<s>
KnightCap	B-Application
is	O
an	O
open	O
source	O
computer	O
chess	B-Application
engine	I-Application
.	O
</s>
<s>
KnightCap	B-Application
is	O
free	B-Application
software	I-Application
released	O
under	O
the	O
GNU	B-License
GPL	I-License
.	O
</s>
<s>
In	O
most	O
ways	O
,	O
KnightCap	B-Application
is	O
a	O
fairly	O
typical	O
modern	O
program	O
.	O
</s>
<s>
It	O
uses	O
bitboard	B-Application
data	O
structures	O
that	O
are	O
slightly	O
different	O
from	O
those	O
that	O
were	O
well	O
known	O
in	O
1996	O
,	O
but	O
obvious	O
enough	O
and	O
probably	O
well	O
known	O
now	O
.	O
</s>
<s>
There	O
is	O
backward	O
pruning	O
using	O
MTD(f )	O
(	O
a	O
method	O
approximately	O
equivalent	O
to	O
Alpha-beta	B-Algorithm
pruning	I-Algorithm
but	O
slightly	O
more	O
efficient	O
in	O
some	O
settings	O
)	O
.	O
</s>
<s>
There	O
is	O
Null-move	B-Algorithm
heuristic	I-Algorithm
.	O
</s>
<s>
The	O
most	O
original	O
feature	O
of	O
KnightCap	B-Application
,	O
introduced	O
in	O
the	O
late	O
1990s	O
,	O
was	O
an	O
experiment	O
in	O
temporal	O
difference	O
learning	O
as	O
applied	O
to	O
chess	O
.	O
</s>
<s>
This	O
technique	O
allowed	O
KnightCap	B-Application
to	O
automatically	O
tune	O
the	O
weights	O
applied	O
to	O
the	O
various	O
features	O
in	O
its	O
evaluation	B-General_Concept
function	I-General_Concept
based	O
on	O
the	O
games	O
it	O
played	O
.	O
</s>
<s>
For	O
a	O
while	O
in	O
the	O
1990s	O
,	O
KnightCap	B-Application
was	O
quite	O
active	O
on	O
chess	B-Application
servers	I-Application
on	O
the	O
Internet	O
,	O
but	O
it	O
is	O
now	O
semi-retired	O
and	O
rarely	O
seen	O
.	O
</s>
