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Chang And Roberts Algorithm
The Chang and Roberts algorithm is a ring-based coordinator election algorithm, employed in distributed computing. The algorithm The algorithm assumes that each process has a Unique Identification (UID) and that the processes can arrange themselves in a unidirectional ring with a communication channel going from each process to the clockwise neighbour. The two part algorithm can be described as follows: # Initially each process in the ring is marked as ''non-participant''. # A process that notices a lack of leader starts an election. It creates an ''election message'' containing its UID. It then sends this message clockwise to its neighbour. # Every time a process sends or forwards an ''election message'', the process also marks itself as a participant. # When a process receives an ''election message'' it compares the UID in the message with its own UID. ## If the UID in the election message is larger, the process unconditionally forwards the ''election message'' in a clockw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ring Network
A ring network is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node – a ring. Data travels from node to node, with each node along the way handling every packet. Rings can be unidirectional, with all traffic travelling either clockwise or anticlockwise around the ring, or bidirectional (as in Synchronous optical networking, SONET/SDH). Because a unidirectional ring topology provides only one pathway between any two nodes, unidirectional ring networks may be disrupted by the failure of a single link. A node failure or cable break might isolate every node attached to the ring. In response, some ring networks add a "counter-rotating ring" (C-Ring) to form a redundant topology: in the event of a break, data are wrapped back onto the complementary ring before reaching the end of the cable, maintaining a path to every node along the resulting C-Ring. Such "dual ring" networks include the ITU-T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leader Election
In distributed computing, leader election is the process of designating a single process as the organizer of some task distributed among several computers (nodes). Before the task has begun, all network nodes are either unaware which node will serve as the "leader" (or coordinator) of the task, or unable to communicate with the current coordinator. After a leader election algorithm has been run, however, each node throughout the network recognizes a particular, unique node as the task leader. The network nodes communicate among themselves in order to decide which of them will get into the "leader" state. For that, they need some method in order to break the symmetry among them. For example, if each node has unique and comparable identities, then the nodes can compare their identities, and decide that the node with the highest identity is the leader. The definition of this problem is often attributed to LeLann, who formalized it as a method to create a new token in a token ring net ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Computing
A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer science that studies distributed systems. The components of a distributed system interact with one another in order to achieve a common goal. Three significant challenges of distributed systems are: maintaining concurrency of components, overcoming the lack of a global clock, and managing the independent failure of components. When a component of one system fails, the entire system does not fail. Examples of distributed systems vary from SOA-based systems to massively multiplayer online games to peer-to-peer applications. A computer program that runs within a distributed system is called a distributed program, and ''distributed programming'' is the process of writing such programs. There are many different types of implementations for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Safety And Liveness Properties
Properties of an execution of a computer program —particularly for concurrent and distributed systems— have long been formulated by giving ''safety properties'' ("bad things don't happen") and ''liveness properties'' ("good things do happen"). A simple example will illustrate safety and liveness. A program is totally correct with respect to a precondition P and postcondition Q if any execution started in a state satisfying P terminates in a state satisfying Q. Total correctness is a conjunction of a safety property and a liveness property: * The safety property prohibits these "bad things": executions that start in a state satisfying P and terminate in a final state that does not satisfy Q. For a program C, this safety property is usually written using the Hoare triple \ C \. * The liveness property, the "good thing", is that execution that starts in a state satisfying P terminates. Note that a ''bad thing'' is discrete, since it happens at a particular place during execution. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Distributed Computing
A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer science that studies distributed systems. The components of a distributed system interact with one another in order to achieve a common goal. Three significant challenges of distributed systems are: maintaining concurrency of components, overcoming the lack of a global clock, and managing the independent failure of components. When a component of one system fails, the entire system does not fail. Examples of distributed systems vary from SOA-based systems to massively multiplayer online games to peer-to-peer applications. A computer program that runs within a distributed system is called a distributed program, and ''distributed programming'' is the process of writing such programs. There are many different types of implementations for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Leader Election
In distributed computing, leader election is the process of designating a single process as the organizer of some task distributed among several computers (nodes). Before the task has begun, all network nodes are either unaware which node will serve as the "leader" (or coordinator) of the task, or unable to communicate with the current coordinator. After a leader election algorithm has been run, however, each node throughout the network recognizes a particular, unique node as the task leader. The network nodes communicate among themselves in order to decide which of them will get into the "leader" state. For that, they need some method in order to break the symmetry among them. For example, if each node has unique and comparable identities, then the nodes can compare their identities, and decide that the node with the highest identity is the leader. The definition of this problem is often attributed to LeLann, who formalized it as a method to create a new token in a token ring net ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bully Algorithm
In distributed computing, the bully algorithm is a method for dynamically electing a coordinator or leader from a group of distributed computer processes. The process with the highest process ID number from amongst the non-failed processes is selected as the coordinator. Assumptions The algorithm assumes that: * the system is synchronous. * processes may fail at any time, including during execution of the algorithm. * a process fails by stopping and returns from failure by restarting. * there is a failure detector which detects failed processes. * message delivery between processes is reliable. * each process knows its own process id and address, and that of every other process. Algorithm The algorithm uses the following message types: * Election Message: Sent to announce election. * Answer (Alive) Message: Responds to the Election message. * Coordinator (Victory) Message: Sent by winner of the election to announce victory. When a process recovers from failure, or the failure d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
HS Algorithm
HS or Hs can stand for: Businesses and brands * HS Produkt, a Croatian firearms manufacturer * ''Helsingin Sanomat'', a newspaper in Finland * Hawker Siddeley, aircraft manufacturing group * Henschel & Son, in aircraft prefixes; e.g., Hs 117 * Head & Shoulders or H&S, a shampoo brand * Harris Scarfe and HS Home, a chain of Australian department stores Science and technology Chemistry * Hassium, symbol Hs, a chemical element * Bisulfide, HS−, a chemical compound derived from H2S * Mercapto radical, •, a radical molecule * Hun stuff (a World War I name for mustard gas) Medicine * hs, medical abbreviation for "hours of sleep" * '' h.s.'', medical abbreviation for the Latin phrase ''hora somni'' ("at bedtime") * Hereditary spherocytosis, a genetic disorder marked by hemolytic anemia * Hidradenitis suppurativa, a skin condition affecting apocrine sweat glands and hair follicles Other uses in science and technology * '.hs', the Haskell programming language's typical filename ex ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
