Determine basic parameters that should be fixed about taxi

[bokae]

Current considerations:

We use a 20x40 grid for the simulation. Let us suppose, that this corresponts to a 2 km x 4 km grid in real space.

Then 1 distance unit (du) corresponds to 100 m.

Our cars move 1 du in 1 time unit (tu). If we suppose that their average velocity while moving is 36 km/h (that is quite optimistic), i.e. 10 m/s, then 1 tu = 10 s, and $v=1\frac{\mathrm{du}}{\mathrm{tu}}$

The average free path between taxis is
$$\overbar{d}=\sqrt{\frac{8\ \mathrm{km}^2}{N_t}},$$

where $N_t$ is the number of taxis in the system.

Now let us consider the request to taxi ratio, or reciprocal system capacity. If $\lambda_r$ requests are made per time unit, then after time $t$, there will be $\lambda_r\cdot t$ requests, that all have an average length $l$. Taxis can travel $vt$ distance during the same time window, so theoretically, if all requests were matched with taxis at once, the reciprocal system capacity would be

$$R=\frac{\lambda_r r l}{N_t vt}.$$

In our current geometry, where there is one base at the center, and base_sigma is 5, $l\approx 8$. So without correct units:

$$R=\frac{8\lambda_r}{N_t}.$$

This means that if we change $\sigma$, that changes $R$ as well!!!

[bokae]

Conversion specification is now given in generate_configs.py. Changing $R$ with changing $\sigma$ is already taken care about.

[bokae]

I think that the parameter issue is done for now, we have more than enough of them.