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Horizon nodes are nodes at depth zero, where a quiescence search is performed. The definition is taken from the papers of Ernst A. Heinz [1] depth == 0 nodes [2]. If the horizon node is an expected Cut-Node, confirmed by the evaluated standing pat score already greater or equal than beta, the horizon node is a leaf with the lower bound score of beta (fail-hard) or the stand pat score (fail-soft). Otherwise, winning captures (or checks) may either cause a beta-cutoff or raise alpha with an exact score at PV-Nodes. At expected All-Nodes with evaluated score (far) below alpha, if no tactical move is available, or due to Delta Pruning good enough to raise alpha, those leaves return alpha (fail-hard) as an upper bound. This may also appear, if this horizon node was not a leaf, since some captures were not pruned, but tried without raising alpha.

Horizon Observatory

800px-Hoheward-Panorama.jpg
Horizon Observatory (left) and horizontal Sundial with Obelisk (right), Hoheward Spoil tip, The Industrial Heritage Trail [3]

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References

  1. ^ Ernst A. Heinz (1998). Extended futility pruning. ICCA Journal, Vol. 21, No 2, ps
  2. ^ Re: simple node definitions question by Robert Hyatt, CCC, September 13, 2004
  3. ^ 360–degree Panorama Photo by Panofreak, April 12, 2009, Hoheward Spoil tip in Herten, North Rhine-Westphalia, Germany, The Industrial Heritage Trail , view over the Ruhr area. The observatory consists of a circular, flat surface of 88 m diameter, and a center forum lowered by 1.50 m with 35 m diameter with two arcs spanning meridian and celestial equator. The horizon observatory is a modern version of prehistoric stone circles and monuments such as Stonehenge. If the observer is located exactly in the lowered center, the plateau of the tip spreads in all directions like an artificial horizon, and with the help of bearing points the sunrise and sunset at summer solstice, winter solstice or equinox can be observed, by means of further bearing points also moon solstices and the precession of Earth's axis based on bearings of fixed stars. The arcs divide the celestial sphere in eastern and western half as well as in northern and southern hemisphere and therefore serve as a solar calendar at day, and at night, with the help of a self-luminous scale as a guide of the night sky, Halden im Ruhrgebiet (German)

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