<s>
In	O
abstract	O
strategy	O
board	O
games	O
,	O
candidate	B-General_Concept
moves	I-General_Concept
are	O
moves	O
which	O
,	O
upon	O
initial	O
observation	O
of	O
the	O
position	O
,	O
seem	O
to	O
warrant	O
further	O
analysis	O
.	O
</s>
<s>
Although	O
in	O
theory	O
the	O
idea	O
of	O
candidate	B-General_Concept
moves	I-General_Concept
can	O
be	O
applied	O
to	O
games	O
such	O
as	O
checkers	O
,	O
go	O
,	O
and	O
xiangqi	O
,	O
it	O
is	O
most	O
often	O
used	O
in	O
the	O
context	O
of	O
chess	B-Application
.	O
</s>
<s>
The	O
idea	O
of	O
candidate	B-General_Concept
moves	I-General_Concept
was	O
first	O
put	O
forth	O
by	O
Grandmaster	O
Alexander	O
Kotov	O
in	O
his	O
book	O
Think	O
Like	O
a	O
Grandmaster	O
.	O
</s>
<s>
In	O
it	O
,	O
Kotov	O
recommended	O
looking	O
for	O
several	O
moves	O
that	O
seemed	O
feasible	O
–	O
the	O
so-called	O
candidate	B-General_Concept
moves	I-General_Concept
–	O
and	O
then	O
analyzing	O
those	O
moves	O
one	O
at	O
a	O
time	O
.	O
</s>
<s>
Although	O
this	O
idea	O
had	O
been	O
practiced	O
by	O
expert	O
chess	B-Application
players	O
for	O
some	O
time	O
,	O
it	O
had	O
never	O
been	O
explicitly	O
articulated	O
,	O
and	O
was	O
relatively	O
unknown	O
to	O
players	O
at	O
the	O
amateur	O
level	O
.	O
</s>
<s>
The	O
idea	O
quickly	O
caught	O
on	O
,	O
and	O
is	O
now	O
considered	O
standard	O
practice	O
among	O
chess	B-Application
players	O
at	O
all	O
levels	O
.	O
</s>
<s>
Many	O
beginning	O
players	O
are	O
taught	O
about	O
candidate	B-General_Concept
moves	I-General_Concept
as	O
soon	O
as	O
they	O
learn	O
to	O
play	O
the	O
game	O
,	O
and	O
there	O
are	O
numerous	O
references	O
to	O
the	O
idea	O
in	O
other	O
chess	B-Application
books	O
.	O
</s>
<s>
Finding	O
the	O
correct	O
candidate	B-General_Concept
moves	I-General_Concept
is	O
often	O
one	O
of	O
the	O
most	O
difficult	O
aspects	O
of	O
becoming	O
a	O
better	O
chess	B-Application
player	O
.	O
</s>
<s>
For	O
example	O
,	O
if	O
a	O
player	O
notices	O
that	O
his	O
opponent	O
's	O
king	O
is	O
on	O
the	O
g8	O
square	O
,	O
and	O
that	O
his	O
knight	O
is	O
on	O
f3	O
,	O
then	O
a	O
candidate	B-General_Concept
move	I-General_Concept
might	O
be	O
Ng5	O
,	O
a	O
fairly	O
common	O
beginning	O
to	O
a	O
sacrifice	O
.	O
</s>
<s>
Once	O
a	O
player	O
has	O
found	O
a	O
good	O
number	O
of	O
candidate	B-General_Concept
moves	I-General_Concept
(	O
every	O
position	O
is	O
different	O
,	O
although	O
four	O
to	O
six	O
moves	O
is	O
usually	O
the	O
norm	O
)	O
,	O
a	O
player	O
may	O
then	O
begin	O
to	O
systematically	O
analyze	O
these	O
moves	O
.	O
</s>
<s>
The	O
idea	O
behind	O
candidate	B-General_Concept
moves	I-General_Concept
is	O
to	O
help	O
structure	O
one	O
's	O
analysis	O
and	O
prevent	O
it	O
from	O
becoming	O
jumbled	O
;	O
inexperienced	O
players	O
who	O
do	O
not	O
carefully	O
consider	O
candidate	B-General_Concept
moves	I-General_Concept
will	O
often	O
find	O
themselves	O
jumping	O
between	O
lines	O
of	O
analysis	O
haphazardly	O
.	O
</s>
<s>
The	O
ability	O
of	O
humans	O
to	O
find	O
candidate	B-General_Concept
moves	I-General_Concept
remains	O
one	O
of	O
the	O
main	O
differences	O
between	O
them	O
and	O
computers	B-Application
.	O
</s>
<s>
Although	O
early	O
chess	B-Application
programmers	O
made	O
admirable	O
efforts	O
to	O
make	O
computers	B-Application
able	O
to	O
select	O
candidate	B-General_Concept
moves	I-General_Concept
(	O
see	O
Type	O
A	O
versus	O
Type	O
B	O
programs	O
)	O
,	O
they	O
never	O
played	O
particularly	O
well	O
,	O
and	O
were	O
soon	O
supplanted	O
by	O
computers	B-Application
using	O
brute-force	B-Algorithm
algorithms	I-Algorithm
(	O
Shenk	O
,	O
2006	O
)	O
.	O
</s>
<s>
The	O
addition	O
of	O
Alphabeta	B-Algorithm
algorithms	O
made	O
the	O
latter	O
type	O
even	O
more	O
feasible	O
.	O
</s>
<s>
Many	O
acknowledged	O
that	O
computers	B-Application
were	O
simply	O
not	O
capable	O
of	O
performing	O
the	O
complex	O
pattern	O
recognition	O
that	O
was	O
required	O
to	O
find	O
appropriate	O
candidate	B-General_Concept
moves	I-General_Concept
,	O
and	O
that	O
it	O
was	O
easier	O
to	O
have	O
computers	B-Application
perform	O
simple	O
exhaustive	B-Algorithm
searches	I-Algorithm
.	O
</s>
<s>
Today	O
,	O
most	O
chess	B-Application
programs	I-Application
still	O
rely	O
mainly	O
on	O
brute-force	B-Algorithm
searches	I-Algorithm
,	O
but	O
as	O
search	O
algorithms	O
have	O
improved	O
,	O
today	O
's	O
chess	B-Application
engines	I-Application
seem	O
more	O
and	O
more	O
to	O
be	O
using	O
candidate	B-General_Concept
moves	I-General_Concept
in	O
their	O
analysis	O
.	O
</s>
<s>
Hydra	B-Architecture
and	O
AlphaZero	B-Application
,	O
for	O
example	O
,	O
are	O
widely	O
considered	O
to	O
be	O
a	O
"	O
Type	O
B	O
"	O
(	O
candidate	B-General_Concept
move	I-General_Concept
finding	O
)	O
computer	O
.	O
</s>
