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for the problem at hand, this hybridization truly appears to confer an advantage over
pure Differential Evolution. I will remark that it seems a bit more difficult to get this
type of hybridization to cooperate well with the various shuffle methods of creating
permutations.
For contrast we go to the opposite extreme and do a huge number of swaps, on a
relatively smaller number of chromosomes and using far fewer iterations. We will reset
our vector with swapped pairs to the original (or best variant found thereof, if we get
improvements). This is to avoid straying far from reasonable vectors, since we now do
many swaps.
This is thus far a 2-opt approach rather than Differential Evolution per se. Nonethe-
less, we notice that the later stages of improvement do come during the actual iterations
of Differential Evolution, and quite possibly those final improvements are due in part to
the maintaining of diversity and the use of mutation and recombination.
Timing[QAP4[mat1
,
mat2
,.
08
,
20
,
60
,.
4
,
2000
,.
6
,
True
,
True]]
locally improved
{
4838
,
4808
}
new low 1
{
iteration, elapsed time, new value
}{
0
,
0
.
048003
,
4808
}
locally improved
{
4808
,
4786
}
new low 2
{
iteration, elapsed time, new value
}{
0
,
0
.
004001
,
4786
}
locally improved
{
4786
,
4738
}
new low 3
{
iteration, elapsed time, new value
}{
0
,
0
.,
4738
}
locally improved
{
4738
,
4690
}
new low 4
{
iteration, elapsed time, new value
}{
0
,
0
.
004
,
4690
}
locally improved
{
4690
,
4614
}
{
}{
0
,
0
.,
4614
}
new low 5
iteration, elapsed time, new value
{
4614
,
4502
}
locally improved
{
}{
0
,
0
.,
4502
}
new low 6
iteration, elapsed time, new value
locally improved
{
4502
,
4406
}
new low 7
{
iteration, elapsed time, new value
}{
0
,
0
.,
4406
}
locally improved
{
4406
,
4370
}
new low 8
{
iteration, elapsed time, new value
}{
0
,
0
.,
4370
}
locally improved
{
4370
,
4342
}
new low 9
{
iteration, elapsed time, new value
}{
0
,
0
.
004
,
4342
}
locally improved
{
4342
,
4226
}
new low 10
{
iteration, elapsed time, new value
}{
0
,
0
.,
4226
}
locally improved
{
4226
,
4178
}
new low 11
{
iteration, elapsed time, new value
}{
0
,
0
.
016001
,
4178
}
locally improved
{
4178
,
4174
}
new low 12
{
iteration, elapsed time, new value
}{
0
,
0
.,
4174
}
locally improved
{
4174
,
4170
}
new low 13
{
iteration, elapsed time, new value
}{
0
,
0
.
016001
,
4170
}
locally improved
{
4170
,
4158
}
new low 14
{
iteration, elapsed time, new value
}{
0
,
0
.
012001
,
4158
}
locally improved
{
4158
,
4114
}
new low 15
{
iteration, elapsed time, new value
}{
0
,
0
.
004
,
4114
}
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