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One Reply Extensions or Singular Reply Extensions are extensions applied if the side to move has only one legal move. Most likely this extension is loss-seeking while in check where legal move generation is used. Therefore One Reply Extensions are combined with check evasion extensions, often considered with additional fractional plies to extend. However, as already pointed out by Bruce Moreland ¹ , there is some risk to create a sequence of check + single response that goes on essentially forever, which requires the One Reply Extension to be constrained.

See also

• Check Extensions
• Singular Extensions

Forum Posts

• One Reply Extension by Nobuhiro Yoshimura, CCC, February 20, 1999
• How to extend if only one reply? by Severi Salminen, CCC, January 23, 2001
• Single Reply Extension by Renze Steenhuisen, CCC, September 20, 2004
• Single legal move - what to do? by Vlad Stamate, CCC, August 12, 2009
• Stockfish - single evasion extensions by Ralph Stoesser, CCC, June 27, 2010 » Stockfish

External Links

• Search Extension from Bruce Moreland's Programming Topics
• Computer Chess Programming Theory - Search Extensions by Colin Frayn
• Programming Details - Slow Chess | Extensions Used, Detailed Description by Jonathan Kreuzer » Slow Chess

References