monte Carlo]] simulation, [[stochastic]] modeling, multimethod modeling) that makes all the modeling almost effortless.

Modern usage of the term "computer simulation" may encompass virtually any computer-based representation.

===Computer science===
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In [[computer science]], simulation has some specialized meanings: [[Alan Turing]] used the term ''simulation'' to refer to what happens when a [[Universal Turing machine|universal machine]] executes a state transition table (in modern terminology, a computer runs a program) that describes the state transitions, inputs and outputs of a subject discrete-state machine.<ref>{{cite web|url=https://web.mit.edu/manoli/turing/www/turing.html|title=Universal Turing Machine|website=web.mit.edu|access-date=18 December 2019}}</ref> The computer simulates the subject machine. Accordingly, in [[theoretical computer science]] the term ''[[simulation preorder|simulation]]'' is a relation between [[state transition system]]s, useful in the study of [[operational semantics]].

Less theoretically, an interesting application of computer simulation is to simulate computers using computers. In [[computer architecture]], a type of simulator, typically called an ''[[emulator]]'', is often used to execute a program that has to run on some inconvenient type of computer (for example, a newly designed computer that has not yet been built or an obsolete computer that is no longer available), or in a tightly controlled testing environment (see [[Computer architecture simulator]] and [[Platform virtualization]]). For example, simulators have been used to debug a [[microprogram]] or sometimes commercial application programs, before the program is downloaded to the target machine. Since the operation of the computer is simulated, all of the information about the computer's operation is directly available to the programmer, and the speed and execution of the simulation can be varied at will.

Simulators may also be used to interpret [[fault tree]]s, or test [[Very Large Scale Integration|VLSI]] logic designs before they are constructed. [[Symbolic simulation]] uses variables to stand for unknown values.

In the field of [[Optimization (mathematics)|optimization]], simulations of physical processes are often used in conjunction with [[evolutionary computation]] to optimize control strategies.