Introduction

Mew currently supports 1 method of modeling Feral DPS, yawning.mew.cat.CatModelSimulator. This page goes on to explaining the underlying principles between the model so that users can gain a better understanding of how it works.

Note: Mew used to support a closed form spreadsheet style model of Feral DPS, but as of recent builds, support for this has been removed in favor of devoting more development time to improving the simulation code. the author does not belive that there is any inherent superiority to either approach and would be interested in seeing an accurate closed form model if one were to be written.

CatModelSimulation

This is a simulation of what a player will do much like SimulationCraft. Given a list of priorities, it will go and simulate the fight repeatedly, and use the results of the simulation to approximate DPS.

Pros:

• Numbers are much more realistic reflection of what is humanly possible assuming a well written priority list ("rotation").
• Hard to formulate effects tend to be better handled. For example, with a proper rotation, cooldowns can be stacked with corresponding impact on DPS. It correctly models other effects such as Tiger's Fury persisting across bleeds and the simulated player can opt to try to take advantage of that.

Cons:

• There is variance in the results. Unless a sufficient number of iterations is chosen, this can be quite large though at the default 10,000 iterations, it is quite small.
• Assuming effort is made to reduce the margin of error, calculation is extremely slow. Simulating the default 3,000,000 seconds of combat takes time.
• It is somewhat more sensitive to encounter duration, although there are options in place that can be used to mitigate this.
• The results are entirely dependent on the quality of the priority list. A custom priority list that only uses Mangle would not give values that are relevant to anyone that's actually good at playing a Feral Druid.
• Results are somewhat harder to interpret. Depending on the various parameters you can get interesting artifacts. For example, when the default Simulator behavior was to use Heroism/Bloodlust at the tail end of the encounter, it massively inflated the value of Blood In The Water.

Further Reading

The SimulationCraft developers explain Formulation vs Simulation in a better manner than I can.