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Heuri: a Scrabble© playing engine using a probability-based heuristic

Abstract

The game of Scrabble has been successfully tackled by two engines: Quackle and Maven. They attain the state-of-the-art in Computer Scrabble. These engines use simulation techniques and precalculated values to achieve superhuman play. This paper presents a Scrabble-playing engine, Heuri, which achieves world championship standards when playing in Spanish, and a very high level when playing in English and French, without using brute-force approaches.One advantage of Heuri is that its calculations, as opposed to many in Quackle, are not precomputed and instead performed for every turn. Spanish match results of different versions of Heuri against humans and two versions of Quackle are presented in this paper. Results against Quackle, in English and French, are also given. The main goal of this paper is to enrich Computer Scrabble with the description of a Scrabble playing program, Heuri, which is differently designed from earlier ones such as Maven and Quackle. An additional goal is to give Scrabble players an excellent strategy for obtaining championship level in Spanish.

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Heuri: a Scrabble© playing engine using a probability-based heuristic

Author: González Romero, Alejandro,Alquézar Mancho, René,Ramírez Flores, Arturo,González Acuña, Francisco,García Olmedo, Ian
Year: 2022
DOI: 10.3233/ICG-220201
Source: https://upcommons.upc.edu/bitstream/2117/365576/1/icga-paper-689-Final.pdf
1
Heu i: A Sc abble Playing Engine Using a P obabili y-Based Heu is ic
Alejand o González Rome o
a,∗
, René Alquéza Mancho
a
, A u o Ramí ez Flo es
b
,
F ancisco González Acuña
c,d
and Ian Ga cía Olmedo
e
a Ciències de la Compu ació, Uni e si a Poli ècnica de Ca alunya, Ba celona, Espanya
E-mails: [email p o ec ed], [email p o ec ed]
b Ciencias de la Compu ación, Cen o de In es igación en Ma emá icas A.C., Guanajua o, México
E-mail: [email p o ec ed]
c Ma emá icas Básicas, Cen o de In es igación en Ma emá icas A.C., Guanajua o, Mexico
E-mail: [email p o ec ed]
d Ins i u o de Ma emá icas (Unidad Cue na aca), Uni e sidad Nacional Au ónoma de México,
Cue na aca, Mo elos, México
e Uni e sidad Nacional Au ónoma de México, Ciudad de México, México
E-mail: [email p o ec ed]
Abs ac . The game o Sc abble has been success ully ackled by wo engines: Quackle and Ma en. They a ain he s a e-o - he-
a in Compu e Sc abble. These engines use simula ion echniques and p ecalcula ed alues o achie e supe human play. This
pape p esen s a Sc abble-playing engine, Heu i, which achie es wo ld championship s anda ds when playing in Spanish, and a
e y high le el when playing in English and F ench, wi hou using b u e- o ce app oaches.One ad an age o Heu i is ha i s
calcula ions, as opposed o many in Quackle, a e no p ecompu ed and ins ead pe o med o e e y u n. Spanish ma ch esul s o
di e en e sions o Heu i agains humans and wo e sions o Quackle a e p esen ed in his pape . Resul s agains Quackle, in
English and F ench, a e also gi en. The main goal o his pape is o en ich Compu e Sc abble wi h he desc ip ion o a Sc abble
playing p og am, Heu i, which is di e en ly designed om ea lie ones such as Ma en and Quackle. An addi ional goal is o
gi e Sc abble playe s an excellen s a egy o ob aining championship le el in Spanish.
Keywo ds: Sc abble, bingo, heu is ic, bingo p obabili y, Heu i, lea e
1. INTRODUCTION
Sc abble is a wo d game in which, in i s ou namen e sion, wo playe s sco e poin s by placing iles, each ile
ep esen ing a le e o o m wo ds on a boa d, a he like in a c osswo d. Wo ld Championship Tou namen s a e
played in many languages, such as English, F ench, and Spanish, English being he mos common.
The AI game adi ion ocuses on games wi h pe ec in o ma ion, wi h Go, Chess, Checke s, Lines o Ac ion,
Re e se, Awa i, Hex, Renju, Amazons, Pen e, e c. domina ing he li e a u e.
A body o li e a u e also exis s on impe ec in o ma ion games (in o he wo ds, hose wi h p i a e in o ma ion),
such as Sc abble, Poke and B idge, o which his a icle con ibu es.
2
I is deba able whe he a s a e-o - he-a Sc abble compu e p og am bea s he bes human. In Wiles (2018) Howa d
Wa ne s a es: “Nigel Richa ds, he op playe in he wo ld, seems o ha e compu e o a b ain. In many ways we
hink he could ac ually be supe io o Quackle he p og am.”
“Edi o ial no e: Acco ding o Fi eThi y Eigh ’s analysis o c oss. ables.com’s da a, Richa ds is echnically anked
highe han Quackle.”(Wiles, 2018).
The e is only one head- o-head encoun e be ween Nigel Richa ds and Quackle, i ook place in he To on o
In e na ional Sc abble Open 2011, Nigel won 473-449.
Spanish Sc abble playe s a e no as good as English Sc abble playe s, pe haps because English Sc abble has been
a ound since he mid 1970’s, and Spanish Sc abble since a ound 2000. Spanish Sc abble playe s can lea n a lo om
playing and wa ching games using s ong bo s. We hink ha humans can lea n a lo om a Sc abble Heu is ic bo
such as Heu i.
E en hough Heu i can play in any language, i a dic iona y is plugged in o i , i pe o ms be e wi h highly in lec ed
languages, such as Spanish and F ench, and is less e ec i e in languages whose e bs ha e ew in lec ions such as
English. The goal o his a icle is o en ich Compu e Sc abble wi h he desc ip ion o a Sc abble playing p og am,
Heu i, designed di e en ly om p e ious ones such as Ma en and Quackle. An addi ional goal o his pape is o gi e
Sc abble playe s an excellen s a egy o achie ing championship le el in Spanish.
Heu i is a Type B p og am. Acco ding o Shannon (1950), a Type B p og am is a selec i e app oach o sea ching in
minimax ees which only conside s a subse o plausible mo es, in con as o b u e- o ce, Type A p og ams.
Quackle, which has a s a e-o - he-a s a u e in Compu e Sc abble, has an engine ha is close o a Type A p og am.
Quackle plays hund eds o housands o sel -play games o p e-calcula e he alues o Supe lea es, which a e
e alua ions o all s ings o leng h 6 o less. On he o he hand, Heu i calcula es he alues o s ings, o leng h 6 o
less, he momen a playe has o make a mo e (wi h he ac ual boa d).
Heu i has achie ed ex emely good esul s in Spanish, agains humans and Quackle, and easonable esul s in English
o F ench, o a Type B p og am, agains Quackle.
The a icle is o ganized in o se e al sec ions. Sec ion 2 men ions he mo e gene a o me hods, desc ibes he s a e-o -
he-a in Compu e Sc abble, and includes some esul s o Heu i ma ches in Spanish agains op-le el Sc abble
playe s and Quackle. Sec ion 3 e e s o he i s Spanish Sc abble p og am played wi h he o icial Fede ación
In e nacional de Sc abble en Español (FISE) ules. Sec ion 4 deals wi h he heu is ics used in he i s , second and
hi d e sions o Heu i and includes e alua ion o mulas as well as he ishing echnique. Ma ch esul s a e p o ided
in Sec ion 5, oge he wi h a compa ison o esul s using di e en languages. Las ly, Sec ion 6 con ains conclusions
and sugges ions o u u e esea ch.
2. SCRABBLE ENGINES
In he 1980’s when compu e s had less memo y, Sc abble engines used a Di ec Acyclic Wo d G aph, DAWG
(Appel and Jacobson,1988), an e icien da a s uc u e o s o ing he Sc abble lexicon, which was bo h ingenious
and memo y sa ing. Today’s compu e memo ies, howe e , make i possible o s o e Sc abble lexicons in se e al
iles wi h a mo e memo y han DAWGs. The Anag am Me hod (González e al., 2018) uses his ype o s o age o
inc ease he speed o mo e gene a ion. Wi h he Anag am Me hod, mo e gene a ion becomes as e han adi ional
mo e gene a o me hods using DAWG o GADDAG (Di ec ed Acyclic G aph p e ixed by i s own in e se) see
Go don (1994).
3
Once a mo e gene a o exis s, he implemen a ion o basic engines based on he mo e ha maximizes he sco e in
each u n is he nex logical s ep. Shapi o (1979) and S ua (1982) a e examples o o e unne s in he de elopmen
o Sc abble engines. Simula ion echniques we e used o o e come he ob ious sho comings o his g eedy
app oach. These echniques conside ed he possible eplies o a playe ’s candida e mo e, he eplies o hose
eplies, and so on o many plies. This me hod, known as simula ion, elies on Mon e Ca lo sampling (B ownlee
Jason, 2019) o gene a e he opponen ’s ack, in si ua ions wi h unce ain y, i s heo e ical basis being he Minimax
echnique (Russell and No ig, 2009) o Game Theo y.
The Ma en p og am (Sheppa d, 2002) de eloped by B ian Sheppa d is one o he e e ences o his pa adigm, as
bo ne ou by i s excellen esul s agains op-le el playe s. Some yea s la e , Ka z-B own and O’Laughlin (2007)
implemen ed Quackle, a powe ul a i icial in elligence Sc abble playe , which also exploi s he simula ion
echnique.
Ma en cons uc s a da a se , gi ing a nume ical alue o se s o iles, ypically o leng h 1,2,3 o 4. The e alua ion
o a lea e is ob ained, oughly, by me ging his wi h o he numbe s in ol ing heu is ics, such as he quo ien
ob ained by di iding he numbe o owels by he numbe o consonan s (Sheppa d, 2002).
Quackle does he same hing concep ually, he di e ence being ha i now conside s nume ical alues o all
s ings o leng h less han 7. These alues a e calcula ed by playing hund eds o housands o Quackle s. Quackle
games (Ka z-B own and O’Laughlin, 2007).
In addi ion o he lea e e alua ions men ioned abo e, he s ong ea u es o Ma en and Quackle include hei
simula ion p ocedu es and, in he case o Quackle, he powe o hei Supe lea es.
A weakness o Ma en and Quackle is he ac ha hei calcula ions a e p ecompu ed, and do no ake in o accoun
he ac ual boa d, as opposed o Heu i’s calcula ions, which a e pe o med e e y u n, using he ac ual boa d.
The au ho s ha e de eloped Heu i (González e al., 2012; Ramí ez e al., 2009; González e al., 2008), an engine
ha uses he Anag am Me hod (González e al., 2018) o gene a e all he legal mo es. Unlike Ma en and Quackle,
o da e, Heu i has no used simula ion o decide which mo e o make. Ins ead, Heu i uses a p obabili y-based
heu is ic o choose he mo e o be played. Se e al ma ches agains op-le el Sc abble playe s ha e con i med
Heu i’s high playing s eng h.
Heu i’s mos impo an ma ch ic o y agains humans, was agains he 2006 and 2008 Wo ld Sc abble Champion
En ic He nandez. Heu i de ea ed he champion 6-0!
In Spanish, Heu i played a 2000-game ma ch agains Quackle using he Speedy Playe , winning 61% o he games.
The Speedy Playe e alua es po en ial mo es wi hou o wa d looking, and Quackle is weake in Spanish since
he e a e no p e-compu ed lea e alues (es ima ed alues o he le e s le on he playe ’s ack) o Spanish. Lea e
alues a e a key ea u e o Quackle’s playing s eng h.
Heu i also played a 1014-game ma ch agains Quackle using he 20-Second Championship Playe bo . This is a
much s onge bo han he Speedy Playe one, since i uses a 20-second simula ion o e e y mo e. Heu i won
53.35% o he games.
4
3. THE BEGINNING
3.1. A Spanish Sc abble P og am
A e a g ea deal o wo k, he eno mous ask o building he lexicon was comple ed. We hen modi ied Sc abble ,
a ee English Sc abble sou ce p og am buil by Ami abh in 1999. The double le e s CH, LL, RR we e added as
well as he le e Ñ. The dis ibu ion was also changed and inally some modi ica ions had o be made o adap o
he ules o Sc abble ou namen s in Spanish, in ol ing he abili y o a playe o choose whe he o change a
ce ain numbe o iles o o pass.
E en ually, we had he i s Spanish Sc abble p og am eady o play wi h he o icial Spanish Sc abble ou namen
ules (FISE ules). Le us call his p og am Sc abble II.
To check ou Spanish lexicon and he unc ionali y o he Sc abble II p og am, a ma ch was played be ween
Sc abble II and an expe human Sc abble playe anked 28 h in he Spanish Sc abble league and 90 h in Wo ld
Spanish Sc abble. The ma ch ollowed he o ma o a baseball Wo ld Se ies ma ch. In o he wo ds, he i s playe
o win ou games wins he ma ch. The human expe won 4-2.
Al hough a i s sigh one migh hink ha a compu e has an eno mous ad an age o e a human because i knows
all he pe missible wo ds, i u ns ou ha his does no su ice o bea a Sc abble expe . This is because Sc abble
II adop s a nai e, g eedy s a egy. I always plays a mo e ha will sco e he highes numbe o poin s a ha
momen . This is an op imal s a egy o duplica e Sc abble, whe e he aim o he game is o make a mo e ha
ob ains he mos poin s e e y u n. Howe e , his is no a good s a egy o no mal Sc abble, since i igno es how
his could a ec he possibili y o making be e mo es in u u e plays. Sc abble II o en ends up wi h poo quali y
acks such as GGLHQPM and since he e is no exchange s a egy, hese acks will end o p e ail, gi ing he
human playe an eno mous ad an age. Fo ins ance, in Sc abble, a good playe usually ies o play a bingo (all
se en iles in one u n), since his gi es 50 bonus poin s. I is he e o e ad isable o keep he blank iles, which can
be played ep esen ing a single chosen pe missible le e . Since Sc abble II always plays a mo e wi h he highes
possible sco e, i ends o ge id o blank iles wi hou necessa ily making a bingo.
Since all hese ea u es we e obse ed, we decided o design an imp o ed e sion o Sc abble II wi h an in e ence
s a egy engine. This engine uses a heu is ic unc ion ha a emp s o make high sco ing mo es while balancing he
ack.
4. MOVE EVALUATOR
4.1. In oduc ion o Heu i
The i s s ep owa ds building a Sc abble engine, wi h an in e ence s a egy ha could balance he ack in play,
was a C unc ion ha ecei ed a 7-le e s ing and calcula ed he p obabili y o making a bingo, o all 128 possible
exchanges o he gi en s ing. To his end, we buil a ile, he sep e s, con aining all he 7-le e s ings ha p oduce
a bingo. An example o how o calcula e his p obabili y is gi en in sec ion 4.2.
An essen ial pa o e alua ing a pa icula mo e in ol es assessing wha will be le on he ack a e he mo e has
been made ( he ack esidue o lea e). Since he e is a 50-poin bonus when you use all you iles, a na u al way o
assess a mo e is o add i s sco e o he expec ed alue ha he lea e will be able o p oduce a bingo in he ollowing
mo e.
5
Se e al ideas abou he heu is ics used by humans when playing Sc abble, such as he use o anag ams, led o he
cons uc ion o he compu e lexicon and he Heu i engine.
4.2. P obabili y and heu is ic o Heu i’s i s engine
An impo an pa o a p og am ha plays Sc abble in Spanish (o any o he language) is deciding wha o lea e on
he ack. In González e al. (2008), we p o ide a nume ical e alua ion as ollows:
= j + p * b − d (1)
whe e j is he numbe o poin s made by he mo e, in which iles a e played (i is assumed he e ha he bag has a
leas iles); j = 0 i he iles a e exchanged a he han played on he boa d; p is he p obabili y o ob aining a 7-
le e bingo i iles a e d awn a andom om a se ha is he union o he bag and he opponen ’s ack (which we
call he “augmen ed bag”); b, he expec ed alue o a bingo, is 77 (an a e age ob ained om 1000 games) o a he :
b = 50 + 2.5( + 1.92 ) (2)
whe e is he numbe o iles d awn om he bag and is he o al numbe o poin s in he lea e; d is a nonnega i e
numbe , which is ze o i he mo e is no weak om a de ensi e poin o iew. I is 20, say, i one places a ile
be ween wo iple wo d sco e squa es, pe mi ing a possible nine- ime , 10 i one plays a owel nex o a p emium
squa e allowing a six- ime , and 5 i he play pe mi s a possible ou - ime .
The equali y o b was ob ained as ollows. Fi s , le b
=
50
+
k * e whe e e is he expec ed
o al o poin s
(wi hou mul iplie s o bonuses) o a bingo. The sum o he alues o he 100 iles is 192, meaning ha he a e age
alue o a ile is 1.92 and e = + 1.92 . Fo example, i he lea e is {ZADO},
wi h
=
14, and we d aw
=
3
iles om he bag, we would expec hese iles o add, on a e age,
* 1.92 = 3 * 1.92. Say hese iles a e {VES}
(adding 6 poin s). Toge he wi h {ZADO} hese iles
o m VEZADOS, gi ing e
=
20 (app oxima ely
+
1.92 ).
Bu mos bingos include p emium squa es
( e y o en, in addi ion o he 50-poin bonus, he wo d sco e is
mul iplied by 2 and some imes 3, 4 o 9). I is he e o e easonable o mul iply e by a cons an k and we ook k
=
2.5 because i o en yields a b alue close o he expe imen al bingo a e age o 77.
Fo example, he equen case whe e
=
3,
= 4 yields b = 50 + 2.5(3 + 1.92 *
4) = 76.7.
I is be e o explain he calcula ion o p using an example:
Wha is he p obabili y ps o ob aining he “sep e ” s ={AAAAÑRR} ( om which one can o m he 7-le e bingo
ARAÑARA) i one has a lea e {AAAÑ}, exchanges {HQV}, he augmen ed bag is “ o al bag – {AAAÑHQV}”
and d aws h ee iles om i ?
Answe : I {AAAÑ} we e no con ained in {AAAAÑRR} p would be 0. Howe e {AAAÑ} is con ained in
{AAAAÑRR} so we conside he di e en se {AAAAÑRR}-{AAAÑ}={ARR}={AR2}
and
he
augmen ed
bag:
{AAAAAAAAARRRBBCCCC...XYZ}={A9R3B2C4...XYZ}.
One
hen compu es ps= C(9, 1) * C(3, 2) / C(93, 3)
(93 is he numbe o iles in he augmen ed bag and he 3 in C(93, 3) is he numbe o iles d awn om he bag)
whe e C(m, n) is he binomial coe icien :
C (m, n) = m (m − 1) (m − 2) . . . (m − n + 1) / n!
(3)

6
The nume a o has n ac o s and C(m,n) is he numbe o n-elemen subse s o a se consis ing o m elemen s.
No e ha he denomina o C(93,3) does no depend on he sep e s.
The p obabili y p o ob aining a 7-le e bingo i one has he lea e {AAAÑ} and he augmen ed bag " o al bag -
{AAAÑHQV}" is he e o e he sum o all ps when s uns o e all sep e s.
4.3. Heu i’s second engine
Al hough Heu i’s i s engine has he essen ial pa o he algo i hm used by Heu i o e alua e a mo e, i equi ed
ce ain imp o emen s. In addi ion o making he engine play be e , hese imp o emen s enabled he engine o s a
playing au oma ically.
In Ramí ez e al. (2009), i was decided o gi e a nume ical e alua ion o all po en ial mo es as ollows:
Le us ecall some essen ial ideas om he las sec ion and in oduce some new ea u es.
An impo an pa o a p og am ha plays Sc abble is he decision o wha o lea e on he ack. In a mo e iles
a e played o exchanged, and n - iles make up he lea e (excluding he endgame,
n
=
7).
The ollowing heu is ic unc ion is used o e alua e all po en ial mo es:
=
j
+
e − d (4)
whe e j is he numbe o poin s made by he mo e, in which iles a e played (i is assumed he e ha he bag
has a leas iles; j
=
0 i iles a e exchanged a he han played); e is he expec ed alue o a bingo, gi en a
lea e , i iles a e d awn andomly om he augmen ed bag, in o he wo ds,
he
union
o
he
bag
and
he
opponen ’s
ack;
d
is
a
nonnega i e
numbe , which
is
ze o
i
he
mo e is no weak om a de ensi e poin o iew.
In (4), d
=
0. Ou o all he po en ial mo es, one wi h maximal is chosen.
To explain ou es ima e o e, a sep e is de ined as a lexicog aphically o de ed s ing o se en cha ac
e s o
{A,B,...,Z,#} (whe e # is a blank) om which a 7-le e wo d can be cons uc ed. Fo example,
{AAAAÑRR}
(yielding ARAÑARA) and {ACEINR#} (yielding RECIBAN) a e sep e s bu {AEEQRY#} and {ADEILOS} a e
no .
The e a e 126,972 sep e s. The ollowing o mula was used o calcula e e:
e=∑
i=1
126,972
pi(50+k σi)
(5)
Le us call Heu i_2 he heu is ic in (5). Heu i_2 is he heu is ic used in he Heu i p og am p esen ed in Ramí ez e
al., (2009).
He e, pi is he p obabili y (which could be ze o) o ob aining he i- h sep e , gi en a lea e consis ing o 7 - iles,
i iles a e andomly d awn om he augmen ed bag; σi is he sum o he alues o he cha ac e s in he i- h sep e .
The exis ence o p emium squa es, hook wo ds, bingos o leng h g ea e han 7 and expe imen a ion ha e led us o
gi e 2.5 as he alue o he cons an k.
The calcula ion o pi was explained (wi h an example) in sec ion 4.2.
7
4.4. Heu i’s hi d engine
Al hough he o mula (5) is a good es ima e o e when he boa d is open, i igno es he ac ha one may ha e a
sep e on he ack which canno be placed as a bingo on he boa d. This o en happens when he boa d is
closed. To accoun o his, one can w i e:
e=∑
i=1
126,972
δipi(50+k σi)
(6)
whe e δi, which depends on he boa d, is 1 i he i- h sep e can be played as a bingo on he boa d and 0
o he wise; ( he boa d is aken be o e he nex opponen ’s mo e). The calcula ion o δi, o all i, which is
independen o he ack, is easible because Heu i has a as mo e gene a o based on anag ams (González e al.,
2018).
A collec ion o 1000 Sc abble games was amassed o classi y he bingos played in hose games in o h ee
ca ego ies by leng h: 1) se en-le e bingos, 2) eigh -le e bingos, and 3) X-le e bingos, wi h X > 8. This
classi ica ion yielded he ollowing esul s:
The o al numbe o bingos in he collec ion o 1000 games was 6073 bingos, di ided as ollows: 2003 se en-le e
bingos, 3972 eigh -le e bingos and 98 bingos wi h mo e han 8 le e s. This ein o ced a p e ious hough : he
heu is ic unc ion should include he p obabili y o making 8-le e as well as 7-le e bingos.
Le us de ine an oc e as a lexicog aphically a anged
s ing o eigh cha ac e s o {A, B, ..., Z,#} (whe e
# is a blank)
om which an 8-le e wo d can be cons uc ed.
A educed oc e is a lexicog aphically o de ed s ing o se en cha ac e s o {A, B, ..., Z, #}, which o ms
an oc e when
adding a sui able new cha ac e . Le a pu e sep e be a sep e ha is no a educed oc e .
The e a e 126,972 sep e s, 5,830 pu e sep e s and 282,214 educed oc e s. No e ha he se o sep e s con ains all
he pu e sep e s and 121,142 educed oc e s ha a e also sep e s. We wish o p o ide an es ima e o he
p obabili y o ob aining a 7-o 8-le e bingo, gi en a lea e and a boa d. The pu e sep e s and he educed oc e s
yield a o al o 288,044.
Then he calcula ion o e is gi en in González e al. (2012) by he o mula:
e=∑
i=1
288,044
δipi(50+k σi)
(7)
Le Heu i_3 be he heu is ic in (7); pi, σi, k and δi we e explained ea lie .
4.5. Fishing
Fishing plays a e impo an because hey seek high sco ing mo es in subsequen u ns. B ian Sheppa d, he
de elope o Ma en, w i es he ollowing in Sheppa d (2002): “Ma en’s lack o a mo e gene a o o ishing may
be i s bigges weakness. All o he mo es ha Ma en o e looked in i s ma ch agains Adam Logan we e ish.”
Heu i ishes ex emely well, which is a key ea u e o a good Sc abble engine.
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In ui i ely, a ish is a mo e ha seeks a bingo in he nex u n. Mo e p ecisely, using Heu i’s p obab
ili y heu is ic,
=
j +e -
d, le us de ine a ish as a mo e whe e e > j (i s expec ed alue o a bingo is g ea e han he poin s
made by he mo e). The mos common example o a ish is an exchange wi h e > 0. Almos all exchanges a e
ishing mo es. Howe e , in he p e-endgame (when he e a e only a ew iles in he bag), a playe may change a Q
ile o a oid being le wi h i a he end. I is likely ha e
=
0 since no mo e bingos can be placed on he boa d, o
i is impossible o cons uc a bingo wi h he playe ’s ack lea e and he iles le inside he bag (González e al.,
2012).
The ollowing is an example o a possible line o play, using Heu i, which shows and in ol es ishing mo es.
Figu e 1 shows he ishing mo es; he playe ’s ack is e uuqh. The i s six mo es a e ishing mo es since e > j.
All mo es excep mo e 7 a e ishing mo es since e > j o all o hem. In 7 hu e,
j
=
24 and e
=
9.515 so j >
e. (In igu e 1, p ep esen s he alue o e).
Fig. 1. Fishing pa 1.
A e playing he bes ishing mo e, (7G he) a le e “e” is d awn, om he bag, and he boa d posi ion is shown in
igu e 2.
Fig. 2. Fishing pa 2.
The nex playe hen exchanges iles. The playe in u n has he ollowing ack: e uuqe and he bes mo e is
shown in igu e 3 (8A u quees which gi es 106 poin s). Ano he equally good mo e is 8A uquees.
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Fig. 3. Fishing pa 3.
5. MATCH RESULTS
5.1. Ma ch Resul s o Heu i’s Fi s Engine
Due o he un inished s a e o he engine, we could only pe o m a ew games o es ou i s heu is ic. The i s
ma ch Heu i played was a ma ch agains an engine ha always played he highes mo e: Heu i won 4-0. Ma ches
agains human beings we e pe o med on he In e ne , which ga e hem an ad an age since hey could consul
wo ds be o e placing hem on he boa d and also had a lo o ime o play. In i s i s ma ch agains a human being,
Heu i won 4-2 agains one o he bes playe s in Colombia, Fe nando Man íquez, wi h an ELO o 2110 ( he highes
ELO in he FISE lis was 2191), anked No.20 in he FISE lis o Sc abble playe s. Ano he impo an ic o y Heu i
sco ed was agains Benjamín Olaizola, om Venezuela, he eigning (2007) wo ld champion who had also won he
wo ld championship in 2001. Wi h an ELO o 2169, he anked second in he in e na ional lis . I was a e y close
game: (Heu i 471 Benjamín Olaizola 465). E en ually, Heu i los he ma ch o Olaizola 2-4. A e Heu i played 17
games agains se e al op- anked playe s, he esul s we e as ollows: Heu i won 10 and los 7, wi h an a e age o
509 poin s pe game.
5.2. Ma ch Resul s o Heu i’s Second Engine
A e playing 40 games agains se e al op- anked playe s, Heu i achie ed he ollowing esul s using he heu is ic
Heu i_2 desc ibed in sec ion 4.3: 27 wins and 13 losses, wi h an a e age game sco e o 511 poin s. Almos all he
ma ches ollowed he o ma o a baseball wo ld se ies: he i s opponen o sco e ou ic o ies won he ma ch.
The mos impo an ma ch ic o y o Heu i was agains 2008 Wo ld Champion En ic He nández, om Spain, also
Wo ld Champion in 2006. This was a longe ma ch, consis ing o a maximum o ele en games o decide he
winne . Heu i de ea ed he Wo ld Champion 6-0! An excellen esul . Heu i also won 4-1 a ma ch agains Ai an
Pé ez om Venezuela, one o he bes playe s in he wo ld, and 2007 and 2008 Runne -up. Pé ez has won wo
Wo ld Championships (in 2013 and 2015). Heu i also de ea ed Aglaia Cons an in, hen he bes playe o
Colombia, wice Na ional Champion o Colombia (2006 and 2009), 4-1. Heu i won ou ma ches and los one: he
emainde o he games we e incomple e ma ches agains o me wo ld champions and na ional champions.