[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 >
> 
>>[jdorje - Mon Oct 03 17:00:27 2005]:
> 
> 
>>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).
> 
> OK.

Patch looks fine.  I *think* the math is correct and -58 corresponds to 
the current -33% penalty, but there should be a comment added in the 
rulesets to this effect.  Another thing you might consider is if 
centimes are accurate enough or if millimes (?) are needed (so it would 
be -585).  Somewhere there will be a rounding error and someone will get 
confused.

-jason