// Evolve implements the inner loop of the evolutionary algorithm.
// The population calls the Evolve method of each genome, in parallel. Then,
// each receiver returns a value to replace it in the next generation.
func Evolve(current evo.Genome, matingPool []evo.Genome) evo.Genome {
// Selection:
// Select each parent using a simple random binary tournament
mom := sel.BinaryTournament(matingPool...).(*tsp)
dad := sel.BinaryTournament(matingPool...).(*tsp)
// Crossover:
// Edge recombination
child := &tsp{gene: pool.Get().([]int)}
perm.EdgeX(child.gene, mom.gene, dad.gene)
// Mutation:
// There is an n% chance for the gene to have n random swaps
// and an n% chance to undergo n steps of a greedy 2-opt hillclimber
for rand.Float64() < 0.1 {
perm.RandSwap(child.gene)
}
for rand.Float64() < 0.1 {
child.TwoOpt()
}
// Replacement:
// Only replace if the child is better or equal
if current.Fitness() > child.Fitness() {
return current
}
return child
}
func TestRandSwap(t *testing.T) {
a := rand.Perm(8)
b := make([]int, 8)
copy(b, a)
perm.RandSwap(b)
swapped := false
i, j := 0, 7
for {
if j <= i {
if !swapped {
t.Fail()
}
return
} else if a[i] == b[i] {
i++
} else if a[j] == b[j] {
j--
} else {
if swapped {
t.Fail()
return
}
b[i], b[j] = b[j], b[i]
swapped = true
}
}
}