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61-627: From its establishment in April 2001 until April 27, 2007, grid.org was the website and organization that ran distributed computing projects such as the United Devices Cancer Research Project, led by Jikku Venkat, Ph.D and was sponsored philanthropically by United Devices (UD) and members participated in volunteer computing by running the UD Agent software (version 3.0). The United Devices Cancer Research Project, which began in 2001,

122-443: A solution for each instance. Instances are questions that we can ask, and solutions are desired answers to these questions. Theoretical computer science seeks to understand which computational problems can be solved by using a computer ( computability theory ) and how efficiently ( computational complexity theory ). Traditionally, it is said that a problem can be solved by using a computer if we can design an algorithm that produces

183-447: A web content management system , so the end-user does not have to worry about the more technical aspects. Secure Sockets Layer (SSL) is used for websites that wish to encrypt the transmitted data. Internet hosting services can run web servers . The scope of web hosting services varies greatly. Some specific types of hosting provided by web host service providers: The host may also provide an interface or control panel for managing

244-474: A common goal for their work. The terms " concurrent computing ", " parallel computing ", and "distributed computing" have much overlap, and no clear distinction exists between them. The same system may be characterized both as "parallel" and "distributed"; the processors in a typical distributed system run concurrently in parallel. Parallel computing may be seen as a particularly tightly coupled form of distributed computing, and distributed computing may be seen as

305-520: A correct solution for any given instance. Such an algorithm can be implemented as a computer program that runs on a general-purpose computer: the program reads a problem instance from input , performs some computation, and produces the solution as output . Formalisms such as random-access machines or universal Turing machines can be used as abstract models of a sequential general-purpose computer executing such an algorithm. The field of concurrent and distributed computing studies similar questions in

366-412: A deadlock. This problem is PSPACE-complete , i.e., it is decidable, but not likely that there is an efficient (centralised, parallel or distributed) algorithm that solves the problem in the case of large networks. Web hosting A web hosting service is a type of Internet hosting service that hosts websites for clients, i.e. it offers the facilities required for them to create and maintain

427-500: A decision problem can be solved in polylogarithmic time by using a polynomial number of processors, then the problem is said to be in the class NC . The class NC can be defined equally well by using the PRAM formalism or Boolean circuits—PRAM machines can simulate Boolean circuits efficiently and vice versa. In the analysis of distributed algorithms, more attention is usually paid on communication operations than computational steps. Perhaps

488-430: A drug. These molecules ( ligands ) are sent to the host computer's UD Agent. When these molecules dock successfully with a target protein this interaction is scored for further investigation. The research consisted of two phases: The IBM -sponsored Human Proteome Folding Project ("HPF"), phase 1, was announced on November 16, 2004 and was completed July 3, 2006. The project operated simultaneously on both grid.org and

549-401: A loosely coupled form of parallel computing. Nevertheless, it is possible to roughly classify concurrent systems as "parallel" or "distributed" using the following criteria: The figure on the right illustrates the difference between distributed and parallel systems. Figure (a) is a schematic view of a typical distributed system; the system is represented as a network topology in which each node

610-431: A much wider sense, even referring to autonomous processes that run on the same physical computer and interact with each other by message passing. While there is no single definition of a distributed system, the following defining properties are commonly used as: A distributed system may have a common goal, such as solving a large computational problem; the user then perceives the collection of autonomous processors as

671-424: A problem is divided into many tasks, each of which is solved by one or more computers, which communicate with each other via message passing. The word distributed in terms such as "distributed system", "distributed programming", and " distributed algorithm " originally referred to computer networks where individual computers were physically distributed within some geographical area. The terms are nowadays used in

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732-488: A result, but the result was returned to grid.org for points only—it was not used for scientific research. The status of the Human Proteome Folding Project caused some discussion on the grid.org forums. Most members wanted to see all available computing power directed toward the still-active cancer project, but UD representative Robby Brewer asserted that "some [users] like the screensaver". As noted above, in

793-654: A schematic architecture allowing for live environment relay. This enables distributed computing functions both within and beyond the parameters of a networked database. Reasons for using distributed systems and distributed computing may include: Examples of distributed systems and applications of distributed computing include the following: According to Reactive Manifesto, reactive distributed systems are responsive, resilient, elastic and message-driven. Subsequently, Reactive systems are more flexible, loosely-coupled and scalable. To make your systems reactive, you are advised to implement Reactive Principles. Reactive Principles are

854-405: A sequential general-purpose computer? The discussion below focuses on the case of multiple computers, although many of the issues are the same for concurrent processes running on a single computer. Three viewpoints are commonly used: In the case of distributed algorithms, computational problems are typically related to graphs. Often the graph that describes the structure of the computer network

915-457: A set of principles and patterns which help to make your cloud native application as well as edge native applications more reactive. Many tasks that we would like to automate by using a computer are of question–answer type: we would like to ask a question and the computer should produce an answer. In theoretical computer science , such tasks are called computational problems . Formally, a computational problem consists of instances together with

976-590: A site and makes it accessible on the World Wide Web . Companies providing web hosting services are sometimes called web hosts . Typically, web hosting requires the following: Until 1991, the Internet was restricted to use only "... for research and education in the sciences and engineering   ..." and was used for email , telnet , FTP and USENET traffic—but only a tiny number of web pages. The World Wide Web protocols had only just been written and not until

1037-454: A specialized set of target molecules that targeted the smallpox virus. The partners of the project included University of Oxford , the University of Western Ontario , Memorial Sloan–Kettering Cancer Center , Essex University , Evotec OAI , Accelrys , and IBM . The World Community Grid largely began because of the success of this project. The Anthrax Research Project was a part of

1098-688: A token ring network in which the token has been lost. Coordinator election algorithms are designed to be economical in terms of total bytes transmitted, and time. The algorithm suggested by Gallager, Humblet, and Spira for general undirected graphs has had a strong impact on the design of distributed algorithms in general, and won the Dijkstra Prize for an influential paper in distributed computing. Many other algorithms were suggested for different kinds of network graphs , such as undirected rings, unidirectional rings, complete graphs, grids, directed Euler graphs, and others. A general method that decouples

1159-434: A unit. Alternatively, each computer may have its own user with individual needs, and the purpose of the distributed system is to coordinate the use of shared resources or provide communication services to the users. Other typical properties of distributed systems include the following: Here are common architectural patterns used for distributed computing: Distributed systems are groups of networked computers which share

1220-477: Is the problem instance. This is illustrated in the following example. Consider the computational problem of finding a coloring of a given graph G . Different fields might take the following approaches: While the field of parallel algorithms has a different focus than the field of distributed algorithms, there is much interaction between the two fields. For example, the Cole–Vishkin algorithm for graph coloring

1281-460: Is web page and small-scale file hosting, where files can be uploaded via File Transfer Protocol (FTP) or a web interface. The files are usually delivered to the Web "as is" or with minimal processing. Many Internet service providers (ISPs) offer this service free to subscribers. Individuals and organizations may also obtain web page hosting from alternative service providers. Free web hosting service

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1342-416: Is a computer and each line connecting the nodes is a communication link. Figure (b) shows the same distributed system in more detail: each computer has its own local memory, and information can be exchanged only by passing messages from one node to another by using the available communication links. Figure (c) shows a parallel system in which each processor has a direct access to a shared memory. The situation

1403-449: Is a field of computer science that studies distributed systems , defined as computer systems whose inter-communicating components are located on different networked computers . The components of a distributed system communicate and coordinate their actions by passing messages to one another in order to achieve a common goal. Three significant challenges of distributed systems are: maintaining concurrency of components, overcoming

1464-403: Is also focused on understanding the asynchronous nature of distributed systems: Note that in distributed systems, latency should be measured through "99th percentile" because "median" and "average" can be misleading. Coordinator election (or leader election ) is the process of designating a single process as the organizer of some task distributed among several computers (nodes). Before

1525-419: Is available in their local D-neighbourhood . Many distributed algorithms are known with the running time much smaller than D rounds, and understanding which problems can be solved by such algorithms is one of the central research questions of the field. Typically an algorithm which solves a problem in polylogarithmic time in the network size is considered efficient in this model. Another commonly used measure

1586-581: Is further complicated by the traditional uses of the terms parallel and distributed algorithm that do not quite match the above definitions of parallel and distributed systems (see below for more detailed discussion). Nevertheless, as a rule of thumb, high-performance parallel computation in a shared-memory multiprocessor uses parallel algorithms while the coordination of a large-scale distributed system uses distributed algorithms. The use of concurrent processes which communicate through message-passing has its roots in operating system architectures studied in

1647-478: Is necessary to interconnect processes running on those CPUs with some sort of communication system . Whether these CPUs share resources or not determines a first distinction between three types of architecture: Distributed programming typically falls into one of several basic architectures: client–server , three-tier , n -tier , or peer-to-peer ; or categories: loose coupling , or tight coupling . Another basic aspect of distributed computing architecture

1708-499: Is offered by different companies with limited services, sometimes supported by advertisements, and often limited when compared to paid hosting. Single page hosting is generally sufficient for personal web pages . Personal website hosting is typically free, advertisement-sponsored, or inexpensive. Business website hosting often has a higher expense depending upon the size and type of the site. Many large companies that are not Internet service providers need to be permanently connected to

1769-492: Is the method of communicating and coordinating work among concurrent processes. Through various message passing protocols, processes may communicate directly with one another, typically in a main/sub relationship. Alternatively, a "database-centric" architecture can enable distributed computing to be done without any form of direct inter-process communication , by utilizing a shared database . Database-centric architecture in particular provides relational processing analytics in

1830-410: Is the number of synchronous communication rounds required to complete the task. This complexity measure is closely related to the diameter of the network. Let D be the diameter of the network. On the one hand, any computable problem can be solved trivially in a synchronous distributed system in approximately 2 D communication rounds: simply gather all information in one location ( D rounds), solve

1891-502: Is the total number of bits transmitted in the network (cf. communication complexity ). The features of this concept are typically captured with the CONGEST(B) model, which is similarly defined as the LOCAL model, but where single messages can only contain B bits. Traditional computational problems take the perspective that the user asks a question, a computer (or a distributed system) processes

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1952-584: 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 microservices to massively multiplayer online games to peer-to-peer applications . Distributed systems cost significantly more than monolithic architectures, primarily due to increased needs for additional hardware, servers, gateways, firewalls, new subnets, proxies, and so on. Also, distributed systems are prone to fallacies of distributed computing . On

2013-400: The web server and installing scripts, as well as other modules and service applications like e-mail. A web server that does not use a control panel for managing the hosting account, is often referred to as a "headless" server. Some hosts specialize in certain software or services (e.g. e-commerce, blogs, etc.). The availability of a website is measured by the percentage of a year in which

2074-399: The "coordinator" 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 coordinator. The definition of this problem is often attributed to LeLann, who formalized it as a method to create a new token in

2135-463: The 1960s. The first widespread distributed systems were local-area networks such as Ethernet , which was invented in the 1970s. ARPANET , one of the predecessors of the Internet , was introduced in the late 1960s, and ARPANET e-mail was invented in the early 1970s. E-mail became the most successful application of ARPANET, and it is probably the earliest example of a large-scale distributed application . In addition to ARPANET (and its successor,

2196-646: The IBM's World Community Grid . It made use of the "Rosetta" software to predict the structure of human proteins in order to help predict the function of proteins. This information may someday be used to help cure a variety of diseases and genetic defects. According to an announcement on the grid.org forums, after the HPF1 project was completed it was left to continue running on grid.org until August 9, 2006. During that time, members whose computers were configured to run this project got new work and spent computing resources calculating

2257-469: The SLA is imperative. Not all providers release uptime statistics. Because web hosting services host websites belonging to their customers, online security is an important concern. When a customer agrees to use a web hosting service, they are relinquishing control of the security of their site to the company that is hosting the site. The level of security that a web hosting service offers is extremely important to

2318-581: The United Devices "Patriot Grid" initiative to fight biological terrorism. It made use of the "LigandFit" software (that had already been used by phase 2 of the Cancer Research project), but with a specialized set of target molecules that targeted the advanced stages of anthrax bacterial infection. The project was operated from January 22, 2002 until February 14, 2002 and ended after a total of 3.57 billion molecules had finished screening. The results of

2379-419: The case of either multiple computers, or a computer that executes a network of interacting processes: which computational problems can be solved in such a network and how efficiently? However, it is not at all obvious what is meant by "solving a problem" in the case of a concurrent or distributed system: for example, what is the task of the algorithm designer, and what is the concurrent or distributed equivalent of

2440-589: The client needing to own the necessary infrastructure required to operate the website. The owners of the websites, also called webmasters , would be able to create a website that would be hosted on the web hosting service's server and published to the web by the web hosting service. As the number of users on the World Wide Web grew, the pressure for companies, both large and small, to have an online presence grew. By 1995, companies such as GeoCities , Angelfire and Tripod were offering free hosting. The most basic

2501-451: The end of 1993 would there be a graphical web browser for Mac or Windows computers. Even after there was some opening up of Internet access, the situation was confused until 1995. To host a website on the internet , an individual or company would need their own computer or server . As not all companies had the budget or expertise to do this, web hosting services began to offer to host users' websites on their own servers, without

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2562-407: The end the redundant HPF1 work on grid.org was halted. The Smallpox Research Grid was a part of United Devices "Patriot Grid" initiative to fight biological terrorism. This project helped analyze potential drug candidates for a medical therapy in the fight against smallpox virus. It made use of the "LigandFit" software (that had already been used by phase 2 of the Cancer Research project), but with

2623-401: The focus has been on designing a distributed system that solves a given problem. A complementary research problem is studying the properties of a given distributed system. The halting problem is an analogous example from the field of centralised computation: we are given a computer program and the task is to decide whether it halts or runs forever. The halting problem is undecidable in

2684-452: The general case, and naturally understanding the behaviour of a computer network is at least as hard as understanding the behaviour of one computer. However, there are many interesting special cases that are decidable. In particular, it is possible to reason about the behaviour of a network of finite-state machines. One example is telling whether a given network of interacting (asynchronous and non-deterministic) finite-state machines can reach

2745-483: The global Internet), other early worldwide computer networks included Usenet and FidoNet from the 1980s, both of which were used to support distributed discussion systems. The study of distributed computing became its own branch of computer science in the late 1970s and early 1980s. The first conference in the field, Symposium on Principles of Distributed Computing (PODC), dates back to 1982, and its counterpart International Symposium on Distributed Computing (DISC)

2806-489: The infra cost must be considered. 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 the message passing mechanism, including pure HTTP, RPC-like connectors and message queues . Distributed computing also refers to the use of distributed systems to solve computational problems. In distributed computing ,

2867-456: The issue of the graph family from the design of the coordinator election algorithm was suggested by Korach, Kutten, and Moran. In order to perform coordination, distributed systems employ the concept of coordinators. The coordinator election problem is to choose a process from among a group of processes on different processors in a distributed system to act as the central coordinator. Several central coordinator election algorithms exist. So far

2928-401: The other hand, a well designed distributed system is more scalable, more durable, more changeable and more fine-tuned than a monolithic application deployed on a single machine. According to Marc Brooker: "a system is scalable in the range where marginal cost of additional workload is nearly constant." Serverless technologies fit this definition but the total cost of ownership, and not just

2989-408: The problem, and inform each node about the solution ( D rounds). On the other hand, if the running time of the algorithm is much smaller than D communication rounds, then the nodes in the network must produce their output without having the possibility to obtain information about distant parts of the network. In other words, the nodes must make globally consistent decisions based on information that

3050-629: The question, then produces an answer and stops. However, there are also problems where the system is required not to stop, including the dining philosophers problem and other similar mutual exclusion problems. In these problems, the distributed system is supposed to continuously coordinate the use of shared resources so that no conflicts or deadlocks occur. There are also fundamental challenges that are unique to distributed computing, for example those related to fault-tolerance . Examples of related problems include consensus problems , Byzantine fault tolerance , and self-stabilisation . Much research

3111-515: The research project were transmitted to biological scientists in order to finish the screening of the computational simulations. The partners of the project included Oxford University . The HMMER Genetic Research project made use of the Hidden Markov model to search for patterns in genetic DNA sequences. The Web Performance Testing project was operated as a commercial opportunity with select web hosting providers in order to help them test

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3172-403: The same place as the boundary between parallel and distributed systems (shared memory vs. message passing). In parallel algorithms, yet another resource in addition to time and space is the number of computers. Indeed, often there is a trade-off between the running time and the number of computers: the problem can be solved faster if there are more computers running in parallel (see speedup ). If

3233-607: The scalability of their server infrastructures under periods of high-demand. In November 2007, grid.org was repositioned by Univa as a community to allow users to interact and discuss open source cluster and grid related topics. It allowed users to download, get support for, contribute to, and report issues about the open source Globus Toolkit based products offered by Univa. Over 100,000 unique visitors were reported in 2008. Around mid 2010 it redirected to Unicluster.org (a Univa product) and by 2012 it redirected to Univa's main site. Distributed computing Distributed computing

3294-423: The simplest model of distributed computing is a synchronous system where all nodes operate in a lockstep fashion. This model is commonly known as the LOCAL model. During each communication round , all nodes in parallel (1) receive the latest messages from their neighbours, (2) perform arbitrary local computation, and (3) send new messages to their neighbors. In such systems, a central complexity measure

3355-465: The systems. This scheduled downtime is often excluded from the SLA timeframe, and needs to be subtracted from the Total Time when availability is calculated. Depending on the wording of an SLA, if the availability of a system drops below that in the signed SLA, a hosting provider often will provide a partial refund for time lost. How downtime is determined changes from provider to provider, therefore reading

3416-432: The task is begun, all network nodes are either unaware which node will serve as the "coordinator" (or leader) of the task, or unable to communicate with the current coordinator. After a coordinator election algorithm has been run, however, each node throughout the network recognizes a particular, unique node as the task coordinator. The network nodes communicate among themselves in order to decide which of them will get into

3477-548: The web to send email, files, etc. to other sites. The company may use the computer as a website host to provide details of their goods and services and facilities for online orders. A complex site calls for a more comprehensive package that provides database support and application development platforms (e.g. ASP.NET , ColdFusion , Java EE , Perl/Plack , PHP or Ruby on Rails ). These facilities allow customers to write or install scripts for applications like forums and content management . Web hosting packages often include

3538-470: The website is publicly accessible and reachable via the Internet. This is different from measuring the uptime of a system. Uptime refers to the system itself being online. Uptime does not take into account being able to reach it as in the event of a network outage. A hosting provider's Service Level Agreement (SLA) may include a certain amount of scheduled downtime per year in order to perform maintenance on

3599-526: Was first held in Ottawa in 1985 as the International Workshop on Distributed Algorithms on Graphs. Various hardware and software architectures are used for distributed computing. At a lower level, it is necessary to interconnect multiple CPUs with some sort of network, regardless of whether that network is printed onto a circuit board or made up of loosely coupled devices and cables. At a higher level, it

3660-423: Was originally presented as a parallel algorithm, but the same technique can also be used directly as a distributed algorithm. Moreover, a parallel algorithm can be implemented either in a parallel system (using shared memory) or in a distributed system (using message passing). The traditional boundary between parallel and distributed algorithms (choose a suitable network vs. run in any given network) does not lie in

3721-668: Was seeking possible drugs for the treatment of cancer using distributed computing . There were around 150,000 users in the United States and 170,000 in Europe along with hundreds of thousands more in other parts of the world. The project was an alliance of several companies and organisations: United Devices released the cancer research screensaver under the principle of using spare computing power. The program, which could be set to run continually, used "virtual screening" to find possible interactions between molecules and target proteins, i.e.

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