(December 27th, 2017, 12:11)Cornflakes Wrote: The district discount mechanism's mysteries have been unveiled! Source post at Civ Fanatics: https://forums.civfanatics.com/threads/d...sm.625743/ The explanation there is somewhat opaque. After reading the post I had to scratch it out with paper and pen to wrap my mind around it, so I'll restate it here in a way that I was able to understand it better. With the following variables defined:
C = total number of completed districts (regardless of type)
P = placed districts of the specific type in question (e.g. Commercial Hub), this includes the sum of completed and uncompleted districts of the specific type
A = available districts to build, which is based on techs discovered. (e.g. Astrology + Writing + Bronze Working = 3 available districts)
For a specific district type, the discount is available only if both of the following are true:
1) C>=A
2) C/A > P
The discount does not apply to Spaceport, Aqueduct or Neighborhood and thus these districts are not included when counting up A & C. Count only Aerodrome, Campus, Commercial Hub, Encampment, Entertainment Complex, Harbor, Holy Site, Industrial Zone & Theater Square. Thus A has a range up to 9.
For an example, say there are 4 total districts complete and 4 possible district types you have the tech to build. Thus C=A=4 and C/A = 4/4 = 1. Let's say at this point you have not placed any Holy Sites (HS) so P = 0. Both conditions are met for the first HS district placed. After placing the first HS, P becomes 1 thus C/A is no longer greater than P. HOWEVER, after completing the HS (or any other district), C/A = 5/4 which is greater than 1 and the discount then applies to the 2nd HS.
Thus it is not always cheaper to lock in districts ASAP! With the discount of 40% it can be significantly cheaper to wait until the discount applies before locking in the cost. With the 40% discount, you would have to research 66% more techs before the cost increase due to techs would out-weight the discount due to waiting to lock-in. In fact, it seems like it would almost always be better to wait to place down any district that is in the minority in your civ until you can get the discount to apply. If you already have exceeded the discount you could achieve in the near future (3rd/4th of the same type) but still want to build another one of the same type then might as well lock in the cost ASAP. Note that the discount mechanism only looks at your districts and techs, which means that it is independent of the other players actions and a perfect opportunity to optimize build/research orders to maximize the number of districts which get the discount. In fact, with careful planning I think it would be possible to achieve the discount on nearly all of the districts built throughout a game.
Theoretically you could get the 40% district discount on all districts except whichever kind you have the most of. I'll use a specific build & research order as an example, which would also work under similar circumstances with alternate build & research orders.
1) Research Astrology, build 2 HS.
2) Research Writing. C=A=2, C/A=1 so the discount would apply to the 1st Campus.
3) Research Bronze Working. After the campus is complete, C=A=3, C/A=1 so the first Encampment is discounted.
4) Research Currency. After the Encampment is complete, C=A=4, C/A=1 so the first CH is discounted.
5) By this time cities are starting to grow. You build a 3rd HS without getting the discount, which makes C/A = 5/4 thus the 2nd Encampment AND 2nd Campus AND 2nd CH now all get the discount.
6) Research Apprenticeship. The 2nd districts from (5) have already been placed and have the discount locked. C/A is 5/5 before any of the 2nd districts complete so you get discount on the first IZ, after any of the 2nd districts complete the ratio is bumped up to 6/5 and the 2nd IZ gets the discount.
7) Repeat (5) & (6) with Drama & Poetery for the Theater, Celestial Navigation for the Harbor, etc. Eventually you'll build the 3rd HS without the discount to enable the 3rd district of each type to get the discount. In theory you could get the discount on every district except the HS in this example, as long as you continue building the other districts evenly. And with the discount at 40% it almost makes the other districts worth building evenly to maintain the discount, especially early on when there aren't many district types available.
Any comments or questions please reply in my duel thread to keep this Expanded Civilopedia thread un-cluttered.
After seeing one or two instances of "missing discounts" in the PBEMs/duels and reviewing the CivFanatics thread I've found that there is a an inadvertent omission in the above:
The values of C and A (completed districts and available district types) are only refreshed when a tech or civic is completed.
The CivFanatics post refers to 'a' and 'b', which are equivalent to 'A' and 'C' in the formulas above.
I've responded here to keep it from getting buried in the duel threads as they get older.
Additional Edit: I've confirmed this using Firetuner. I started a game, gave myself two settlers, founded cities, "researched" pottery, writing & astrology. Holy Sites and Campus districts were the same price. Placed two campuses, no change. "Researched" sailing, holy sites were now discounted.