[0.12.26] Inserters get stuck feeding stone to furnace

[JasonC]

Factorio 0.12.26 (alpha), full version, Windows 7, 64-bit

Inserters are not aware that 2 stones are required to create a brick in a stone furnace, therefore they get stuck after picking up a non-stone material from mixed-material conveyer belts when there is already one stone in the furnace.

For example, if there is an empty, fueled stone furnace being fed by an inserter, and the following materials arrive on the belt in order: a stone, copper ore, a stone, the inserter will load the first stone, grab the copper, then get stuck over the furnace holding the copper, since the furnace is expecting another stone.

What I believe *should* happen is the inserter shouldn't pick up the copper at all, just like it doesn't pick up other materials that aren't valid in a stone furnace (e.g. it will never pick up copper plates).

The quick fix right now is to manually remove the stone from the stone furnace, then things will start moving again.

The way to avoid it completely is to never mix stone with other materials on a conveyer belt that feeds a stone furnace.

[daniel34]

This is not a bug. The furnace has 'generic' inputs, where the item in the slot determines what's being created, so the inserter can't know it shouldn't insert the copper ore.
As you already mentioned, the solution is to not mix stone with other ores.

See also:
[0.12.26] Furnaces/Inserters Stuck Again
[0.12.16] Furnace operation halts with inserter

[Zeblote]

That's bs, of course the inserter can know not to grab copper if it can't actually insert it.

The solution is to improve the inserters, not make everyone have to work around it.

[JasonC]

I don't understand, though. The inserter knows not to, say, insert an iron plate.

And even if it's not a bug, it's not very fun and doesn't make a lot of sense. That's why people keep reporting it.

[Koub]

That's not a major issue : you just need to have different belts for different ressources. That's abour how work every single industrial belt system I know of... Or to use smart inserters instead of basic ones.

[Zeblote]

It's still a bug, an inserter should never grab a resource it can't actually insert.

[JasonC]

Yeah I'm still not sure how this can be viewed as not a bug.

An inserter won't attempt to pick up iron ore if there is some copper ore in the resource slot of a furnace already. It won't attempt to pick up copper if there is already iron.

If the inserter already doesn't pick up X when there's already Y in the resource slot, how is it not a bug if it e.g. picks up copper or iron while there's already stone in the resource slot?

Even assembly factories and stuff, inserters will never pick up something that isn't needed. The inserters are smart enough in all cases to figure out what to pick up *except* for furnaces with stone in them. How is that not a bug? Why would stone be an exception to the inserter's normal behavior of not picking up incompatible / unwanted items?

If there's 1 stone already in the resource slot and the inserter picks up an incompatible item (like copper or iron), that doesn't seem right given that in all other cases it does the right thing...

[Arch666Angel]

Not a bug if you want to handle mixed belts, you just need smart inserters, yes regular inserters are dumb and they are supposed to be.

[Zeblote]

Not a bug if you want to handle mixed belts, you just need smart inserters, yes regular inserters are dumb and they are supposed to be.

It's still a bug, an inserter should never grab a resource it can't actually insert.

[warped04]

I don't think it's a bug, but...I had a decent sized copper vein, with 2 stone modules mixed in with the copper. It was early game, so I didn't have smart inserters. It was a real slow down, but I managed to filter through the stone real quick by mining everything into the chest and two smart inserters onto the proper belts.

[Arch666Angel]

Not a bug if you want to handle mixed belts, you just need smart inserters, yes regular inserters are dumb and they are supposed to be.

It's still a bug, an inserter should never grab a resource it can't actually insert.

So where is the problem? It could theoretically insert the item, that there is already something in the furnace is a whole other problem, but like I said there is an entity - the smart inserter - that is set up for these use cases, so why should regular inserters be smarter than they are at the moment. Or let me put it in matters of programming: regular inserter has one check: can i put the item into the furnace, the smart inserter has several condition to check. That is limitation by design, if you think its silly just mod all your inserters to be smart and be done with it.

[JasonC]

So where is the problem? It could theoretically insert the item...

No, it can't. There is already stone in the furnace, so it couldn't insert anything else but stone. If you are talking about that furnaces accept stone in general, that's still not an explanation, as, for example, a regular inserter will not attempt to pick up iron if there is already copper in the furnace, even though iron can theoretically be inserted into a furnace.

... Or let me put it in matters of programming: regular inserter has one check: can i put the item into the furnace, ...

Exactly. And that check isn't working properly (the regular inserter tries to put copper/iron in the furnace when there is already one stone in it, even though it can't put those items in the furnace).

So still not sure how that isn't a bug.

Smart inserters are irrelevant. The issue at hand is that regular inserters are already smart enough to know not to pick up items they can't insert, except in the one specific case of them trying to insert incorrect items in a furnace when the furnace has stone in it. Outside of that case, regular inserter do just fine about not picking up items they can't insert.

[Zeblote]

Not a bug if you want to handle mixed belts, you just need smart inserters, yes regular inserters are dumb and they are supposed to be.

It's still a bug, an inserter should never grab a resource it can't actually insert.

So where is the problem? It could theoretically insert the item

No, it can't, the slot is blocked with a stone, and will not free on it's own.

Using a smart inserter does not fix the problem either, as we have to add all 3 resources to the filter in order to make a multi-resource smelter. So I have no idea what your point here is.

[Arch666Angel]

So what you both are describing is not a problem with the inserter, if it was a bug at all you could argue that there is an issue with the smelters auto setting recipes depending on what has been put into them. I'll try to explain it in steps:

case 1: the furnace is empty -> no recipe is set
-inserter could input anything that is set as an ingredient in a furnace recipe: (iron ore, copper ore, stone, iron plate)

case 2: the furnace has a full set of ingredients for one of the recipes -> a recipe is set for the furnace
-inserter can only input the same resource for which the recipe is set

The problem is, that you need two pieces of stone for the recipe to be set, but before that there is not recipe and therefore no limitation of what the inserter can put into the furnace. So you see the problem is not with the inserter itself, but with the mechanic of auto setting recipes, it works well with single ingredient/item recipes, but it will run into issues with recipes which require more that one item/ingredient.
Smart inserters can help in the way that you can regulate which resources are input in which quantities if you want to make multi resource setups.

[Zeblote]

It doesnt matter where the bug is exactly. Once a stone is in the furnace it has a receipe (stone bricks) and the inserter should not grab iron or copper ores.

[JasonC]

I ran a more controlled experiment and can describe the issue more concretely now.

I made four groups of four unfueled furnaces. In each group I loaded exactly 1 of stone, iron ore, copper ore, and an iron plate into the input slot of each furnace:



The significant thing to notice is that for outputs that take more than one resource for input (bricks and steel), the output graphic doesn't appear over the furnace. It's also important to note that for the furnaces that do show their output icons, it's not because they started working - none of these furnaces have any fuel and haven't done any work yet:



The next thing I did was let an inserter attempt to insert each of stone, iron ore, copper ore, and iron plates into each (leaving the furnaces unfueled so they didn't process anything). Here are the results. In the image, green arrows mean the inserter correctly loaded more resources. Green X's mean the inserter correctly did not attempt to pick up an incompatible resource. Red means the inserter picked up an incompatible resource, attempted to load it, and got stuck:



The only way to clear the stuck inserter is to manually remove the current input resource from the furnace, or rebuild the inserter, or rebuild the furnace. Also just to confirm, every single type of inserter shows the same problem (each of these furnaces has 1 stone in its input slot, with copper ore provided to the inserters) (also yeah I know the long handed inserter doesn't have a source, it did then I edited the belt to make it more photogenic after they got stuck and forgot about that ):



So the issue is a combination of a few things, all working together to create a weird situation:

1. Furnaces don't know what their output will be until all resources have been inserted to create one output (so a furnace needs 2 stone, or 1 iron ore, or 1 copper ore, or 5 iron plates before it knows its output).
2. The furnace input remains "open" until the output type is known, rather than looking at what's currently in the input slot.
3. All types of inserters will blindly insert any one of the theoretically acceptable resources (stone, iron ore, copper ore, iron plate) into a furnace when it's input is "open".

From this, I now believe the issue is with the furnace rather than the inserter, as the inserter logic seems consistent, it's just that the furnace leaves its input "open" when less than the required number of resources are in the input slot, regardless of whether or not there's something there already. Any one of the following would alleviate this (corresponds to list above):

1. Fix furnaces to know what their output will be as soon as the first resource is in the input slot, rather than the last. This way as soon as one stone or one iron plate was in there, the furnace would know that it's producing bricks or steel immediately, the input would no longer be "open" and would be constrained to the appropriate resource, and the inserter would do the right thing. This should be combined with the current behavior, not replace it completely: you don't want to only rely on the input slot, because you don't want inserters getting stuck trying to put e.g. copper ore into a furnace with an empty input slot but a backlog of iron plates sitting in its output.
2. Fix furnace inputs so the input remains "open" until a resource is placed in it, rather than having the input state rely on whether the output is known or not. This would have the same effect on inserters as above. The problem here though is I'm pretty sure it would make it more difficult for furnaces in multi-resource smelters to switch from one resource to another. Not sure though, would have to think about it.
3. As mentioned above, the inserters actually seem to be behaving just fine, so there isn't really any way to alleviate the problem here by changing inserter behavior without breaking a bunch of other stuff.

#1 is probably the best approach, if an approach is to be made at all.

Maybe I should file a new bug report for clarity now that this has been cleared up? It's the furnace behavior that's causing the issue.

[Rseding91]

After reading over all the discussion here I don't believe there's anything worth changing.

At this point it's part of the logistic challenge to properly handle the ore being sent to your furnaces just like it's part of the challenge to properly handle the items sent to an assembling machine so no one belt backs up and doesn't allow other items to flow in.

There are multiple ways to solve this particular challenge already in the game and spending time to tweak how the furnaces/inserters work together doesn't seem like time well spent right now. Not to say it will never change in the future.

[JasonC]

After reading over all the discussion here I don't believe there's anything worth changing.

Well that's that, I guess. But I'll maintain it's a bug until the day I die / forget about this conversation (whichever comes first... one of these things will happen this week, I'm hoping it's the latter).

I don't agree that it is just like the challenge of handling items sent to an assembling machine, since an inserter will never actually pick up the wrong item in that case. You'll just have belts stuck, then you can remove the items from the belt. You don't have to manually rebuild an assembling machine or inserter, or remove stuck items from the machine's input slot through its gui if a belt backs up. The consequences of the furnace issue require more manual intervention.

Also the constraint that "multi resource smelters work fine, as long as all recipes take only one resource as input" feels... weird, doesn't it? I'd at least consider some way to make the issue more obvious if it's going to remain. I don't have any ideas for that. All I known is a backed up belt is immediately apparent and intuitive. This one certainly catches one by surprise and can be subtle when there's a lot of furnaces (also don't forget this [non-]issue has been reported by at least a couple other people -- maybe it's just that the effect isn't clear).

Besides that, I don't have anything else to add! Thanks for reading through this.

Oh, incidentally, I did discover a weird edge case issue when I was messing around above (on the surface it looks similar to this one but it's not).

[Arch666Angel]

It doesnt matter where the bug is exactly. Once a stone is in the furnace it has a receipe (stone bricks) and the inserter should not grab iron or copper ores.

No thats not the case and thats the issue @JasonC has shown in his post, the stone/brick recipe will only be set if all the ingredients for the bricks (2 x stone) are in the furnace, only then will the recipe be set and only then will the inserter input only stone.

If you want to try it, set the recipes for iron and copper plates to require two of an ore instead of one and look at the mess it makes.

And counterwise a simple solution to your problem is to set the brick recipe to require only one stone.

@JasonC
Nice effort there, this better explains it than my words: One thing what you refer to as output symbols are actually the icons for the recipes, which can be the same as individual items. Congratulation you are now fit for basic modding

[JasonC]

After reading over all the discussion here I don't believe there's anything worth changing.

Oh, btw, is this still "Not A Bug"? Or can I at least get some personal validation and have it upgraded to "Won't Fix"?

Nice effort there ...

The most important thing to note in that post is how awesome my free-hand red question mark came out on a touchpad.