<s>
Computer	B-Application
chess	I-Application
includes	O
both	O
hardware	O
(	O
dedicated	O
computers	O
)	O
and	O
software	O
capable	O
of	O
playing	O
chess	B-Application
.	O
</s>
<s>
Computer	B-Application
chess	I-Application
provides	O
opportunities	O
for	O
players	O
to	O
practice	O
even	O
in	O
the	O
absence	O
of	O
human	O
opponents	O
,	O
and	O
also	O
provides	O
opportunities	O
for	O
analysis	O
,	O
entertainment	O
and	O
training	O
.	O
</s>
<s>
Computer	B-Application
chess	I-Application
applications	O
that	O
play	O
at	O
the	O
level	O
of	O
a	O
chess	B-Application
master	O
or	O
higher	O
are	O
available	O
on	O
hardware	O
from	O
supercomputers	B-Architecture
to	O
smart	B-Application
phones	I-Application
.	O
</s>
<s>
Standalone	O
chess-playing	B-Application
machines	I-Application
are	O
also	O
available	O
.	O
</s>
<s>
Stockfish	B-Application
,	O
GNU	B-Application
Chess	I-Application
,	O
Fruit	B-Application
,	O
and	O
other	O
free	O
open	O
source	O
applications	O
are	O
available	O
for	O
various	O
platforms	O
.	O
</s>
<s>
Computer	B-Application
chess	I-Application
applications	O
,	O
whether	O
implemented	O
in	O
hardware	O
or	O
software	O
,	O
utilize	O
different	O
strategies	O
than	O
humans	O
to	O
choose	O
their	O
moves	O
:	O
they	O
use	O
heuristic	B-Algorithm
methods	I-Algorithm
to	O
build	O
,	O
search	O
and	O
evaluate	O
trees	B-Application
representing	O
sequences	O
of	O
moves	O
from	O
the	O
current	O
position	O
and	O
attempt	O
to	O
execute	O
the	O
best	O
such	O
sequence	O
during	O
play	O
.	O
</s>
<s>
Such	O
trees	B-Application
are	O
typically	O
quite	O
large	O
,	O
thousands	O
to	O
millions	O
of	O
nodes	O
.	O
</s>
<s>
The	O
computational	O
speed	O
of	O
modern	O
computers	O
,	O
capable	O
of	O
processing	O
tens	O
of	O
thousands	O
to	O
hundreds	O
of	O
thousands	O
of	O
nodes	O
or	O
more	O
per	O
second	O
,	O
along	O
with	O
extension	O
and	O
reduction	O
heuristics	B-Algorithm
that	O
narrow	O
the	O
tree	O
to	O
mostly	O
relevant	O
nodes	O
,	O
make	O
such	O
an	O
approach	O
effective	O
.	O
</s>
<s>
The	O
first	O
chess	B-Application
machines	I-Application
capable	O
of	O
playing	O
chess	B-Application
or	O
reduced	O
chess-like	O
games	O
were	O
software	O
programs	O
running	O
on	O
digital	O
computers	O
early	O
in	O
the	O
vacuum-tube	B-Device
computer	I-Device
age	O
(	O
1950s	O
)	O
.	O
</s>
<s>
Within	O
40	O
years	O
,	O
in	O
1997	O
,	O
chess	B-Application
engines	I-Application
running	O
on	O
super-computers	B-Architecture
or	O
specialized	O
hardware	O
were	O
capable	O
of	O
defeating	O
even	O
the	O
best	O
human	O
players	O
.	O
</s>
<s>
By	O
2006	O
,	O
programs	B-General_Concept
running	I-General_Concept
on	I-General_Concept
desktop	I-General_Concept
PCs	I-General_Concept
had	O
attained	O
the	O
same	O
capability	O
.	O
</s>
<s>
Nevertheless	O
,	O
solving	O
chess	B-Application
is	O
not	O
currently	O
possible	O
for	O
modern	O
computers	O
due	O
to	O
the	O
game	O
's	O
extremely	O
large	O
number	O
of	O
possible	O
variations	O
.	O
</s>
<s>
Computer	B-Application
chess	I-Application
was	O
once	O
considered	O
the	O
"	O
Drosophila	O
of	O
AI	O
"	O
,	O
the	O
edge	O
of	O
knowledge	O
engineering	O
.	O
</s>
<s>
The	O
field	O
is	O
now	O
considered	O
a	O
scientifically	O
completed	O
paradigm	O
,	O
and	O
playing	O
chess	B-Application
is	O
a	O
mundane	O
computing	O
activity	O
.	O
</s>
<s>
Chess	O
machines/programs	O
are	O
available	O
in	O
several	O
different	O
forms	O
:	O
stand-alone	O
chess	B-Application
machines	I-Application
(	O
usually	O
a	O
microprocessor	O
running	O
a	O
software	O
chess	B-Application
program	I-Application
,	O
but	O
sometimes	O
as	O
a	O
specialized	O
hardware	O
machine	O
)	O
,	O
software	O
programs	O
running	O
on	O
standard	O
PCs	O
,	O
web	O
sites	O
,	O
and	O
apps	O
for	O
mobile	O
devices	O
.	O
</s>
<s>
Programs	O
run	O
on	O
everything	O
from	O
super-computers	B-Architecture
to	O
smartphones	B-Application
.	O
</s>
<s>
Performance	O
will	O
vary	O
modestly	O
with	O
processor	O
speed	O
,	O
but	O
sufficient	O
memory	O
to	O
hold	O
a	O
large	O
transposition	B-General_Concept
table	I-General_Concept
(	O
up	O
to	O
several	O
gigabytes	O
or	O
more	O
)	O
is	O
more	O
important	O
to	O
playing	O
strength	O
than	O
processor	O
speed	O
.	O
</s>
<s>
Most	O
available	O
commercial	O
chess	B-Application
programs	I-Application
and	O
machines	O
can	O
play	O
at	O
super-grandmaster	O
strength	O
(	O
Elo	O
2700	O
or	O
more	O
)	O
,	O
and	O
take	O
advantage	O
of	O
multi-core	O
and	O
hyperthreaded	O
computer	O
CPU	B-Device
architectures	O
.	O
</s>
<s>
Top	O
programs	O
such	O
as	O
Stockfish	B-Application
have	O
surpassed	O
even	O
world	O
champion	O
caliber	O
players	O
.	O
</s>
<s>
Most	O
chess	B-Application
programs	I-Application
comprise	O
a	O
chess	B-Application
engine	I-Application
connected	O
to	O
a	O
GUI	B-Application
,	O
such	O
as	O
Winboard	B-Application
or	O
Chessbase	O
.	O
</s>
<s>
Playing	O
strength	O
,	O
time	O
controls	O
,	O
and	O
other	O
performance-related	O
settings	O
are	O
adjustable	O
from	O
the	O
GUI	B-Application
.	O
</s>
<s>
Most	O
GUIs	B-Application
also	O
allow	O
the	O
player	O
to	O
set	O
up	O
and	O
to	O
edit	O
positions	O
,	O
to	O
reverse	O
moves	O
,	O
to	O
offer	O
and	O
to	O
accept	O
draws	O
(	O
and	O
resign	O
)	O
,	O
to	O
request	O
and	O
to	O
receive	O
move	O
recommendations	O
,	O
and	O
to	O
show	O
the	O
engine	B-Application
's	O
analysis	O
as	O
the	O
game	O
progresses	O
.	O
</s>
<s>
There	O
are	O
a	O
few	O
chess	B-Application
engines	I-Application
such	O
as	O
Sargon	B-Application
,	O
IPPOLIT	B-Application
,	O
Stockfish	B-Application
,	O
Crafty	B-Application
,	O
Fruit	B-Application
,	O
Leela	B-Application
Chess	I-Application
Zero	I-Application
and	O
GNU	B-Application
Chess	I-Application
which	O
can	O
be	O
downloaded	O
(	O
or	O
source	O
code	O
otherwise	O
obtained	O
)	O
from	O
the	O
Internet	O
free	O
of	O
charge	O
.	O
</s>
<s>
Perhaps	O
the	O
most	O
common	O
type	O
of	O
chess	B-Application
software	I-Application
are	O
programs	O
that	O
simply	O
play	O
chess	B-Application
.	O
</s>
<s>
The	O
chess	B-Application
engine	I-Application
,	O
which	O
calculates	O
the	O
moves	O
,	O
and	O
the	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
are	O
sometimes	O
separate	O
programs	O
.	O
</s>
<s>
Different	O
engines	O
can	O
be	O
connected	O
to	O
the	O
GUI	B-Application
,	O
permitting	O
play	O
against	O
different	O
styles	O
of	O
opponent	O
.	O
</s>
<s>
Engines	O
often	O
have	O
a	O
simple	O
text	O
command-line	B-Application
interface	I-Application
,	O
while	O
GUIs	B-Application
may	O
offer	O
a	O
variety	O
of	O
piece	O
sets	O
,	O
board	O
styles	O
,	O
or	O
even	O
3D	O
or	O
animated	O
pieces	O
.	O
</s>
<s>
Because	O
recent	O
engines	O
are	O
so	O
capable	O
,	O
engines	O
or	O
GUIs	B-Application
may	O
offer	O
some	O
way	O
of	O
handicapping	O
the	O
engine	B-Application
's	O
ability	O
,	O
to	O
improve	O
the	O
odds	O
for	O
a	O
win	O
by	O
the	O
human	O
player	O
.	O
</s>
<s>
Universal	B-General_Concept
Chess	I-General_Concept
Interface	I-General_Concept
(	O
UCI	O
)	O
engines	O
such	O
Fritz	B-Application
or	O
Rybka	B-Application
may	O
have	O
a	O
built	O
in	O
mechanism	O
for	O
reducing	O
the	O
Elo	O
rating	O
of	O
the	O
engine	B-Application
(	O
via	O
UCI	O
's	O
uci_limitstrength	O
and	O
uci_elo	O
parameters	O
)	O
.	O
</s>
<s>
Some	O
versions	O
of	O
Fritz	B-Application
have	O
a	O
Handicap	O
and	O
Fun	O
mode	O
for	O
limiting	O
the	O
current	O
engine	B-Application
or	O
changing	O
the	O
percentage	O
of	O
mistakes	O
it	O
makes	O
or	O
changing	O
its	O
style	O
.	O
</s>
<s>
Fritz	B-Application
also	O
has	O
a	O
Friend	O
Mode	O
where	O
during	O
the	O
game	O
it	O
tries	O
to	O
match	O
the	O
level	O
of	O
the	O
player	O
.	O
</s>
<s>
Chess	B-Application
databases	O
allow	O
users	O
to	O
search	O
through	O
a	O
large	O
library	O
of	O
historical	O
games	O
,	O
analyze	O
them	O
,	O
check	O
statistics	O
,	O
and	O
formulate	O
an	O
opening	O
repertoire	O
.	O
</s>
<s>
Chessbase	O
(	O
for	O
PC	O
)	O
is	O
a	O
common	O
program	O
for	O
these	O
purposes	O
amongst	O
professional	O
players	O
,	O
but	O
there	O
are	O
alternatives	O
such	O
as	O
Shane	B-Language
's	I-Language
Chess	I-Language
Information	I-Language
Database	I-Language
(	O
Scid	B-Language
)	O
for	O
Windows	O
,	O
Mac	O
or	O
Linux	O
,	O
Chess	B-Application
Assistant	O
for	O
PC	O
,	O
Gerhard	O
Kalab	O
's	O
Chess	B-Application
PGN	O
Master	O
for	O
Android	O
or	O
Giordano	O
Vicoli	O
's	O
Chess-Studio	O
for	O
iOS	O
.	O
</s>
<s>
Chess	B-Application
training	O
programs	O
teach	O
chess	B-Application
.	O
</s>
<s>
Stefan	O
Meyer-Kahlen	O
offers	O
Shredder	B-Application
Chess	I-Application
Tutor	O
based	O
on	O
the	O
Step	O
coursebooks	O
of	O
Rob	O
Brunia	O
and	O
Cor	O
Van	O
Wijgerden	O
.	O
</s>
<s>
Chessbase	O
has	O
Fritz	B-Application
and	I-Application
Chesster	I-Application
for	O
children	O
.	O
</s>
<s>
Convekta	O
provides	O
a	O
large	O
number	O
of	O
training	O
apps	O
such	O
as	O
CT-ART	O
and	O
its	O
Chess	B-Application
King	O
line	O
based	O
on	O
tutorials	O
by	O
GM	O
Alexander	O
Kalinin	O
and	O
Maxim	O
Blokh	O
.	O
</s>
<s>
There	O
is	O
also	O
software	B-Application
for	I-Application
handling	I-Application
chess	I-Application
problems	I-Application
.	O
</s>
<s>
After	O
discovering	O
refutation	O
screening	O
—	O
the	O
application	O
of	O
alpha	B-Algorithm
–	I-Algorithm
beta	I-Algorithm
pruning	I-Algorithm
to	O
optimizing	O
move	O
evaluation	O
—	O
in	O
1957	O
,	O
a	O
team	O
at	O
Carnegie	O
Mellon	O
University	O
predicted	O
that	O
a	O
computer	O
would	O
defeat	O
the	O
world	O
human	O
champion	O
by	O
1967	O
.	O
</s>
<s>
Researchers	O
worked	O
to	O
improve	O
programs	O
 '	O
ability	O
to	O
identify	O
killer	B-Algorithm
heuristics	I-Algorithm
,	O
unusually	O
high-scoring	O
moves	O
to	O
reexamine	O
when	O
evaluating	O
other	O
branches	O
,	O
but	O
into	O
the	O
1970s	O
most	O
top	O
chess	B-Application
players	O
believed	O
that	O
computers	O
would	O
not	O
soon	O
be	O
able	O
to	O
play	O
at	O
a	O
Master	O
level	O
.	O
</s>
<s>
In	O
1968	O
International	O
Master	O
David	O
Levy	O
made	O
a	O
famous	O
bet	O
that	O
no	O
chess	B-Application
computer	I-Application
would	O
be	O
able	O
to	O
beat	O
him	O
within	O
ten	O
years	O
,	O
and	O
in	O
1976	O
Senior	O
Master	O
and	O
professor	O
of	O
psychology	O
Eliot	O
Hearst	O
of	O
Indiana	O
University	O
wrote	O
that	O
"	O
the	O
only	O
way	O
a	O
current	O
computer	O
program	O
could	O
ever	O
win	O
a	O
single	O
game	O
against	O
a	O
master	O
player	O
would	O
be	O
for	O
the	O
master	O
,	O
perhaps	O
in	O
a	O
drunken	O
stupor	O
while	O
playing	O
50	O
games	O
simultaneously	O
,	O
to	O
commit	O
some	O
once-in-a-year	O
blunder	O
"	O
.	O
</s>
<s>
In	O
the	O
late	O
1970s	O
chess	B-Application
programs	I-Application
suddenly	O
began	O
defeating	O
highly	O
skilled	O
human	O
players	O
.	O
</s>
<s>
The	O
year	O
of	O
Hearst	O
's	O
statement	O
,	O
Northwestern	O
University	O
's	O
Chess	B-Application
4.5	O
at	O
the	O
Paul	O
Masson	O
American	O
Chess	B-Application
Championship	O
's	O
Class	O
B	O
level	O
became	O
the	O
first	O
to	O
win	O
a	O
human	O
tournament	O
.	O
</s>
<s>
Levy	O
won	O
his	O
bet	O
in	O
1978	O
by	O
beating	O
Chess	B-Application
4.7	O
,	O
but	O
it	O
achieved	O
the	O
first	O
computer	O
victory	O
against	O
a	O
Master-class	O
player	O
at	O
the	O
tournament	O
level	O
by	O
winning	O
one	O
of	O
the	O
six	O
games	O
.	O
</s>
<s>
In	O
1980	O
Belle	B-General_Concept
began	O
often	O
defeating	O
Masters	O
.	O
</s>
<s>
The	O
sudden	O
improvement	O
without	O
a	O
theoretical	O
breakthrough	O
was	O
unexpected	O
,	O
as	O
many	O
did	O
not	O
expect	O
that	O
Belle	B-General_Concept
's	O
ability	O
to	O
examine	O
100,000	O
positions	O
a	O
second	O
—	O
about	O
eight	O
plies	O
—	O
would	O
be	O
sufficient	O
.	O
</s>
<s>
The	O
Spracklens	O
,	O
creators	O
of	O
the	O
successful	O
microcomputer	O
program	O
Sargon	B-Application
,	O
estimated	O
that	O
90%	O
of	O
the	O
improvement	O
came	O
from	O
faster	O
evaluation	O
speed	O
and	O
only	O
10%	O
from	O
improved	O
evaluations	O
.	O
</s>
<s>
New	O
Scientist	O
stated	O
in	O
1982	O
that	O
computers	O
"	O
play	O
terrible	O
chess	B-Application
...	O
clumsy	O
,	O
inefficient	O
,	O
diffuse	O
,	O
and	O
just	O
plain	O
ugly	O
"	O
,	O
but	O
humans	O
lost	O
to	O
them	O
by	O
making	O
"	O
horrible	O
blunders	O
,	O
astonishing	O
lapses	O
,	O
incomprehensible	O
oversights	O
,	O
gross	O
miscalculations	O
,	O
and	O
the	O
like	O
"	O
much	O
more	O
often	O
than	O
they	O
realized	O
;	O
"	O
in	O
short	O
,	O
computers	O
win	O
primarily	O
through	O
their	O
ability	O
to	O
find	O
and	O
exploit	O
miscalculations	O
in	O
human	O
initiatives	O
"	O
.	O
</s>
<s>
By	O
1982	O
,	O
microcomputer	O
chess	B-Application
programs	I-Application
could	O
evaluate	O
up	O
to	O
1,500	O
moves	O
a	O
second	O
and	O
were	O
as	O
strong	O
as	O
mainframe	B-Architecture
chess	B-Application
programs	I-Application
of	O
five	O
years	O
earlier	O
,	O
able	O
to	O
defeat	O
a	O
majority	O
of	O
amateur	O
players	O
.	O
</s>
<s>
While	O
reviewing	O
SPOC	O
in	O
1984	O
,	O
BYTE	B-Application
wrote	O
that	O
"	O
Computers	O
—	O
mainframes	B-Architecture
,	O
minis	O
,	O
and	O
micros	O
—	O
tend	O
to	O
play	O
ugly	O
,	O
inelegant	O
chess	B-Application
"	O
,	O
but	O
noted	O
Robert	O
Byrne	O
's	O
statement	O
that	O
"	O
tactically	O
they	O
are	O
freer	O
from	O
error	O
than	O
the	O
average	O
human	O
player	O
"	O
.	O
</s>
<s>
The	O
magazine	O
described	O
SPOC	O
as	O
a	O
"	O
state-of-the-art	O
chess	B-Application
program	I-Application
"	O
for	O
the	O
IBM	O
PC	O
with	O
a	O
"	O
surprisingly	O
high	O
"	O
level	O
of	O
play	O
,	O
and	O
estimated	O
its	O
USCF	O
rating	O
as	O
1700	O
(	O
Class	O
B	O
)	O
.	O
</s>
<s>
At	O
the	O
1982	O
North	O
American	O
Computer	B-Application
Chess	I-Application
Championship	O
,	O
Monroe	O
Newborn	O
predicted	O
that	O
a	O
chess	B-Application
program	I-Application
could	O
become	O
world	O
champion	O
within	O
five	O
years	O
;	O
tournament	O
director	O
and	O
International	O
Master	O
Michael	O
Valvo	O
predicted	O
ten	O
years	O
;	O
the	O
Spracklens	O
predicted	O
15	O
;	O
Ken	O
Thompson	O
predicted	O
more	O
than	O
20	O
;	O
and	O
others	O
predicted	O
that	O
it	O
would	O
never	O
happen	O
.	O
</s>
<s>
In	O
1989	O
,	O
Levy	O
was	O
defeated	O
by	O
Deep	B-General_Concept
Thought	I-General_Concept
in	O
an	O
exhibition	O
match	O
.	O
</s>
<s>
Deep	B-General_Concept
Thought	I-General_Concept
,	O
however	O
,	O
was	O
still	O
considerably	O
below	O
World	O
Championship	O
level	O
,	O
as	O
the	O
reigning	O
world	O
champion	O
,	O
Garry	O
Kasparov	O
,	O
demonstrated	O
in	O
two	O
strong	O
wins	O
in	O
1989	O
.	O
</s>
<s>
It	O
was	O
not	O
until	O
a	O
1996	O
match	O
with	O
IBM	O
's	O
Deep	B-General_Concept
Blue	I-General_Concept
that	O
Kasparov	O
lost	O
his	O
first	O
game	O
to	O
a	O
computer	O
at	O
tournament	O
time	O
controls	O
in	O
Deep	B-General_Concept
Blue	I-General_Concept
versus	O
Kasparov	O
,	O
1996	O
,	O
game	O
1	O
.	O
</s>
<s>
In	O
May	O
1997	O
,	O
an	O
updated	O
version	O
of	O
Deep	B-General_Concept
Blue	I-General_Concept
defeated	O
Kasparov	O
3½	O
–	O
2½	O
in	O
a	O
return	O
match	O
.	O
</s>
<s>
With	O
increasing	O
processing	O
power	O
and	O
improved	O
evaluation	B-General_Concept
functions	I-General_Concept
,	O
chess	B-Application
programs	I-Application
running	O
on	O
commercially	O
available	O
workstations	O
began	O
to	O
rival	O
top	O
flight	O
players	O
.	O
</s>
<s>
In	O
1998	O
,	O
Rebel	B-Application
10	I-Application
defeated	O
Viswanathan	O
Anand	O
,	O
who	O
at	O
the	O
time	O
was	O
ranked	O
second	O
in	O
the	O
world	O
,	O
by	O
a	O
score	O
of	O
5	O
–	O
3	O
.	O
</s>
<s>
Out	O
of	O
the	O
eight	O
games	O
,	O
four	O
were	O
blitz	O
games	O
(	O
five	O
minutes	O
plus	O
five	O
seconds	O
Fischer	O
delay	O
for	O
each	O
move	O
)	O
;	O
these	O
Rebel	B-Application
won	O
3	O
–	O
1	O
.	O
</s>
<s>
Two	O
were	O
semi-blitz	O
games	O
(	O
fifteen	O
minutes	O
for	O
each	O
side	O
)	O
that	O
Rebel	B-Application
won	O
as	O
well	O
(	O
1½	O
–	O
½	O
)	O
.	O
</s>
<s>
In	O
the	O
early	O
2000s	O
,	O
commercially	O
available	O
programs	O
such	O
as	O
Junior	B-Application
and	O
Fritz	B-Application
were	O
able	O
to	O
draw	O
matches	O
against	O
former	O
world	O
champion	O
Garry	O
Kasparov	O
and	O
classical	O
world	O
champion	O
Vladimir	O
Kramnik	O
.	O
</s>
<s>
In	O
October	O
2002	O
,	O
Vladimir	O
Kramnik	O
and	O
Deep	B-Application
Fritz	I-Application
competed	O
in	O
the	O
eight-game	O
Brains	B-General_Concept
in	I-General_Concept
Bahrain	I-General_Concept
match	O
,	O
which	O
ended	O
in	O
a	O
draw	O
.	O
</s>
<s>
Kramnik	O
won	O
games	O
2	O
and	O
3	O
by	O
"	O
conventional	O
"	O
anti-computer	B-General_Concept
tactics	I-General_Concept
–	O
play	O
conservatively	O
for	O
a	O
long-term	O
advantage	O
the	O
computer	O
is	O
not	O
able	O
to	O
see	O
in	O
its	O
game	O
tree	O
search	O
.	O
</s>
<s>
Fritz	B-Application
,	O
however	O
,	O
won	O
game	O
5	O
after	O
a	O
severe	O
blunder	O
by	O
Kramnik	O
.	O
</s>
<s>
True	O
to	O
form	O
,	O
Fritz	B-Application
found	O
a	O
watertight	O
defense	O
and	O
Kramnik	O
's	O
attack	O
petered	O
out	O
leaving	O
him	O
in	O
a	O
bad	O
position	O
.	O
</s>
<s>
However	O
,	O
post-game	O
human	O
and	O
computer	O
analysis	O
has	O
shown	O
that	O
the	O
Fritz	B-Application
program	O
was	O
unlikely	O
to	O
have	O
been	O
able	O
to	O
force	O
a	O
win	O
and	O
Kramnik	O
effectively	O
sacrificed	O
a	O
drawn	O
position	O
.	O
</s>
<s>
In	O
January	O
2003	O
,	O
Kasparov	O
played	O
Junior	B-Application
,	O
another	O
chess	B-Application
computer	I-Application
program	O
,	O
in	O
New	O
York	O
City	O
.	O
</s>
<s>
In	O
November	O
2003	O
,	O
Kasparov	O
played	O
X3D	B-Application
Fritz	I-Application
.	O
</s>
<s>
In	O
2005	O
,	O
Hydra	B-Architecture
,	O
a	O
dedicated	O
chess	B-Application
computer	I-Application
with	O
custom	O
hardware	O
and	O
sixty-four	O
processors	O
and	O
also	O
winner	O
of	O
the	O
14th	O
IPCCC	O
in	O
2005	O
,	O
defeated	O
seventh-ranked	O
Michael	O
Adams	O
5½	O
–	O
½	O
in	O
a	O
six-game	O
match	O
(	O
though	O
Adams	O
 '	O
preparation	O
was	O
far	O
less	O
thorough	O
than	O
Kramnik	O
's	O
for	O
the	O
2002	O
series	O
)	O
.	O
</s>
<s>
In	O
November	O
–	O
December	O
2006	O
,	O
World	O
Champion	O
Vladimir	O
Kramnik	O
played	O
Deep	B-Application
Fritz	I-Application
.	O
</s>
<s>
There	O
was	O
speculation	O
that	O
interest	O
in	O
human	O
–	O
computer	B-Application
chess	I-Application
competition	O
would	O
plummet	O
as	O
a	O
result	O
of	O
the	O
2006	O
Kramnik-Deep	O
Fritz	O
match	O
.	O
</s>
<s>
Human	B-General_Concept
–	I-General_Concept
computer	I-General_Concept
chess	I-General_Concept
matches	I-General_Concept
showed	O
the	O
best	O
computer	O
systems	O
overtaking	O
human	O
chess	B-Application
champions	O
in	O
the	O
late	O
1990s	O
.	O
</s>
<s>
The	O
highest	O
rating	O
obtained	O
by	O
a	O
computer	O
in	O
human	O
competition	O
was	O
Deep	B-General_Concept
Thought	I-General_Concept
's	O
USCF	O
rating	O
of	O
2551	O
in	O
1988	O
and	O
FIDE	O
no	O
longer	O
accepts	O
human	O
–	O
computer	O
results	O
in	O
their	O
rating	O
lists	O
.	O
</s>
<s>
In	O
2016	O
,	O
the	O
Swedish	O
Chess	B-Application
Computer	I-Application
Association	O
rated	O
computer	O
program	O
Komodo	B-Application
at	O
3361	O
.	O
</s>
<s>
Chess	B-Application
engines	I-Application
continue	O
to	O
improve	O
.	O
</s>
<s>
In	O
2009	O
,	O
chess	B-Application
engines	I-Application
running	O
on	O
slower	O
hardware	O
have	O
reached	O
the	O
grandmaster	O
level	O
.	O
</s>
<s>
A	O
mobile	O
phone	O
won	O
a	O
category	O
6	O
tournament	O
with	O
a	O
performance	O
rating	O
2898	O
:	O
chess	B-Application
engine	I-Application
Hiarcs	B-Application
13	O
running	O
inside	O
Pocket	B-Application
Fritz	I-Application
4	O
on	O
the	O
mobile	O
phone	O
HTC	O
Touch	O
HD	O
won	O
the	O
Copa	O
Mercosur	O
tournament	O
in	O
Buenos	O
Aires	O
,	O
Argentina	O
with	O
9	O
wins	O
and	O
1	O
draw	O
on	O
August	O
4	O
–	O
14	O
,	O
2009	O
.	O
</s>
<s>
Pocket	B-Application
Fritz	I-Application
4	O
searches	O
fewer	O
than	O
20,000	O
positions	O
per	O
second	O
.	O
</s>
<s>
This	O
is	O
in	O
contrast	O
to	O
supercomputers	B-Architecture
such	O
as	O
Deep	B-General_Concept
Blue	I-General_Concept
that	O
searched	O
200million	O
positions	O
per	O
second	O
.	O
</s>
<s>
Advanced	B-General_Concept
Chess	I-General_Concept
is	O
a	O
form	O
of	O
chess	B-Application
developed	O
in	O
1998	O
by	O
Kasparov	O
where	O
a	O
human	O
plays	O
against	O
another	O
human	O
,	O
and	O
both	O
have	O
access	O
to	O
computers	O
to	O
enhance	O
their	O
strength	O
.	O
</s>
<s>
This	O
has	O
been	O
proven	O
in	O
numerous	O
occasions	O
,	O
such	O
as	O
at	O
Freestyle	B-General_Concept
Chess	I-General_Concept
events	O
.	O
</s>
<s>
Players	O
today	O
are	O
inclined	O
to	O
treat	O
chess	B-Application
engines	I-Application
as	O
analysis	O
tools	O
rather	O
than	O
opponents	O
.	O
</s>
<s>
Chess	B-Application
grandmaster	O
Andrew	O
Soltis	O
stated	O
in	O
2016	O
"	O
The	O
computers	O
are	O
just	O
much	O
too	O
good	O
"	O
and	O
that	O
world	O
champion	O
Magnus	O
Carlsen	O
wo	O
n't	O
play	O
computer	B-Application
chess	I-Application
because	O
"	O
he	O
just	O
loses	O
all	O
the	O
time	O
and	O
there	O
's	O
nothing	O
more	O
depressing	O
than	O
losing	O
without	O
even	O
being	O
in	O
the	O
game.	O
"	O
</s>
<s>
Since	O
the	O
era	O
of	O
mechanical	O
machines	O
that	O
played	O
rook	O
and	O
king	O
endings	O
and	O
electrical	O
machines	O
that	O
played	O
other	O
games	O
like	O
hex	O
in	O
the	O
early	O
years	O
of	O
the	O
20th	O
century	O
,	O
scientists	O
and	O
theoreticians	O
have	O
sought	O
to	O
develop	O
a	O
procedural	O
representation	O
of	O
how	O
humans	O
learn	O
,	O
remember	O
,	O
think	O
and	O
apply	O
knowledge	O
,	O
and	O
the	O
game	O
of	O
chess	B-Application
,	O
because	O
of	O
its	O
daunting	O
complexity	O
,	O
became	O
the	O
"	O
Drosophila	O
of	O
artificial	O
intelligence	O
(	O
AI	O
)	O
"	O
.	O
</s>
<s>
The	O
procedural	O
resolution	O
of	O
complexity	O
became	O
synonymous	O
with	O
thinking	O
,	O
and	O
early	O
computers	O
,	O
even	O
before	O
the	O
chess	B-Application
automaton	O
era	O
,	O
were	O
popularly	O
referred	O
to	O
as	O
"	O
electronic	O
brains	O
"	O
.	O
</s>
<s>
Several	O
different	O
schema	O
were	O
devised	O
starting	O
in	O
the	O
latter	O
half	O
of	O
the	O
20th	O
century	O
to	O
represent	O
knowledge	O
and	O
thinking	O
,	O
as	O
applied	O
to	O
playing	O
the	O
game	O
of	O
chess	B-Application
(	O
and	O
other	O
games	O
like	O
checkers	O
)	O
:	O
</s>
<s>
Using	O
"	O
ends-and-means	O
"	O
heuristics	B-Algorithm
a	O
human	O
chess	B-Application
player	O
can	O
intuitively	O
determine	O
optimal	O
outcomes	O
and	O
how	O
to	O
achieve	O
them	O
regardless	O
of	O
the	O
number	O
of	O
moves	O
necessary	O
,	O
but	O
a	O
computer	O
must	O
be	O
systematic	O
in	O
its	O
analysis	O
.	O
</s>
<s>
On	O
average	O
there	O
are	O
more	O
than	O
30	O
legal	O
moves	O
per	O
chess	B-Application
position	O
,	O
so	O
a	O
computer	O
must	O
examine	O
a	O
quadrillion	O
possibilities	O
to	O
look	O
ahead	O
ten	O
plies	O
(	O
five	O
full	O
moves	O
)	O
;	O
one	O
that	O
could	O
examine	O
a	O
million	O
positions	O
a	O
second	O
would	O
require	O
more	O
than	O
30	O
years	O
.	O
</s>
<s>
The	O
earliest	O
attempts	O
at	O
procedural	O
representations	O
of	O
playing	O
chess	B-Application
predated	O
the	O
digital	O
electronic	O
age	O
,	O
but	O
it	O
was	O
the	O
stored	O
program	O
digital	O
computer	O
that	O
gave	O
scope	O
to	O
calculating	O
such	O
complexity	O
.	O
</s>
<s>
Claude	O
Shannon	O
,	O
in	O
1949	O
,	O
laid	O
out	O
the	O
principles	O
of	O
algorithmic	O
solution	O
of	O
chess	B-Application
.	O
</s>
<s>
In	O
that	O
paper	O
,	O
the	O
game	O
is	O
represented	O
by	O
a	O
"	O
tree	O
"	O
,	O
or	O
digital	O
data	B-General_Concept
structure	I-General_Concept
of	O
choices	O
(	O
branches	O
)	O
corresponding	O
to	O
moves	O
.	O
</s>
<s>
The	O
impossibility	O
of	O
representing	O
an	O
entire	O
game	O
of	O
chess	B-Application
by	O
constructing	O
a	O
tree	O
from	O
first	O
move	O
to	O
last	O
was	O
immediately	O
apparent	O
:	O
there	O
are	O
an	O
average	O
of	O
36	O
moves	O
per	O
position	O
in	O
chess	B-Application
and	O
an	O
average	O
game	O
lasts	O
about	O
35	O
moves	O
to	O
resignation	O
(	O
60-80	O
moves	O
if	O
played	O
to	O
checkmate	O
,	O
stalemate	O
,	O
or	O
other	O
draw	O
)	O
.	O
</s>
<s>
Searching	O
and	O
comparing	O
operations	O
on	O
the	O
tree	O
were	O
well	O
suited	O
to	O
computer	O
calculation	O
;	O
the	O
representation	O
of	O
subtle	O
chess	B-Application
knowledge	O
in	O
the	O
evaluation	B-General_Concept
function	I-General_Concept
was	O
not	O
.	O
</s>
<s>
The	O
early	O
chess	B-Application
programs	I-Application
suffered	O
in	O
both	O
areas	O
:	O
searching	O
the	O
vast	O
tree	O
required	O
computational	O
resources	O
far	O
beyond	O
those	O
available	O
,	O
and	O
what	O
chess	B-Application
knowledge	O
was	O
useful	O
and	O
how	O
it	O
was	O
to	O
be	O
encoded	O
would	O
take	O
decades	O
to	O
discover	O
.	O
</s>
<s>
The	O
developers	O
of	O
a	O
chess-playing	O
computer	O
system	O
must	O
decide	O
on	O
a	O
number	O
of	O
fundamental	O
implementation	O
issues	O
.	O
</s>
<s>
Board	B-General_Concept
representation	I-General_Concept
–	O
how	O
a	O
single	O
position	O
is	O
represented	O
in	O
data	B-General_Concept
structures	I-General_Concept
;	O
</s>
<s>
Leaf	B-General_Concept
evaluation	I-General_Concept
–	O
how	O
to	O
evaluate	O
the	O
value	O
of	O
a	O
board	O
position	O
,	O
if	O
no	O
further	O
search	O
will	O
be	O
done	O
from	O
that	O
position	O
.	O
</s>
<s>
Adriaan	O
de	O
Groot	O
interviewed	O
a	O
number	O
of	O
chess	B-Application
players	O
of	O
varying	O
strengths	O
,	O
and	O
concluded	O
that	O
both	O
masters	O
and	O
beginners	O
look	O
at	O
around	O
forty	O
to	O
fifty	O
positions	O
before	O
deciding	O
which	O
move	O
to	O
play	O
.	O
</s>
<s>
More	O
evidence	O
for	O
this	O
being	O
the	O
case	O
is	O
the	O
way	O
that	O
good	O
human	O
players	O
find	O
it	O
much	O
easier	O
to	O
recall	O
positions	O
from	O
genuine	O
chess	B-Application
games	O
,	O
breaking	O
them	O
down	O
into	O
a	O
small	O
number	O
of	O
recognizable	O
sub-positions	O
,	O
rather	O
than	O
completely	O
random	O
arrangements	O
of	O
the	O
same	O
pieces	O
.	O
</s>
<s>
The	O
equivalent	O
of	O
this	O
in	O
computer	B-Application
chess	I-Application
are	O
evaluation	B-General_Concept
functions	I-General_Concept
for	O
leaf	B-General_Concept
evaluation	I-General_Concept
,	O
which	O
correspond	O
to	O
the	O
human	O
players	O
 '	O
pattern	O
recognition	O
skills	O
,	O
and	O
the	O
use	O
of	O
machine	O
learning	O
techniques	O
in	O
training	O
them	O
,	O
such	O
as	O
Texel	O
tuning	O
,	O
stochastic	B-Algorithm
gradient	I-Algorithm
descent	I-Algorithm
,	O
and	O
reinforcement	O
learning	O
,	O
which	O
corresponds	O
to	O
building	O
experience	O
in	O
human	O
players	O
.	O
</s>
<s>
This	O
allows	O
modern	O
programs	O
to	O
examine	O
some	O
lines	O
in	O
much	O
greater	O
depth	O
than	O
others	O
by	O
using	O
forwards	O
pruning	O
and	O
other	O
selective	O
heuristics	B-Algorithm
to	O
simply	O
not	O
consider	O
moves	O
the	O
program	O
assume	O
to	O
be	O
poor	O
through	O
their	O
evaluation	B-General_Concept
function	I-General_Concept
,	O
in	O
the	O
same	O
way	O
that	O
human	O
players	O
do	O
.	O
</s>
<s>
The	O
only	O
fundamental	O
difference	O
between	O
a	O
computer	O
program	O
and	O
a	O
human	O
in	O
this	O
sense	O
is	O
that	O
a	O
computer	O
program	O
can	O
search	O
much	O
deeper	O
than	O
a	O
human	O
player	O
could	O
,	O
allowing	O
it	O
to	O
search	O
more	O
nodes	O
and	O
bypass	O
the	O
horizon	B-General_Concept
effect	I-General_Concept
to	O
a	O
much	O
greater	O
extent	O
than	O
is	O
possible	O
with	O
human	O
players	O
.	O
</s>
<s>
Computer	B-Application
chess	I-Application
programs	O
usually	O
support	O
a	O
number	O
of	O
common	O
de	O
facto	O
standards	O
.	O
</s>
<s>
Older	O
chess	B-Application
programs	I-Application
often	O
only	O
understood	O
long	O
algebraic	O
notation	O
,	O
but	O
today	O
users	O
expect	O
chess	B-Application
programs	I-Application
to	O
understand	O
standard	O
algebraic	O
chess	B-Application
notation	O
.	O
</s>
<s>
Starting	O
in	O
the	O
late	O
1990s	O
,	O
programmers	O
began	O
to	O
develop	O
separately	O
engines	O
(	O
with	O
a	O
command-line	B-Application
interface	I-Application
which	O
calculates	O
which	O
moves	O
are	O
strongest	O
in	O
a	O
position	O
)	O
or	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
which	O
provides	O
the	O
player	O
with	O
a	O
chessboard	O
they	O
can	O
see	O
,	O
and	O
pieces	O
that	O
can	O
be	O
moved	O
.	O
</s>
<s>
Engines	O
communicate	O
their	O
moves	O
to	O
the	O
GUI	B-Application
using	O
a	O
protocol	O
such	O
as	O
the	O
Chess	B-Application
Engine	I-Application
Communication	O
Protocol	O
(	O
CECP	O
)	O
or	O
Universal	B-General_Concept
Chess	I-General_Concept
Interface	I-General_Concept
(	O
UCI	O
)	O
.	O
</s>
<s>
By	O
dividing	O
chess	B-Application
programs	I-Application
into	O
these	O
two	O
pieces	O
,	O
developers	O
can	O
write	O
only	O
the	O
user	O
interface	O
,	O
or	O
only	O
the	O
engine	B-Application
,	O
without	O
needing	O
to	O
write	O
both	O
parts	O
of	O
the	O
program	O
.	O
</s>
<s>
(	O
See	O
also	O
chess	B-Application
engine	I-Application
.	O
)	O
</s>
<s>
Developers	O
have	O
to	O
decide	O
whether	O
to	O
connect	O
the	O
engine	B-Application
to	O
an	O
opening	O
book	O
and/or	O
endgame	O
tablebases	O
or	O
leave	O
this	O
to	O
the	O
GUI	B-Application
.	O
</s>
<s>
The	O
data	B-General_Concept
structure	I-General_Concept
used	O
to	O
represent	O
each	O
chess	B-Application
position	O
is	O
key	O
to	O
the	O
performance	O
of	O
move	O
generation	O
and	O
position	O
evaluation	O
.	O
</s>
<s>
Methods	O
include	O
pieces	O
stored	O
in	O
an	O
array	O
(	O
"	O
mailbox	O
"	O
and	O
"	O
0x88	O
"	O
)	O
,	O
piece	O
positions	O
stored	O
in	O
a	O
list	O
(	O
"	O
piece	O
list	O
"	O
)	O
,	O
collections	O
of	O
bit-sets	O
for	O
piece	O
locations	O
(	O
"	O
bitboards	B-Application
"	O
)	O
,	O
and	O
huffman	B-General_Concept
coded	I-General_Concept
positions	O
for	O
compact	O
long-term	O
storage	O
.	O
</s>
<s>
Computer	B-Application
chess	I-Application
programs	O
consider	O
chess	B-Application
moves	O
as	O
a	O
game	O
tree	O
.	O
</s>
<s>
One	O
particular	O
type	O
of	O
search	O
algorithm	O
used	O
in	O
computer	B-Application
chess	I-Application
are	O
minimax	B-Algorithm
search	O
algorithms	O
,	O
where	O
at	O
each	O
ply	O
the	O
"	O
best	O
"	O
move	O
by	O
the	O
player	O
is	O
selected	O
;	O
one	O
player	O
is	O
trying	O
to	O
maximize	O
the	O
score	O
,	O
the	O
other	O
to	O
minimize	O
it	O
.	O
</s>
<s>
This	O
search	O
process	O
is	O
called	O
minimax	B-Algorithm
.	O
</s>
<s>
A	O
naive	O
implementation	O
of	O
the	O
minimax	B-Algorithm
algorithm	I-Algorithm
can	O
only	O
search	O
to	O
a	O
small	O
depth	O
in	O
a	O
practical	O
amount	O
of	O
time	O
,	O
so	O
various	O
methods	O
have	O
been	O
devised	O
to	O
greatly	O
speed	O
the	O
search	O
for	O
good	O
moves	O
.	O
</s>
<s>
Alpha	B-Algorithm
–	I-Algorithm
beta	I-Algorithm
pruning	I-Algorithm
,	O
a	O
system	O
of	O
defining	O
upper	O
and	O
lower	O
bounds	O
on	O
possible	O
search	O
results	O
and	O
searching	O
until	O
the	O
bounds	O
coincided	O
,	O
is	O
typically	O
used	O
to	O
reduce	O
the	O
search	O
space	O
of	O
the	O
program	O
.	O
</s>
<s>
In	O
addition	O
,	O
various	O
selective	O
search	O
heuristics	B-Algorithm
,	O
such	O
as	O
quiescence	B-General_Concept
search	I-General_Concept
,	O
forward	O
pruning	O
,	O
search	O
extensions	O
and	O
search	O
reductions	O
,	O
are	O
also	O
used	O
as	O
well	O
.	O
</s>
<s>
These	O
heuristics	B-Algorithm
are	O
triggered	O
based	O
on	O
certain	O
conditions	O
in	O
an	O
attempt	O
to	O
weed	O
out	O
obviously	O
bad	O
moves	O
(	O
history	O
moves	O
)	O
or	O
to	O
investigate	O
interesting	O
nodes	O
(	O
e.g.	O
</s>
<s>
These	O
selective	O
search	O
heuristics	B-Algorithm
have	O
to	O
be	O
used	O
very	O
carefully	O
however	O
.	O
</s>
<s>
Monte	B-Application
Carlo	I-Application
tree	I-Application
search	I-Application
(	O
MCTS	O
)	O
is	O
a	O
heuristic	B-Algorithm
search	O
algorithm	O
which	O
expands	O
the	O
search	O
tree	O
based	O
on	O
random	O
sampling	O
of	O
the	O
search	O
space	O
.	O
</s>
<s>
A	O
version	O
of	O
Monte	B-Application
Carlo	I-Application
tree	I-Application
search	I-Application
commonly	O
used	O
in	O
computer	B-Application
chess	I-Application
is	O
PUCT	O
,	O
Predictor	O
and	O
Upper	O
Confidence	O
bounds	O
applied	O
to	O
Trees	B-Application
.	O
</s>
<s>
DeepMind	O
's	O
AlphaZero	B-Application
and	O
Leela	B-Application
Chess	I-Application
Zero	I-Application
uses	O
MCTS	O
instead	O
of	O
minimax	B-Algorithm
.	O
</s>
<s>
Such	O
engines	O
use	O
batching	B-General_Concept
on	O
graphics	B-Architecture
processing	I-Architecture
units	I-Architecture
in	O
order	O
to	O
calculate	O
their	O
evaluation	B-General_Concept
functions	I-General_Concept
and	O
policy	O
(	O
move	O
selection	O
)	O
,	O
and	O
therefore	O
require	O
a	O
parallel	B-Operating_System
search	O
algorithm	O
as	O
calculations	O
on	O
the	O
GPU	B-Architecture
are	O
inherently	O
parallel	B-Operating_System
.	O
</s>
<s>
The	O
minimax	B-Algorithm
and	O
alpha-beta	B-Algorithm
pruning	I-Algorithm
algorithms	O
used	O
in	O
computer	B-Application
chess	I-Application
are	O
inherently	O
serial	O
algorithms	O
,	O
so	O
would	O
not	O
work	O
well	O
with	O
batching	B-General_Concept
on	O
the	O
GPU	B-Architecture
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
MCTS	O
is	O
a	O
good	O
alternative	O
,	O
because	O
the	O
random	O
sampling	O
used	O
in	O
Monte	B-Application
Carlo	I-Application
tree	I-Application
search	I-Application
lends	O
itself	O
well	O
to	O
parallel	B-Operating_System
computing	I-Operating_System
,	O
and	O
is	O
why	O
nearly	O
all	O
engines	O
which	O
support	O
calculations	O
on	O
the	O
GPU	B-Architecture
use	O
MCTS	O
instead	O
of	O
alpha-beta	B-Algorithm
.	O
</s>
<s>
Many	O
other	O
optimizations	O
can	O
be	O
used	O
to	O
make	O
chess-playing	B-Application
programs	I-Application
stronger	O
.	O
</s>
<s>
For	O
example	O
,	O
transposition	B-General_Concept
tables	I-General_Concept
are	O
used	O
to	O
record	O
positions	O
that	O
have	O
been	O
previously	O
evaluated	O
,	O
to	O
save	O
recalculation	O
of	O
them	O
.	O
</s>
<s>
The	O
drawback	O
is	O
that	O
transposition	B-General_Concept
tables	I-General_Concept
at	O
deep	O
ply	O
depths	O
can	O
get	O
quite	O
large	O
–	O
tens	O
to	O
hundreds	O
of	O
millions	O
of	O
entries	O
.	O
</s>
<s>
IBM	O
's	O
Deep	B-General_Concept
Blue	I-General_Concept
transposition	B-General_Concept
table	I-General_Concept
in	O
1996	O
,	O
for	O
example	O
was	O
500million	O
entries	O
.	O
</s>
<s>
Transposition	B-General_Concept
tables	I-General_Concept
that	O
are	O
too	O
small	O
can	O
result	O
in	O
spending	O
more	O
time	O
searching	O
for	O
non-existent	O
entries	O
due	O
to	O
threshing	O
than	O
the	O
time	O
saved	O
by	O
entries	O
found	O
.	O
</s>
<s>
Many	O
chess	B-Application
engines	I-Application
use	O
pondering	O
,	O
searching	O
to	O
deeper	O
levels	O
on	O
the	O
opponent	O
's	O
time	O
,	O
similar	O
to	O
human	O
beings	O
,	O
to	O
increase	O
their	O
playing	O
strength	O
.	O
</s>
<s>
Of	O
course	O
,	O
faster	O
hardware	O
and	O
additional	O
memory	O
can	O
improve	O
chess	B-Application
program	I-Application
playing	O
strength	O
.	O
</s>
<s>
Most	O
modern	O
programs	O
are	O
designed	O
to	O
take	O
advantage	O
of	O
multiple	O
cores	O
to	O
do	O
parallel	B-Operating_System
search	O
.	O
</s>
<s>
Other	O
programs	O
are	O
designed	O
to	O
run	O
on	O
a	O
general	O
purpose	O
computer	O
and	O
allocate	O
move	O
generation	O
,	O
parallel	B-Operating_System
search	O
,	O
or	O
evaluation	O
to	O
dedicated	O
processors	O
or	O
specialized	O
co-processors	O
.	O
</s>
<s>
He	O
predicted	O
the	O
two	O
main	O
possible	O
search	O
strategies	O
which	O
would	O
be	O
used	O
,	O
which	O
he	O
labeled	O
"	O
Type	O
A	O
"	O
and	O
"	O
Type	O
B	O
"	O
,	O
before	O
anyone	O
had	O
programmed	O
a	O
computer	O
to	O
play	O
chess	B-Application
.	O
</s>
<s>
Type	O
A	O
programs	O
would	O
use	O
a	O
"	O
brute	B-Algorithm
force	I-Algorithm
"	O
approach	O
,	O
examining	O
every	O
possible	O
position	O
for	O
a	O
fixed	O
number	O
of	O
moves	O
using	O
a	O
pure	O
naive	O
minimax	B-Algorithm
algorithm	I-Algorithm
.	O
</s>
<s>
First	O
,	O
with	O
approximately	O
thirty	O
moves	O
possible	O
in	O
a	O
typical	O
real-life	O
position	O
,	O
he	O
expected	O
that	O
searching	O
the	O
approximately	O
109	O
positions	O
involved	O
in	O
looking	O
three	O
moves	O
ahead	O
for	O
both	O
sides	O
(	O
six	O
plies	O
)	O
would	O
take	O
about	O
sixteen	O
minutes	O
,	O
even	O
in	O
the	O
"	O
very	O
optimistic	O
"	O
case	O
that	O
the	O
chess	B-Application
computer	I-Application
evaluated	O
a	O
million	O
positions	O
every	O
second	O
.	O
</s>
<s>
An	O
later	O
search	O
algorithm	O
called	O
alpha	B-Algorithm
–	I-Algorithm
beta	I-Algorithm
pruning	I-Algorithm
,	O
a	O
system	O
of	O
defining	O
upper	O
and	O
lower	O
bounds	O
on	O
possible	O
search	O
results	O
and	O
searching	O
until	O
the	O
bounds	O
coincided	O
,	O
reduced	O
the	O
branching	O
factor	O
of	O
the	O
game	O
tree	O
logarithmically	O
,	O
but	O
it	O
still	O
was	O
not	O
feasible	O
for	O
chess	B-Application
programs	I-Application
at	O
the	O
time	O
to	O
exploit	O
the	O
exponential	O
explosion	O
of	O
the	O
tree	O
.	O
</s>
<s>
He	O
expected	O
that	O
adapting	O
minimax	B-Algorithm
to	O
cope	O
with	O
this	O
would	O
greatly	O
increase	O
the	O
number	O
of	O
positions	O
needing	O
to	O
be	O
looked	O
at	O
and	O
slow	O
the	O
program	O
down	O
still	O
further	O
.	O
</s>
<s>
This	O
led	O
naturally	O
to	O
what	O
is	O
referred	O
to	O
as	O
"	O
selective	O
search	O
"	O
or	O
"	O
type	O
B	O
search	O
"	O
,	O
using	O
chess	B-Application
knowledge	O
(	O
heuristics	B-Algorithm
)	O
to	O
select	O
a	O
few	O
presumably	O
good	O
moves	O
from	O
each	O
position	O
to	O
search	O
,	O
and	O
prune	O
away	O
the	O
others	O
without	O
searching	O
.	O
</s>
<s>
Employ	O
a	O
quiescence	B-General_Concept
search	I-General_Concept
.	O
</s>
<s>
The	O
best	O
program	O
produced	O
in	O
this	O
early	O
period	O
was	O
Mac	B-Application
Hack	I-Application
VI	I-Application
in	O
1967	O
;	O
it	O
played	O
at	O
the	O
about	O
the	O
same	O
level	O
as	O
the	O
average	O
amateur	O
(	O
C	O
class	O
on	O
the	O
United	O
States	O
Chess	B-Application
Federation	O
rating	O
scale	O
)	O
.	O
</s>
<s>
Meanwhile	O
,	O
hardware	O
continued	O
to	O
improve	O
,	O
and	O
in	O
1974	O
,	O
brute	B-Algorithm
force	I-Algorithm
searching	O
was	O
implemented	O
for	O
the	O
first	O
time	O
in	O
the	O
Northwestern	O
University	O
Chess	B-Application
4.0	O
program	O
.	O
</s>
<s>
They	O
discovered	O
that	O
the	O
time	O
required	O
to	O
simply	O
search	O
all	O
the	O
moves	O
was	O
much	O
less	O
than	O
the	O
time	O
required	O
to	O
apply	O
knowledge-intensive	O
heuristics	B-Algorithm
to	O
select	O
just	O
a	O
few	O
of	O
them	O
,	O
and	O
the	O
benefit	O
of	O
not	O
prematurely	O
or	O
inadvertently	O
pruning	O
away	O
good	O
moves	O
resulted	O
in	O
substantially	O
stronger	O
performance	O
.	O
</s>
<s>
In	O
the	O
1980s	O
and	O
1990s	O
,	O
progress	O
was	O
finally	O
made	O
in	O
the	O
selective	O
search	O
paradigm	O
,	O
with	O
the	O
development	O
of	O
quiescence	B-General_Concept
search	I-General_Concept
,	O
null	O
move	O
pruning	O
,	O
and	O
other	O
modern	O
selective	O
search	O
heuristics	B-Algorithm
.	O
</s>
<s>
These	O
heuristics	B-Algorithm
had	O
far	O
fewer	O
mistakes	O
than	O
earlier	O
heuristics	B-Algorithm
did	O
,	O
and	O
was	O
found	O
to	O
be	O
worth	O
the	O
extra	O
time	O
it	O
saved	O
because	O
it	O
could	O
search	O
deeper	O
and	O
widely	O
adopted	O
by	O
many	O
engines	O
.	O
</s>
<s>
While	O
many	O
modern	O
programs	O
do	O
use	O
alpha-beta	B-Algorithm
search	I-Algorithm
as	O
a	O
substrate	O
for	O
their	O
search	O
algorithm	O
,	O
these	O
additional	O
selective	O
search	O
heuristics	B-Algorithm
used	O
in	O
modern	O
programs	O
means	O
that	O
the	O
program	O
no	O
longer	O
does	O
a	O
"	O
brute	B-Algorithm
force	I-Algorithm
"	O
search	O
.	O
</s>
<s>
Instead	O
they	O
heavily	O
rely	O
on	O
these	O
selective	O
search	O
heuristics	B-Algorithm
to	O
extend	O
lines	O
the	O
program	O
considers	O
good	O
and	O
prune	O
and	O
reduce	O
lines	O
the	O
program	O
considers	O
bad	O
,	O
to	O
the	O
point	O
where	O
most	O
of	O
the	O
nodes	O
on	O
the	O
search	O
tree	O
are	O
pruned	O
away	O
,	O
enabling	O
modern	O
programs	O
to	O
search	O
very	O
deep	O
.	O
</s>
<s>
In	O
2006	O
,	O
Rémi	O
Coulom	O
created	O
Monte	B-Application
Carlo	I-Application
tree	I-Application
search	I-Application
,	O
another	O
kind	O
of	O
type	O
B	O
selective	O
search	O
.	O
</s>
<s>
In	O
2007	O
,	O
an	O
adaption	O
of	O
Monte	B-Application
Carlo	I-Application
tree	I-Application
search	I-Application
called	O
Upper	O
Confidence	O
bounds	O
applied	O
to	O
Trees	B-Application
or	O
UCT	O
for	O
short	O
was	O
created	O
by	O
Levente	O
Kocsis	O
and	O
Csaba	O
Szepesvári	O
.	O
</s>
<s>
In	O
2011	O
,	O
Chris	O
Rosin	O
developed	O
a	O
variation	O
of	O
UCT	O
called	O
Predictor	O
+	O
Upper	O
Confidence	O
bounds	O
applied	O
to	O
Trees	B-Application
,	O
or	O
PUCT	O
for	O
short	O
.	O
</s>
<s>
PUCT	O
was	O
then	O
used	O
in	O
AlphaZero	B-Application
in	O
2017	O
,	O
and	O
later	O
in	O
Leela	B-Application
Chess	I-Application
Zero	I-Application
in	O
2018	O
.	O
</s>
<s>
In	O
the	O
1970s	O
,	O
most	O
chess	B-Application
programs	I-Application
ran	O
on	O
super	B-Architecture
computers	I-Architecture
like	O
Control	O
Data	O
Cyber	O
176s	O
or	O
Cray-1s	O
,	O
indicative	O
that	O
during	O
that	O
developmental	O
period	O
for	O
computer	B-Application
chess	I-Application
,	O
processing	O
power	O
was	O
the	O
limiting	O
factor	O
in	O
performance	O
.	O
</s>
<s>
Most	O
chess	B-Application
programs	I-Application
struggled	O
to	O
search	O
to	O
a	O
depth	O
greater	O
than	O
3	O
ply	O
.	O
</s>
<s>
It	O
was	O
not	O
until	O
the	O
hardware	O
chess	B-Application
machines	I-Application
of	O
the	O
1980s	O
,	O
that	O
a	O
relationship	O
between	O
processor	O
speed	O
and	O
knowledge	O
encoded	O
in	O
the	O
evaluation	B-General_Concept
function	I-General_Concept
became	O
apparent	O
.	O
</s>
<s>
For	O
most	O
chess	B-Application
positions	O
,	O
computers	O
cannot	O
look	O
ahead	O
to	O
all	O
possible	O
final	O
positions	O
.	O
</s>
<s>
The	O
algorithm	O
that	O
evaluates	O
leaves	O
is	O
termed	O
the	O
"	O
evaluation	B-General_Concept
function	I-General_Concept
"	O
,	O
and	O
these	O
algorithms	O
are	O
often	O
vastly	O
different	O
between	O
different	O
chess	B-Application
programs	I-Application
.	O
</s>
<s>
Evaluation	B-General_Concept
functions	I-General_Concept
typically	O
evaluate	O
positions	O
in	O
hundredths	O
of	O
a	O
pawn	O
(	O
called	O
a	O
centipawn	O
)	O
,	O
where	O
by	O
convention	O
,	O
a	O
positive	O
evaluation	O
favors	O
White	O
,	O
and	O
a	O
negative	O
evaluation	O
favors	O
Black	O
.	O
</s>
<s>
However	O
,	O
some	O
evaluation	B-General_Concept
function	I-General_Concept
output	O
win/draw/loss	O
percentages	O
instead	O
of	O
centipawns	O
.	O
</s>
<s>
Historically	O
,	O
handcrafted	O
evaluation	B-General_Concept
functions	I-General_Concept
consider	O
material	O
value	O
along	O
with	O
other	O
factors	O
affecting	O
the	O
strength	O
of	O
each	O
side	O
.	O
</s>
<s>
(	O
See	O
Chess	B-Application
piece	O
relative	O
value	O
.	O
)	O
</s>
<s>
In	O
addition	O
to	O
points	O
for	O
pieces	O
,	O
most	O
handcrafted	O
evaluation	B-General_Concept
functions	I-General_Concept
take	O
many	O
factors	O
into	O
account	O
,	O
such	O
as	O
pawn	O
structure	O
,	O
the	O
fact	O
that	O
a	O
pair	O
of	O
bishops	O
are	O
usually	O
worth	O
more	O
,	O
centralized	O
pieces	O
are	O
worth	O
more	O
,	O
and	O
so	O
on	O
.	O
</s>
<s>
Machine	O
learning	O
techniques	O
such	O
as	O
Texel	O
turning	O
,	O
stochastic	B-Algorithm
gradient	I-Algorithm
descent	I-Algorithm
,	O
or	O
reinforcement	O
learning	O
are	O
usually	O
used	O
to	O
optimise	O
handcrafted	O
evaluation	B-General_Concept
functions	I-General_Concept
.	O
</s>
<s>
Most	O
modern	O
evaluation	B-General_Concept
functions	I-General_Concept
make	O
use	O
of	O
neural	B-Architecture
networks	I-Architecture
.	O
</s>
<s>
The	O
most	O
common	O
evaluation	B-General_Concept
function	I-General_Concept
in	O
use	O
today	O
is	O
the	O
efficiently	B-General_Concept
updatable	I-General_Concept
neural	I-General_Concept
network	I-General_Concept
,	O
which	O
is	O
a	O
shallow	O
neural	B-Architecture
network	I-Architecture
whose	O
inputs	O
are	O
piece-square	O
tables	O
.	O
</s>
<s>
Piece-square	O
tables	O
are	O
a	O
set	O
of	O
64	O
values	O
corresponding	O
to	O
the	O
squares	O
of	O
the	O
chessboard	O
,	O
and	O
there	O
typically	O
exists	O
a	O
piece-square	O
table	O
for	O
every	O
piece	O
and	O
colour	O
,	O
resulting	O
in	O
12	O
piece-square	O
tables	O
and	O
thus	O
768	O
inputs	O
into	O
the	O
neural	B-Architecture
network	I-Architecture
.	O
</s>
<s>
In	O
addition	O
,	O
some	O
engines	O
use	O
deep	O
neural	B-Architecture
networks	I-Architecture
in	O
their	O
evaluation	B-General_Concept
function	I-General_Concept
.	O
</s>
<s>
Neural	B-Architecture
networks	I-Architecture
are	O
usually	O
trained	O
using	O
some	O
reinforcement	O
learning	O
algorithm	O
,	O
in	O
conjunction	O
with	O
supervised	B-General_Concept
learning	I-General_Concept
or	O
unsupervised	B-General_Concept
learning	I-General_Concept
.	O
</s>
<s>
The	O
output	O
of	O
the	O
evaluation	B-General_Concept
function	I-General_Concept
is	O
a	O
single	O
scalar	O
,	O
quantized	O
in	O
centipawns	O
or	O
other	O
units	O
,	O
which	O
is	O
,	O
in	O
the	O
case	O
of	O
handcrafted	O
evaluation	B-General_Concept
functions	I-General_Concept
,	O
a	O
weighted	O
summation	O
of	O
the	O
various	O
factors	O
described	O
,	O
or	O
in	O
the	O
case	O
of	O
neural	B-Architecture
network	I-Architecture
based	O
evaluation	B-General_Concept
functions	I-General_Concept
,	O
the	O
output	O
of	O
the	O
head	O
of	O
the	O
neural	B-Architecture
network	I-Architecture
.	O
</s>
<s>
The	O
evaluation	O
putatively	O
represents	O
or	O
approximates	O
the	O
value	O
of	O
the	O
subtree	B-Application
below	O
the	O
evaluated	O
node	O
as	O
if	O
it	O
had	O
been	O
searched	O
to	O
termination	O
,	O
i.e.	O
</s>
<s>
Endgame	O
play	O
had	O
long	O
been	O
one	O
of	O
the	O
great	O
weaknesses	O
of	O
chess	B-Application
programs	I-Application
because	O
of	O
the	O
depth	O
of	O
search	O
needed	O
.	O
</s>
<s>
To	O
solve	O
this	O
problem	O
,	O
computers	O
have	O
been	O
used	O
to	O
analyze	O
some	O
chess	B-Application
endgame	O
positions	O
completely	O
,	O
starting	O
with	O
king	O
and	O
pawn	O
against	O
king	O
.	O
</s>
<s>
In	O
1977	O
Thompson	O
's	O
Belle	B-General_Concept
chess	B-Application
machine	I-Application
used	O
the	O
endgame	O
tablebase	O
for	O
a	O
king	O
and	O
rook	O
against	O
king	O
and	O
queen	O
and	O
was	O
able	O
to	O
draw	O
that	O
theoretically	O
lost	O
ending	O
against	O
several	O
masters	O
(	O
see	O
Philidor	O
position	O
#Queen	O
versus	O
rook	O
)	O
.	O
</s>
<s>
Other	O
positions	O
,	O
long	O
believed	O
to	O
be	O
won	O
,	O
turned	O
out	O
to	O
take	O
more	O
moves	O
against	O
perfect	O
play	O
to	O
actually	O
win	O
than	O
were	O
allowed	O
by	O
chess	B-Application
's	O
fifty-move	O
rule	O
.	O
</s>
<s>
As	O
a	O
consequence	O
,	O
for	O
some	O
years	O
the	O
official	O
FIDE	O
rules	O
of	O
chess	B-Application
were	O
changed	O
to	O
extend	O
the	O
number	O
of	O
moves	O
allowed	O
in	O
these	O
endings	O
.	O
</s>
<s>
Over	O
the	O
years	O
,	O
other	O
endgame	O
database	O
formats	O
have	O
been	O
released	O
including	O
the	O
Edward	O
Tablebase	O
,	O
the	O
De	O
Koning	O
Database	O
and	O
the	O
Nalimov	O
Tablebase	O
which	O
is	O
used	O
by	O
many	O
chess	B-Application
programs	I-Application
such	O
as	O
Rybka	B-Application
,	O
Shredder	B-Application
and	O
Fritz	B-Application
.	O
</s>
<s>
Programmers	O
using	O
the	O
Lomonosov	O
supercomputers	B-Architecture
in	O
Moscow	O
have	O
completed	O
a	O
chess	B-Application
tablebase	O
for	O
all	O
endgames	O
with	O
seven	O
pieces	O
or	O
fewer	O
(	O
trivial	O
endgame	O
positions	O
are	O
excluded	O
,	O
such	O
as	O
six	O
white	O
pieces	O
versus	O
a	O
lone	O
black	O
king	O
)	O
.	O
</s>
<s>
One	O
reason	O
for	O
this	O
is	O
that	O
if	O
the	O
rules	O
of	O
chess	B-Application
were	O
to	O
be	O
changed	O
once	O
more	O
,	O
giving	O
more	O
time	O
to	O
win	O
such	O
positions	O
,	O
it	O
will	O
not	O
be	O
necessary	O
to	O
regenerate	O
all	O
the	O
tablebases	O
.	O
</s>
<s>
The	O
Nalimov	O
tablebases	O
,	O
which	O
use	O
state-of-the-art	O
compression	B-General_Concept
techniques	I-General_Concept
,	O
require	O
7.05	O
GB	O
of	O
hard	O
disk	O
space	O
for	O
all	O
five-piece	O
endings	O
.	O
</s>
<s>
Chess	B-Application
engines	I-Application
,	O
like	O
human	O
beings	O
,	O
may	O
save	O
processing	O
time	O
as	O
well	O
as	O
select	O
strong	O
variations	O
as	O
expounded	O
by	O
the	O
masters	O
,	O
by	O
referencing	O
an	O
opening	O
book	O
stored	O
in	O
a	O
disk	O
database	O
.	O
</s>
<s>
Since	O
the	O
openings	O
have	O
been	O
studied	O
in	O
depth	O
by	O
the	O
masters	O
for	O
centuries	O
,	O
and	O
some	O
are	O
known	O
to	O
well	O
into	O
the	O
middle	O
game	O
,	O
the	O
valuations	O
of	O
specific	O
variations	O
by	O
the	O
masters	O
will	O
usually	O
be	O
superior	O
to	O
the	O
general	O
heuristics	B-Algorithm
of	O
the	O
program	O
.	O
</s>
<s>
While	O
at	O
one	O
time	O
,	O
playing	O
an	O
out-of-book	O
move	O
in	O
order	O
to	O
put	O
the	O
chess	B-Application
program	I-Application
onto	O
its	O
own	O
resources	O
might	O
have	O
been	O
an	O
effective	O
strategy	O
because	O
chess	B-Application
opening	O
books	O
were	O
selective	O
to	O
the	O
program	O
's	O
playing	O
style	O
,	O
and	O
programs	O
had	O
notable	O
weaknesses	O
relative	O
to	O
humans	O
,	O
that	O
is	O
no	O
longer	O
true	O
today	O
.	O
</s>
<s>
Even	O
if	O
it	O
does	O
not	O
,	O
playing	O
out-of-book	O
may	O
be	O
much	O
better	O
for	O
tactically	O
sharp	O
chess	B-Application
programs	I-Application
than	O
for	O
humans	O
who	O
have	O
to	O
discover	O
strong	O
moves	O
in	O
an	O
unfamiliar	O
variation	O
over	O
the	O
board	O
.	O
</s>
<s>
CEGT	B-General_Concept
,	O
CSS	O
,	O
SSDF	O
,	O
WBEC	O
,	O
REBEL	B-Application
,	O
FGRL	O
,	O
and	O
IPON	O
maintain	O
rating	O
lists	O
allowing	O
fans	O
to	O
compare	O
the	O
strength	O
of	O
engines	O
.	O
</s>
<s>
Various	O
versions	O
of	O
Stockfish	B-Application
,	O
Komodo	B-Application
,	O
Leela	B-Application
Chess	I-Application
Zero	I-Application
,	O
and	O
Fat	B-Application
Fritz	I-Application
dominate	O
the	O
rating	O
lists	O
in	O
the	O
early	O
2020s	O
.	O
</s>
<s>
CCRL	O
(	O
Computer	B-Application
Chess	I-Application
Rating	O
Lists	O
)	O
is	O
an	O
organisation	O
that	O
tests	O
computer	B-Application
chess	I-Application
engines	O
 '	O
strength	O
by	O
playing	O
the	O
programs	O
against	O
each	O
other	O
.	O
</s>
<s>
Pondering	O
(	O
or	O
permanent	O
brain	O
)	O
is	O
switched	O
off	O
and	O
timing	O
is	O
adjusted	O
to	O
the	O
AMD64	O
X2	O
4600+	O
(	O
2.4GHz	O
)	O
CPU	B-Device
by	O
using	O
Crafty	B-Application
19.17	I-Application
BH	I-Application
as	O
a	O
benchmark	O
.	O
</s>
<s>
Generic	O
,	O
neutral	O
opening	O
books	O
are	O
used	O
(	O
as	O
opposed	O
to	O
the	O
engine	B-Application
's	O
own	O
book	O
)	O
up	O
to	O
a	O
limit	O
of	O
12	O
moves	O
into	O
the	O
game	O
alongside	O
4	O
or	O
5	O
man	O
tablebases	O
.	O
</s>
<s>
The	O
idea	O
of	O
creating	O
a	O
chess-playing	B-Application
machine	I-Application
dates	O
back	O
to	O
the	O
eighteenth	O
century	O
.	O
</s>
<s>
Around	O
1769	O
,	O
the	O
chess	B-Application
playing	O
automaton	O
called	O
The	O
Turk	O
,	O
created	O
by	O
Hungarian	O
inventor	O
Farkas	O
Kempelen	O
,	O
became	O
famous	O
before	O
being	O
exposed	O
as	O
a	O
hoax	O
.	O
</s>
<s>
Before	O
the	O
development	O
of	O
digital	O
computing	O
,	O
serious	O
trials	O
based	O
on	O
automata	O
such	O
as	O
El	O
Ajedrecista	O
of	O
1912	O
which	O
played	O
a	O
king	O
and	O
rook	O
versus	O
king	O
ending	O
,	O
were	O
too	O
complex	O
and	O
limited	O
to	O
be	O
useful	O
for	O
playing	O
full	O
games	O
of	O
chess	B-Application
.	O
</s>
<s>
The	O
field	O
of	O
mechanical	O
chess	B-Application
research	O
languished	O
until	O
the	O
advent	O
of	O
the	O
digital	O
computer	O
in	O
the	O
1950s	O
.	O
</s>
<s>
Since	O
then	O
,	O
chess	B-Application
enthusiasts	O
and	O
computer	O
engineers	O
have	O
built	O
,	O
with	O
increasing	O
degrees	O
of	O
seriousness	O
and	O
success	O
,	O
chess-playing	B-Application
machines	I-Application
and	O
computer	O
programs	O
.	O
</s>
<s>
One	O
of	O
the	O
few	O
chess	B-Application
grandmasters	O
to	O
devote	O
himself	O
seriously	O
to	O
computer	B-Application
chess	I-Application
was	O
former	O
World	O
Chess	B-Application
Champion	O
Mikhail	O
Botvinnik	O
,	O
who	O
wrote	O
several	O
works	O
on	O
the	O
subject	O
.	O
</s>
<s>
In	O
1965	O
Botvinnik	O
was	O
a	O
consultant	O
to	O
the	O
ITEP	O
team	O
in	O
a	O
US-Soviet	O
computer	B-Application
chess	I-Application
match	O
(	O
see	O
Kotok-McCarthy	B-Application
)	O
.	O
</s>
<s>
One	O
developmental	O
milestone	O
occurred	O
when	O
the	O
team	O
from	O
Northwestern	O
University	O
,	O
which	O
was	O
responsible	O
for	O
the	O
Chess	B-Application
series	O
of	O
programs	O
and	O
won	O
the	O
first	O
three	O
ACM	O
Computer	B-Application
Chess	I-Application
Championships	O
(	O
1970	O
–	O
72	O
)	O
,	O
abandoned	O
type	O
B	O
searching	O
in	O
1973	O
.	O
</s>
<s>
The	O
resulting	O
program	O
,	O
Chess	B-Application
4.0	O
,	O
won	O
that	O
year	O
's	O
championship	O
and	O
its	O
successors	O
went	O
on	O
to	O
come	O
in	O
second	O
in	O
both	O
the	O
1974	O
ACM	O
Championship	O
and	O
that	O
year	O
's	O
inaugural	O
World	O
Computer	B-Application
Chess	I-Application
Championship	O
,	O
before	O
winning	O
the	O
ACM	O
Championship	O
again	O
in	O
1975	O
,	O
1976	O
and	O
1977	O
.	O
</s>
<s>
In	O
fact	O
,	O
Chess	B-Application
4.0	O
set	O
the	O
paradigm	O
that	O
was	O
and	O
still	O
is	O
followed	O
essentially	O
by	O
all	O
modern	O
Chess	B-Application
programs	I-Application
today	O
,	O
and	O
that	O
had	O
been	O
successfully	O
started	O
by	O
the	O
Russian	O
ITEP	O
in	O
1965	O
.	O
</s>
<s>
In	O
1978	O
,	O
an	O
early	O
rendition	O
of	O
Ken	O
Thompson	O
's	O
hardware	O
chess	B-Application
machine	I-Application
Belle	B-General_Concept
,	O
entered	O
and	O
won	O
the	O
North	O
American	O
Computer	B-Application
Chess	I-Application
Championship	O
over	O
the	O
dominant	O
Northwestern	O
University	O
Chess	B-Application
4.7	O
.	O
</s>
<s>
Technological	O
advances	O
by	O
orders	O
of	O
magnitude	O
in	O
processing	O
power	O
have	O
made	O
the	O
brute	B-Algorithm
force	I-Algorithm
approach	O
far	O
more	O
incisive	O
than	O
was	O
the	O
case	O
in	O
the	O
early	O
years	O
.	O
</s>
<s>
The	O
result	O
is	O
that	O
a	O
very	O
solid	O
,	O
tactical	O
AI	O
player	O
aided	O
by	O
some	O
limited	O
positional	O
knowledge	O
built	O
in	O
by	O
the	O
evaluation	B-General_Concept
function	I-General_Concept
and	O
pruning/extension	O
rules	O
began	O
to	O
match	O
the	O
best	O
players	O
in	O
the	O
world	O
.	O
</s>
<s>
It	O
turned	O
out	O
to	O
produce	O
excellent	O
results	O
,	O
at	O
least	O
in	O
the	O
field	O
of	O
chess	B-Application
,	O
to	O
let	O
computers	O
do	O
what	O
they	O
do	O
best	O
(	O
calculate	O
)	O
rather	O
than	O
coax	O
them	O
into	O
imitating	O
human	O
thought	O
processes	O
and	O
knowledge	O
.	O
</s>
<s>
In	O
1997	O
Deep	B-General_Concept
Blue	I-General_Concept
,	O
a	O
brute-force	O
machine	O
capable	O
of	O
examining	O
500million	O
nodes	O
per	O
second	O
,	O
defeated	O
World	O
Champion	O
Garry	O
Kasparov	O
,	O
marking	O
the	O
first	O
time	O
a	O
computer	O
has	O
defeated	O
a	O
reigning	O
world	O
chess	B-Application
champion	O
in	O
standard	O
time	O
control	O
.	O
</s>
<s>
In	O
2016	O
,	O
NPR	O
asked	O
experts	O
to	O
characterize	O
the	O
playing	O
style	O
of	O
computer	B-Application
chess	I-Application
engines	O
.	O
</s>
<s>
While	O
neural	B-Architecture
networks	I-Architecture
have	O
been	O
used	O
in	O
the	O
evaluation	B-General_Concept
functions	I-General_Concept
of	O
chess	B-Application
engines	I-Application
since	O
the	O
late	O
1980s	O
,	O
with	O
programs	O
such	O
as	O
NeuroChess	O
,	O
Morph	O
,	O
Blondie25	O
,	O
Giraffe	O
,	O
AlphaZero	B-Application
,	O
and	O
MuZero	B-Application
,	O
neural	B-Architecture
networks	I-Architecture
did	O
not	O
become	O
widely	O
adopted	O
by	O
chess	B-Application
engines	I-Application
until	O
the	O
arrival	O
of	O
efficiently	B-General_Concept
updatable	I-General_Concept
neural	I-General_Concept
networks	I-General_Concept
in	O
the	O
summer	O
of	O
2020	O
.	O
</s>
<s>
Efficiently	B-General_Concept
updatable	I-General_Concept
neural	I-General_Concept
networks	I-General_Concept
were	O
originally	O
developed	O
in	O
computer	B-Application
shogi	I-Application
in	O
2018	O
by	O
Yu	O
Nasu	O
,	O
and	O
had	O
to	O
be	O
first	O
ported	O
to	O
a	O
derivative	O
of	O
Stockfish	B-Application
called	O
Stockfish	B-Application
NNUE	B-General_Concept
on	O
31	O
May	O
2020	O
,	O
and	O
integrated	O
into	O
the	O
official	O
Stockfish	B-Application
engine	B-Application
on	O
6	O
August	O
2020	O
,	O
before	O
other	O
chess	B-Application
programmers	O
began	O
to	O
adopt	O
neural	B-Architecture
networks	I-Architecture
into	O
their	O
engines	O
.	O
</s>
<s>
Some	O
people	O
,	O
such	O
as	O
the	O
Royal	O
Society	O
's	O
Venki	O
Ramakrishnan	O
,	O
believe	O
that	O
AlphaZero	B-Application
lead	O
to	O
the	O
widespread	O
adoption	O
of	O
neural	B-Architecture
networks	I-Architecture
in	O
chess	B-Application
engines	I-Application
.	O
</s>
<s>
However	O
,	O
AlphaZero	B-Application
influenced	O
very	O
few	O
engines	O
to	O
begin	O
using	O
neural	B-Architecture
networks	I-Architecture
,	O
and	O
those	O
tended	O
to	O
be	O
new	O
experimental	O
engines	O
such	O
as	O
Leela	B-Application
Chess	I-Application
Zero	I-Application
,	O
which	O
began	O
specifically	O
to	O
replicate	O
the	O
AlphaZero	B-Application
paper	O
.	O
</s>
<s>
The	O
deep	O
neural	B-Architecture
networks	I-Architecture
used	O
in	O
AlphaZero	B-Application
's	O
evaluation	B-General_Concept
function	I-General_Concept
required	O
expensive	O
graphics	B-Architecture
processing	I-Architecture
units	I-Architecture
,	O
which	O
were	O
not	O
compatible	O
with	O
existing	O
chess	B-Application
engines	I-Application
.	O
</s>
<s>
The	O
vast	O
majority	O
of	O
chess	B-Application
engines	I-Application
only	O
use	O
central	B-General_Concept
processing	I-General_Concept
units	I-General_Concept
,	O
and	O
computing	O
and	O
processing	O
information	O
on	O
the	O
GPUs	B-Architecture
require	O
special	O
libraries	B-Library
in	O
the	O
backend	O
such	O
as	O
Nvidia	O
's	O
CUDA	B-Architecture
,	O
which	O
none	O
of	O
the	O
engines	O
had	O
access	O
to	O
.	O
</s>
<s>
Thus	O
the	O
vast	O
majority	O
of	O
chess	B-Application
engines	I-Application
such	O
as	O
Komodo	B-Application
and	O
Stockfish	B-Application
continued	O
to	O
use	O
handcrafted	O
evaluation	B-General_Concept
functions	I-General_Concept
until	O
efficiently	B-General_Concept
updatable	I-General_Concept
neural	I-General_Concept
networks	I-General_Concept
were	O
ported	O
to	O
computer	B-Application
chess	I-Application
in	O
2020	O
,	O
which	O
did	O
not	O
require	O
either	O
the	O
use	O
of	O
GPUs	B-Architecture
or	O
libraries	B-Library
like	O
CUDA	B-Architecture
at	O
all	O
.	O
</s>
<s>
Even	O
then	O
,	O
the	O
neural	B-Architecture
networks	I-Architecture
used	O
in	O
computer	B-Application
chess	I-Application
are	O
fairly	O
shallow	O
,	O
and	O
the	O
deep	B-Algorithm
reinforcement	I-Algorithm
learning	I-Algorithm
methods	O
pioneered	O
by	O
AlphaZero	B-Application
are	O
still	O
extremely	O
rare	O
in	O
computer	B-Application
chess	I-Application
.	O
</s>
<s>
Presented	O
as	O
a	O
chess-playing	O
automaton	O
,	O
it	O
is	O
secretly	O
operated	O
by	O
a	O
human	O
player	O
hidden	O
inside	O
the	O
machine	O
.	O
</s>
<s>
1868	O
–	O
Charles	O
Hooper	O
presents	O
the	O
Ajeeb	O
automaton	O
which	O
also	O
has	O
a	O
human	O
chess	B-Application
player	O
hidden	O
inside	O
.	O
</s>
<s>
1941	O
–	O
Predating	O
comparable	O
work	O
by	O
at	O
least	O
a	O
decade	O
,	O
Konrad	O
Zuse	O
develops	O
computer	B-Application
chess	I-Application
algorithms	O
in	O
his	O
Plankalkül	B-Language
programming	O
formalism	O
.	O
</s>
<s>
1948	O
–	O
Norbert	O
Wiener	O
's	O
book	O
Cybernetics	O
describes	O
how	O
a	O
chess	B-Application
program	I-Application
could	O
be	O
developed	O
using	O
a	O
depth-limited	O
minimax	B-Algorithm
search	O
with	O
an	O
evaluation	B-General_Concept
function	I-General_Concept
.	O
</s>
<s>
1950	O
–	O
Claude	O
Shannon	O
publishes	O
"	O
Programming	O
a	O
Computer	O
for	O
Playing	O
Chess	B-Application
"	O
,	O
one	O
of	O
the	O
first	O
papers	O
on	O
the	O
algorithmic	O
methods	O
of	O
computer	B-Application
chess	I-Application
.	O
</s>
<s>
1951	O
–	O
Alan	O
Turing	O
is	O
first	O
to	O
publish	O
a	O
program	O
,	O
developed	O
on	O
paper	O
,	O
that	O
was	O
capable	O
of	O
playing	O
a	O
full	O
game	O
of	O
chess	B-Application
(	O
dubbed	O
Turochamp	O
)	O
.	O
</s>
<s>
1952	O
–	O
Dietrich	O
Prinz	O
develops	O
a	O
program	O
that	O
solves	O
chess	B-Application
problems	O
.	O
</s>
<s>
1956	O
–	O
Los	O
Alamos	O
chess	B-Application
is	O
the	O
first	O
program	O
to	O
play	O
a	O
chess-like	O
game	O
,	O
developed	O
by	O
Paul	O
Stein	O
and	O
Mark	O
Wells	O
for	O
the	O
MANIAC	B-Device
I	I-Device
computer	O
.	O
</s>
<s>
1956	O
–	O
John	O
McCarthy	O
invents	O
the	O
alpha	B-Algorithm
–	I-Algorithm
beta	I-Algorithm
search	I-Algorithm
algorithm	O
.	O
</s>
<s>
1957	O
–	O
The	O
first	O
programs	O
that	O
can	O
play	O
a	O
full	O
game	O
of	O
chess	B-Application
are	O
developed	O
,	O
one	O
by	O
Alex	O
Bernstein	O
and	O
one	O
by	O
Russian	O
programmers	O
using	O
a	O
BESM	B-Device
.	O
</s>
<s>
1958	O
–	O
NSS	O
becomes	O
the	O
first	O
chess	B-Application
program	I-Application
to	O
use	O
the	O
alpha	B-Algorithm
–	I-Algorithm
beta	I-Algorithm
search	I-Algorithm
algorithm	O
.	O
</s>
<s>
1962	O
–	O
The	O
first	O
program	O
to	O
play	O
credibly	O
,	O
Kotok-McCarthy	B-Application
,	O
is	O
published	O
at	O
MIT	O
.	O
</s>
<s>
1963	O
–	O
Grandmaster	O
David	O
Bronstein	O
defeats	O
an	O
M-20	O
running	O
an	O
early	O
chess	B-Application
program	I-Application
.	O
</s>
<s>
1966	O
–	O
67	O
–	O
The	O
first	O
chess	B-Application
match	O
between	O
computer	O
programs	O
is	O
played	O
.	O
</s>
<s>
Moscow	O
Institute	O
for	O
Theoretical	O
and	O
Experimental	O
Physics	O
(	O
ITEP	O
)	O
defeats	O
Kotok-McCarthy	B-Application
at	O
Stanford	O
University	O
by	O
telegraph	O
over	O
nine	O
months	O
.	O
</s>
<s>
1967	O
–	O
Mac	B-Application
Hack	I-Application
VI	I-Application
,	O
by	O
Richard	O
Greenblatt	O
et	O
al	O
.	O
</s>
<s>
introduces	O
transposition	B-General_Concept
tables	I-General_Concept
and	O
employs	O
dozens	O
of	O
carefully	O
tuned	O
move	O
selection	O
heuristics	B-Algorithm
;	O
it	O
becomes	O
the	O
first	O
program	O
to	O
defeat	O
a	O
person	O
in	O
tournament	O
play	O
.	O
</s>
<s>
Mac	B-Application
Hack	I-Application
VI	I-Application
played	O
about	O
C	O
class	O
level	O
.	O
</s>
<s>
1968	O
–	O
Scottish	O
chess	B-Application
champion	O
David	O
Levy	O
makes	O
a	O
500	O
pound	O
bet	O
with	O
AI	O
pioneers	O
John	O
McCarthy	O
and	O
Donald	O
Michie	O
that	O
no	O
computer	O
program	O
would	O
win	O
a	O
chess	B-Application
match	O
against	O
him	O
within	O
10	O
years	O
.	O
</s>
<s>
1970	O
–	O
Monty	O
Newborn	O
and	O
the	O
Association	O
for	O
Computing	O
Machinery	O
organize	O
the	O
first	O
North	O
American	O
Computer	B-Application
Chess	I-Application
Championships	O
in	O
New	O
York	O
.	O
</s>
<s>
1971	O
–	O
Ken	O
Thompson	O
,	O
an	O
American	O
Computer	O
scientist	O
at	O
Bell	O
Labs	O
and	O
creator	O
of	O
the	O
Unix	B-Application
operating	I-Application
system	I-Application
,	O
writes	O
his	O
first	O
chess-playing	B-Application
program	I-Application
called	O
"	O
chess	B-Application
"	O
for	O
the	O
earliest	O
version	O
of	O
Unix	B-Application
.	O
</s>
<s>
1974	O
–	O
David	O
Levy	O
,	O
Ben	O
Mittman	O
and	O
Monty	O
Newborn	O
organize	O
the	O
first	O
World	O
Computer	B-Application
Chess	I-Application
Championship	O
which	O
is	O
won	O
by	O
the	O
Russian	O
program	O
Kaissa	O
.	O
</s>
<s>
1975	O
–	O
After	O
nearly	O
a	O
decade	O
of	O
only	O
marginal	O
progress	O
since	O
the	O
high-water	O
mark	O
of	O
Greenblatt	O
's	O
MacHack	B-Application
VI	O
in	O
1967	O
,	O
Northwestern	O
University	O
Chess	B-Application
4.5	O
is	O
introduced	O
featuring	O
full-width	O
search	O
,	O
and	O
innovations	O
of	O
bitboards	B-Application
and	O
iterative	O
deepening	O
.	O
</s>
<s>
It	O
also	O
reinstated	O
a	O
transposition	B-General_Concept
table	I-General_Concept
as	O
first	O
seen	O
in	O
Greenblatt	O
's	O
program	O
.	O
</s>
<s>
Chess	B-Application
4.5	O
played	O
strong	O
B-class	O
and	O
won	O
the	O
3rd	O
World	O
Computer	B-Application
Chess	I-Application
Championship	O
the	O
next	O
year	O
.	O
</s>
<s>
Northwestern	O
University	O
Chess	B-Application
and	O
its	O
descendants	O
dominated	O
computer	B-Application
chess	I-Application
until	O
the	O
era	O
of	O
hardware	O
chess	B-Application
machines	I-Application
in	O
the	O
early	O
1980s	O
.	O
</s>
<s>
1976	O
–	O
In	O
December	O
,	O
Canadian	O
programmer	O
Peter	O
R	O
.	O
Jennings	O
releases	O
Microchess	B-Application
,	O
the	O
first	O
game	O
for	O
microcomputers	O
to	O
be	O
sold	O
.	O
</s>
<s>
1977	O
–	O
In	O
March	O
,	O
Fidelity	O
Electronics	O
releases	O
Chess	B-Application
Challenger	O
,	O
the	O
first	O
dedicated	O
chess	B-Application
computer	I-Application
to	O
be	O
sold	O
.	O
</s>
<s>
The	O
International	O
Computer	B-Application
Chess	I-Application
Association	O
is	O
founded	O
by	O
chess	B-Application
programmers	O
to	O
organize	O
computer	B-Application
chess	I-Application
championships	O
and	O
report	O
on	O
research	O
and	O
advancements	O
on	O
computer	B-Application
chess	I-Application
in	O
their	O
journal	O
.	O
</s>
<s>
Also	O
that	O
year	O
,	O
Applied	O
Concepts	O
released	O
Boris	O
,	O
a	O
dedicated	O
chess	B-Application
computer	I-Application
in	O
a	O
wooden	O
box	O
with	O
plastic	O
chess	B-Application
pieces	O
and	O
a	O
folding	O
board	O
.	O
</s>
<s>
1978	O
–	O
David	O
Levy	O
wins	O
the	O
bet	O
made	O
10	O
years	O
earlier	O
,	O
defeating	O
Chess	B-Application
4.7	O
in	O
a	O
six-game	O
match	O
by	O
a	O
score	O
of	O
4½	O
–	O
1½	O
.	O
</s>
<s>
1979	O
–	O
Frederic	O
Friedel	O
organizes	O
a	O
match	O
between	O
IM	O
David	O
Levy	O
and	O
Chess	B-Application
4.8	O
,	O
which	O
is	O
broadcast	O
on	O
German	O
television	O
.	O
</s>
<s>
Levy	O
and	O
Chess	B-Application
4.8	O
,	O
running	O
on	O
a	O
CDC	O
Cyber	O
176	O
,	O
the	O
most	O
powerful	O
computer	O
in	O
the	O
world	O
,	O
fought	O
a	O
grueling	O
89	O
move	O
draw	O
.	O
</s>
<s>
In	O
Germany	O
,	O
Hegener	B-General_Concept
&	I-General_Concept
Glaser	I-General_Concept
release	O
their	O
first	O
Mephisto	B-General_Concept
dedicated	O
chess	B-Application
computer	I-Application
.	O
</s>
<s>
The	O
USCF	O
prohibits	O
computers	O
from	O
competing	O
in	O
human	O
tournaments	O
except	O
when	O
represented	O
by	O
the	O
chess	B-Application
systems	O
 '	O
creators	O
.	O
</s>
<s>
The	O
Fredkin	O
Prize	O
,	O
offering	O
$	O
100,000	O
to	O
the	O
creator	O
of	O
the	O
first	O
chess	B-Application
machine	I-Application
to	O
defeat	O
the	O
world	O
chess	B-Application
champion	O
,	O
is	O
established	O
.	O
</s>
<s>
1981	O
–	O
Cray	B-General_Concept
Blitz	I-General_Concept
wins	O
the	O
Mississippi	O
State	O
Championship	O
with	O
a	O
perfect	O
5	O
–	O
0	O
score	O
and	O
a	O
performance	O
rating	O
of	O
2258	O
.	O
</s>
<s>
1984	O
–	O
The	O
German	O
Company	O
Hegener	B-General_Concept
&	I-General_Concept
Glaser	I-General_Concept
's	O
Mephisto	B-General_Concept
line	O
of	O
dedicated	O
chess	B-Application
computers	I-Application
begins	O
a	O
long	O
streak	O
of	O
victories	O
(	O
1984	O
–	O
1990	O
)	O
in	O
the	O
World	O
Microcomputer	O
Championship	O
using	O
dedicated	O
computers	O
running	O
programs	O
ChessGenius	B-Application
and	O
Rebel	B-Application
.	O
</s>
<s>
1986	O
–	O
Software	O
Country	O
(	O
see	O
Software	O
Toolworks	O
)	O
released	O
Chessmaster	B-Application
2000	I-Application
based	O
on	O
an	O
engine	B-Application
by	O
David	O
Kittinger	O
,	O
the	O
first	O
edition	O
of	O
what	O
was	O
to	O
become	O
the	O
world	O
's	O
best	O
selling	O
line	O
of	O
chess	B-Application
programs	I-Application
.	O
</s>
<s>
1987	O
–	O
Frederic	O
Friedel	O
and	O
physicist	O
Matthias	O
Wüllenweber	O
found	O
Chessbase	O
,	O
releasing	O
the	O
first	O
chess	B-Application
database	O
program	O
.	O
</s>
<s>
Stuart	O
Cracraft	O
releases	O
GNU	B-Application
Chess	I-Application
,	O
one	O
of	O
the	O
first	O
'	O
chess	B-Application
engines	I-Application
 '	I-Application
to	O
be	O
bundled	O
with	O
a	O
separate	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
,	O
.	O
</s>
<s>
1988	O
–	O
HiTech	B-General_Concept
,	O
developed	O
by	O
Hans	O
Berliner	O
and	O
Carl	O
Ebeling	O
,	O
wins	O
a	O
match	O
against	O
grandmaster	O
Arnold	O
Denker	O
3½	O
–	O
½	O
.	O
</s>
<s>
Deep	B-General_Concept
Thought	I-General_Concept
shares	O
first	O
place	O
with	O
Tony	O
Miles	O
in	O
the	O
Software	O
Toolworks	O
Championship	O
,	O
ahead	O
of	O
former	O
world	O
champion	O
Mikhail	O
Tal	O
and	O
several	O
grandmasters	O
including	O
Samuel	O
Reshevsky	O
,	O
Walter	O
Browne	O
and	O
Mikhail	O
Gurevich	O
.	O
</s>
<s>
1989	O
–	O
Deep	B-General_Concept
Thought	I-General_Concept
demolishes	O
David	O
Levy	O
in	O
a	O
4-game	O
match	O
0	O
–	O
4	O
,	O
bringing	O
to	O
an	O
end	O
his	O
famous	O
series	O
of	O
wagers	O
starting	O
in	O
1968	O
.	O
</s>
<s>
1990	O
–	O
On	O
April	O
25	O
,	O
former	O
world	O
champion	O
Anatoly	O
Karpov	O
lost	O
in	O
a	O
simul	O
to	O
Hegener	B-General_Concept
&	I-General_Concept
Glaser	I-General_Concept
's	O
Mephisto	B-General_Concept
Portorose	O
M68030	O
chess	B-Application
computer	I-Application
.	O
</s>
<s>
1992	O
–	O
ChessMachine	B-General_Concept
wins	O
the	O
7th	O
World	O
Computer	B-Application
Chess	I-Application
Championship	O
,	O
the	O
first	O
time	O
a	O
microcomputer	O
beat	O
mainframes	B-Architecture
.	O
</s>
<s>
Chess	B-Application
programs	I-Application
running	O
on	O
personal	O
computers	O
surpass	O
Mephisto	B-General_Concept
's	O
dedicated	O
chess	B-Application
computers	I-Application
to	O
win	O
the	O
Microcomputer	O
Championship	O
,	O
marking	O
a	O
shift	O
from	O
dedicated	O
chess	B-Application
hardware	O
to	O
software	O
on	O
multipurpose	O
personal	O
computers	O
.	O
</s>
<s>
1995	O
–	O
Fritz	B-Application
3	I-Application
,	O
running	O
on	O
a	O
90Mhz	O
Pentium	O
PC	O
,	O
beats	O
Deep	O
Thought-2	O
dedicated	O
chess	B-Application
machine	I-Application
,	O
and	O
programs	O
running	O
on	O
several	O
super-computers	B-Architecture
,	O
to	O
win	O
the	O
8th	O
World	O
Computer	B-Application
Chess	I-Application
Championships	O
in	O
Hong	O
Kong	O
.	O
</s>
<s>
This	O
marks	O
the	O
first	O
time	O
a	O
chess	B-Application
program	I-Application
running	O
on	O
commodity	O
hardware	O
defeats	O
specialized	O
chess	B-Application
machines	I-Application
and	O
massive	O
super-computers	B-Architecture
,	O
indicating	O
a	O
shift	O
in	O
emphasis	O
from	O
brute	O
computational	O
power	O
to	O
algorithmic	O
improvements	O
in	O
the	O
evolution	O
of	O
chess	B-Application
engines	I-Application
.	O
</s>
<s>
1996	O
–	O
IBM	O
's	O
Deep	B-General_Concept
Blue	I-General_Concept
loses	O
a	O
six-game	O
match	O
against	O
Garry	O
Kasparov	O
,	O
2	O
–	O
4	O
.	O
</s>
<s>
2000	O
–	O
Stefan	O
Meyer-Kahlen	O
and	O
Rudolf	O
Huber	O
draft	O
the	O
Universal	B-General_Concept
Chess	I-General_Concept
Interface	I-General_Concept
,	O
a	O
protocol	O
for	O
GUIs	B-Application
to	O
talk	O
to	O
engines	O
that	O
would	O
gradually	O
become	O
the	O
main	O
form	O
new	O
engines	O
would	O
take	O
.	O
</s>
<s>
2002	O
–	O
Vladimir	O
Kramnik	O
draws	O
an	O
eight-game	O
match	O
against	O
Deep	B-Application
Fritz	I-Application
.	O
</s>
<s>
2003	O
–	O
Kasparov	O
draws	O
a	O
six-game	O
match	O
against	O
Deep	B-Application
Junior	I-Application
and	O
draws	O
a	O
four-game	O
match	O
against	O
X3D	B-Application
Fritz	I-Application
.	O
</s>
<s>
2004	O
–	O
a	O
team	O
of	O
computers	O
(	O
Hydra	B-Architecture
,	O
Deep	B-Application
Junior	I-Application
and	O
Fritz	B-Application
)	O
wins	O
8½	O
–	O
3½	O
against	O
a	O
strong	O
human	O
team	O
formed	O
by	O
Veselin	O
Topalov	O
,	O
Ruslan	O
Ponomariov	O
and	O
Sergey	O
Karjakin	O
,	O
who	O
had	O
an	O
average	O
Elo	O
rating	O
of	O
2681	O
.	O
</s>
<s>
Fabien	O
Letouzey	O
releases	O
the	O
source	O
code	O
for	O
Fruit	B-Application
2.1	O
,	O
an	O
engine	B-Application
quite	O
competitive	O
with	O
the	O
top	O
closed-source	O
engines	O
of	O
the	O
time	O
.	O
</s>
<s>
2005	O
–	O
Rybka	B-Application
wins	O
the	O
IPCCC	O
tournament	O
and	O
very	O
quickly	O
afterwards	O
becomes	O
the	O
strongest	O
engine	B-Application
.	O
</s>
<s>
2006	O
–	O
The	O
world	O
champion	O
,	O
Vladimir	O
Kramnik	O
,	O
is	O
defeated	O
4	O
–	O
2	O
by	O
Deep	B-Application
Fritz	I-Application
.	O
</s>
<s>
2009	O
–	O
Pocket	B-Application
Fritz	I-Application
.	O
</s>
<s>
4	O
running	O
on	O
a	O
smartphone	B-Application
,	O
wins	O
Copa	O
Mercosur	O
,	O
an	O
International	O
Master	O
level	O
tournament	O
,	O
scoring	O
9½/10	O
and	O
earning	O
a	O
performance	O
rating	O
of	O
2900	O
.	O
</s>
<s>
A	O
group	O
of	O
pseudonymous	O
Russian	O
programmers	O
release	O
the	O
source	O
code	O
of	O
Ippolit	B-Application
,	O
an	O
engine	B-Application
seemingly	O
stronger	O
than	O
Rybka	B-Application
.	O
</s>
<s>
This	O
becomes	O
the	O
basis	O
for	O
the	O
engines	O
Robbolito	O
and	O
Ivanhoe	O
,	O
and	O
many	O
engine	B-Application
authors	O
adopt	O
ideas	O
from	O
it	O
.	O
</s>
<s>
2010	O
–	O
Before	O
the	O
World	O
Chess	B-Application
Championship	O
2010	O
,	O
Topalov	O
prepares	O
by	O
sparring	O
against	O
the	O
supercomputer	B-Architecture
Blue	O
Gene	O
with	O
8,192	O
processors	O
capable	O
of	O
500trillion	O
(	O
5	O
×	O
1014	O
)	O
floating-point	O
operations	O
per	O
second	O
.	O
</s>
<s>
Rybka	B-Application
developer	O
,	O
Vasik	O
Rajlich	O
,	O
accuses	O
Ippolit	B-Application
of	O
being	O
a	O
clone	O
of	O
Rybka	B-Application
.	O
</s>
<s>
2011	O
–	O
The	O
ICGA	O
strips	O
Rybka	B-Application
of	O
its	O
WCCC	O
titles	O
.	O
</s>
<s>
2017	O
–	O
AlphaZero	B-Application
,	O
a	O
neural	O
net-based	O
digital	O
automaton	O
,	O
beats	O
Stockfish	B-Application
28	O
–	O
0	O
,	O
with	O
72	O
draws	O
,	O
in	O
a	O
100-game	O
match	O
.	O
</s>
<s>
2018	O
-	O
Efficiently	B-General_Concept
updatable	I-General_Concept
neural	I-General_Concept
network	I-General_Concept
(	O
NNUE	B-General_Concept
)	O
evaluation	O
is	O
invented	O
for	O
computer	B-Application
shogi	I-Application
.	O
</s>
<s>
2019	O
–	O
Leela	B-Application
Chess	I-Application
Zero	I-Application
(	O
LCZero	B-Application
v0.21.1-nT40.T8.610	O
)	O
,	O
a	O
chess	B-Application
engine	I-Application
based	O
on	O
AlphaZero	B-Application
,	O
defeats	O
Stockfish	B-Application
19050918	O
in	O
a	O
100-game	O
match	O
with	O
the	O
final	O
score	O
53.5	O
to	O
46.5	O
to	O
win	O
TCEC	O
season	O
15	O
.	O
</s>
<s>
2020	O
-	O
NNUE	B-General_Concept
is	O
added	O
to	O
Stockfish	B-Application
evaluation	O
,	O
noticeably	O
increasing	O
its	O
strength	O
.	O
</s>
<s>
These	O
chess	B-Application
playing	O
systems	O
include	O
custom	O
hardware	O
with	O
approx	O
.	O
</s>
<s>
MuZero	B-Application
2019	O
(	O
similar	O
hardware	O
to	O
its	O
predecessor	O
AlphaZero	B-Application
,	O
non-specific	O
to	O
Chess	B-Application
or	O
e.g.	O
</s>
<s>
In	O
the	O
late	O
1970s	O
to	O
early	O
1990s	O
,	O
there	O
was	O
a	O
competitive	O
market	O
for	O
dedicated	O
chess	B-Application
computers	I-Application
.	O
</s>
<s>
Boris	O
in	O
1977	O
and	O
Boris	O
Diplomat	O
in	O
1979	O
,	O
chess	B-Application
computers	I-Application
including	O
pieces	O
and	O
board	O
,	O
sold	O
by	O
Applied	O
Concepts	O
Inc	O
.	O
</s>
<s>
Chess	B-Application
Challenger	O
,	O
a	O
line	O
of	O
chess	B-Application
computers	I-Application
sold	O
by	O
Fidelity	O
Electronics	O
from	O
1977	O
to	O
1992	O
.	O
</s>
<s>
These	O
models	O
won	O
the	O
first	O
four	O
World	O
Microcomputer	O
Chess	B-Application
Championships	O
.	O
</s>
<s>
ChessMachine	B-General_Concept
,	O
an	O
ARM-based	O
dedicated	O
computer	O
,	O
which	O
could	O
run	O
two	O
engines	O
:	O
</s>
<s>
"	O
The	O
King	O
"	O
,	O
which	O
later	O
became	O
the	O
Chessmaster	O
engine	B-Application
,	O
was	O
also	O
used	O
in	O
the	O
TASC	O
R30	O
dedicated	O
computer	O
.	O
</s>
<s>
Gideon	O
,	O
a	O
version	O
of	O
Rebel	B-Application
,	O
in	O
1992	O
became	O
the	O
first	O
microcomputer	O
to	O
win	O
the	O
World	O
Computer	B-Application
Chess	I-Application
Championship	O
.	O
</s>
<s>
Mephisto	B-General_Concept
,	O
a	O
line	O
of	O
chess	B-Application
computers	I-Application
sold	O
by	O
Hegener	B-General_Concept
&	I-General_Concept
Glaser	I-General_Concept
.	O
</s>
<s>
The	O
units	O
won	O
six	O
consecutive	O
World	O
Microcomputer	O
Chess	B-Application
Championships	O
.	O
</s>
<s>
Phoenix	O
Chess	B-Application
Systems	O
makes	O
limited	O
edition	O
units	O
based	O
around	O
StrongARM	B-Device
and	O
XScale	B-Application
processors	O
running	O
modern	O
engines	O
and	O
emulating	O
classic	O
engines	O
.	O
</s>
<s>
They	O
bought	O
out	O
Hegener	B-General_Concept
&	I-General_Concept
Glaser	I-General_Concept
and	O
its	O
Mephisto	B-General_Concept
brand	O
in	O
1994	O
.	O
</s>
<s>
Recently	O
,	O
some	O
hobbyists	O
have	O
been	O
using	O
the	O
Multi	B-Application
Emulator	I-Application
Super	I-Application
System	I-Application
to	O
run	O
the	O
chess	B-Application
programs	I-Application
created	O
for	O
Fidelity	O
or	O
Hegener	B-General_Concept
&	I-General_Concept
Glaser	I-General_Concept
's	O
Mephisto	B-General_Concept
computers	O
on	O
modern	O
64-bit	O
operating	O
systems	O
such	O
as	O
Windows	B-Operating_System
10	I-Operating_System
.	O
</s>
<s>
The	O
author	O
of	O
Rebel	B-Application
,	O
Ed	B-Application
Schröder	I-Application
has	O
also	O
adapted	O
three	O
of	O
the	O
Hegener	B-General_Concept
&	I-General_Concept
Glaser	I-General_Concept
Mephisto	B-General_Concept
's	O
he	O
wrote	O
to	O
work	O
as	O
UCI	O
engines	O
.	O
</s>
<s>
These	O
programs	O
can	O
be	O
run	O
on	O
MS-DOS	O
,	O
and	O
can	O
be	O
run	O
on	O
64-bit	O
Windows	B-Operating_System
10	I-Operating_System
via	O
emulators	O
such	O
as	O
DOSBox	B-Application
or	O
Qemu	B-Application
:	O
</s>
<s>
Well-known	O
computer	B-Application
chess	I-Application
theorists	O
include	O
:	O
</s>
<s>
The	O
prospects	O
of	O
completely	O
solving	O
chess	B-Application
are	O
generally	O
considered	O
to	O
be	O
rather	O
remote	O
.	O
</s>
<s>
It	O
is	O
widely	O
conjectured	O
that	O
there	O
is	O
no	O
computationally	O
inexpensive	O
method	O
to	O
solve	O
chess	B-Application
even	O
in	O
the	O
weak	O
sense	O
of	O
determining	O
with	O
certainty	O
the	O
value	O
of	O
the	O
initial	O
position	O
,	O
and	O
hence	O
the	O
idea	O
of	O
solving	O
chess	B-Application
in	O
the	O
stronger	O
sense	O
of	O
obtaining	O
a	O
practically	O
usable	O
description	O
of	O
a	O
strategy	O
for	O
perfect	O
play	O
for	O
either	O
side	O
seems	O
unrealistic	O
today	O
.	O
</s>
<s>
However	O
,	O
it	O
has	O
not	O
been	O
proven	O
that	O
no	O
computationally	O
cheap	O
way	O
of	O
determining	O
the	O
best	O
move	O
in	O
a	O
chess	B-Application
position	O
exists	O
,	O
nor	O
even	O
that	O
a	O
traditional	O
alpha	B-Algorithm
–	I-Algorithm
beta	I-Algorithm
searcher	O
running	O
on	O
present-day	O
computing	O
hardware	O
could	O
not	O
solve	O
the	O
initial	O
position	O
in	O
an	O
acceptable	O
amount	O
of	O
time	O
.	O
</s>
<s>
The	O
difficulty	O
in	O
proving	O
the	O
latter	O
lies	O
in	O
the	O
fact	O
that	O
,	O
while	O
the	O
number	O
of	O
board	O
positions	O
that	O
could	O
happen	O
in	O
the	O
course	O
of	O
a	O
chess	B-Application
game	O
is	O
huge	O
(	O
on	O
the	O
order	O
of	O
at	O
least	O
1043	O
to	O
1047	O
)	O
,	O
it	O
is	O
hard	O
to	O
rule	O
out	O
with	O
mathematical	O
certainty	O
the	O
possibility	O
that	O
the	O
initial	O
position	O
allows	O
either	O
side	O
to	O
force	O
a	O
mate	O
or	O
a	O
threefold	O
repetition	O
after	O
relatively	O
few	O
moves	O
,	O
in	O
which	O
case	O
the	O
search	O
tree	O
might	O
encompass	O
only	O
a	O
very	O
small	O
subset	O
of	O
the	O
set	O
of	O
possible	O
positions	O
.	O
</s>
<s>
It	O
has	O
been	O
mathematically	O
proven	O
that	O
generalized	O
chess	B-Application
(	O
chess	B-Application
played	O
with	O
an	O
arbitrarily	O
large	O
number	O
of	O
pieces	O
on	O
an	O
arbitrarily	O
large	O
chessboard	O
)	O
is	O
EXPTIME-complete	O
,	O
meaning	O
that	O
determining	O
the	O
winning	O
side	O
in	O
an	O
arbitrary	O
position	O
of	O
generalized	O
chess	B-Application
provably	O
takes	O
exponential	O
time	O
in	O
the	O
worst	O
case	O
;	O
however	O
,	O
this	O
theoretical	O
result	O
gives	O
no	O
lower	O
bound	O
on	O
the	O
amount	O
of	O
work	O
required	O
to	O
solve	O
ordinary	O
8x8	O
chess	B-Application
.	O
</s>
<s>
A	O
"	O
chess	B-Application
engine	I-Application
"	O
is	O
software	O
that	O
calculates	O
and	O
orders	O
which	O
moves	O
are	O
the	O
strongest	O
to	O
play	O
in	O
a	O
given	O
position	O
.	O
</s>
<s>
Engine	B-Application
authors	O
focus	O
on	O
improving	O
the	O
play	O
of	O
their	O
engines	O
,	O
often	O
just	O
importing	O
the	O
engine	B-Application
into	O
a	O
graphical	B-Application
user	I-Application
interface	I-Application
(	O
GUI	B-Application
)	O
developed	O
by	O
someone	O
else	O
.	O
</s>
<s>
Engines	O
communicate	O
with	O
the	O
GUI	B-Application
by	O
standardized	O
protocols	O
such	O
as	O
the	O
nowadays	O
ubiquitous	O
Universal	B-General_Concept
Chess	I-General_Concept
Interface	I-General_Concept
developed	O
by	O
Stefan	O
Meyer-Kahlen	O
and	O
Franz	O
Huber	O
.	O
</s>
<s>
There	O
are	O
others	O
,	O
like	O
the	O
Chess	B-Application
Engine	I-Application
Communication	O
Protocol	O
developed	O
by	O
Tim	O
Mann	O
for	O
GNU	B-Application
Chess	I-Application
and	O
Winboard	B-Application
.	O
</s>
<s>
Chessbase	O
has	O
its	O
own	O
proprietary	O
protocol	O
,	O
and	O
at	O
one	O
time	O
Millennium	O
2000	O
had	O
another	O
protocol	O
used	O
for	O
ChessGenius	B-Application
.	O
</s>
<s>
Chess	B-Application
engines	I-Application
are	O
regularly	O
matched	O
against	O
each	O
other	O
at	O
dedicated	O
chess	B-Application
engine	I-Application
tournaments	O
.	O
</s>
<s>
In	O
1997	O
,	O
the	O
Internet	O
Chess	B-Application
Club	O
released	O
its	O
first	O
Java	O
client	O
for	O
playing	O
chess	B-Application
online	O
against	O
other	O
people	O
inside	O
one	O
's	O
webbrowser	O
.	O
</s>
<s>
This	O
was	O
probably	O
one	O
of	O
the	O
first	O
chess	B-Application
web	O
apps	O
.	O
</s>
<s>
Free	O
Internet	O
Chess	B-Application
Server	O
followed	O
soon	O
after	O
with	O
a	O
similar	O
client	O
.	O
</s>
<s>
In	O
2004	O
,	O
International	O
Correspondence	O
Chess	B-Application
Federation	O
opened	O
up	O
a	O
web	O
server	O
to	O
replace	O
their	O
email-based	O
system	O
.	O
</s>
<s>
Chess.com	B-Application
started	O
offering	O
Live	O
Chess	B-Application
in	O
2007	O
.	O
</s>
<s>
The	O
now	O
defunct	O
Chess	B-Application
Tactics	O
Server	O
opened	O
its	O
site	O
in	O
2006	O
,	O
followed	O
by	O
Chesstempo	O
the	O
next	O
year	O
,	O
and	O
Chess.com	B-Application
added	O
its	O
Tactics	O
Trainer	O
in	O
2008	O
.	O
</s>
<s>
Chessbase	O
took	O
their	O
chess	B-Application
game	O
database	O
online	O
in	O
1998	O
.	O
</s>
<s>
Another	O
early	O
chess	B-Application
game	O
databases	O
was	O
Chess	B-Application
Lab	O
,	O
which	O
started	O
in	O
1999	O
.	O
</s>
<s>
New	O
In	O
Chess	B-Application
had	O
initially	O
tried	O
to	O
compete	O
with	O
Chessbase	O
by	O
releasing	O
a	O
NICBase	O
program	O
for	O
Windows	O
3.x	O
,	O
but	O
eventually	O
,	O
decided	O
to	O
give	O
up	O
on	O
software	O
,	O
and	O
instead	O
focus	O
on	O
their	O
online	O
database	O
starting	O
in	O
2002	O
.	O
</s>
<s>
One	O
could	O
play	O
against	O
the	O
engine	B-Application
Shredder	B-Application
online	O
from	O
2006	O
.	O
</s>
<s>
In	O
2015	O
,	O
Chessbase	O
added	O
a	O
play	O
Fritz	B-Application
web	O
app	O
,	O
as	O
well	O
as	O
My	O
Games	O
for	O
storing	O
one	O
's	O
games	O
.	O
</s>
<s>
Starting	O
in	O
2007	O
,	O
Chess.com	B-Application
offered	O
the	O
content	O
of	O
the	O
training	O
program	O
,	O
Chess	B-Application
Mentor	O
,	O
to	O
their	O
customers	O
online	O
.	O
</s>
