how many logistic/construction robots needed?

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brunzenstein
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how many logistic/construction robots needed?

Post by brunzenstein » Sat Apr 23, 2016 12:26 pm

Is there a crude rule of thumb regarding the ideal equivalent between the two robot flavors?
And how many?
Or is the more of each, the better?

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Re: how many logistic/construction robots needed?

Post by Koub » Sat Apr 23, 2016 2:23 pm

There is totally no "right" or even "not too bad" ratio. My advice : build more if you need more throughput (like if 80% of your robots are permanently busy, or if it takes too long to build or transport your stuff).
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Re: how many logistic/construction robots needed?

Post by BlakeMW » Sat Apr 23, 2016 3:34 pm

Depends entirely on your needs. As a rule of thumb? 100 construction bots and 500 logistic bots is enough to start doing logistics on a useful scale (or at least a scale comparable to the size of a factory required to research the logistic system and the upgrades in the first place, or say, launch a rocket using a bot factory).
Last edited by BlakeMW on Sat Apr 23, 2016 6:36 pm, edited 2 times in total.

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Re: how many logistic/construction robots needed?

Post by Xterminator » Sat Apr 23, 2016 4:59 pm

I don't think there is any standard number. Typically you will probably need more Logistics bots than construction ones unless your doing a ton of Blueprint building and not much actual production using Logistics bots.

A good way to tell is just wat h the number of bots in the system ( by mousing over a Logistics chest), and if all or nearly all the bots are being used most the time then you need more. If there always seems to be some idle, then you probably don't need any new ones yet. :)
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Re: how many logistic/construction robots needed?

Post by Amarula » Fri May 10, 2019 2:38 pm

Is there any updated advice on planning how many logistic robots you need for a given configuration. I tried searching the forums, but there are so many hits on logistics, bots, and how many; this is the most relevant search result that I found.

I have just started my first use of a significant bot design factory (for green circuits if it makes any difference). Yes, I am direct inserting from the cable factories into the circuit factories. While I can see that all my robots are busy, I am not sure about just adding more, as they all need a place to charge. And I need to balance room for beacons as well as roboports.

I am looking for any experience, or better yet formulas, to balance: quantities to be delivered, distance to cover, number/location of provider/requester chests, numbers of roboports, and numbers of logistic robots.

Thanks in advance!

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Re: how many logistic/construction robots needed?

Post by pieterhulsen » Fri May 10, 2019 3:06 pm

Amarula wrote:
Fri May 10, 2019 2:38 pm
Is there any updated advice on planning how many logistic robots you need for a given configuration. I tried searching the forums, but there are so many hits on logistics, bots, and how many; this is the most relevant search result that I found.

I have just started my first use of a significant bot design factory (for green circuits if it makes any difference). Yes, I am direct inserting from the cable factories into the circuit factories. While I can see that all my robots are busy, I am not sure about just adding more, as they all need a place to charge. And I need to balance room for beacons as well as roboports.

I am looking for any experience, or better yet formulas, to balance: quantities to be delivered, distance to cover, number/location of provider/requester chests, numbers of roboports, and numbers of logistic robots.

Thanks in advance!
You need to visually look at what is happening.
If you see a lot of robots hovering at the roboports to recharge then adding more roboports is wise.
But if all bots are busy then that is usually a good clue that you need more bots.

THere are no formulas or anything like that as far as I know, since you can make bases in different ways.
I need very little logistic bots because I design belt factories with logistic for a few scarce items and supplying me personally.
But I need a lot of construction bots for building the base.

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Re: how many logistic/construction robots needed?

Post by adam_bise » Fri May 10, 2019 10:11 pm

Trying to figure out a formula would depend on your bot speed and cargo capacity levels. I haven't seen a formula, but it would be interesting to come up with one.

You'd have to figure out recharge time per bot per roboport, distance vs bot speed vs max charge distance. How many roboports in the delivery path for each request, and item request rate vs cargo capacity.

It may be easier to just set up a requester chest with a few of each bot and set it next to a roboport wired to show bot stats. Wire up to combinators like available logi < 1 output logi 1 to a filter inserter between requester and roboport with set filter via signal option.

You'd still have to do what pieterhulsen mentioned and consider adding more roboports to high traffic areas.

Honestly I think it would be more work to figure out the math in this case than to just eyeball it and tweak your setup. There is an option "show logistic bots on map" in the F4 debug menu.

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Re: how many logistic/construction robots needed?

Post by zOldBulldog » Fri May 10, 2019 11:59 pm

The best way to estimate how many bots you need of each kind is to not do it at all.

I am away from my computer but if you Google you can find designs that will monitor the total number of bots of each kind and how busy they are... then build them and deploy them to a roboport as needed.

If your bots are idle, none get produced. If your bots are very busy then it keeps producing them.

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Re: how many logistic/construction robots needed?

Post by Zavian » Sat May 11, 2019 12:27 am

zOldBulldog wrote:
Fri May 10, 2019 11:59 pm
The best way to estimate how many bots you need of each kind is to not do it at all.

I am away from my computer but if you Google you can find designs that will monitor the total number of bots of each kind and how busy they are... then build them and deploy them to a roboport as needed.

If your bots are idle, none get produced. If your bots are very busy then it keeps producing them.
I've yet to see a design that won't overproduce bots when the real issue is not enough charging. Personally I just check the active bots by hovering over a roboport if I'm wondering whether I need more bots.

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Re: how many logistic/construction robots needed?

Post by zOldBulldog » Sat May 11, 2019 12:40 am

Zavian wrote:
Sat May 11, 2019 12:27 am
zOldBulldog wrote:
Fri May 10, 2019 11:59 pm
The best way to estimate how many bots you need of each kind is to not do it at all.

I am away from my computer but if you Google you can find designs that will monitor the total number of bots of each kind and how busy they are... then build them and deploy them to a roboport as needed.

If your bots are idle, none get produced. If your bots are very busy then it keeps producing them.
I've yet to see a design that won't overproduce bots when the real issue is not enough charging. Personally I just check the active bots by hovering over a roboport if I'm wondering whether I need more bots.
The one I use does it pretty much like what you do by hand. It monitors total and available bot signals of a roboport and control the inserted that puts new bots into a roboport when appropriate.

If you don't like the existing designs, use those signals to design your own.

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Re: how many logistic/construction robots needed?

Post by Zavian » Sat May 11, 2019 4:30 am

Zavian wrote:
Sat May 11, 2019 12:27 am
I've yet to see a design that won't overproduce bots when the real issue is not enough charging.
zOldBulldog wrote:
Sat May 11, 2019 12:40 am
The one I use does it pretty much like what you do by hand. It monitors total and available bot signals of a roboport and control the inserted that puts new bots into a roboport when appropriate.

If you don't like the existing designs, use those signals to design your own.
You seem to miss the point. None of the designs can distinguish between no bots available because there is not enough charging, and no bots available because you need more bots. The charging information isn't exposed to the circuit network. (Yes, I could probably design something with accumulators to measure power consumption of roboports, and hence detect when I might need more charging, but I'm not interested in adding that to every roboport).

The Mk1 Eyeball is the simplest and most reliable way to detect the not enough charging issue. In that case I need to add more charging rather than more bots. Adding bots without adding more charging will just mean there are more bots queuing up waiting to charge.

There are also plenty of other things that the automatic systems don't know about. Like if I am about to boost bot throughput by researching bot cargo capacity/bot movement speed. So I prefer adding more bots manually when I notice I'm short on bots. (Note I generally don't do large scale bot based production. Most of my bases only use around 200-250 bots mainly supplying me and my construction/artillery trains, and low volume production of things like radars and satellites. When I do use bots based production, then that is almost always in separate outposts connected by trains. Even there I prefer to hand add bots till I decide an outpost has enough).

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Re: how many logistic/construction robots needed?

Post by zOldBulldog » Sat May 11, 2019 10:01 am

@zavian,

I see what you mean now. Although I can't say I ever had your issue.

I don't do much bot-based production either, but I do use bots extensively for rapid constructiion/deconstruction, a lot of logistic trash collection/resorting and some bot-based deliveries. My bot population typically stabilizes around 800-1500 bots, which seems correct as during spikes of activity they do seem to be all busy.

My roboport strategy typically involves a large grid of roboport at 1.5 chunk separation in the malls/malls station/solar/nuclear/incinerator area with auto-produced bots, no bots in my volume production areas (except for 100-200 construction bots in each production or military outpost, mainly used for expansions/deconstructions handled via blueprint and supply train deliveries).

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Re: how many logistic/construction robots needed?

Post by Amarula » Sat May 11, 2019 1:48 pm

Thanks all for your feedback. I perhaps should have mentioned I am using a sector based map (or grid), where if I need more of X, I plunk down a new sector and copy over the blueprint for making X. Yes, I could tweak the design while watching how it works, to come up with an ok pattern to duplicate, but I am one of those that really prefers to sketch out a design, check out the numbers, and say, yep that should do 'er, before I start building.

And I am one of those who enjoy working out the math, so I have started working on some formulas.
I have observed that busy robots will sometimes start towards a target, turn around and go back to the roboport to charge. Not sure how to account for that in my formula yet ;-)

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Re: how many logistic/construction robots needed?

Post by Qon » Sat May 11, 2019 3:34 pm

Amarula wrote:
Sat May 11, 2019 1:48 pm
And I am one of those who enjoy working out the math, so I have started working on some formulas.
I have observed that busy robots will sometimes start towards a target, turn around and go back to the roboport to charge. Not sure how to account for that in my formula yet ;-)
Approximate. Robots are a bit chaotic and a formula that gives you a precise answer requires a full Factorio simulation in your formula with your savefile as input. Someone has already written that formula down and sent it to you in machine eeadable format. Use it or make your own approximation ;)

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Re: how many logistic/construction robots needed?

Post by Amarula » Sat May 11, 2019 6:51 pm

So I started looking up some details in the wiki, and there seem to be a couple of pieces missing. A robot uses 5Kj/m any time it is traveling, but there is also some unspecified energy cost per tile traveled. I also did not see any definition of how much energy the robot has when fully charged.

When it runs out of power, the robot heads back to the roboport to charge at 20% of normal speed (including any researched speed bonus). The roboport has 4 x 1MW charging ports. It can charge between 50-70 robots per minute; so from 3.5 to 4.8 seconds to recharge each robot. Without knowing what affects the charging time, I can't know the exact time, but an estimate of 4 seconds is probably close enough given that the travel time is going to be a lot longer. But it would be fun to know :-)

Without knowing the energy storage, and the power cost per tile traveled I am kind of stuck.
Can anyone point to any further information on robotic power use? Thanks!

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Re: how many logistic/construction robots needed?

Post by Qon » Sat May 11, 2019 7:53 pm

Amarula wrote:
Sat May 11, 2019 6:51 pm
So I started looking up some details in the wiki, and there seem to be a couple of pieces missing. A robot uses 5Kj/m any time it is traveling, but there is also some unspecified energy cost per tile traveled. I also did not see any definition of how much energy the robot has when fully charged.
meter = tile. You said energy/tile twice.
Amarula wrote:
Sat May 11, 2019 6:51 pm
Without knowing the energy storage, and the power cost per tile traveled I am kind of stuck.
Can anyone point to any further information on robotic power use? Thanks!
viewtopic.php?f=6&t=70369

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Re: how many logistic/construction robots needed?

Post by Amarula » Sun May 12, 2019 1:55 pm

Thank you for the additional clarification, and the link to the post that had a link to the missing information!

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Re: how many logistic/construction robots needed?

Post by hale42 » Sun Jun 09, 2019 3:06 pm

I just made a blueprint that added bots when the available bots dropped to low and removed them when they got to high. it works crazy well. when I concrete my entire base it will jump up to 20k bots then plummet down to 100 or so when the work is complete.

edit 10*stack size*#wagons(per time) should give you your consumption and thus the number of bots needed. Then I think all you need is the distance traveled for the power aspect of it and that will give you how many robos you need to charge em all back up. (side note may want to set your miners to stop working if there is enough ore in storage to fill a train when it arrives. so you get a continuous average distance traveled.)

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Re: how many logistic/construction robots needed?

Post by Ormy » Tue Jun 11, 2019 10:55 am

The number of bots required and their energy consumption depends heavily on the length of the journeys they take which makes things very chaotic if there are many different journeys the bots can travel.

Simple example, logistic network containing 1 roboport, , N bots, 1 requester chest and 1 provider chest (providing the item(s) that requester is requesting). Here there is only 1 possible journey (from provider chest to requester chest and back, via the roboport for charging) so you could probably devise a formula to calculate the number of bots needed for a certain throughput (given inputs of bot cargo size and speed, and distance of the journey and detour distance to roboport).

As soon as you add another journey or other roboports to the same network, bots will dynamically switch between journeys/tasks as they are needed and also pause at different roboports to recharge along the way. It will be impossible to use a formula as there are a multitude of journeys and no way to predict when a specific robot will take a given journey and when it might swap to another journey or task, and no way to predict which roboport it will stop to charge at.

The only way to keep things deterministic and predictable is to have only one journey per logistic network. But that kind of defeats the whole point of a logistic network.

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Re: how many logistic/construction robots needed?

Post by jcranmer » Thu Jun 13, 2019 3:34 am

Ormy wrote:
Tue Jun 11, 2019 10:55 am
As soon as you add another journey or other roboports to the same network, bots will dynamically switch between journeys/tasks as they are needed and also pause at different roboports to recharge along the way. It will be impossible to use a formula as there are a multitude of journeys and no way to predict when a specific robot will take a given journey and when it might swap to another journey or task, and no way to predict which roboport it will stop to charge at.

The only way to keep things deterministic and predictable is to have only one journey per logistic network. But that kind of defeats the whole point of a logistic network.
You're not thinking hard enough. If you impose some constraints, you actually get a simple algorithm that can tell you how many robots you need to keep the throughput of a logistics system maxed out. Those constraints are:
  • Steady-state solution. There's a uniform drain (measured in items/sec) on each of the requesters, and a maximum uniform supply (measured in items/secs) on each of the suppliers; nothing builds up in any chest. This doesn't quite work for things like train stations, because there's a need to balance unloading from different cars, but it should work well enough to give you a ballpark.
  • Sufficient number of roboports to handle the robot charging demand. A roboport can only handle about 50-100 robots. If there are too few roboports, then the throughput crashes because robots are queuing up to charge. It's easy enough to provide these roboports, though.
  • Roboports are sufficiently well-placed that robots don't have to go far out of their way to reach a charging point. Essentially, the detour time (but not the charging time) we're fixing to be 0. This isn't that hard to guarantee, it just means ensuring that the roboports are placed interior to your network rather than exterior.
  • Request amounts are set high enough that there's no "ringing" going on in the network. There should always be a request outstanding for the requester chest to be supplied, so there's no downtime where the requester isn't providing the desired drain but there's no more robots being queued up to supply it because the entire demand is en route.
With that model, it's just solving a bipartite matching twice. You have a set of requester chests at various points in the grid, a set of provider chests at various points in the grid, and a complete set of paths for each pair of requester/provider. First, greedily pick the shortest path between a requester and a provider, take the minimum of the provider's supply and the requester's demand and divide by robot carrying capacity to calculate the robots per second that you need on that route. When you're done, you'll know how many robots can be supplied per second at each requester and how many are demanded at each provider. So you can repeat the process to compute how many robots need to deadhead along each path to be able to fulfill another request. Multiply the number of robots/second along each path (in both directions) by the length of the path to get the total robot-tiles/second your network needs to sustain the throughput. Divide that number by the robot's average speed (taking into account that its speed is 0 when charging) to get the number of robots you need to sustain throughput.

I don't know what the actual planning algorithm for robots is, but this model is likely to be the most correct when you have too few robots and so there's no sleeping robots in the network. With sleeping robots, I think you're overestimating charge times, but an actual simulation would probably find there to be a hysteresis effect going on where temporarily exceeding the steady-state demand induces the need to start charging, causing the throughput to crash back down to the limit when you take into account charging. The number estimated from above is not going to be precisely accurate, but it should be close enough to be satisfactory for all needs when a little bit of padding for safety is added.

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