Arena Newsletter and Blog

Welcome to the Arena Tips and Tricks column! We’ll be using this section of the newsletter to highlight features of Arena that we want to call to your attention – either they may not be as well known, or they’re very valuable and deserve a second glance. For our first column, we’ll be starting with the A() Variable.

So how does a good simulation project go bad? We will address some of the most common issues we have encountered in simulation projects across a wide range of industries.

There are various methods of reading in data to a model in Arena, one of the more popular methods is the Direct Read feature which allows you to read in data directly to Variables and Expressions.  Variable data can be read in at the beginning of the simulation; replication or prior to the model being compiled (PreCheck).  Expressions only allow you to read in data prior to the model run so the PreCheck option is the only one available and defined by default.

So you have completed your Arena simulation project. You slaved over input data and extracting the system description from the experts. You developed a detailed functional specification to guide you through the model development. You developed the Arena model in sections so you could easily verify it. You spent several hours with the system experts to validate the Arena model to make sure it had the correct fidelity. And you ran several scenarios to find the best of several alternatives to achieve the objective stated in your functional specification. Now you're finished and you feel really good!!

When developing a model of a large system, you may have multiple large two-dimensional variable arrays that describe equipment parameters, facility characteristics, or other aspects of your system. Many times you can streamline your modeling effort by collecting these two-dimensional arrays under one “umbrella” and then pointing to the specific piece of information where needed in your logic. For instance, let’s say your supply chain model needs to define specific information for several different sites. Each site has up to 1000 SKUs and each SKU has a unique activity time for up to 20 activities. For clarity, you want to have each site’s information stored in its own uniquely-named, two-dimensional variable array. Furthermore, you anticipate the logic for the activities at each site will be similar, regardless of the site. Only the actual data values are expected to be different.

In recent years, there has been a growing interest in Agent Based Modeling (ABM).  Many people equate the type of problem to be solved with the tool.  In other words, people think there is agent based simulation software and then there is discrete event simulation software.  However, this is a simplistic and limited way to look at the issue.  In fact, the term agent based does not describe the simulation tool, it describes the simulation problem.  In its 35+ year history, Arena has implemented a number of features to model these sorts of agent based problems.  In this Consultant’s Corner we will touch on some important capabilities:  decision logic and control logic. 

If you’ve attended my training class before, worked on a project with me, or even sat in on a sales call in which I provided engineering support, I’m sure you’ve heard me stress the importance of building a functional specification.  This functional specification will be the road map for the project.

There are several key phases to any simulation project to ensure success:

In Discrete Event Simulation one issue we must resolve is the number of concurrent entities in the model. If that number gets “large” then model run speed can be impacted. In the typical systems that we model this usually does not become an issue either because we will not have a large concurrent number or because our computers are really fast. 

According to Wikipedia, skill-based routing (SBR) is a call-assignment strategy used in call centers to assign incoming calls to the most suitable agent, instead of simply choosing the next available agent. However, many types of systems have aspects where skill-based routing should be considered – retail, quick service restaurant, and even manufacturing and maintenance systems can utilize the technique. Skill-based routing occurs anytime an entity needs to be directed to a resource with the most applicable skill sets or capabilities. In this fashion, entities can be processed by resources that can provide better service or faster completion of the task.