I am relatively new to FAF and was therefore reading guides about the game. One of the guides I enjoyed most was the praying mantis guide to faf which attempts to provide some mathematically substantiated advice. However, the guide is badly out of date (and unfinished) due to new balancing patches messing up his old calculations. So here I am doing some of my own calculations, feel free to ask me to work out some other things you might have been wondered about. If I think your question is interesting, I'll happily spend an evening sandboxing/spreadsheeting it out to write another one of these forum posts.
This post will be mostly about maximizing your economy as far as the numbers go. As such there will most likely be cases where the numbers say it is more efficient to do one thing, say surround a T3 Pgen with T2 Mass Fabs. Whilst in practice this might be horrendous advice. T2 Mass Fabs build closely together tend to have a Rube Goldberg like effect once one of them dies, an effect that may very well cost you both all 16 T2 mass fabs and the T3 Pgen which is quite costly. So if high rated players in the comments have some input on stuff that looks good on paper but plays out badly in reality I'll be happy to edit those comments into this post as quotes.
I know there were some disagreements about Mass Equivalent Units (MEU) but I couldn't find the contents of these disagreements on the old forum. I do however think it to logical for there to be some kind of linear relationships between mass and energy, I however don't really know what shape this relationship should take. Perhaps it shifts depending on your techlevel/faction/theater of war.
Explanation of the labels
The first thing that strikes me is that the repay time for a T3 mex is actually slightly shorter than adding a mass storage adjacent to a T2 mex. Why then is it nevertheless meta to ring at T2 and only then upgrade to T3? I assume this might be the case because mass storage is much cheaper to build. A mass storage can therefore be finished much faster than a T3 mex upgrade. Thus it can start paying its cost back sooner as well. So for the ~11 tick repay time advantage to kick in one would need the buildpower to finish the T3 mex upgrade less than 11 ticks slower than building a T2 mass storage. That would take more than (3944-250)/11~=336 buildpower meaning 66+ T1 engies and is therefore practically infeasible.
If this doesn't immediately make sense think about the aeon paragon, since it produces an effectively infinite amount of mass and energy it's repay time is zero ticks. However no aeon player in his right mind would build a paragon before their first T1 mex. Because finishing the paragon based of the ACU eco takes so long that it is faster to first build up your eco a lot more before going for the paragon.
Another reason for building mass storage earlier is the the possiblity of double adjacency for mass storages on maps like dualgap and astrocrater. However one does have to hit T2 mexes before thinking about mass storage as even with 4 adjacent T1 mexes the (mass) repay time of a mass storage is 800/4=200>150 ticks. However at 2 T2 mexes adjacent the repay time is 266.7/2<150 so if you have an adjacent T2 mex it is worth building a mass storage in-between before upgrading the rest of your mexes to T2. Especially if we add to this the fact that the mass storage building is cheaper than the T2 upgrade meaning it starts paying back its own cost earlier as well.
Then as to the RAS SACUs seeming less efficient than the T3 Power & 16 T2 Mass fab template even though RAS SACUs seem to be the meta. Do not forget that the SACUs include the buildpower of roughly 2 T3 engies and on top of that can shoot. If one were to compensate the cost of the aeon RAS SACU for the cost of 2 T3 Engies their cost in mass becomes 6450-624=5826 dropping their mass repay time to ~530 ticks. If you also take the energy cost into account and look at MEU repay time it drops from ~406 to ~370. Perhaps some would say that a base with lots of SACUs walking around also needs less t1 pd for teleport protection and one might be able to talk the repay time down a little further. But I'd rather leave these kinds of more ambiguous considerations up to the pros.
One thing that is a certain advantage of SACUs over Pgen+Massfab combos is the fact that they take up a lot less space and as such require less shielding which is a mass and energy savings. On top of that they are more sturdy and less explosive making them less prone to game losing chain reactions.
I don't fully understand how adjacency works yet, but here is a first look at some of the experiments I did. I'd like to look into adjacency more but in order to do so it would be helpful to have a map where I can fully surround a factory and quantum gateway with mexes, and a UI mod that allows me to see the economy of a building with more decimal places behind the comma than the regular in-game economic view button.
The first experiment I did was testing adjacency for an aeon quantum gateway producing RAS SACUs as this is one of the most expensive things a building can do on a mass per tick basis. As you can see higher tech mexes provide more savings. A point of not is that the savings caused by a single T1 mex adjacent is better than the bonus derived from putting a mass storage next to a T3 mex.
Aeon Quantum Gateway producing RAS SACUs
If we do the same experiment for a UEF factory producing percivals we get a similar result. Here to having a production building adjacent is more efficient than ringing with mass storages.
UEF Landfactory producing Percivals
Now I did all these tests producing the most expensive units As this is what you would be producing late game. This was partly due to my inability to see enough digits behind the comma on the economy view and partly because the savings early game are not very good.
Whilst the earlygame mass savings might not be very impressive on a per tick basis the lump sum is quite a bit more attractive. Not building mass storages early game means not having to spend 200 mass on a mass storage building where you build your factories adjacent to your mexes. The savings of one mass storage roughly equals to 4 T1 tanks. One mass storage next to a T2 mex would take ~300 ticks to pay for those 4 tanks.
The conclusion to take from this is that it is probably worthwhile to build your factories next to mexes rather than leaving their sides open to eventually build mass storages there. However wherever no factory will fit or once no more factories are needed you should still build mass storages adjacent to your T2 mexes. I will most likely look into this further once I have a better method to do so.
Adjacency bonusses next to factories can also be achieved using mass fabs but due to quite limited savings and the explosion danger I don't think it is worth it. Nevertheless my findings were that when surrounding a quantum gateway producing RAS SACUs with 20 T2 mass fabs the mass/tick drops from -33 to -28 making for a mass/tick savings of 0.25 per massfab this would drop their mass repay ticks to 160. Surrounding the same quantum gateway with T3 mass fabs causes a drop from -33 to -28 for a savings of 1.25 per T3 mass fab, dropping their mass repay ticks from 250 ticks to ~232 ticks. However surrounding the quantum gateway with T3 mass fabs leaves 8 adjacent spaces open. So the cheapest one can produce RAS SACUs is with 4 T3- and 8 T2 mass fabs at -26 mass/tick.
Some people's mouths might be watering thinking about the adjacency bonus they can get using kennels/hives to produce T4 units. If you are one of these people I'm sorry to tell you that neither kennels nor hives get adjacency savings like factories do.
I'd love to read this kind of stuff without having to do all the work . As such for any of you inspired to take on the job of contributing to the forum, I'd like to try to lower the barrier of entry as low as possible. Thus here are all the tools, guides and methods I used.
It seems nodeBB (this forums forum software) allows for markdown notation, a kind of simplified latex like text formatting language. To write with headers and all the other formatting I used have a look at the ultimate guide to markdown. Markdown also allows for the creation of tables. Some versions allow for even fancier ones than the one I have in this forum post, like being able to merge cells, but it seems the version of markdown used on this forum is not one of the fancy types. Another feature some of the more fancy versions of markdown have is to allow for dollarsign dollarsign latexstyle formula dollarsign dollarsign. If the administrator of this forum is able to add this functionality with some plugin this would be greatly appreciated! An efficient way to create these tables is to use Tables Generator this allows you to copy paste from excel making the process of converting your spreadsheet into markdown relatively painless although some manual formatting might still be required.
One can find detailed information on all units in the faf unit database.
I did the sandboxing in a single player sandbox victory condition game by using the all ACU's sim mod (take care to turn on prebuilt units and sandbox victory in the lobby settings). I found the best map to use is astrocrater battles rich as all the masspoints are close together allowing for lots of adjacency options. Ecoing up to near infinite eco doesn't take very long and the flat open terrain makes it easy to build whatever you want to test out. For the exceptionally curious the replay ID is 12644739.
Answered some of your questions here and condensed your tables into what really matters when you’re actually starting out. No one needs to worry about exact values for adjacency or efficiency of mass fabs really.
You probably don’t understand adjacency because there are buildings with exceptions to the general rule, like gateways.
Everything about adjacency is explained in the wiki page on adjacency https://wiki.faforever.com/index.php?title=Adjacency_Bonus