Nodes per Second

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Nodes per Second, (NPS) a measure of the chess program's speed. But whereas comparing different version of the same program is fine, comparisons between different engines are more difficult, since programmers use different schemes of counting nodes. The reciprocal of NPS is time per node, which translates to processor cycles per node.

=Counting Nodes= Some programs include incrementing the counter after a call to:
 * the Search Function
 * the Evaluation Function
 * Make Move

The first approach suffers from the fact that most of selectivity techniques, where a node is pruned completely, tend to improve nodes per second. The second approach is heavily dependent on the fact whether evaluation function is called in interior nodes or in the quiescence search only. The third overemphasizes the difference between legal and pseudo-legal move generation.

=See also=
 * Depth
 * Knowledge
 * Node
 * Interior Node
 * Leaf Node


 * Moves
 * Playing Strength
 * Position
 * Search Statistics
 * The Technology Curve

=Forum Posts=

1995 ...

 * Speed of chess programs? by Jan Eric Larsson, rgcc, August 29, 1995
 * quiescent vs non-quiescent node counting by Robert Hyatt, rgcc, July 01, 1996
 * nodes per second - how to count? by Peter Kappler, rgcc, January 20, 1997
 * The Crafty-Rebel NPS challenge... by Ed Schröder, rgcc, February 26, 1997
 * The Crafty-Rebel NPS challenge started!!! by Ed Schröder, rgcc, March 07, 1997
 * Rebel-Crafty NPS Challenge by Amir Ban, rgcc, March 19, 1997
 * NPS challenge will end after game one... by Ed Schröder, rgcc, March 26, 1997
 * NPS by Andreas Mader, CCC, November 14, 1997
 * Node counting confusion by Don Dailey, CCC, January 17, 1998
 * Nodes per second........ by James Robertson, CCC, September 26, 1998
 * NPS and ply depth by Enrique Irazoqui, CCC, January 28, 1999
 * WCCC and some NPS observations by Jouni Uski, CCC, June 23, 1999 » WCCC 1999

2000 ...

 * DB NPS (anyone know the position used)? by Chris Carson, CCC, January 25, 2000 » Deep Blue
 * typical nps on single cpus by Will Singleton, CCC, February 13, 2000
 * What is the average nodes per second for minimax? by Leonid, CCC, June 15, 2000
 * Is the NPS for minimax devided by NPS in alpha-beta = 5 ? by Leonid, CCC, June 16, 2000
 * Is the NPS tend to grow at the end of the game? by Leonid, CCC, July 22, 2000
 * A story about NPS by Severi Salminen, CCC, January 26, 2001
 * What is the average NPS and Depth of Top Programs? by Joshua Lee, CCC, July 26, 2001
 * Playing the NPS game by Gian-Carlo Pascutto, CCC, September 26, 2001
 * High NPS vs. Low NPS by Russell Reagan, CCC, November 25, 2001
 * Measuring NPS... by Joel Veness, CCC, November 17, 2002
 * C and C++ --- NPS by Arshad F. Syed, CCC, December 23, 2002
 * n/s again... by Stefano Gemma, CCC, May 07, 2004
 * how to calculate nps? by Peter Alloysius, CCC, July 19, 2004

2005 ...

 * NPS by David B. Weller, Winboard Forum, August 27, 2005 » Xpdnt
 * Rybka's NPS - one presumption by Vladan Vučković, CCC, February 16, 2006 » Rybka
 * Transposition Table and nps drop by Mathieu Pagé, CCC, February 27, 2008 » Transposition Table
 * To Jeroen and interested minds, re. Tiger node count by Christophe Théron, CCC, August 15, 2008
 * nps scaling by Daniel Shawul, CCC, March 01, 2009 » Parallel Search

2010 ...

 * Node counting by BB+, OpenChess Forum, January 20, 2011 » Rybka
 * How do you count nodes? by Edsel Apostol, CCC, September 04, 2011
 * Comparative nodes per second by Larry Kaufman, CCC, April 10, 2012
 * Current data - threads-nps efficiency up to 32 threads by Andreas Strangmüller, CCC, October 24, 2014 » Parallel Search, Thread

2015 ...

 * SMP NPS measurements by Peter Österlund, CCC, August 06, 2017 » Lazy SMP, Parallel Search
 * Nodes/sec. with last new CPU's! by Vael Jean-Paul, CCC, August 27, 2017
 * Reliable speed comparison: some math required by Marco Costalba, CCC, February 27, 2018 » Optimization
 * strategies for finding slowdows in lazy smp by Folkert van Heusden, CCC, June 04, 2019 » Lazy SMP, Thread

=External Links=
 * Counting from Wikipedia
 * Counting problem (complexity) from Wikipedia


 * Measurement from Wikipedia
 * Level of measurement from Wikipedia


 * Speed from Wikipedia
 * Foot per second from Wikipedia
 * Knot (unit) from Wikipedia
 * Metre per second from Wikipedia


 * Time from Wikipedia
 * Second from Wikipedia
 * Frequency from Wikipedia
 * Cycle per second from Wikipedia
 * Instruction cycle from Wikipedia
 * Instructions per second

=References=

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