Model of computation

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For another meaning, see Computer model.

In computability theory and computational complexity theory, a model of computation is the definition of the set of allowable operations used in computation and their respective costs. Only assuming a certain model of computation is it possible to analyze the computational resources required, such as the execution time or memory space or to discuss the limitations of algorithms or computers.

In model-driven engineering, the model of computation explains how the behaviour of the whole system is the result of the behaviour of each of its components.

In discussing asymptotic estimates of computational complexity, it is common to specify a computational model in terms of primitive operations allowed which have unit cost, or simply unit-cost operations.

There are many models of computation, differing in the set of admissible operations and their computations cost. They fall into the following broad categories: abstract machine (abstract computer), used in proofs of computability and upper bounds on computational complexity of algorithms, and decision tree models, used in proofs of lower bounds on computational complexity of algorithmic problems.