<s>
Natural	B-Algorithm
evolution	I-Algorithm
strategies	I-Algorithm
(	O
NES	O
)	O
are	O
a	O
family	O
of	O
numerical	O
optimization	O
algorithms	O
for	O
black	B-Device
box	I-Device
problems	O
.	O
</s>
<s>
Similar	O
in	O
spirit	O
to	O
evolution	B-Algorithm
strategies	I-Algorithm
,	O
they	O
iteratively	O
update	O
the	O
(	O
continuous	O
)	O
parameters	O
of	O
a	O
search	O
distribution	O
by	O
following	O
the	O
natural	O
gradient	O
towards	O
higher	O
expected	O
fitness	O
.	O
</s>
<s>
NES	O
then	O
performs	O
a	O
gradient	B-Algorithm
ascent	I-Algorithm
step	O
along	O
the	O
natural	O
gradient	O
,	O
a	O
second	O
order	O
method	O
which	O
,	O
unlike	O
the	O
plain	O
gradient	O
,	O
renormalizes	O
the	O
update	O
with	O
respect	O
to	O
uncertainty	O
.	O
</s>
<s>
In	O
high	O
dimensions	O
,	O
on	O
the	O
other	O
hand	O
,	O
a	O
more	O
scalable	O
alternative	O
is	O
to	O
limit	O
the	O
covariance	O
to	O
the	O
diagonal	B-Algorithm
only	O
.	O
</s>
<s>
through	O
gradient	B-Algorithm
ascent	I-Algorithm
.	O
</s>
