Ali Ahrari

UNSW Sydney | UNSW · Systems and Computing

This report presents the results of a dynamic multimodal optimization method formed by the integration of the adaptive multilevel prediction (AMLP) method with the recent variant of co-variance matrix self-adaptation evolution strategy with repelling subpopulation (RS-CMSAESII) on the test problems of the CEC'2022 competition on seeking multiple op...

This study integrates adaptive multilevel prediction (AMLP) with a static multimodal solver based on evolution strategies with repelling subpopulations (RS-ES) to develop a method for dynamic multimodal optimization. In the resultant method, denoted by AMLP-RS-ES, static multimodal optimization is performed using RS-ES while AMLP predicts the locat...

This is the MATLAB code of adaptive multilevel prediction method integrated with an improved covariance matrix self-adaptation evolution strategy with repelling subpopulations (AMLP-RS-CMSA-ESII). Please check the readme.pdf file for the instructions and license before use.

This is version 1.0 of the Python code of Improved Covariance Matrix Self-Adaptation Evolution Strategy with Repelling Subpopulations (RS-CMSA-ESII) [1]. This code has been extracted from the original code that was used for the publication [1] for improved readability. This code has been developed and verified with Python 3.7.4 and Python 3.7.9. Mo...

This chapter provides an introduction to the basic ideas and formulations underlying evolutionary algorithms (EAs) for parameter optimization. It discusses the advantages and disadvantaged of EAs in comparison with classical optimization methods. A detailed review of genetic algorithms, the most well-known class of EAs, is provided alongside a gene...

PyDDRBG is a Python framework for generating tunable test problems for static and dynamic multimodal optimization. It allows for quick and simple generation of a set of predefined problems for non-experienced users, as well as highly customized problems for more experienced users. It easily integrates with an arbitrary optimization method. It can c...

Explicit and implicit averaging are two well-known strategies for noisy optimization. Both strategies can counteract the disruptive effect of noise; however, a critical question remains: which one is more efficient? This question has been raised in many studies, with conflicting preferences and, in some cases, findings. Nevertheless, theoretical fi...

The covariance matrix self-adaptation evolution strategy with repelling subpopulations (RS-CMSA-ES) is one of the most successful multimodal optimization methods currently available. However, some of its components may become inefficient in certain situations. This study introduces the second variant of this method, called RS-CMSA-ESII. It improves...

This work presents a niching method based on the concept of repelling subpopulations for multimodal optimization. It utilizes several existing concepts and techniques in order to develop a new multimodal optimization algorithm that does not make any of specific assumptions on the shape, size, and distribution of minima. In the proposed method, seve...

The Resource-Constrained Project Scheduling Problem (RCPSP) is a challenging optimization problem. In RCPSPs, it is very common to consider homogeneous activities, which means all activities require all types of resources. In practice, the activities are often singular because they usually require one single resource to execute an activity. The exi...

This report presents results of benchmarking an improved version RS-CMSA-ES on the test suite employed for WCCI/CEC'2020 competition on niching methods for multimodal optimization. An upper-level description of the improvement to the existing RS-CMSA-ES code is provided.

In most existing studies on dynamic multimodal optimization (DMMO), numerical simulations have been performed using the Moving Peaks Benchmark (MPB), which is a two-decade-old test suite that cannot simulate some critical aspects of DMMO problems. This study proposes the Deterministic Distortion and Rotation Benchmark (DDRB), a method to generate d...

This study develops an adaptive multilevel prediction (AMLP) method to detect and track multiple global optima over time. First, it formulates a multilevel prediction approach in which a higher-level prediction improves the accuracy of the lower-level prediction to reduce the prediction error, enabling it to capture more complex patterns in the cha...

A reinitialization approach is an effective way of generalizing a static multi-objective optimization method to a dynamic one. It is usually comprised of a prediction operator for predicting the approximate location(s) of the optimal solution(s) and a variation operator for enhancing the diversity of the reinitialized solution(s) after a change. Wh...

Many engineering design problems are associated with computationally expensive and time-consuming simulations for design evaluation. In such problems, each candidate design should be selected carefully, even though it means extra algorithmic complexity. This study develops the Proximity-based Surrogate-Assisted Evolutionary Algorithm (PSA-EA) that...

Prediction methods are useful tools for dynamic multiobjective optimization (DMO), especially if the changes roughly follow some patterns. Multi-model prediction methods, in particular, may capture different types of change patterns; however, they should address two issues. First, they should define a similarity measure that can correctly find the...

Reported best solutions by FSD-ES-IIb [1] for two large scale truss optimization problems. Simply run the following files to visualize the best design: • ‘replot_960bar_grid.m’ for the 960-bar grid structure • ‘replot_759bar_bridge.m’ for 759-bar physical design area problem These files also perform the structural analysis and report the normaliz...

Considerable academic research has been conducted on truss design optimization by standard metaheuristic methods; however, the generic nature of these methods becomes inefficient for problems with many decision variables. This may explain the simplicity of the relevant test problems in the academic literature in comparison with real structures. To...

This is the MATLAB code for “A New Prediction Approach for Dynamic Multiobjective Optimization” This code is free to use provided that the corresponding publication is cited: Ahrari, A., Elsayed, S., Sarker, R., & Essam, D. (2019, June). A New Prediction Approach for Dynamic Multiobjective Optimization. In 2019 IEEE Congress on Evolutionary Compu...

This is the source code of Source code of covariance matrix self-adaptation with repelling subpopulations (RS-CMSA) [1,2] in MATLAB. The method ranked 1st in GECCO’2016 and CEC’2016 competitions for multimodal optimization. To use the code, please see the instructions in ‘main_script.m’. [1] Ahrari, A., Deb, K., & Preuss, M. (2016). Multimodal Opti...

This is the source code of the grenade explosion method (GEM), checked on 11/5/2015. Please read the file “Readme.pdf” for instructions

This study proposes a novel procedure for generating parametric scalable functions with diverse properties to strengthen numerical evaluation of niching methods. It combines three simple basic functions to form a composite multimodal function, in which the function parameter controls the number of global minima. The resultant composite function may...

This report presents the benchmarking results of Covariance Matrix Self Adaption Evolution Strategy with Repelling Subpopulations (RS-CMSA) on the CEC2013 test suite. The benchmarking follows restrictions required by GECCO 2017 competition on multimodal optimization. In particular, no problem dependent parameter tuning is performed. A few minor mod...

MATLAB code of the niching test problems proposed in ”A Novel Class of Test Problems for Performance Evaluation of Niching Methods”

Inspired by the lateral line of aquatic vertebrates, an artificial lateral line (ALL) system can localize and track an underwater moving object by analyzing the ambient flow caused by its motion. There are several studies on object detection, localization and tracking by ALL systems, but only a few have investigated the optimal design of the ALL sy...

This study develops a method for optimum design of an artificial lateral line system, which tracks underwater objects by using the extended Kalman Filter (EKF). Sensor noise and model uncertainty are considered for design optimization. Dependency of the optimum setting of the EKF and the design parameters on the amount of uncertainty is investigate...

This folder includes the files (in MATLAB) to plot and analyze the reported solutions found by FSD-ES or FSD-ES-II in the corresponding publications [1,2,3]. Please mention the publication if you are using these data. To simulate the reported solution, simply run the m-file whose name, starting with ‘confirm’, includes the name of the problem. The...

An artificial lateral line (ALL) system consists of a set of flow sensors around a fish-like body. An ALL system aims to identify surrounding moving objects, a common example of which is a vibrating sphere, called a dipole. Accurate identification of a vibrating dipole is a challenging task because of the presence of different types of uncertainty...

During the recent decades, many niching methods have been proposed and empirically verified on some available test problems. They often rely on some particular assumptions associated with the distribution, shape and size of the basins, which can seldom be made in practical optimization problems. This study utilizes several existing concepts and tec...

This is the source code of FSD-ES II. The full paper has been published in Computers&Structures [1]. Please read the readme.pdf first. [1]Ahrari, A., & Deb, K. (2016). An improved fully stressed design evolution strategy for layout optimization of truss structures. Computers & Structures, 164, 127-144. doi:10.1016/j.compstruc.2015.11.009

During the recent decade, truss optimization by meta-heuristics has gradually replaced deterministic and optimality criteria-based methods. While they may provide some advantages regarding their robustness and ability to avoid local minima, the required evaluation budget grows fast when the number of design variables is increased. This practically...

Evolution strategies traditionally employ the comma or the plus scheme for selection. The concept of intermediate selection schemes was introduced in 1995, in which individuals may survive limited but more than one generation; however, research on this topic has remained dormant. During the recent decade, the comma scheme has emerged as the preferr...

The most effective scheme of truss optimization considers the combined effect of topology, shape and size (TSS); however, most available studies on truss optimization by metaheuristics concentrated on one or two of the above aspects. The presence of diverse design variables and constraints in TSS optimization may account for such limited applicabil...

A simple, yet efficient scheme for adaptation of population size in Evolution Strategies (ESs) that utilize global intermediate/weighted recombination is presented. At the first step, a measure to quantify multimodality of the region under exploration is introduced. This quantity is iteratively updated based on the history of the algorithmic perfor...

During the recent decades, much effort has been dedicated to revise and improve the evolution operators of evolutionary algorithms. This article aims at minimums of an efficient mutation operator in continuous problems for which reachability, scalability, unbiasedness and isotropy have already been considered necessary. A new requirement, called ro...

Following the principles of the state-of-the-art Evolution Strategies in continuous optimization, a novel algorithm is introduced which simultaneously optimizes shape and size of truss structures. The algorithm, called Fully Stressed Design Evolution Strategy (FSD-ES), combines advantages of the well-known deterministic approach of Fully Stressed D...

It has been demonstrated that fluoride prophylactic agents may cause hydrogen absorption in NiTi wires and degrade their mechanical properties. To investigate the effect of a fluoride mouthwash on load-deflection characteristics of three types of nickel-titanium-based orthodontic archwires. Twenty maxillary 0.016 inch round specimens from each of t...

The aim of this study was to evaluate the load-deflection characteristics of three types of nickel-titanium wires and investigate the effects of recycling on superelastic properties of them. Thirty specimens for any of the single-strand Ni-Ti (Rematitan "Lite'), multi-strand Ni-Ti (SPEED Supercable) and Copper Ni-Ti (Damon Copper Ni-Ti) were tested...

Previous researches have disclosed that the excellent performance of some evolutionary algorithms (EAs) highly depends on existence of some properties in the structure of the objective function. Unlike classical benchmark functions, randomly generated multimodal functions do not have any of these properties. Having been improved, a function generat...

This work presents a new optimization technique called Grenade Explosion Method (GEM). The fundamental concepts and ideas which underlie the method are fully explained. It is seen that this simple and robust algorithm is quite powerful in finding all global and some local optima of multimodal functions. The method is tested with several multimodal...

Although evolutionary algorithms (EAs) have some operators which let them explore the whole search domain, still they get trapped in local minima when multimodality of the objective function is increased. To improve the performance of EAs, many optimization techniques or operators have been introduced in recent years. However, it seems that these m...

A new optimization technique called Grenade Explosion Method (GEM) is introduced and its underlying ideas, including the concept of Optimal Search Direction (OSD), are elaborated. The applicability and efficiency of the technique is demonstrated using standard benchmark functions. Comparison of the results with those of other, widely-used, evolutio...