Changes

as proposed and examined by [[Rainer Feldmann]] <ref>[[Rainer Feldmann]] ('''1997'''). ''Fail-High Reductions.'' [[Advances in Computer Chess 8]], available as [http://citeseerx.ist.psu.edu/viewdoc/download;jsessionid=4399933A9FAE32A9C855DED714120C66?doi=10.1.1.51.4897&rep=rep1&type=pdf pdf] from [http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.51.4897 CiteSeerX]</ref>, and implemented in the program [[Zugzwang (Program)|Zugzwang]], are based on the [[Null Move Observation]] (NMO) - similar to the [[Null Move Pruning|Null Move Heuristic]] (NMH). The idea is to search to shallower [[Depth|depth]] at [[Chess Position|positions]] that are seemingly quiet and where the side to move has established a substantial advantage, according to a static [[Evaluation|evaluation]]. Apart from the [[Evaluation Function|evaluation function]], the heuristic requires an additional function that returns a value indicating threats against the side to move and therefor the quietness of a position.