Node

the fundamental unit in [|graph theory] and, applied to [|computer science], basic unit to structure and link devices of a [|network] as well as data, such as items of a linked list or [|tree structure]. This page is about the **node** of the search tree in the game of chess, which represents the alternating white and black to move positions and keeps its state dependent on the [|tree traversal]. Inside a depth-first search, nodes are usually counted at top of the recursive search routine, i.e. for the purpose to determine nodes per second. The move is the [|directed edge] which connects an ordered pair of nodes or positions.
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 * [[image:Bonatti-caput_et_cauda_draconis.jpg link="https://commons.wikimedia.org/wiki/File:Bonatti-caput_et_cauda_draconis.PNG"]] ||~  || **Node**, ([|vertex])

Nodes are classified by their topological properties inside the search tree, and in context of alpha-beta and its enhancements, by their type as expected in accordance to the minimal tree before searching this node, or as determined after searching the node. || toc =Node Types= Node Types of the minimal tree - enumerated as classified by Knuth and Moore:
 * The Dragon's Head and Tail ||~  ||^   ||
 * 1) PV-Node Knuth's **Type 1**
 * 2) Cut-Node Knuth's **Type 2**, also called fail-high node
 * 3) All-Node Knuth's **Type 3**, also called fail-low node

PV-nodes are often treated differently by the search - see Principal Variation Search or Internal Iterative Deepening for examples.

=Topology=
 * Root Node - depth = D
 * Leftmost Node - are always PV-nodes (* see note below
 * Sibling Node
 * Interior Node
 * Leaf Node
 * Terminal Node

//*) That leftmost nodes are always PV-nodes, does not imply each PV-node is leftmost - since we have to deal with real search trees rather than minimal ones.//
 * ~ Zero ||~ based depth by ||~ Heinz ||~  ||~ vs. ||~ Hyatt ||~ ambiguity ||
 * ~  || Horizon Node ||> 0 ||~   ||||> - || //(* ambiguity// ||
 * ~  || Frontier Node ||> 1 ||~   ||||> 0 || //(* ambiguity// ||
 * ~  || Pre Frontier Node ||> 2 ||~   ||||> 1 || //(* ambiguity// ||
 * ~  || Quiescent Node ||||||||> <= 0  ||   ||


 * ) //There seems an ambiguity according to the definition of frontier versus horizon nodes.//.

=See also=
 * Chess Position
 * Nodes per second
 * Principal variation
 * Score

=Forum Posts=

1995 ...

 * [|quiescent vs non-quiescent node counting] by Robert Hyatt, rgcc, July 01, 1996
 * [|Node counting confusion] by Don Dailey, CCC, January 17, 1998
 * [|Bratko-Kopec Test - Node Counts] by Peter McKenzie, CCC, June 17, 1998 » Bratko-Kopec Test
 * [|nodes per ply] by Leonid, CCC, June 10, 1999

2000 ...

 * [|How to count the nodes?] by Benny Antonsson, CCC, February 25, 2002
 * [|ALL node definition] by Alvaro Cardoso, CCC, February 21, 2003
 * [|simple node definitions question] by Michael Henderson, CCC, September 13, 2004

2005 ...

 * [|To Jeroen and interested minds, re. Tiger node count] by Christophe Théron, CCC, August 15, 2008

2010 ...

 * [|Node counting] by BB+, OpenChess Forum, January 20, 2011 » Rybka
 * [|How do you count nodes?] by Edsel Apostol, CCC, September 04, 2011

2015 ...

 * [|counting nodes vs counting evaluations] by Ed Schröder, CCC, July 19, 2015

=External Links=
 * [|Node from Wikipedia]
 * [|Vertex (graph theory) from Wikipedia]
 * [|Node (computer science) from Wikipedia]
 * [|Node (networking) from Wikipedia]
 * [|Orbital node from Wikipedia]

=References= =What links here?= include page="Node" component="backlinks" limit="100"
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