Profiling: reduce use of can_eat

[richelbilderbeek]

Is your feature request related to a problem? Please describe.

In recent Travis CI build logs we can observe that 44% of all run-time is spent in can_eat.

Now we can rationally speed up the program, let's reduce the number of times it is called!

What we can see, is that when can_eat is called for any agent, can_eat will always return the same std::vector. We can store that std::vector internally in an agent.

Describe the solution you'd like

• [x] Write down the current run-time speed for the profiling setup here:

Measured	Runtime speed
Before	6:02

• [x] Within an agent add to the private section:

/// The types of agents this agent can eat
/// Added as a result of profiling
std::vector<agent_type> m_prey;

• [x] Initialize m_prey at the constructor of agent, by calling can_eat
• [x] Replace all other calls to can_eat by using m_prey instead

Do not make a getter for m_prey! It's an implementation detail that should not be exposed.

• [x] Measure the speed increase

Measured	Runtime speed
Before	6:02
After	2:40

• If speed is reduced, undo all changes!
• If speed is increased, keep the changes.

Describe alternatives you've considered

None.

Additional context

None,

[richelbilderbeek]

@robkruger: I assign you this Issue. Feel free to delegate it to others, as long as you take the responsibility to ensure the code is actually sped up!

[robkruger]

The program sped up significantly👍

[richelbilderbeek]

I see here the new speed is 2m12.

Well done!