Experimental Analysis of Effort Estimation Using Artificial Neural Network

Transcription

1 International Journal of Electronics and Computer Science Engineering 1817 Available Online at ISSN Experimental Analysis of Effort Estimation Using Artificial Neural Network Anjana Bawa 1 2, Mrs.Rama Chawla 1 2 Department of Computer Sciences and Engineering 1 D.V.I.E.T Karnal, kurukshetra University 2 D.V.I.E.T Karnal, kurukshetra University 1 - er.anjana@gmail.com Abstract- Failures of software are mainly due to the faulty project management practices, which include effort estimation. Continuous changing scenarios of software development technology make effort estimation more challenging. Accurate software cost estimates are critical to both developers and customers. They can be used for generating request for proposals, contract negotiations, scheduling, monitoring and control. The exact relationship between the attributes of the effort estimation is difficult to establish. A neural network is good at discovering relationships and pattern in the data. So, in this paper we will discuss how we predict the effort using Neural Network learning techniques and a comparative analysis of different ANNs in effort estimation. Keywords Algorithmic models, Effort Estimation, SLOC. I. INTRODUCTION In recent years, the developments of large-scale software projects gain a growing interest. Being able to define, the software size, the development duration and the required facilities became more and more a challenging task. The reason is software architecture, requirements, tools and techniques became more complex. Software estimates are the basis for project bidding, budgeting and planning. These are critical practices in the software industry, because poor budgeting and planning often has dramatic consequences. When budgets and plans are too pessimistic, business opportunities can be lost, while over-optimism may be followed by significant losses. Software effort estimation is the process of predicting the most realistic use of effort required to develop or maintain software. Effort estimates are used to calculate effort in person-months (PM) for the Software Development work elements of the Work Breakdown Structure (WBS). Accurate Effort Estimation is important because: It can help to classify and prioritize development projects with respect to an overall business plan. It can be used to determine what resources to commit. It can be used to assess the impact of changes and support re-planning. Projects can be easier to manage and control when resources are better matched to real needs. Customers expect actual development costs to be in line with estimated costs. 1.1 Algorithmic models Algorithmic models (AM) calibrate pre-specified formulas for estimating development effort from historical data. Inputs to these models may include the experience of the development team, the required reliability of the software, the programming language in which the software is to be written, and an estimate of the final number of delivered source lines of code (SLOC). Basically algorithmic model is formula based model which takes historical cost information and which is based on the size of the software. Algorithmic model includes two most popular models used as follows: a) COCOMO model b) Putnam s model and slim 1.2 ANN in Effort Estimation

2 IJECSE,Volume1,Number 3 Anjana Bawa and Mrs.Rama Chawla 1818 Artificial Neural Network is used in effort estimation due to its ability to learn from previous data. It is also able to model complex relationships between the dependent (effort) and independent variables (cost drivers). In addition, it has the ability to generalize from the training data set thus enabling it to produce acceptable result for previously unseen data. Most of the work in the application of neural network to effort estimation made use of cascade correlation and Back-propagation algorithm. Artificial Neural Network (ANN) is a massively parallel adaptive network of simple nonlinear computing elements called Neurons, which are intended to abstract and model some of the functionality of the human nervous system in an attempt to partially capture some of its computational strengths. An artificial neural network comprises of eight basic components: (i)neurons, (ii)activation function, (iii)signal function, (iv)pattern of connectivity, (v)activity aggregation rule, (vi) activation rule, (vii) learning rule and (viii)environment. Figure 1. Architecture of an artificial neuron After an ANN is created it must go through the process of learning or training. The process of modifying the weights in the connections between network layers with the objective of achieving the expected output is called training a network. There are two approaches for training supervised and unsupervised.in supervised training, both the inputs and the outputs are provided. The network then processes the inputs, compares its resulting outputs against the desired outputs and error is calculated. In unsupervised training, the network is provided with inputs but not with desired outputs. The system itself must then decide what features it will use to group the input data. Most of the work in the application of neural network to effort estimation made use of Back-propagation algorithm and cascade correlation. Many different models of neural nets have been proposed for solving many complex real life problems. The 7 steps for effort estimation using ANN can be summarized as follows: 1. Data Collection: Collect data for previously developed projects like LOC, method used, and other characteristics. 2. Division of dataset: Divide the number of data into two parts training set & validation set. 3. ANN Design: Design the neural network with number of neurons in input layers same as the number of characteristics of the project. 4. Training: Feed the training set first to train the neural network. 5. Validation: After training is over then validate the ANN with the validation set data. 6. Testing: Finally test the created ANN by feeding test dataset.

3 Experimental Analysis of Effort Estimation Using Artificial Neural Network Error calculation: Check the performance of the ANN. If satisfactory then stop, else again go to step (3) make some changes to the network parameters and proceed. Once the ANN is ready, simulation with the ANN can be conducted with the parameter of any new project and it will output the estimated effort for that project. 2.1 Experimental Setup Data II. PROPOSED ALGORITHM Results in neural networks will be calculated by taking historical data of 50 projects which is divided into three parts: 20 projects data for training the network, 10 projects for validating the network and 10 projects for testing the network. Table 2.1: Data used for training the Neural Network PROJECT NO. SIZE EFFORT Table 2.2: Data used for validating the Neural Network PROJECT NO. SIZE EFFORT Table 2.3: Data used for testing the Neural Network PROJECT NO. SIZE EFFORT Experimental parameters Parameters used for performing the operation in neural networks are as follows:

4 IJECSE,Volume1,Number 3 Anjana Bawa and Mrs.Rama Chawla 1820 Table 2.4: Parameters for Neural Networks learning algorithms in Neural Network Tool of MATLAB Parameters Back-Propagation Learning Algorithms Cascade Correlation Learning Algorithms Network Type Feed-forward backprop Cascade-forward backprop Training function TRAINLM TRAINLM Performance function MSE MSE Number of neurons 2 2 Transfer function PURELIN PURELIN No. of epochs III. Experiment and Result 3.1 Evaluations of Results In this section we will analyze the results of neural network learning algorithms i.e. Back-propagation learning Algorithms, Cascade Correlation learning algorithms and COCOMO Model of software engineering. Matlab 7.0 software platform is use to perform the experiment. Comparison of these cost prediction techniques will be done on the basis of results evaluated and then values of RMSE and MMRE will be calculated and compared Comparison of Different Cost Prediction Techniques In this section effort using COCOMO Model and Neural Network learning algorithms will be compared. Values are given in the following table: Table 3.1: Comparison between COCOMO Model, Back-propagation learning algorithm and Cascade Correlation learning algorithm Project No. Size (KLOC) Actual Effort COCOMO Model Back-Propagation Cascade Correlation

5 Experimental Analysis of Effort Estimation Using Artificial Neural Network 1821 Figure 3.1 Comparison of COCOMO Model, Back-propagtion and Cascade Correlation learning algorithms Above graph shows that effort calculated using Cascade Correlation learning algorithm,back-propogation and COCOMO Model.The result of the three shows that the cascade correlation is nearest to the actual effort as compared to other effort estimation techniques Error Prediction of Different Effort Estimation Techniques In this section error will be calculated between different effort estimation Techniques and the actual effort. To calculate the error following formule will be used: = Where E rror is the output error, E is the actual effort, E is the estimated effort So the formule used for COCOMO Model,Back-propagation and cascade correlation wil be 1 = 2 = 3 = Where E is the actual effort, E 1 error of COCOMO Model E coc is the estimated effort using COCOMO Model E 2 error of Back-propagation learning algorithm E back is the estimated effort using Back-propagation learning E 3 error of Cascade Correlation learning algorithm E casc is the estimated effort using Cascade Correlation learning. Table 3.2 Output error of different effort estimation Techniques

6 IJECSE,Volume1,Number 3 Anjana Bawa and Mrs.Rama Chawla 1822 Project No. Size COCOMO Back- Cascade Actual Effort (KLOC) Model(E 1 ) Propagation(E 2 ) Correlation(E 3 ) Mean These error values will be used to calculate the RMSE and MMRE as follows: = ( ( ( (( )! ) " ))) = (( ( ( )! /!)) Where N is total number of projects Table 3.3 Performance Evaluation of COCOMO, Back-propagation and Cascade Correlation learning algorithms Performance Criteria COCOMO Model Back- propagation Cascade Correlation RMSE MMRE Following graphs shows the comparison using RMSE(Root Mean Square Error). Figure 3.2 Comparison using RMSE Following graphs shows the comparison using MMRE(Mean Magnitude Relative Error) of different effort estimation techniques.

7 Experimental Analysis of Effort Estimation Using Artificial Neural Network 1823 Figure 3.3 Comparison using MMRE Comparison using RMSE and MMRE shows that Cascade Correlation is better than Back-propagtion and COCOMO Model. Accuracy is high in the Cascade Correlation. IV. CONCLUSION Estimation is one of the crucial tasks in software project management. To produce a better estimate, we must improve our understanding of these project attributes and their causal relationships, model the impact of evolving environment, and develop effective ways of measuring software complexity. Here three most popular approaches were suggested to predict the software effort estimation. In one hand COCOMO which has been already proven and successfully applied in the software effort estimation field and in other hand the Back-propagation learning algorithm and cascade-correlation learning algorithm in Neural Network that has been extensively used in lieu of COCOMO estimation and have demonstrated their strength in predicting problem. To get accurate results the neural network depends only on adjustments of weights from hidden layer of network to output layer of neural network. We have used the 50 projects data set to validate, train and simulate the network. This simulation with dataset has been carried out using Matlab NN tool box. All for ANN are trained using trainlm algorithm. After testing the network it is concluded that learning algorithms of neural network perform better then the COCOMO model and from learning algorithms Cascade correlation performs better then the Back-propagation learning algorithm. It has less error values, so accuracy is high in Cascade Correlation. The results from our simulation shows that Cascade feed- forward neural network give the best performance, among all. V. REFERENCE [1] Ch. Satyananda Reddy, P. Sankara Rao, KVSVN Raju, V. Valli Kumari, A New Approach For Estimating Software Effort Using RBFN Network, IJCSNS International Journal of Computer Science and Network Security, VOL.8 No. 7,July 2008 [2] Bilge Başkeleş, Burak Turhan, Ayşe Bener Department of Computer Engineering, Boğaziçi University, Software Effort Estimation Using Machine Learning Methods, 2007 IEEE computer society [3] S. Kanmani, J. Kathiravan, S. Senthil Kumar and M. Shanmugam, Neural Networks Based Effort Estimation using Class Points for OO Systems,IEEE proceedings of the International Conference on Computing: Theory and Applications(ICCTA 2007) [4] Nasser Tadayon, Neural Network Approach for Software Cost Estimation, IEEE proceedings of the International Conference on Information Technology: Coding and Computing (ITCC 2005) [5] Konstantinos Adamopoulos, Application of Back Propagation Learning Algorithms on Multilayer Perceptrons, Department of Computing May [6] Christopher M. Fraser, Neural Networks: A Review from a Statistical Perspective, Hayward Statistics(2000)

8 IJECSE,Volume1,Number 3 Anjana Bawa and Mrs.Rama Chawla 1824 [7] Kiyoshi Kawaguchi, Backpropagation Learning Algorithm, Wikipedia.org, June [8] Hareton Leung, Zhang Fan, Software Cost Estimation, Department of Computing, Hong Kong, 1999 [9] Clark, B., Chulani, S. and Boehm, B. (1998), Calibrating the COCOMO II Post Architecture Model, International Conference on Software Engineering, Apr [10] Cascade Correlation Architecture and Learning Algorithms for Neural Networks, Wikipedia.org, Nov [11] K. Srinivasan and D. Fisher, Machine learning approaches to estimating software development effort, IEEE Trans. Soft. Eng., vol.21, no.2, Feb. 1995, pp [12] Christos Stergiou and Dimitrios Siganos, Neural Networks,1995 [13] S.E. Fahlman and C. Lebiere, The cascade-correlation learning architecture,technical Report CMU-CS , Carnegie Mellon University, [14] Bisio, and F. Malabocchia Cost estimation of software projects through case base reasoning, 1st Intl. Conf. on Case-Based Reasoning Research & Development, Springer-Verlag, 1995, pp