## 2 Literature Review
### Simulation Project Techniques  
Simulation is also one of the most useful and effective techniques to analyze a complex and dynamic project, which helping the decision maker to recognize the effect of various dependent variables and complex scenarios on the project's behavior. Furthermore, project simulation can be used in different aspects of project management, can help researchers to gain many accurate and realistic outputs according to set inputs and also to investigate different scenarios as summarized below. As described in Section 2.1, the use of simulation techniques and simulators has emerged as an effective tool to generate varied experiments in this area. A method called Special Purpose Simulation (SPS) is utilized [29] which is a tool to optimize workforce forecast loading and leveling resources. SPS is a simulation model manages to optimize resource supplies and requirements for conducting a petrochemical project, considering standard discipline necessities and involvements. A project model has been designed [30] which simulates the developmental process of the project in a realistic manner and produces information concerning three different monitoring systems. In this paper, factors influencing the total cost and performance of project are also accounted for by changes occurring in the project plan and rates of inflation. In a similar vein, a research framework was developed to enable project managers to approximately calculate completion time of the project and dive deep into the main factors which influence the estimation for complex engineering projects being executed concurrently [31]. Their proposed framework is composed of three main procedures: data gathering, simulation, and data analysis with ANOVA. A number of studies have been developed to scrutinize various factors affecting project cost estimations. [PERSON] focused on understanding different factors influencing project contractors' cost estimating practices [32]. In this study, 24 factors were identified by conducting a comparative study analyzing 84 UK contractors categorized into four classes ranging from very small, small, medium to large firms. [PERSON] and [PERSON] presented a thorough quantitative estimation approach which can offer initial along with updated project estimates from manageability or feasibility study until project completion [33]. A dynamic simulation-based crashing methodology was introduced to assess project networks and determine the optimum crashing configuration that reduces the average project cost to a minimum level because of delayed penalties and crashing costs [34]. Their dynamic method allows us to assess the project network to design a crashing strategy at the very onset of the project execution and also during the time that the project is being performed. As described in Section 2.2, EVM concepts were used as a basis to analyze simulation techniques in a number of research investigations. In a study, the efficiency of controlling a project was analyzed [5]. A Monte-Carlo simulation was used to validate the project data of the study whether fictitious or empirical. Upon noticing warning control parameters, we must take corrective actions to put the project back into the correct path whenever a problem occurs. This set of information offered by the Schedule Risk Analyses (SRA) along with EVM information which is mostly the sensitivity information is obtained during project control. The effects of different activities on risk and the expected completion time of the project were described [8]. In another study, [PERSON] used Planned Value Management (PVM), Earned Duration Management (EDM) and Earned Schedule Management (ESM) as the three earned value methods to study the prediction of project duration in EVM [16]. In conclusion, it can be seen that, to a considerable degree, these studies were conducted with the aim of designing a project simulator.