perturb_tour_4exc: Random 4-exchange transformation
Description
It performs a random 4-exchange transformation to a cycle.
Usage
perturb_tour_4exc(C, V, n)
Value
The 4-exchanged cycle.
Arguments
C
Cycle to be 4-exchanged
V
1:n list, positions to draw from
n
Number of vertices of the cycle
Author
Cesar Asensio
Details
The transformation is carried out by randomly selecting four
non-mutually incident edges from the cycle. Upon eliminating
these four edges, we obtain four pieces ci of the original
cycle. The 4-exchanged cycle is c1, c4, c3, c2. This is a
typical 4-exchange which cannot be constructed using
2-exchanges and therefore it is used by local search routines
as an escape from 2-opt local minima.