Additonal foreword by lvl_50_noob

Permanent barracks are better than none, if;

B / ( A x D ) is bigger than 15

*(As Generals have +10% building costs, these vales are also 10% higher for them. 100 -> 110, and 500 -> 550)

Where
A is your total land
B is the amount of Gold spent on troops per hour
D is the gold increase factor
(The gold increase factor is the average amount your income is increased by trade agreements, and alchemy per hour)


Guide by Big Al from Oz at http://warbookforums.com/smf/index.php?topic=370.0


People might enjoy this post more than others I've made,
because whether you should build Barracks or not,
depends entirely on your personal playing style and Hero Type.

However, how many Barracks you build (if you build them),
does not depend on style or type.
If Barracks are worth building, you should go for the full 25%.

How can you tell if Barracks are for you?
Well, the maths is simple,
but you will need to work out
how much you spend on troops per acre you own.

For example, a General will probably only buy elites.
His income will probably be over 30 gold per acre,
he can maintain 8 elites per acre with plenty to spare.
8 elites per acre at 700 each
costs a General 5,600 gold per acre to progress.

Should he use Barracks? Yes, if:

gold saved on troops > gold lost from Mines

(half troop cost per acre) x (rate of progress per hour)
> (25% lost mines) x (30 gold per hour) x (3*(trade agreements)*5% + 1)

OR

Use Barracks if your daily rate of progress is greater than
414 divided by troop cost per acre.
Otherwise don't!

For our General above, the answer is Yes if he grows more than about 7.5% per day.
The percentage depends on Hero Type, and your speed obviously depends on you,
but if you are under the percentage, you are only wasting money if you buy Barracks.
However, if you are over the percentage, you are also wasting money
if you don't buy Barracks.
Of course, either way, if you get it wrong, you often won't notice,
because slow growers often don't worry about being inefficient,
and fast growers are so fast they're often happy anyway.

If you check your account at 8pm each day,
and keep a record of what your acreage is,
and then again of where you're at before you put your account to bed,
you'll start to have an idea of how quickly you make progress.

How do you organize your army?
If you can't say what you put on each acre,
you've got some thinking to do.
How far to do you aim to expand each day?
If you don't know, again you've got something to work out.

Stabilize your strategy.
We all learn by trial and error,
but gradually we settle into patterns
then we tweak those
as we work out how we can be more efficient.

Think about it, a Defense Per Acre (DPA) is made up of troops per acre.
Don't get confused about various sizes of kingdom,
just work out how best to use 100 Acres, then do it over and over!

Further comment by Big Al:

If you only ever buy soldiers from dealers, and/or only gain elites by raising the dead, Barracks are no use are they?

For some players, and some workable strategies, at least, Barrack are no use.
When are Barracks useful?

If you grow by buying land and defending it, but never by attacking, like a Turtle Visionary,
forgetting land lost to attacks for a moment, growth rate can be calculated exactly,
given the way you occupy each acre.
I solved that algebraically and checked with various examples.

The more troops a Turtle uses to defend, the more likely he is to need Barracks, because he is spending more on troops.
However, the more he defends, the less his income, so the slower his growth with fewer troops to cover it.
The break even points for Barracks to be worthwhile for a Visionary Turtle are the solutions to a quadratic equation,
both of which imply negative income.
What that means in real life is that Visionary Turtles never benefit from Barracks.

What we are all seeing is that TIME, income and cost are the variables.
Time is key.

There are two separate questions we've looked at.

• 1. When is it worth buying Barracks, then rebuilding Mines (spending 25%*acres*(500+500)) to save on a big troop purchase?
• 2. When is it worth maintaining 25% Barracks permanently?

I haven't posted about question 1 yet, 'cause others have scrutinized it in a range of fascinating ways.
It seems to me, the answer is straight forward.
If the cost of a one-off troop purchase is greater than 500 times acreage it is worth doing, otherwise it isn't.
Precisely as has been said by others.
This solution is actually independent of any time considerations.

A rather fascinating extention of the question, that others have proposed,
views regular progress in the game as being income accumulation,
up to a point when troops are then purchased.
Obviously time is introduced into this problem.
I haven't checked the methodology or the calculations sufficiently to comment as yet.

In my post above, I am only addressing the question of permanent Barracks.
There is no cost to building or rebuilding in this case, because they are permanent.
Instead the cost is lost income (which is not a cost in the temporary Barracks case).
Different questions, different costs.

I propose above that a natural way of expressing when permanent Barracks are worth it is as follows.
The continuous opportunity cost of 25% lost mine income is warranted
when the discount on continuous purchase of troops exceeds this amount.
In other words, it is worth it when the cost of occupying new territory exceeds a certain thresshold.
Since cost per acre of occupation is constant, it is the amount of new territory that matters.
If I conquer 1 acre per day, I need few troops, I do not need Barracks.
If I double in size every hour, I will certainly need Barracks.
Where's the cross-over / break-even point?

The Barracks-break-even-rate is inversely proportional to troop cost per acre.
For convenience, I express this solution in terms of percentage growth per day,
hence we get AL's constant <wink> -- 414.

Plug in the numbers, and sure enough, Visionaries don't need 'em and 'Mongers do (surprise, surprise).
But what about the rest of the world? What should they do?
Simple -- work out what they use to occupy land when they grow,
work out how much they realistically grow each day.
Alternatively, they can use the formula to calculate a target,
The General in the post above upgrades 5 elites per conquered acre,
He needs 7% growth per day to pay for his Barracks
(or he might as well not have them).

The fact is, Barracks cost money every hour, you have to work to pay for them.

Why I think there is a problem.
A long time ago, I worked out what I wanted per acre.
I stopped growing in order to "fill up" my land.
I worked out there was no point chasing more land
when what I already had was not full.
(The game guide says beware of overexpansion!)
Moving from full land at A to full land at A+d
is a much shorter distance than moving from
underdeveloped land at A to full land at A+d.
Now I only move from full land to full land.
I have to stop and "fill up" at some stage,
alternatively, I'm effectively deciding some lower level of occupation is adequate.
Or, even worse, I'm actually lowering my level of occupation as I increase in size.

I think it is because many players overextend that they get confused.
They are trying to grow, when they first need to fill up.
True growth is moving from full to full.
Filling doesn't take that long, and you get hit less,
because all the overextenders get hit first.

This is relevant to thinking about Barracks,
because Barracks look extra attractive
when you know in your heart you need a lot more troops
for where you're at, as well as to grow beyond it.
And maybe they are, because you've got some catching up to do.
But the most efficient long term decision depends on a stable pattern of play.

Inefficient players will probably benefit from Barracks,
because they're always recovering from hits and struggling to fill their land,
and yet they also tend to go off and overextend yet again.

They'd be quite right to say the maths doesn't help them too.
They experience such volitility, how can inflexible maths help?
They need to see that there's a small finite limit
to how much you can crowd onto any given acreage
reach that, and then move forward more realistically.
Suddenly, not only will growth stabilize, it will increase also.

All it takes is a decision, it doesn't even take much time, or cost much gold.
I can't make that decision for anyone, I can only help them see why it needs to be made.

Further post by Aosh:


Perhaps I should have added to Case B the clause that (AND amount you plan to spend > 500A). Of course
if the amount is any less, it would contradict case A, which is the most simple and least error prone equation.

Perhaps for case B I should have said:
If time between purchasing troops < 29 hours, then no matter what, the full mine / temp barracks strategy does not make sense (should use constant barracks)

However, as you noted, having a time greater than 29 hours does NOT necessarily mean you should do temp mines.

I made a boolean table of the 3 conditions mentioned in each cases A, B, C:

t < 29 G > 500A at 25% barracks can purchase...* constant barracks temp barracks no barracks
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
T T T Y N N
T T F Y N N
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
T F T Y N N
T F F N N Y
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
F T T N Y N
F T F N Y N
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
F F T Y N N
F F F N N Y

*if, at 25% barracks, in one hour you can purchase on avg over 17.25A/C units, where A is the number of acres and C is the cost per unit with no barracks.

In summary:

if G > 500A
if t < 29 hours
constant barracks
else
temp barracks
else
if at 25% you can purchase...
constant barracks
else
all mines (no barracks)

I think this cleanly fixes the issues you had with Case B regarding if 't' is greater or less than 29 hours. That criteria only comes into play when you have G > 500A, where G is amount of gold you are willing to spend on troops at that moment. Thus 1 soldier (G = 100) is not a counter example.

It's a little late, so I haven't completely thought it through but I thought I would post my thoughts before sleeping.
If you find any logic flaws, please do voice them. I'm glad you made me think about it more.. I'm a bit more confident this time around.