SSIIMMUULLAATTIIOONN MMOODDEELLIINNGG AANNDD AANNAALLYYSSIISS WWIITTHH AARREENNAA TT.. AAllttiiookk aanndd BB.. MMeellaammeedd CChhaapptteerr 55 AArreennaa BBaassiiccss Altiok / Melamed Simulation Modeling and Analysis with Arena 1 Chapter 5 The Arena Simulation System • Arena is a powerful simulation environment • consists of modeling object templates, called modules, and transactions that move among them, called entities • has a visual front-end • built around SIMAN block-oriented language constructs and other facilities • SIMAN consists of two classes of objects: • Blocks are basic logic constructs that represent operations, such as SEIZE blocks that model seizing of a facility by a transaction entity, while RELEASE blocks release the facility for use by other transaction entities • Elements are objects that represent facilities, such as RESOURCES and QUEUES • Arena modules are are selected from template panels • examples: Basic Process, Advanced Process, Advanced Transfer • Arena modules are high-level constructs that functionally equivalent to sets of SIMAN blocks and/or elements, and internally are built of SIMAN blocks and/or elements Altiok / Melamed Simulation Modeling and Analysis with Arena 2 Chapter 5 The Arena Home Screen Title Bar MenuBar RunInteraction Toolbar ViewToolbar Standard DrawingToolbar Animate Toolbar Toolbar Animate Transfer Template Toolbar Panel ModelWindow Canvas ProjectBar Flowchart View Toolbar ModelWindow Canvas Spreadsheet View Altiok / Melamed Simulation Modeling and Analysis with Arena 3 Chapter 5 Example: A Simple Workstation • Consider a single workstation, known in queueing theory as the M/M/1 queue, where • there is a machine with an infinite buffer in front of it • jobs arrive randomly and wait in the buffer while the machine is busy • jobs are processed by the machine and then leave the system • job inter-arrival times are exponentially distributed with mean 30 minutes • job processing times are exponentially distributed with mean 24 minutes Create 1 Process 1 Dispose 1 0 0 0 Altiok / Melamed Simulation Modeling and Analysis with Arena 4 Chapter 5 Simulation Objects and Actions • Simulating the above workstation calls for the following actions: • jobs are created, one at a time, according to their arrival distribution • if the machine is busy processing another job, then the arriving job is queued in the buffer • when a job advances to the head of the buffer, it seizes the machine for processing once it becomes available, and holds it for a time period, sampled from its processing-time distribution • on process completion, the job departs the machine and is removed from the system • Simulation objects and their actions and interactions • are modeled by Arena modules • parameterized by associated dialog boxes Altiok / Melamed Simulation Modeling and Analysis with Arena 5 Chapter 5 Create Module • The Create module generates a stream of arrivals of Arena entities (jobs, people, messages, etc.) Dialog box for a Create module Altiok / Melamed Simulation Modeling and Analysis with Arena 6 Chapter 5 Create Module (Cont.) • The Type pull-down menu for the Time Between Arrivals field offers the following options: • Random (exponential inter-arrival times with mean given in the Value field) • Schedule (allows the user to create arrival schedules using the Schedule module from the Basic Process template panel • Constant (specifies fixed inter arrival times) • Expression (any type of inter-arrival time pattern specified by an Arena expression, including Arena distributions) Altiok / Melamed Simulation Modeling and Analysis with Arena 7 Chapter 5 Process Module • The Process module processes (serves) Arena entities Dialog box for a Process module Altiok / Melamed Simulation Modeling and Analysis with Arena 8 Chapter 5 Process Module (Cont.) • The Action field option, selected from the pull-down menu, is Seize Delay Release, which stands for a sequence of SEIZE, DELAY and RELEASE SIMAN blocks • SEIZE and RELEASE blocks are used to model contention for a resource possessing a capacity (e.g., machines) • when resource capacity is exhausted, the entities contending for the resource must wait until the resource is released • thus, the SEIZE block operates like a gate between entities and a resource • the processing (holding) time of a resource (called Machine in the example) by an entity is specified via a DELAY block within the Process module Altiok / Melamed Simulation Modeling and Analysis with Arena 9 Chapter 5 Dispose Module • The Dispose module implements an entity “sunset” mechanism • entities that enter it are simply discarded Altiok / Melamed Simulation Modeling and Analysis with Arena 10 Chapter 5