Forge - return on investment - warning: math

Ok, my intuition told me that forges are a waste of time. So I did the math to decide when they're actually good.

So, consider two situations: either a particular city builds military units continuously, or it builds a forge first, and then military. The question is, how long until the city with the forge has produced more than the city without?

I'll assume the cities are producing longswords for the convenience of actual numbers.

Numbers:
forge cost 225 resources
forge maintenance 2 gpt
forge bonus 15%
longsword cost 225 resources
longsword rush 740 gold.
(Those are epic pace.)

T = how many turns are devoted to construction
P = production value of the city.
N = number of longswords produced.

Without the forge:
N = T*P/225 + 2*T/740
(the second term is the number of longswords that can be rush-built with the maintenance that was not paid since there is no forge)

Building a forge first:
N = (T*P-225)*1.15/225

Equate the two, and do some algebra:

T = 259 / (0.15*P-0.608)

is the number of turns elapsed before the city that builds the forge first builds more longswords than the one that doesn't build a forge.

So, chart this vs P (production of the city):

If the city production is 4 or less, then the forge never pays off - the maintenance cost exceeds the cost of rush buying the units.


So we see that you need a pretty good city to get your money back in less than a hundred years. Furthermore, you have to build 9 or 10 longswords to get any advantage. In my opinion, (a) any city with a high enough production to benefit from a forge should be building wonders instead and (b) you might not even need enough units to make it worthwhile.

Conclusion: Never build forges.

Second conclusion is that maintenance in this game is a real pain.

Meh, maintenance hasn't really bothered me that much, but forges/stables/other +% production buildings do seem too weak to be worth building.
I think changing the +% production to a static +(some number here) hammers when building land units/horses/etc would make these buildings much more appealing.

The same analysis can be done on workshops. For a workshop, the time to payoff is

T = 900 / (P - 2.5)

where I've assumed the buildings that are being built would cost 4 gold/resource to rush. These rush costs vary, but 4 reasonable for large buildings.

This is much better than the forge payoff time. In fact, for a 20 production city, the workshop pays off in 50 years (from when you start building the workshop). For a 30 production city, payoff is in 32 years.

This result seems too often for too many buildings.

The forge is not a bad idea if you are improving your infrastructure to create more advanced units later on more quickly. A good example of this is when you are about to build spaceship parts.

The main question with the +% production buildings is usually if you are able to do anything more useful with your money.

Basically I like them for everything you cant buy with money, basically wonders, spaceship parts and sometimes culture (if no culture CS are left).

But yes, I see no real reason for the unit production buildings

CharonJr

Forge is worthless, once you have the time to make it worth it, might as well buy all your units.

Other production buildings are mainly for wonders. I buy them all when I have to build something large to squeeze out a few more turns.

So essentially all military buildings, defense buildings, and a good chunk of production-enhancing buildings are useless.

Building costs and maintenance seriously need balancing.

It seems to me there are two mutually exclusive questions that arise from this analysis:

(1) If the developers were aware of this and did the calculations beforehand, we can assume that forges are deliberately this way. If so, the question is, "What effect on overall gameplay were they trying to achieve?"

(2) If the developers were not aware of this because they did not do the calculations beforehand, the question becomes, "Why didn't they want to work this through?"

Trying to think the best of the development team, and picking (1) above, I am still perplexed as to any possible answer.

well done! I as a rule never buy anything with maintenance except for roads, monuments, happy buildings, and granaries.

Great analysis. For those of us that don't speak math, the conclusions from this kind of exercise can be very helpful. Thanks for providing this information.

In my (unreleased) mod I changed the Forge to 1 upkeep and some extra XP for melee units (keeping the bonus to land units production).

The big difficulty in this game is that buildings don't scale well between the eras. A forge gets a better return in the end game than when it should be built.

Consider stadiums and coliseums. In the classical era a coliseum is great value as an extra happiness is an extra person is great. In the late game a stadium looks to provide value because any happiness becomes a modern era person who provides a lot more. Unfortunately there's no scaling going on. The coliseum and stadium are still both available to build in the modern era and the coliseum hasn't scaled down, it's just better than the stadium. All buildings suffer this way.

I'd say this is one of the greatest failings of CIV5 design and I don't know how they're going to fix it. Almost all buildings scale badly from era to era. It seems to be inherent to the whole game. Late game buildings have been designed to give modest returns in specialized cities and are generally rubbish. The designers should give players end game buildings that put power into their hands and then let them use that power to the best advantage. Early buildings should provide power in their era and see diminishing returns in the late game. That would improve CIV5 enormously.

stormerne said:

It seems to me there are two mutually exclusive questions that arise from this analysis:

(1) If the developers were aware of this and did the calculations beforehand, we can assume that forges are deliberately this way. If so, the question is, "What effect on overall gameplay were they trying to achieve?"

(2) If the developers were not aware of this because they did not do the calculations beforehand, the question becomes, "Why didn't they want to work this through?"

Trying to think the best of the development team, and picking (1) above, I am still perplexed as to any possible answer.

Click to expand...

Yep. "Harry, what do you think about 15% for forges? 225P? I didn't work it out, but it's just a game, so let's use those numbers."

do it for quick speed

pretty sure rush buying is significantly difernet

I really, really hope that OP is putting these skills to effective use in the real world

Is knowledge of basic algebra really that bad? I'd hate to hear what kind of education you value.

I would not put it past the developers to not having worked out the numbers. It's pretty obvious the game was under some pressure to be released earlier than they would have liked, so they probably put some offhand numbers in and they can easily tweak it later.

Yoshimune said:

Is knowledge of basic algebra really that bad? I'd hate to hear what kind of education you value.

I would not put it past the developers to not having worked out the numbers. It's pretty obvious the game was under some pressure to be released earlier than they would have liked, so they probably put some offhand numbers in and they can easily tweak it later.

Click to expand...

Well it wasn't easy enough to be made into the first major patch...

To be fair, there were no building changes in the patch. I'm hoping for some massive rework of the tile outputs to make city placement more interesting and improve hammers, which would greatly change the results of the OP. It may end up that the building is fine by itself. They need to work from the ground up (literally) before they can start making building balance changes.