A Comparative Representation Approach to Modern Heuristic Search Methods in a Job Shop

The job shop problem is among the class of NP- hard combinatorial problems. This Research paper addresses the problem of static job shop scheduling on the job-based representation and the rule based representations. The popular search techniques like the genetic algorithm and simulated annealing are used for the determination of the objectives like minimizations of the makespan time and mean flow time. Various rules like the SPT, LPT, MWKR, and LWKR are used for the objective function to attain the results. The summary of results from this paper gives a conclusion that the genetic algorithm gives better results in the makespan time determination on both the job based representation and the rule based representation and the simulated annealing algorithm gives the better results in the mean flow time in both the representations

Upgrading evolutionary algorithms through multiplicity for multiobjective optimization in job shop scheduling problems

In previous works the ability of CPS-MCPC (an evolutionary, co-operative, population search method with multiple crossovers per couple) to build well delineated Pareto fronts in diverse multiobjective optimization problems (MOOPs) was demonstrated. To test the potential of the novel method when dealing with the Job Shop Scheduling Problem (JSSP), regular and non-regular objectives functions were chosen. They were the makespan and the mean absolute deviation (of job completion times from a common due date, an earliness/tardiness related problem). Diverse representations such as priority list representation (PLR), job-based representation (JBR) and operation-based representation (OBR) among others were implemented and tested. The latter showed to be the best one. As a good parameter setting can enhance the behaviour of an evolutionary algorithm distinct parameters combinations were implemented and their influence studied. Multiple crossovers on multiple parents (MCMP), a powerful multirecombination method showed some enhancement in single objective optimization when compared with MCPC. This paper shows the influence of different recombination schemes when building the Pareto front under OBR and using the best parameter settings determined in previous works on a set of demonstrative Lawrence´s instances. Details of implementation and results are discussed.Eje: Sistemas inteligentesRed de Universidades con Carreras en Informática (RedUNCI

Particle swarm optimization applied to job shop scheduling

In this project we have to apply the particle swarm optimization algorithm to job shop scheduling problem. Job shop scheduling is a combinatorial optimization problem where we have to arrange the jobs which may or may not be processed in every machine in a particular sequence and each machine has a different sequence of jobs. Job shop scheduling is a complex extended version of flow shop scheduling which is a problem where each job is processed through each and every machine and each machine has a same sequence of jobs. Our main objective in both kind of problem is to arrange the jobs in a sequence which gives minimum value of make span. PSO (Particle swarm optimization) helps us to find a combination of job sequence which has the least make span. In PSO a swarm of particles which have definite position and velocity for each job. In PSO, to find the combinations we use a heuristic rule called Smallest Position Value (SPV). According to smallest position value rule jobs are arranged in ascending order of their positions i.e. job having least position value is put first in sequence. In this project PSO is first applied to flow shop scheduling problem. This is done to understand how PSO algorithm can be applied to scheduling problem as flow shop scheduling problem is a simple problem. After Understanding the PSO algorithm, the algorithm is extended to apply in job shop scheduling problem for n jobs and m machines

Job Shop Scheduling Using Artificial Immune System

Efficiency in job shop scheduling plays an important role when a large number of jobs and machines are considered. The job shop scheduling problems are one of the NP hard problems. Many heuristic methods give solutions with near optimal results. This work deals with the job shop scheduling using Artificial Immune System. Operation based representation is used to decode the schedule in the algorithm. The mutations used in the algorithm are inverse mutation and pair wise exchange mutation and a receptor editing process is also used. A C++ code was generated to use the algorithm for finding the optimal solution. The input parameters are operation time and operation sequence for each job in the machines provided. This work used the makespan values of the schedules to compare the results

Upgrading evolutionary algorithms through multiplicity for multiobjective optimization in job shop scheduling problems

In previous works the ability of CPS-MCPC (an evolutionary, co-operative, population search method with multiple crossovers per couple) to build well delineated Pareto fronts in diverse multiobjective optimization problems (MOOPs) was demonstrated. To test the potential of the novel method when dealing with the Job Shop Scheduling Problem (JSSP), regular and non-regular objectives functions were chosen. They were the makespan and the mean absolute deviation (of job completion times from a common due date, an earliness/tardiness related problem). Diverse representations such as priority list representation (PLR), job-based representation (JBR) and operation-based representation (OBR) among others were implemented and tested. The latter showed to be the best one. As a good parameter setting can enhance the behaviour of an evolutionary algorithm distinct parameters combinations were implemented and their influence studied. Multiple crossovers on multiple parents (MCMP), a powerful multirecombination method showed some enhancement in single objective optimization when compared with MCPC. This paper shows the influence of different recombination schemes when building the Pareto front under OBR and using the best parameter settings determined in previous works on a set of demonstrative Lawrence´s instances. Details of implementation and results are discussed.Eje: Sistemas inteligentesRed de Universidades con Carreras en Informática (RedUNCI

ADAPTIVE, MULTI-OBJECTIVE JOB SHOP SCHEDULING USING GENETIC ALGORITHMS

This research proposes a method to solve the adaptive, multi-objective job shop scheduling problem. Adaptive scheduling is necessary to deal with internal and external disruptions faced in real life manufacturing environments. Minimizing the mean tardiness for jobs to effectively meet customer due date requirements and minimizing mean flow time to reduce the lead time jobs spend in the system are optimized simultaneously. An asexual reproduction genetic algorithm with multiple mutation strategies is developed to solve the multi-objective optimization problem. The model is tested for single day and multi-day adaptive scheduling. Results are compared with those available in the literature for standard problems and using priority dispatching rules. The findings indicate that the genetic algorithm model can find good solutions within short computational time

An analysis on selection methods and multirecombination in evolutionary search when solving the job shop scheduling problem

Evolutionary algorithms (EAs) can be used as optimisation mechanisms. Based on the model of natural evolution, they work on populations of individuals instead of on single solutions. In this way, the search is performed in a parallel manner. During the last decades, there has been an increasing interest in evolutionary algorithms to solve scheduling problems. One important feature in these algorithms is the selection of individuals. Selection is the operation by which individuals (i.e. their chromosomes) are selected for mating. To emulate natural selection, individuals with higher fitness should be selected with higher probability, and thus it is one of the operators where the fitness plays an important role. There are many different models of selection (some are not biologically plausible). Commonly, proportional, ranking, tournament selection and stochastic universal sampling are used. EAs considered in this work are improved with a multiplicity feature to solve the job shop scheduling problems (JSSP). The algorithm applied here, multiple crossovers on multiple parents (MCMP), considers more than two parents for reproduction with the possibility to generate multiple children. This approach uses a permutation representation for the chromosome. The objective of this work is to compare the algorithms performance using different selection mechanisms and to analyse the different crossover methods developed to apply MCMP with a permutation representation.Eje: Sistemas inteligentesRed de Universidades con Carreras en Informática (RedUNCI

Perancangan Ban Pembuatan Perangkat Lunak Untuk Penjadualan Job Shop Dengan Menggunakan Algoritma Genetik

Sistem produksi yang melibatkan banyak proses, mesin dan juga waktu proses yang bervariasi, membutuhkan penjadualan yang tepat. Salah satu tipe penjadualan yang digunakan adalah job shop. Penjadualan job shop memiliki bermacam jenis dan dapat diselesaikan dengan beberapa metode. Tujuan penjadualan adalah menentukan urutan pengerjaan job pada mesin yang disediakan dengan waktu minimal, yang disebut makespan. Pada tugas akhir ini digunakan algoritma genetik untuk menyelesaikan permasalahan yang hanya dibatasi pada penjadualan job shop klasik dengan pola kedatangan job statis. Sebagai pembanding digunakan metode heuristik dengan menggunakan aturan prioritas (priority dispatching role), dalam hal ini shortest processing time (SPT). Hasil algoritma genetik yang diharapkan adalah diperoleh makespan lebih kecil dalam waktu yang lebih cepat dari pada menggunakan SPT. Algoritma genetik yang dibuat menggunakan representasi permutasi job yang disebut dengan job based representation. Operator tukar silang menggunakan order dan position based crossover. Sedangkan operator mutasi menggunakan reciprocal exchange dan insertion. Metode seleksi menggunakan roulette wheel dan elitism.Untuk memperoleh parameter algoritma genetik yang dapat menghasilkan makespan minimal, uji coba dilakukan dalam beberapa dimensi permasalahan, yain1 dengan memberikan data jumlah job dan mesin serta nilai ukuran populasi, tingkat tukar silang, dan tingkat mutasi yang berbeda - beda. Dari beberapa parameter algoritma genetik tersebut dapat ditemukan nilai parameter yang dapat menghasilkan makespan minimal. Kemudian dengan jumlah job dan mesin yang sama pada uji coba algoritma genetik in1 dilakukan uji coba pada metode SPT. Hasil yang diperoleh adalah algoritma genetik dapat menghasilkan makespan lebih kecil dengan waktu lebih cepat dari pada SPT. Selain itu juga dikaji cara tmtuk memperkirakan parameter algoritma genetik

Reinforcement Learning Approach for Multi-Agent Flexible Scheduling Problems

Scheduling plays an important role in automated production. Its impact can be found in various fields such as the manufacturing industry, the service industry and the technology industry. A scheduling problem (NP-hard) is a task of finding a sequence of job assignments on a given set of machines with the goal of optimizing the objective defined. Methods such as Operation Research, Dispatching Rules, and Combinatorial Optimization have been applied to scheduling problems but no solution guarantees to find the optimal solution. The recent development of Reinforcement Learning has shown success in sequential decision-making problems. This research presents a Reinforcement Learning approach for scheduling problems. In particular, this study delivers an OpenAI gym environment with search-space reduction for Job Shop Scheduling Problems and provides a heuristic-guided Q-Learning solution with state-of-the-art performance for Multi-agent Flexible Job Shop Problems

Job Scheduling with Genetic Algorithm

In this paper, we have used a Genetic Algorithm (GA) approach for providing a solution to the Job Scheduling Problem (JSP) of placing 5000 jobs on 806 machines. The GA starts off with a randomly generated population of 100 chromosomes, each of which represents a random placement of jobs on machines. The population then goes through the process of reproduction, crossover and mutation to create a new population for the next generation until a predefined number of generations are reached. Since the performance of a GA depends on the parameters like population size, crossover rate and mutation rate, a series of experiments were conducted in order to identify the best parameter combination to achieve good solutions to the JSP by balancing makespan with the running time. We found that a crossover rate of 0.3, a mutation rate of 0.15 and a population size of 100 yield the best results