<s>
defining	O
a	O
modification	O
of	O
local	B-Algorithm
search	I-Algorithm
or	O
hill	B-Algorithm
climbing	I-Algorithm
methods	I-Algorithm
for	O
solving	O
discrete	O
optimization	O
problems	O
.	O
</s>
<s>
Local	B-Algorithm
search	I-Algorithm
methods	O
can	O
get	O
stuck	O
in	O
a	O
local	O
minimum	O
,	O
where	O
no	O
improving	O
neighbors	O
are	O
available	O
.	O
</s>
<s>
A	O
simple	O
modification	O
consists	O
of	O
iterating	O
calls	O
to	O
the	O
local	B-Algorithm
search	I-Algorithm
routine	O
,	O
each	O
time	O
starting	O
from	O
a	O
different	O
initial	O
configuration	O
.	O
</s>
<s>
This	O
is	O
called	O
repeated	O
local	B-Algorithm
search	I-Algorithm
,	O
and	O
implies	O
that	O
the	O
knowledge	O
obtained	O
during	O
the	O
previous	O
local	B-Algorithm
search	I-Algorithm
phases	O
is	O
not	O
used	O
.	O
</s>
<s>
Learning	O
implies	O
that	O
the	O
previous	O
history	O
,	O
for	O
example	O
the	O
memory	O
about	O
the	O
previously	O
found	O
local	O
minima	O
,	O
is	O
mined	O
to	O
produce	O
better	O
and	O
better	O
starting	O
points	O
for	O
local	B-Algorithm
search	I-Algorithm
.	O
</s>
<s>
Iterated	B-Algorithm
Local	I-Algorithm
Search	I-Algorithm
is	O
based	O
on	O
building	O
a	O
sequence	O
of	O
locally	O
optimal	O
solutions	O
by	O
:	O
</s>
<s>
applying	O
local	B-Algorithm
search	I-Algorithm
after	O
starting	O
from	O
the	O
modified	O
solution	O
.	O
</s>
<s>
For	O
instance	O
Battiti	O
and	O
Protasi	O
proposed	O
a	O
reactive	O
search	O
algorithm	O
for	O
MAX-SAT	B-Application
which	O
fits	O
perfectly	O
into	O
the	O
ILS	O
framework	O
.	O
</s>
<s>
They	O
perform	O
a	O
"	O
directed	O
"	O
perturbation	O
scheme	O
which	O
is	O
implemented	O
by	O
a	O
tabu	B-Algorithm
search	I-Algorithm
algorithm	O
and	O
after	O
each	O
perturbation	O
they	O
apply	O
a	O
standard	O
local	O
descent	O
algorithm	O
.	O
</s>
<s>
The	O
method	O
has	O
been	O
applied	O
to	O
several	O
combinatorial	O
optimization	O
problems	O
including	O
the	O
Job	B-Algorithm
Shop	I-Algorithm
Scheduling	I-Algorithm
problems	O
,	O
Flow-Shop	O
Problems	O
,	O
Vehicle	B-Algorithm
Routing	I-Algorithm
Problems	I-Algorithm
as	O
well	O
as	O
many	O
others	O
.	O
</s>
