perturb_tour_4exc {gor}

Random 4-exchange transformation

Description

It performs a random 4-exchange transformation to a cycle.

Usage

perturb_tour_4exc(C, V, n)

Arguments

C

Cycle to be 4-exchanged

V

1:n list, positions to draw from

n

Number of vertices of the cycle

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.

Value

The 4-exchanged cycle.

Author(s)

Cesar Asensio

Examples

set.seed(1)
perturb_tour_4exc(1:9, 1:9, 9)   # 2 3 9 1 7 8 4 5 6