<s>
It	O
was	O
observed	O
in	O
evolution	B-Algorithm
strategies	I-Algorithm
that	O
significant	O
progress	O
toward	O
the	O
fitness/objective	O
function	O
's	O
optimum	O
,	O
generally	O
,	O
can	O
only	O
happen	O
in	O
a	O
narrow	O
band	O
of	O
the	O
mutation	O
step	O
size	O
σ	O
.	O
</s>
<s>
That	O
narrow	O
band	O
is	O
called	O
evolution	B-Algorithm
window	I-Algorithm
.	O
</s>
<s>
There	O
are	O
three	O
well-known	O
methods	O
to	O
adapt	O
the	O
mutation	O
step	O
size	O
σ	O
in	O
evolution	B-Algorithm
strategies	I-Algorithm
:	O
</s>
<s>
On	O
simple	O
functions	O
all	O
of	O
them	O
have	O
been	O
empirically	O
shown	O
to	O
keep	O
the	O
step	O
size	O
within	O
the	O
evolution	B-Algorithm
window	I-Algorithm
.	O
</s>
