Power Doubling Bug

[asl97]

It's hard for me to clearly explain in words on how to reproduce it so I will just post a whole bunch of pictures.

It is possible to abuse this to generate six times as much energy. For example, using the nuclear generator, that means 600000, although the alarm would be ringing and it would melt down.

the first energy update seem to have some kind of race condition or something... last image in another angle, to clearly show how to build it.

---

Note: bug is NOT fix by https://github.com/minetest-mods/technic/commit/33455328bd4fbfacd26e3f02b77f2b54bea982d9 See https://github.com/minetest-mods/technic/issues/277#issuecomment-293822014

[Ekdohibs]

Explanation of why it doubles power: The two switching stations run independent networks, and each of them get the same amount of energy from the solar panel and put it in the battery box. Now, the question is how to fix this: it means that a generator has to check it is not connected to several different networks; likewise, a consumer should check the same thing. This is non-trivial, though.

[pyrollo]

Shouldn't it be sufficient to add all Producer and Receiver nodes to all_nodes table in function check_node_subp of switching_station.lua ?

[numberZero]

add all Producer and Receiver nodes to all_nodes table It seems that that would have a side-effect: machine would work as a cable.

Instead, machine should keep its network ID so that the SW can check should it run that machine.

[HybridDog]

The machines should all have an internal capacitor. The gametime at the time of the last access is stored in meta and when accessing the machine, the energy it produced over time is sent all at once. Giving battery boxes a limited band width (and adding a capacitor node to compensate) is too intricate because of sudden glitches after entering a chunk which wasn't loaded for a long time. The decision whether battery boxes gain evenly spread amount of energy or one gets all until it's full can be made by the switching station. When multiple switching stations are connected to one network, the older ones should become inactive.

[VanessaE]

@HybridDog's comments notwithstanding, is this still a problem?

[VanessaE]

This should be fixed now, now that batteries will only draw from the bottom (like they were supposed to)

[asl97]

@VanessaE The problem ain't the battery lol. Just because we can no longer gather the power from the different network into one point doesn't mean we can't power stuff directly off each of the network

If people really want to gather them together, they can use the power converter as proxy.

---

Screenshots of five compressor powering off one lv array solar

used power: 300 x 5 = 1500 power supply: 500

[VanessaE]

obviously there's more work to do :stuck_out_tongue:

[numberZero]

One possible workaround: #313 Another one: make machines connect from one direction only. Actually that is only needed for generators not consuming fuel (and supply convertors), as for fuel-consuming generators increased power output implies increased fuel consumption, and for other machines increased speed implies increased power consumption, so that’s not that problematic and may even be considered a feature.

By the way, there is at least one legitimate use for connecting a battery box from several sides simultaneously: this way it works as a shield between two networks, protecting each from overload in another one.

[VanessaE]

In the original implementation of this mod, machines only connected from the bottom (except for the supply converter).

I like your idea of making all power-producing nodes only connect from the bottom; indeed there's zero reason to allow all-sides from something thin like a solar panel.

[Desour]

About the solar panel: It would be very nice if they would behave to each other as cable. So you could make plates of solar panels. But this should be limited, so we could add some connected solar array structure. But for sure the connection to sides makes no sense.

Only one connecting side to cables with all machines would be very inconvenient.

It could be good if only suppliers behave as cable but not demanders.

[HybridDog]

As l already tried to suggest (https://github.com/minetest-mods/technic/issues/277#issuecomment-284513625), if you change the machine functions by passing network info and individual dtime, the dtime would be 0 (nearly), the solar panel multiplies its output with dtime and so it doesn't make additional power. There'd be network nodes' polling, the passed network info is a table containing the available power, etc., and the passed dtime is the gametime difference between the current and previous poll (stored in meta). The producing nodes need to give power that consuming nodes can use it, thus there need to be different flags:

• bare_producer: e.g. watermill, coal generator, solar panel (solar panel may request a higher polling frequency), reactor core
• secondary_producer: e.g. battery box, which firstly tells how many power it can offer, then in another function it gives the amount of power requested in the params
• consumer: e.g. quarry, they have priorities, e.g. supply converter gets less power than furnace, and they can tell whether they need lots of power at once or can gradually consume power (battery box)

Machines can have multiple flags, e.g. consumer and secondary_producer for supply converter and battery box.

[numberZero]

@HybridDog that’s overcomplicated IMO. Just imagine how would these capacitors exchange energy all the time. If you want to write something complex, make it load all the networks in memory and process independently from ABMs, chunk loading, etc.; that complexity would be useful at least.

[HybridDog]

numberZero, my changes already reduce meta usage. Currently the amount of power machines produce is stored in meta.

[numberZero]

@HybridDog maybe I misunderstood you. Actually the meta is used already for so-called punching, that’s really ugly, but your suggestion may make that of more use. Still, my suggestion https://github.com/minetest-mods/technic/issues/277#issuecomment-213726588 is simpler IMO. See also #351, it’s not directly related but some things become trivial when you work with RAM instead of meta.

[HybridDog]

lf l understand it correctly, currently the power demand, production, activity etc. are stored in meta. In my suggestion only the time of last access is saved in meta (or ram) (and machine specific information, e.g. furnace inventories). l assume the complicated part may be keeping compatibility with old machines.

[Ekdohibs]

I am currently rewriting the whole technic power distribution system, both to make it more efficient and to fix these kinds of bugs, so this bug will probably be fixed when this is done.

[numberZero]

@HybridDog well, if you store that in RAM, meta is not updated each second, that’s what is important. But IMO it’s difficult to make such system reliable as it has to work with fractions (that is, floats). What if input and output are matched exactly, and there is no batbox in the network? (e.g. 2 HV solar panels connected to a supply converter).

On the other hand, this way the system may not need to be updated each second; instead, calculations may be done only when necessary (i.e. when something changes, or a player tries to look into, etc.) So... if you can do that reliably, that would be very good. Although as @Ekdohibs rewrites exactly that code, you probably need to cooperate in some way.

[HybridDog]

[Meta updating each second] is important.

It isn't, l'm suggesting to not use meta for technic related information in the machine definitions (it may still be used for inventory etc.). The machines' technic functions get a table with information as parameter and can use and change those informations (e.g. available power in the network). So the last access to a machine can easily be cached.

What if input and output are matched exactly, and there is no batbox in the network? (e.g. 2 HV solar panels connected to a supply converter).

The HV solar panels request a polling interval of 1 second (because time of day changes). The switching station polls the network.

• At first the producers (solar panels) are handled, each of them increase the value in the network information which tells how much power is available.
• Now the supply converter is questioned about how much power it needs. The supply converter takes as much power as the target network needs it, so it polls the target network. If there's remaining available power in the network which does not belong to battery boxes, the supply converter gets all that power.
• If there's remaining power from the solar panels, it vanishes.

The target network can also ask the supply converter to poll the network with the solar panels.

[numberZero]

[Meta updating each second] is important.

@rubenwardy, now you seem to misunderstood me. I meant that not to update meta each second is important: that reduces disk and network usage greatly.

And just a question: are you aware of floats’ imprecise nature? Or you plan to work with integers only? The error is (usually) tiny, but if you had an exact match, as in my example (BTW, I meant old-style SC consuming exactly 10 kPU), you may and often will lose it.

[HybridDog]

exact matches are very unrealistic. In your example you maybe would never loose it because due to server lag, the update step would be >= 1 second. And you could add a capacitor functionality to the SC.