[Freeciv-Dev] Re: (PR#14170) Replace "Trade_revenue_reduce" tech flag with proper effect

["Jason Short" <jdorje@xxxxxxxxxxxxxxxxxxxxx>]

<URL: http://bugs.freeciv.org/Ticket/Display.html?id=14170 >

Mateusz Stefek wrote:
> <URL: http://bugs.freeciv.org/Ticket/Display.html?id=14170 >
> 
> This patch replaces the "Trade_revenue_reduce" tech flag with proper effect.

> -
> -  /* Check for technologies that reduce trade revenues. */
> -  for (i = 0; i < num_known_tech_with_flag(city_owner(pc1),
> -                                        TF_TRADE_REVENUE_REDUCE); i++) {
> -    tb = (tb * 2) / 3;
> -  }
> +  
> +  /* Trade_revenue_bonus increases revenue by 18.9% (pow(1.189, 4) ~= 2.0) */
> +  bonus = get_city_bonus(pc1, EFT_TRADE_REVENUE_BONUS);
> +  
> +  tb = (float)tb * pow(1.189, bonus);

This should definitely be an effect.  But where do you get 1.189?  The 
fourth root of 2?  But why isn't this just 2/3 (or 1.5 if you want to 
invert it)?  If you want to change the logic around, change it to be 
simpler: a power of 2, in centimes (so a value of -100 means cutting the 
trade in half).

   tb = (double)tb * pow(2, (double)bonus / 100.0);

then for the current case where each cuts it by 33% you'd want -58 I 
think (log2(2/3) = log(2/3) / log(2) ~= -0.5849).

As a separate question, is this really a good feature?  Should we 
consider removing this from the rulesets?  Why does trade drop by 
discrete increments when a tech is discovered that logically should 
*increase* trade?

-jason