Editing Parallel computing (section)

=====Cluster computing=====
{{main|Computer cluster}}

[[File:Beowulf.jpg|right|thumbnail|upright|A [[Beowulf (computing)|Beowulf cluster]]]]

A cluster is a group of loosely coupled computers that work together closely, so that in some respects they can be regarded as a single computer.<ref>[http://www.webopedia.com/TERM/c/clustering.html What is clustering?] Webopedia computer dictionary. Retrieved on November 7, 2007.</ref> Clusters are composed of multiple standalone machines connected by a network. While machines in a cluster do not have to be symmetric, [[Load balancing (computing)|load balancing]] is more difficult if they are not. The most common type of cluster is the [[Beowulf (computing)|Beowulf cluster]], which is a cluster implemented on multiple identical [[commercial off-the-shelf]] computers connected with a [[TCP/IP]] [[Ethernet]] [[local area network]].<ref>[https://www.pcmag.com/encyclopedia_term/0,2542,t=Beowulf&i=38548,00.asp Beowulf definition.] {{Webarchive|url=https://web.archive.org/web/20121010215231/https://www.pcmag.com/encyclopedia_term/0%2C2542%2Ct%3DBeowulf%26i%3D38548%2C00.asp |date=2012-10-10 }} ''PC Magazine''. Retrieved on November 7, 2007.</ref> Beowulf technology was originally developed by [[Thomas Sterling (computing)|Thomas Sterling]] and [[Donald Becker]]. 87% of all [[TOP500|Top500]] supercomputers are clusters.<ref>{{Cite web|url=https://www.top500.org/statistics/list/|title=List Statistics {{!}} TOP500 Supercomputer Sites|website=www.top500.org|language=en|access-date=2018-08-05}}</ref> The remaining are Massively Parallel Processors, explained below.

Because grid computing systems (described below) can easily handle embarrassingly parallel problems, modern clusters are typically designed to handle more difficult problems—problems that require nodes to share intermediate results with each other more often. This requires a high bandwidth and, more importantly, a low-[[latency (engineering)|latency]] interconnection network. Many historic and current supercomputers use customized high-performance network hardware specifically designed for cluster computing, such as the Cray Gemini network.<ref>[https://www.nersc.gov/users/computational-systems/hopper/configuration/interconnect/ "Interconnect"] {{webarchive|url=https://web.archive.org/web/20150128133120/https://www.nersc.gov/users/computational-systems/hopper/configuration/interconnect/ |date=2015-01-28 }}.</ref> As of 2014, most current supercomputers use some off-the-shelf standard network hardware, often [[Myrinet]], [[InfiniBand]], or [[Gigabit Ethernet]].