Distributed simulation protocols: HLA vs. DIS, MMORPGs
Architecture: Deterministic vs. Stochastic
Deterministic
Generates the same output every iteration, given the same inputs.
Produces single-point results.
Examples: Newtonian models of physical systems, systems without random elements, climate models, model-predictive control systems (usually)
Stochastic
Can generate different outputs every iteration, given the same inputs (though groups of iterations should be repeatable with constant random number seeds).
Produces a range of results.
Examples: Quantum mechanical models of physical systems, systems with random elements, epidemiological models, maintenance models, project/risk models
Architecture: Deterministic vs. Stochastic (continued)
Involves running multiple trials of complex models including combinations of numerous randomly generated outcomes that yield a range of complex results.
Models may incorporate scheduled and unscheduled elements.
Process Automation is an example of simulating activities that used to be done by humans.
A typical business process may be thought of as a human-in-the-loop simulation, parts of which may be automated.
If the interaction of a human with a computer's user interface is automated, that is a form of Robotic Process Automation, and that has been done for decades. (I implemented Filenet terminal interfaces to legacy mainframes in 1994.)
Screen-scraping and text/gesture inputs.
UIPath and Selenium are more current examples.
Resources Required for Simulation
Computing power
Memory (dynamic and static)
Obtainable input data
Valid behavioral data
Choosing the right level of granularity
Outputs in actionable form
The Limits of Simulation
What changes could require more computing resources (processing and memory)?
more/smaller nodes
more/smaller time steps (Courant Limit)
more interactions
larger matrix calculations
more physical effects considered
more components included (e.g., atmospheric gases)
The Limits of Simulation (continued)
If you were going to simulate an atom, what would you have to include?
What would it take to do it?
The Limits of Simulation (continued)
What if you tried to simulate the entire Universe?