Dr Tracey England Discrete Event Simulation

OR Methods “Soft” methods Methods to help structure ill- structured problem situations Methods for more structured problems -parameters difficult to quantify Methods to calculate an attribute of a system Deterministic methods Stochastic methods Statistical methods Static Monte Carlo simulation methods Probabilistic methods Logic methods Methods to replicate or forecast system behaviour Deterministic replication methods Stochastic replication methods Complexity understanding methods Optimization methods Optimization of deterministic systems Optimization of stochastic systems Taxonomy of OR methods Williams, T (2008) Management Science in Practice, Wiley. p.101

What is Discrete Event Simulation? Models a system as a sequence of discrete events in time. Each event occurs at a certain instant in time. The simulation keeps track of the time and the next event in the list to be triggered. May undertake several runs of the model and then look at the results, e.g. mean waiting time, utilisation.

DES Software Open source – SIMPY: python based software Commercial packages – SIMUL8 – ANYLOGIC

Where I have used DES Trauma and Orthopaedic Unit, Royal Gwent Hospital Glaucoma, Lucentis, Cornea and paediatric outpatient clinics, Royal Gwent Hospital ABMU Out of hours NHS Direct Wales

Why it has been useful Visual representation that aids discussion between the different people involved. Use of “what-if” scenarios to evaluate different options. To “try before you buy” – allows you to model systems before they are built for real

Resources Staff Computers and equipment Rooms

Timings

Outputs

DES in Ophthalmology

NHS Direct Screenshot