# Computer bridge

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Computer_bridge
> Markdown URL: https://mediated.wiki/source/Computer_bridge.md
> Source: https://en.wikipedia.org/wiki/Computer_bridge
> Source revision: 1303977319
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Playing of contract bridge with computer software

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Computer bridge" – news · newspapers · books · scholar · JSTOR (October 2016) (Learn how and when to remove this message)

**Computer bridge** is the playing of the game [contract bridge](/source/Contract_bridge) using computer software. After years of limited progress, since around the end of the 20th century the field of computer bridge has made major advances. In 1996 the [American Contract Bridge League](/source/American_Contract_Bridge_League) (ACBL) established an official World Computer-Bridge Championship, to be held annually along with a major bridge event. The first championship took place in 1997 at the North American Bridge Championships in Albuquerque. Since 1999 the event has been conducted as a joint activity of the American Contract Bridge League and the [World Bridge Federation](/source/World_Bridge_Federation). Alvin Levy, ACBL Board member, initiated this championship and has coordinated the event annually since its inception. The event history, articles and publications, analysis, and playing records can be found at the official website.

## World Computer-Bridge Championship

The World Computer-Bridge Championship is typically played as a round robin followed by a knock-out between the top four contestants.[1][2] Winners of the annual event are:

- 1997 *Bridge Baron*

- 1998 *GIB*

- 1999 *GIB*

- 2000 *Meadowlark Bridge*

- 2001 *Jack*

- 2002 *Jack*

- 2003 *Jack*

- 2004 *Jack*

- 2005 *Wbridge5*

- 2006 *Jack*

- 2007 *Wbridge5*

- 2008 *Wbridge5*

- 2009 *Jack*

- 2010 *Jack*

- 2011 *Shark Bridge*

- 2012 *Jack*

- 2013 *Jack*

- 2014 *Shark Bridge*

- 2015 *Jack*

- 2016 *Wbridge5*[3]

- 2017 *Wbridge5*[4]

- 2018 *Wbridge5*[5]

- 2019 *Micro Bridge*[6]

- 2020- championships cancelled

Since 2022, "Unofficial Computer Bridge Championships" have been held.[7] The format is a round-robin event, followed by a semi-final and then a final, with scoring in IMPs (and Victory Points may be used to resolve ties). In 2022, due to "technical difficulties" the round-robin was replaced by a quarter-final.

Winners of the annual event are:

- 2022 *Wbridge 5.12*

- 2023 *Qplus 15.3*

- 2024 in preparation

## Computers versus humans

In [Zia Mahmood](/source/Zia_Mahmood)'s book, *Bridge, My Way* (1992), Zia offered a £1 million bet that no four-person team of his choosing would be beaten by a computer. A few years later the bridge program *GIB* (which can stand for either "Ginsberg’s Intelligent Bridgeplayer" or "[Goren](/source/Charles_Goren) In a Box"),[8] brainchild of American computer scientist Matthew Ginsberg,[9] proved capable of expert declarer plays like [winkle squeezes](/source/Winkle_squeeze) in play tests. In 1996, Zia withdrew his bet. Two years later, *GIB* became the world champion in computer bridge, and also had a 12th place score (11210) in declarer play compared to 34 of the top humans in the 1998 Par Contest (including Zia Mahmood).[10] However, such a par contest measures technical bridge analysis skills only[*[clarification needed](https://en.wikipedia.org/wiki/Wikipedia:Please_clarify)*], and in 1999 Zia beat various computer programs, including *GIB*, in an individual round robin match.[11]

Further progress in the field of computer bridge has resulted in stronger bridge playing programs, including *Jack* [12] and *Wbridge5*.[13] These programs have been ranked highly in national bridge rankings. A series of articles published in 2005 and 2006 in the Dutch bridge magazine [*IMP*](/source/List_of_significant_bridge_books_and_magazines) describes matches between five-time computer bridge world champion *Jack* and seven top Dutch pairs including a [Bermuda Bowl](/source/Bermuda_Bowl) winner and two reigning European champions. A total of 196 boards were played. *Jack* defeated three out of the seven pairs (including the European champions). Overall, the program lost by a small margin (359 versus 385 [IMPs](/source/International_Match_Point)).[*[volume and issue needed](https://en.wikipedia.org/wiki/Wikipedia:Citing_sources)*]

In 2009, Phillip Martin, an expert player, began a four-year project in which he played against the champion bridge program, Jack. He played one hand at one table, with Jack playing the other three; at another table, Jack played the same cards at all four seats, producing a comparison result. He posted his results and analysis in a blog he titled *The Gargoyle Chronicles*.[14] The program was no match for Martin, who won every contest by large margins.

## Cardplay algorithms

Bridge poses challenges to its players that are different from board games such as [chess](/source/Chess) and [go](/source/Go_(game)). Most notably, bridge is a [stochastic](/source/Stochastic) game of incomplete information. At the start of a deal, the information available to each player is limited to just his/her own cards. During the bidding and the subsequent play, more information becomes available via the bidding of the other three players at the table, the cards of the partner of the declarer (the dummy) being put open on the table, and the cards played at each trick. However, it is usually only at the end of the play that full information is obtained.

Today's top-level bridge programs deal with this probabilistic nature by [generating many samples](/source/Monte_Carlo_method) representing the unknown hands. Each sample is generated at random, but constrained to be compatible with all information available so far from the bidding and the play. Next, the result of different lines of play are tested against optimal defense for each sample. This testing is done using a so-called "double-dummy solver" that uses extensive search algorithms to determine the optimum line of play for both parties. The line of play that generates the best score averaged over all samples is selected as the optimal play.

Efficient double-dummy solvers are key to successful bridge-playing programs. Also, as the amount of computation increases with sample size, techniques such as [importance sampling](/source/Importance_sampling) are used to generate sets of samples that are of minimum size but still representative.

## Comparison to other strategy games

While bridge is a game of incomplete information, a double-dummy solver analyses a simplified version of the game where there is [perfect information](/source/Perfect_information); the bidding is ignored, the contract (trump suit and declarer) is given, and all players are assumed to know all cards from the very start. The solver can therefore use many of the [game tree](/source/Game_tree) search techniques typically used in solving two-player perfect-information win/lose/draw games such as [chess](/source/Chess), [go](/source/Go_(game)) and [reversi](/source/Reversi). However, there are some significant differences.

- Although double-dummy bridge is in practice a competition between two generalised players, each "player" controls two hands and the cards must be played in a correct order that reflects four players. (It makes a difference which of the four hands wins a trick and must lead the next trick.)

- Double-dummy bridge is not simply win/lose/draw and not exactly [zero-sum](/source/Zero-sum), but constant-sum since two playing sides compete for 13 tricks. It is trivial to transform a constant-sum game into a zero-sum game. Moreover, the goal (and the risk management strategy) in general contract bridge depends not only on the contract but also on the form of tournament (due to differences in scoring systems affecting the optimal general strategy). However, once the game has been reduced to deterministic double-dummy analysis, the goal is simple: one can without loss of generality aim to maximize the number of tricks taken.

- Bridge is incrementally scored; each played trick contributes irreversibly to the final "score" in terms of tricks won or lost. This is in contrast to games where the final outcome is more or less open until the game ends. In bridge, the already determined tricks provide natural lower and upper bounds for [alpha–beta pruning](/source/Alpha%E2%80%93beta_pruning), and the interval shrinks naturally as the search goes deeper. Other games typically need an artificial [evaluation function](/source/Evaluation_function) to enable alpha–beta pruning at limited depth, or must search to a leaf node before pruning is possible.

- It is relatively inexpensive to compute "sure winners" in various positions in a double-dummy solver. This information improves the pruning. It can be regarded as a kind of [evaluation function](/source/Evaluation_function), however while the latter in other games is an approximation of the value of the position, the former is a definitive lower bound on the value of the position.

- During the course of double-dummy game tree search, one can establish equivalence classes consisting of cards with apparently equal value in a particular position. Only one card from each equivalence class needs to be considered in the subtree search, and furthermore, when using a [transposition table](/source/Transposition_table), equivalence classes can be exploited to improve the hit rate. This has been described as *partition search* by Matthew Ginsberg.

Unsolved problem in computer science

Is the problem of [deciding](/source/Decision_problem) the winner in double-dummy bridge [hard](/source/Computational_complexity_theory#Reduction) in any [complexity class](/source/Complexity_class)?

[More unsolved problems in computer science](/source/List_of_unsolved_problems_in_computer_science)

- Numerous strategy games have been proven hard in a [complexity class](/source/Complexity_class), meaning that any problem in that complexity class can be reduced in [polynomial time](/source/Polynomial-time_reduction) to that problem. For example, generalized x × x [chess](/source/Chess) has been proven [EXPTIME](/source/EXPTIME)-complete (both in EXPTIME and EXPTIME-hard), effectively meaning that it is among the hardest problems in EXPTIME. However, since there is no natural structure to exploit in double-dummy bridge towards a hardness proof or disproof, unlike in a board game, the question of hardness remains.[15]

## The future

In comparison to [computer chess](/source/Computer_chess), computer bridge has not reached world-class level, but the top robots have demonstrated a consistently high level of play. (See analysis of the last few years of play at [www.computerbridge.com](http://www.computerbridge.com).) However see below the Philippe Pionchon's article (1984). Yet, whereas computer chess has taught programmers little about building machines that offer human-like intelligence, more [intuitive](/source/Intuition_(knowledge)) and probabilistic games such as [bridge](/source/Contract_bridge) might provide a better testing ground.

The question of whether bridge-playing programs will reach world-class level in the foreseeable future is not easy to answer. Computer bridge has not attracted an amount of interest anywhere near to that of computer chess. On the other hand, much progress has been made in the last decade by researchers working in the field.

Regardless of bridge robots' level of play, computer bridge already has changed the analysis of the game. Commercially available double-dummy programs can solve bridge problems in which all four hands are known, typically within a fraction of a second. These days, few editors of [books](/source/List_of_bridge_books) and [magazines](/source/List_of_bridge_magazines) will solely rely on humans to analyse bridge problems before publications. Also, more and more bridge players and coaches utilize computer analysis in the *post-mortem* of a match.

## See also

- [List of computer science awards](/source/List_of_computer_science_awards)

- [Computer Olympiad](/source/Computer_Olympiad)

- [Monte Carlo method](/source/Monte_Carlo_method)

- [Monte Carlo tree search](/source/Monte_Carlo_tree_search)

- [Importance sampling](/source/Importance_sampling)

- [Hanabi (card game)](/source/Hanabi_(card_game))

## References

1. **[^](#cite_ref-1)** [ACBL/WBF World Computer-Bridge Championship Official Site](http://www.computerbridge.com)

1. **[^](#cite_ref-2)** [World Computer Bridge Championship - List of contestants and their links](http://www.jackbridge.com/ewkprt.htm)

1. **[^](#cite_ref-3)** ["20th Ourgame World Computer-Bridge Championship"](https://www.allevybridge.com/allevy/computerbridge/2016scores.html). *World Computer-Bridge Championship*. Retrieved 3 November 2019.

1. **[^](#cite_ref-4)** ["21st World Computer-Bridge Championship"](https://www.allevybridge.com/allevy/computerbridge/2017_scores5.html). *World Computer-Bridge Championship*. Retrieved 3 November 2019.

1. **[^](#cite_ref-5)** ["22nd World Computer-Bridge Championship"](https://www.allevybridge.com/allevy/computerbridge/2018_scores.html). *World Computer-Bridge Championship*. Retrieved 3 November 2019.

1. **[^](#cite_ref-6)** ["23rd World Computer-Bridge Championship December 2-7, 2019 San Francisco, CA, USA at the ACBL's NABC"](http://www.allevybridge.com/allevy/computerbridge/2019_scores.html). *World Computer-Bridge Championship*. Retrieved 14 December 2019.

1. **[^](#cite_ref-7)** ["Christine Goulden's Robot Bridge Site"](https://robot-bridge.co.uk). *World Unofficial Computer Bridge Championship*. Retrieved 24 December 2023.

1. **[^](#cite_ref-8)** [Bridge Base Online Help](http://www.bridgebase.com/help/3/common/text/index.html?topic=gib)

1. **[^](#cite_ref-Ginsberg_9-0)** [Ginsberg profile](http://www.cirl.uoregon.edu/~ginsberg/)

1. **[^](#cite_ref-10)** ["Rosenberg Wins Par Contest"](http://www.worldbridge.org/bulletin/98_2%20Lille/pdf/bul_02.pdf) (PDF).

1. **[^](#cite_ref-11)** [Foreword to *Man vs Machine - The Bridge Match of the Millennium*](http://www.msoworld.com/mindzine/news/bridge/reviews/misc/man.html) [Archived](https://web.archive.org/web/20060514115301/http://msoworld.com/mindzine/news/bridge/reviews/misc/man.html) 2006-05-14 at the [Wayback Machine](/source/Wayback_Machine)

1. **[^](#cite_ref-12)** [Jack homepage](http://www.jackbridge.com/eindex.htm)

1. **[^](#cite_ref-13)** [WBridge5 homepage (in French)](http://www.wbridge5.com)

1. **[^](#cite_ref-14)** ["The Gargoyle Chronicles: Board 1"](http://thegargoylechronicles.blogspot.com/2009/09/introduction-and-board-1.html). 15 September 2009.

1. **[^](#cite_ref-15)** [Hearn, Robert Aubrey](/source/Bob_Hearn) (2006). *Games, puzzles, and computation* (Doctoral).

## External links

- [World Computer-Bridge Championship – ACBL/WBF bridge-bot world championship](https://bridgebotchampionship.com/) (official website)

- BridgeGuys (23 October 2013). ["Participating Computer Bridge Software for the World Computer Bridge Championship and the History of these Software Programs"](https://web.archive.org/web/20161108180002/http://www.bridgeguys.com/CGlossary/Computer/CBProgrammers.pdf) (PDF). Archived from [the original](http://www.bridgeguys.com/CGlossary/Computer/CBProgrammers.pdf) (PDF) on November 8, 2016.

- Ginsberg, Matthew L. (1999). ["GIB: Steps Toward an Expert-Level Bridge-Playing Program"](https://citeseerx.ist.psu.edu/doc/10.1.1.52.2188). pp. 584–589. [CiteSeerX](/source/CiteSeerX_(identifier)) [10.1.1.52.2188](https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.52.2188).

- Bethe, Paul M (January 14, 2010). ["The State of Automated Bridge Play"](http://ephman.org/bridgeReview200908.pdf) (PDF).

- Philippe Pionchon (1984). ["Artificial intelligence and Bridge game"](http://www.will-bridge.us/bridge/bridge-artificial-intelligence.htm). *Le Bridgeur Review*. Classic analysis of AI applied to bridge.

v t e Contract bridge Overview General Auction bridge Bridge ethics Bridge-O-Rama Bridge maxims Bridge Murder case Bridge scoring Bridge whist Bridgette Cheating in bridge Chicago Computer bridge Contract bridge Contract bridge diagram Duplicate bridge Duplicate bridge movements Five-suit bridge Goulash Glossary of contract bridge terms High card by suit History of contract bridge Laws of Duplicate Bridge Masterpoints Minibridge Neuberg formula Rubber bridge Screen Singaporean bridge Suit Traveling scoreslip Trump Vugraph Bidding General Balanced hand Balancing (bridge) Bidding box Bidding system Board (bridge) Bridge convention Brown sticker Convention card Cue bid Five-card majors Forcing bid Forcing pass Game try Hand evaluation Honor point count Inverted minors Law of total tricks Losing-Trick Count Major suit Minor suit Optimum contract and par contract Overcall Preempt Prepared opening bid Principle of fast arrival Psychic bid Quantitative notrump bids Reverse (bridge) Sacrifice (bridge) Shooting (bridge) Single suiter Stolen bid Strong pass Takeout double Three suiter Two suiter Useful space principle Void (cards) Weak two bid Zar Points Systems List of bidding systems 2/1 game forcing Acol Bidding system Blue Club Boring Club Bridge Base Basic Bridge World Standard Canapé (bridge) Carrot Club EHAA Fantunes Highly unusual method Kaplan–Sheinwold Little Major Moscito Polish Club Precision Club Roman Club Romex system Säffle Spade Standard American Strong club system Conventions List of bidding conventions Card play General List of play techniques Avoidance play Beer card Caddy Card reading Duck Endplay Entry Grosvenor gambit Hold up Percentage play Pin (bridge) Principle of restricted choice Probabilities Revoke Ruff Shooting Smother play Tempo Trump promotion Uppercut Vacant Places Declarer play Basic: Finesse Safety play Coups: Alcatraz coup Bath coup Belladonna coup Coup Coup en passant Crocodile coup Deschapelles coup Devil's coup Loser on loser Merrimac coup Morton's fork coup Scissors coup Trump coup Vienna coup Squeezes: Backwash squeeze Cannibal squeeze Clash squeeze Compound squeeze Criss-cross squeeze Double squeeze Entry squeeze Entry-shifting squeeze Guard squeeze Knockout squeeze Non-simultaneous double squeeze Progressive squeeze Pseudo-squeeze Saturated squeeze Simple squeeze Simultaneous double squeeze Single-suit squeeze Squeeze play Stepping-stone squeeze Strip squeeze Triple squeeze Trump squeeze Vice squeeze Winkle squeeze Suit combinations: Suit combination Defender play Forcing defense Journalist leads Opening lead Rule of 10-12 Rule of 11 Rusinow leads Signal Smith signal People and organizations General ACBL Youngest Life Master List of contract bridge people Bridge Headquarters Players by country Australia Austria Brazil Britain Bulgaria Canada China Denmark Netherlands Egypt England Fiction France Germany Hungary India Ireland Israel Italy Mexico Monaco New Zealand Norway Pakistan Poland Russia Sweden Switzerland Taiwan United States Other lists List of bridge people with Wikipedia (English) articles List of bridge administrators List of bridge writers Teams Blue Team Dallas Aces Four Aces Clubs Bridge Base Online Cavendish Club Crockford's Galatasaray Bridge Team Melville Bridge Club Portland Club (London) Savoy Club Governing bodies American Bridge Association American Contract Bridge League Austrian Bridge Federation Brazilian Bridge Federation Bridge Federation of India British Bridge League Canadian Bridge Federation Dutch Bridge Federation English Bridge Union European Bridge League Hungarian Bridge Federation International Mind Sports Association List of contract bridge governing bodies Norwegian Bridge Federation South African Bridge Federation United States Bridge Federation World Bridge Federation Championships General List of bridge competitions and awards World Bermuda Bowl Bridge at the 2008 World Mind Sports Games Bridge at the 2012 World Mind Sports Games Cavendish Invitational Computer Olympiad McConnell Cup Rosenblum Cup Senior Bowl (bridge) Triple crown of bridge Venice Cup WBF Youth Award World Bridge Championships World IMP Pairs Championship World Junior Pairs Championship World Junior Teams Championship World Mind Sports Games World Mixed Pairs Championship World Mixed Teams Championship World Open Pairs Championship World Senior Pairs Championship World Senior Teams Championship World Team Olympiad World Transnational Open Teams Championship World Women Pairs Championship National and Zonal Buffett Cup Camrose Trophy Commonwealth Nations Bridge Championships European Universities Bridge Championships Gold Cup (bridge) North American bridge Championships: ACBL King or Queen of Bridge Edgar Kaplan Blue Ribbon Pairs Bruce LM–5000 Pairs Chicago Mixed Board-a-Match Fall National Open Pairs Fast Open Pairs Fishbein Trophy Goren Trophy Grand National Teams Hilliard Mixed Pairs Jacoby Open Swiss Teams Keohane North American Swiss Teams Lebhar IMP Pairs Leventritt Silver Ribbon Pairs Machlin Women's Swiss Teams Manfield Non-Life Master Pairs Marcus Cup Master Individual Mini-Blue Ribbon Pairs Mini-Spingold Mitchell Board-a-Match Teams Mott-Smith Trophy Nail Life Master Open Pairs National 199er Pairs National 49er Pairs National 99er Pairs Non-Life Master Swiss Teams Norman Kay Platinum Pairs North American Bridge Championships North American Pairs Red Ribbon Pairs Reisinger Rockwell Mixed Pairs Roth Open Swiss Teams Senior Knockout Teams Silodor Open Pairs Smith Life Master Women's Pairs Spingold Sternberg Women's Board-a-Match Teams Truscott Senior Swiss Teams United States Bridge Championships - Open Vanderbilt Trophy Von Zedtwitz Life Master Pairs Wagar Women's Knockout Teams Wernher Open Pairs Whitehead Women's Pairs Young LM–1500 Pairs Publications and resources Books List of contract bridge books Master Point Press Bibliographies: Edwin Kantar bibliography Hugh Kelsey bibliography Terence Reese bibliography Books: 25 Bridge Conventions You Should Know Bridge Squeezes Complete The Cardturner Contract Bridge for Beginners Design for Bidding The Official Encyclopedia of Bridge Planning the Play of a Bridge Hand Right Through the Pack Magazines List of contract bridge magazines Magazines: Bridge d'Italia Bridge Magazine The Bridge World TV and Radio Grand Slam (BBC TV) External links Bridge Base Basic

---
Adapted from the Wikipedia article [Computer bridge](https://en.wikipedia.org/wiki/Computer_bridge) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Computer_bridge?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.