1
Define Entities and Resources
First clarify who flows, who waits, and which resources are limited - such as customers, tasks, counters, machines.
Discrete-Event Simulation
Systems don't 'flow continuously', but jump to the next state when events occur
Discrete event simulation focuses on 'moments when state changes': customer arrivals, machine idle times, task completions, resource releases. When there are no events in between, the system doesn't need to calculate anything - that's what makes it efficient and intuitive.
Event-Driven
Queuing & Waiting
Resource Allocation
Throughput & Bottlenecks
The Intuition of DES
System state is only updated when events occur, making it ideal for process systems like queuing, manufacturing, logistics, hospitals, and call centers.
State
Number of people in queue, server busy status, current simulation time.
Events
Arrivals, service starts, service completions, resource releases all trigger system transitions.
Resources
Limited resources like counters, machines, doctors, parking spots determine congestion and waiting.
Output
Waiting time, utilization, throughput, queue length are the final results to read.
Understanding the Method
The core of DES is 'time jumps to the next critical event'
Instead of calculating second by second, it jumps directly to the moment when 'next customer arrives' or 'next service completes'. This makes process simulation highly efficient.
2
Define Events
Arrivals, service starts, service ends, departures - these events are the only triggers for state changes.
3
Jump Time to Next Event
The system doesn't need to calculate during idle periods, but jumps directly to the next state change.
4
Measure Process Performance
Queue length, resource utilization, average waiting time, and throughput are the most important outputs after simulation.
Teaching Experiment on This Page
We use a multi-server queuing system to demonstrate DES. You'll see: when arrival rate slightly exceeds processing rate, the queue suddenly spirals out of control - this is the most intuitive view of process bottlenecks.
Interactive Lab
Speed up arrivals, slow down service, see when congestion starts
This is an event-driven queuing system. Each click of 'Advance one event' jumps time directly to the next critical moment.
Queuing System View
Left = arrival entrance, middle = waiting queue, right = service counters. Watch when customers start queuing and when the system recovers.
Waiting
In Service
Completed
Queue Length Curve
When arrival rate slightly exceeds processing capacity, the queue curve keeps rising - clear evidence of bottleneck.Recent Event Log
DES is essentially a sequence of events. Each item listed here represents a moment when system state truly changed.Click 'Advance One Event' to see arrival, service start, and completion timeline.
When to Use
When system performance is determined by processes, resources, and waiting
Hospital registration, call centers, factory scheduling, logistics sorting, toll booths, airport security - all are ideal for DES to understand bottlenecks.
System Advances by Events
If state changes mainly at moments like arrivals, completions, switches rather than continuous smooth changes, DES is natural.
Resources Are Limited
Limited resources like servers, machines, workstations, vehicles, beds naturally create waiting and congestion - DES excels here.
You Need to Identify Bottlenecks
If you need to answer 'Will adding a counter help?' 'Which step is most congested?' 'Will waiting explode?', DES is very direct.