<s>
Extremal	B-Algorithm
optimization	I-Algorithm
(	O
EO	O
)	O
is	O
an	O
optimization	O
heuristic	B-Algorithm
inspired	O
by	O
the	O
Bak	O
–	O
Sneppen	O
model	O
of	O
self-organized	O
criticality	O
from	O
the	O
field	O
of	O
statistical	O
physics	O
.	O
</s>
<s>
This	O
heuristic	B-Algorithm
was	O
designed	O
initially	O
to	O
address	O
combinatorial	O
optimization	O
problems	O
such	O
as	O
the	O
travelling	B-Algorithm
salesman	I-Algorithm
problem	I-Algorithm
and	O
spin	O
glasses	O
,	O
although	O
the	O
technique	O
has	O
been	O
demonstrated	O
to	O
function	O
in	O
optimization	O
domains	O
.	O
</s>
<s>
Another	O
piece	O
in	O
the	O
puzzle	O
is	O
work	O
on	O
computational	O
complexity	O
,	O
specifically	O
that	O
critical	O
points	O
have	O
been	O
shown	O
to	O
exist	O
in	O
NP-complete	O
problems	O
,	O
where	O
near-optimum	O
solutions	O
are	O
widely	O
dispersed	O
and	O
separated	O
by	O
barriers	O
in	O
the	O
search	O
space	O
causing	O
local	B-Algorithm
search	I-Algorithm
algorithms	I-Algorithm
to	O
get	O
stuck	O
or	O
severely	O
hampered	O
.	O
</s>
<s>
It	O
was	O
the	O
evolutionary	O
self-organised	O
criticality	O
model	O
by	O
Bak	O
and	O
Sneppen	O
and	O
the	O
observation	O
of	O
critical	O
points	O
in	O
combinatorial	O
optimisation	O
problems	O
that	O
lead	O
to	O
the	O
development	O
of	O
Extremal	B-Algorithm
Optimization	I-Algorithm
by	O
Stefan	O
Boettcher	O
and	O
Allon	O
Percus	O
.	O
</s>
<s>
EO	O
was	O
designed	O
as	O
a	O
local	B-Algorithm
search	I-Algorithm
algorithm	O
for	O
combinatorial	O
optimization	O
problems	O
.	O
</s>
<s>
Unlike	O
genetic	B-Algorithm
algorithms	I-Algorithm
,	O
which	O
work	O
with	O
a	O
population	O
of	O
candidate	O
solutions	O
,	O
EO	O
evolves	O
a	O
single	O
solution	O
and	O
makes	O
local	O
modifications	O
to	O
the	O
worst	O
components	O
.	O
</s>
<s>
This	O
differs	O
from	O
holistic	O
approaches	O
such	O
as	O
ant	B-Algorithm
colony	I-Algorithm
optimization	I-Algorithm
and	O
evolutionary	O
computation	O
that	O
assign	O
equal-fitness	O
to	O
all	O
components	O
of	O
a	O
solution	O
based	O
upon	O
their	O
collective	O
evaluation	O
against	O
an	O
objective	O
function	O
.	O
</s>
<s>
The	O
technique	O
is	O
a	O
fine-grained	O
search	O
,	O
and	O
superficially	O
resembles	O
a	O
hill	B-Algorithm
climbing	I-Algorithm
(	O
local	B-Algorithm
search	I-Algorithm
)	O
technique	O
.	O
</s>
<s>
A	O
more	O
detailed	O
examination	O
reveals	O
some	O
interesting	O
principles	O
,	O
which	O
may	O
have	O
applicability	O
and	O
even	O
some	O
similarity	O
to	O
broader	O
population-based	O
approaches	O
(	O
evolutionary	O
computation	O
and	O
artificial	B-Algorithm
immune	I-Algorithm
system	I-Algorithm
)	O
.	O
</s>
<s>
This	O
is	O
obviously	O
at	O
odds	O
with	O
genetic	B-Algorithm
algorithms	I-Algorithm
,	O
the	O
quintessential	O
evolutionary	O
computation	O
algorithm	O
that	O
selects	O
good	O
solutions	O
in	O
an	O
attempt	O
to	O
make	O
better	O
solutions	O
.	O
</s>
<s>
The	O
resulting	O
dynamics	O
of	O
this	O
simple	O
principle	O
is	O
firstly	O
a	O
robust	O
hill	B-Algorithm
climbing	I-Algorithm
search	O
behaviour	O
,	O
and	O
secondly	O
a	O
diversity	O
mechanism	O
that	O
resembles	O
that	O
of	O
multiple-restart	O
search	O
.	O
</s>
<s>
It	O
is	O
these	O
crashes	O
or	O
dramatic	O
jumps	O
in	O
the	O
search	O
space	O
that	O
permit	O
the	O
algorithm	O
to	O
escape	O
local	O
optima	O
and	O
differentiate	O
this	O
approach	O
from	O
other	O
local	B-Algorithm
search	I-Algorithm
procedures	O
.	O
</s>
<s>
EO	O
has	O
primarily	O
been	O
applied	O
to	O
combinatorial	O
problems	O
such	O
as	O
graph	O
partitioning	O
and	O
the	O
travelling	B-Algorithm
salesman	I-Algorithm
problem	I-Algorithm
,	O
as	O
well	O
as	O
problems	O
from	O
statistical	O
physics	O
such	O
as	O
spin	O
glasses	O
.	O
</s>
<s>
Generalised	O
extremal	B-Algorithm
optimization	I-Algorithm
(	O
GEO	O
)	O
was	O
developed	O
to	O
operate	O
on	O
bit	O
strings	O
where	O
component	O
quality	O
is	O
determined	O
by	O
the	O
absolute	O
rate	O
of	O
change	O
of	O
the	O
bit	O
,	O
or	O
the	O
bits	O
contribution	O
to	O
holistic	O
solution	O
quality	O
.	O
</s>
<s>
Another	O
similar	O
extension	O
to	O
EO	O
is	O
Continuous	O
Extremal	B-Algorithm
Optimization	I-Algorithm
(	O
CEO	O
)	O
.	O
</s>
<s>
EO	O
has	O
been	O
applied	O
to	O
image	O
rasterization	O
as	O
well	O
as	O
used	O
as	O
a	O
local	B-Algorithm
search	I-Algorithm
after	O
using	O
ant	B-Algorithm
colony	I-Algorithm
optimization	I-Algorithm
.	O
</s>
