Models
Many tasks that we would like to automate by application a computer are of question–answer type: we would like to ask a catechism and the computer should aftermath an answer. In abstruse computer science, such tasks are alleged computational problems. Formally, a computational botheration consists of instances calm with a band-aid for anniversary instance. Instances are questions that we can ask, and solutions are adapted answers to these questions.
Theoretical computer science seeks to accept which computational problems can be apparent by application a computer (computability theory) and how calmly (computational complication theory). Traditionally, it is said that a botheration can be apparent by application a computer if we can architecture an algorithm that produces a actual band-aid for any accustomed instance. Such an algorithm can be implemented as a computer affairs that runs on a general-purpose computer: the affairs reads a botheration instance from input, performs some computation, and produces the band-aid as output. Formalisms such as accidental admission machines or accepted Turing machines can be acclimated as abstruse models of a consecutive general-purpose computer active such an algorithm.
The acreage of circumstantial and broadcast accretion studies agnate questions in the case of either assorted computers, or a computer that executes a arrangement of interacting processes: which computational problems can be apparent in such a arrangement and how efficiently? However, it is not at all accessible what is meant by “solving a problem” in the case of a circumstantial or broadcast system: for example, what is the assignment of the algorithm designer, and what is the circumstantial or broadcast agnate of a consecutive general-purpose computer?
The altercation beneath focusses on the case of assorted computers, although abounding of the issues are the aforementioned for circumstantial processes active on a distinct computer.
Three viewpoints are frequently used:
Parallel algorithms in shared-memory model
All computers accept admission to a aggregate memory. The algorithm artist chooses the affairs accomplished by anniversary computer.
One abstruse archetypal is the alongside accidental admission machines (PRAM) that are used.23 However, the classical PRAM archetypal assumes ancillary admission to the aggregate memory.
A archetypal that is afterpiece to the behavior of real-world multiprocessor machines and takes into annual the use of apparatus instructions, such as Compare-and-swap (CAS), is that of asynchronous aggregate memory. There is a advanced anatomy of assignment on this model, a arbitrary of which can be begin in the literature.2425
Parallel algorithms in message-passing model
The algorithm artist chooses the anatomy of the network, as able-bodied as the affairs accomplished by anniversary computer.
Models such as Boolean circuits and allocation networks are used.26 A Boolean ambit can be apparent as a computer network: anniversary aboideau is a computer that runs an acutely simple computer program. Similarly, a allocation arrangement can be apparent as a computer network: anniversary comparator is a computer.
Distributed algorithms in message-passing model
The algorithm artist alone chooses the computer program. All computers run the aforementioned program. The arrangement charge assignment accurately behindhand of the anatomy of the network.
A frequently acclimated archetypal is a blueprint with one finite-state apparatus per node.
In the case of broadcast algorithms, computational problems are about accompanying to graphs. Often the blueprint that describes the anatomy of the computer arrangement is the botheration instance. This is illustrated in the afterward example.
edit An example
Consider the computational botheration of award a appearance of a accustomed blueprint G. Different fields ability booty the afterward approaches:
Centralized algorithms
The blueprint G is encoded as a string, and the cord is accustomed as ascribe to a computer. The computer affairs finds a appearance of the graph, encodes the appearance as a string, and outputs the result.
Parallel algorithms
Again, the blueprint G is encoded as a string. However, assorted computers can admission the aforementioned cord in parallel. Anniversary computer ability focus on one allotment of the blueprint and aftermath a colouring for that part.
The capital focus is on high-performance ciphering that exploits the processing ability of assorted computers in parallel.
Many tasks that we would like to automate by application a computer are of question–answer type: we would like to ask a catechism and the computer should aftermath an answer. In abstruse computer science, such tasks are alleged computational problems. Formally, a computational botheration consists of instances calm with a band-aid for anniversary instance. Instances are questions that we can ask, and solutions are adapted answers to these questions.
Theoretical computer science seeks to accept which computational problems can be apparent by application a computer (computability theory) and how calmly (computational complication theory). Traditionally, it is said that a botheration can be apparent by application a computer if we can architecture an algorithm that produces a actual band-aid for any accustomed instance. Such an algorithm can be implemented as a computer affairs that runs on a general-purpose computer: the affairs reads a botheration instance from input, performs some computation, and produces the band-aid as output. Formalisms such as accidental admission machines or accepted Turing machines can be acclimated as abstruse models of a consecutive general-purpose computer active such an algorithm.
The acreage of circumstantial and broadcast accretion studies agnate questions in the case of either assorted computers, or a computer that executes a arrangement of interacting processes: which computational problems can be apparent in such a arrangement and how efficiently? However, it is not at all accessible what is meant by “solving a problem” in the case of a circumstantial or broadcast system: for example, what is the assignment of the algorithm designer, and what is the circumstantial or broadcast agnate of a consecutive general-purpose computer?
The altercation beneath focusses on the case of assorted computers, although abounding of the issues are the aforementioned for circumstantial processes active on a distinct computer.
Three viewpoints are frequently used:
Parallel algorithms in shared-memory model
All computers accept admission to a aggregate memory. The algorithm artist chooses the affairs accomplished by anniversary computer.
One abstruse archetypal is the alongside accidental admission machines (PRAM) that are used.23 However, the classical PRAM archetypal assumes ancillary admission to the aggregate memory.
A archetypal that is afterpiece to the behavior of real-world multiprocessor machines and takes into annual the use of apparatus instructions, such as Compare-and-swap (CAS), is that of asynchronous aggregate memory. There is a advanced anatomy of assignment on this model, a arbitrary of which can be begin in the literature.2425
Parallel algorithms in message-passing model
The algorithm artist chooses the anatomy of the network, as able-bodied as the affairs accomplished by anniversary computer.
Models such as Boolean circuits and allocation networks are used.26 A Boolean ambit can be apparent as a computer network: anniversary aboideau is a computer that runs an acutely simple computer program. Similarly, a allocation arrangement can be apparent as a computer network: anniversary comparator is a computer.
Distributed algorithms in message-passing model
The algorithm artist alone chooses the computer program. All computers run the aforementioned program. The arrangement charge assignment accurately behindhand of the anatomy of the network.
A frequently acclimated archetypal is a blueprint with one finite-state apparatus per node.
In the case of broadcast algorithms, computational problems are about accompanying to graphs. Often the blueprint that describes the anatomy of the computer arrangement is the botheration instance. This is illustrated in the afterward example.
edit An example
Consider the computational botheration of award a appearance of a accustomed blueprint G. Different fields ability booty the afterward approaches:
Centralized algorithms
The blueprint G is encoded as a string, and the cord is accustomed as ascribe to a computer. The computer affairs finds a appearance of the graph, encodes the appearance as a string, and outputs the result.
Parallel algorithms
Again, the blueprint G is encoded as a string. However, assorted computers can admission the aforementioned cord in parallel. Anniversary computer ability focus on one allotment of the blueprint and aftermath a colouring for that part.
The capital focus is on high-performance ciphering that exploits the processing ability of assorted computers in parallel.
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