Modified cuckoo search: A new gradient free optimisation algorithm
S. Walton
⇑
, O. Hassan, K. Morgan, M.R. Brown
College of Engineering, Swansea University, Swansea SA2 8PP, Wales, UK
article info
Article history:
Received 13 January 2011
Accepted 14 June 2011
Available online 22 July 2011
abstract
A new robust optimisation algorithm, w hich can be regarded as a modification of the
recently developed cuckoo search, is presented. The modification involves the addition
of information exchange between the top eggs, or the best solutions. Standard optimisation
benchmarking functions are used to test the effects of these modifications and it is demon-
strated that, in most cases, the modified cuckoo search performs as well as, or better than,
the standard cuckoo search, a particle swarm optimiser, and a differential evolution strat-
egy. In particular the modified cuckoo search shows a high convergence rate to the true
global minimum even at high numbe rs of dimensions.
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
The practicality of using gradient based optimisation
techniques has been reduced by the difficulty of generating
automatically objective functions and their derivatives for
highly non-linear engineering problems [1]. During the
1950s and 1960s, computer scientists investigated the pos-
sibility of applying the concepts of evolution as an optimi-
sation tool for engineers and this gave birth to a subclass of
gradient free methods called genetic algorithms (GA) [2].
Since then many other algorithms have been developed
that have been inspired by nature, for example particle
swarm optimisation (PSO) [3], differential evolution (DE)
[4] and, more recently, the cuckoo search (CS) [5]. These
are heuristic techniques which make use of a large popula-
tion of possible designs at each iteration. For each member
of the population, the objective function is evaluated and a
fitness is assigned. A set of rules is then used to move the
population towards the optimum solution. Although this
results in a global search without the need to calculate
objective function gradients [5], the large number of objec-
tive function evaluations means the computational effi-
ciency of these procedures is often inferior to classical
gradient-based methods [6]. The problem is exacerbated
when considering applications where a single objective
function evaluation represents a significant computational
cost, such as fluid flow problems [6–8].
New optimisation algorithms are often tested by apply-
ing them to benchmark problems which have known ana-
lytical optimum fitnesses. For example, Bratton and
Kennedy [3] compare several PSO algorithms by running
30 trials each for 300,000 objective function evaluations
and comparing the fitness value obtained with the known
optimum fitness. Yang and Deb [5] compared CS to PSO
over 100 trials for each objective function. They allowed
the algorithms to run until the spread of fitnesses in the
population was smaller than 10
5
. This resulted in large
numbers of objective function evaluations, from 3015 to
110,523, depending upon the method used and the bench-
mark problem. This number of objective function evalua-
tions would not be feasible for application to practical
engineering problems with costly objective functions. The
common threads in these benchmarking tests is the appli-
cation of these techniques to problems with known min-
ima, with a defined stopping criterion, and the large
number of objective function evaluations.
In a real world application of an optimisation technique,
it is very difficult to define a stopping criterion. For exam-
ple, in the design of an aerofoil, the objective function might
represent the calculation of the ratio of the lift coefficient to
the drag coefficient. In this case, the designer would want
to maximise this quantity under certain constraints, the
maximum value is unknown and may not be unique.
0960-0779/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.chaos.2011.06.004
⇑
Corresponding author.
E-mail address: 512465@swansea.ac.uk (S. Walton).
Chaos, Solitons & Fractals 44 (2011) 710–718
Contents lists available at ScienceDirect
Chaos, Solitons & Fractals
Nonlinear Science, and Nonequilibrium and Complex Phenomena
journal homepage: www.elsevier.com/locate/chaos