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performance comparison with original BA. If a random value (
r
p
) is greater than the
emission pulse rate (
r
i
) of the bats, the bats will carry out the refined search designed.
In other words, the execution probability of refined search is 1-
for each bat. In this
step, the bats attempt to find a better location by slightly explore near the current best
bat. In BA, the bats slightly move based on the average loudness (
A
t
) of all the bats at
iteration
t
to search a better location near the current best bat. However, the average
loudness is decreasing with the iterations increasing. The smaller the average loud-
ness is, the narrower the search region is. The search region of bats is centralized near
the current best bat. This centralized search easily makes bats falling into the local
optimal solution. In GBA, the bats search a better location near the current best bat
according to their frequency by Eq. (14). The movement do not be seriously affected
by iteration in proposed approach. The search region is elastic to enhance the possibil-
ity with position updating.
, 1,1
(14)
where
is the current best bat.
is the random number with uniform distribution.
is the frequency of bat
i
at iteration
t
.
is the found new location by slight
movement.
Step 4. Update the Current Best Bat
The current best bat may be replaced due to the position updating of some bats. Once
the current best bat is changed, the flight direction of bats toward the current best bat
will be different next iteration. The current best bat with the finest quality is selected
after comparing with all position of bats as shown in Eq. (15). This current best bat
will lead other bats toward the search direction of global optimal solution.
,
(15)
Step 5. Divers Search
Divers search is an early-stage resolution to conflict between bats, proposed in this paper.
When the bats are trapped in conflict solution, a divers search is involved in GBA to
strengthen the global search. The velocity of bats will be randomly modified to search
new location by Eq. (16). There are three exploration strategies including excavate near
position, excavate near location and disorder, to be adopted according to a random value
(
R
) for each dimension as shown in Eq. (17), if R=1, the bat explore new location based
on its current position. If R=2, the bat explores new locations near its current location.
The bats attempt to carefully discover the better position near their own position and
location in these two exploration strategies. Otherwise, when R=3, the bat randomly
selects a location in solution space to exploit new search region.
,
,
, ∈2,2
(16)
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