[2.0.76] Trains randomly pausing at waypoint stations

[reduke]

I can't figure out the logic of this yet, but sometimes, trains with a waypoint in their orders will momentarily pause at that waypoint (and not at/next to a signal)

Other times, with the same train or the same waypoint, there is no pause...

I can load up the same saved game repeatedly, and in one particular holding area, the next 4 trains to arrive will always pause, the 5th one will not pause, and the 6th one will pause.

These trains all have shared orders, the waypoints are all copy-pasted from each other, each lane has the same signalling, etc...

Something strange seems to be going on.

Location of holding area in question: -272.9,2004.3

First 6 trains all arrive within 30 in-game seconds or so.

new362.zip

Thanks!

[mmmPI]

the save isn't available

from the description an hypothesis could be something like : the waypoint has a condition about something like cargo full / empty , and not all the trains are loaded the same

there are other cases where it's difficult to predict if the train will stop for 0 second, loosing all momentum, or if not, that may be one of those more trickier one too ^^

[reduke]

I have tried twice to add the save - each time the preview window shows it properly added but it doesn't show up in the post...

None of the waypoints have any conditions - if they did then they would not be waypoints.

[reduke]

Also, for whomever moved this from Bug Reports to Gameplay Help, I would appreciate if this can be moved back, as this is to my mind clearly unexpected and unpredictable behaviour - classic signs of a bug.


Thank you.

[Loewchen]

So far you have not shown anything.

[reduke]

Hopefully this Google drive link will help demonstrate: https://drive.google.com/file/d/1q5TmlZ ... sp=sharing

Thanks.

edit: log attached

factorio-current.log

(6.63 KiB) Downloaded 38 times

ps: it would be helpful if the forum attachment text could be changed to 30MiB instead of 1GiB to match the bug report guidelines if there is a problem with uploading files between these sizes.

[reduke]

Has anyone got any insight on this buggy train behaviour? I would appreciate it being moved back to bugs so it can get some investigation, if that is what is required.

Thank you!

[boskid]

I did a quick look into this save file and i will move this to Bug reports because this behavior seems incorrect.

Usually with waypoints, there are cases where a train is allowed to stop and it happens when a train is unable to find a path continuation when braking point reaches the waypoint. Looking at this save file, the IronPlatePick stations are all without train limits so the trains should never be blocked by limits value. With relevant debug layers enabled, i noticed that the issue is that train is unable to find a path continuation because pathfinder is told that the train is currently within chain signal section (passed a chain signal and did not leave it yet) which enables a special pathfinder logic for finding a path that must be possible to be immediately reserved by a train up to a first non-chain signal (finding a path that leaves out of an intersection without stopping).

It looks like in this situation a trains pathfinder should be given information for being in-chain-signal-section based not on the current train state but based on the last signal on the train's path since this continuation will be used to extend trains path.

You can workaround this issue by adding a regular rail signal (not chain signal) right after waypoint while keeping the chain signal later before rail merge. By having this signal a trains pathfinder that is constrained by an in-chain-signal section case will see that the regular signal can be immediately reserved and it leads out of the chain section which moves it back to a regular pathfinding rule and this will make it correctly find rest of the path up to IronPlatePick station.

Relevant debug layers:

133309-bug.png (9.24 MiB) Viewed 530 times

[boskid]

Thanks for the report. Issue is now fixed for 2.1.

Workaround mentioned earlier is valid: placing a rail signal after a train stop will make the trains pathfinder able to find a path and as such the train will not attempt to stop at the waypoint station.

[reduke]

Thank you very much for fixing it!

[mmmPI]

I have tried twice to add the save - each time the preview window shows it properly added but it doesn't show up in the post...

None of the waypoints have any conditions - if they did then they would not be waypoints.

Really glad this was fixed, the issue with the savegame was maybe its size being too large for the forum, i know it says 1CiB but it doesn't appear too reliable above 30 MB i think, thanks for pushing thru !

I was curious because there are cases were it is tricky to understand when a train would pass through a waypoint without stopping even if it has a condition, like "cargo empty" unlike "signal count" would be condition that could be verified without the train stopping.To allow for such waypoints "with conditions" . I knew i didn't have a proper rule of thumb there so i wanted to peak at the save if there was one, and well it's not necessary anymore i guess i'll make new rules of thumb in 2.1

[Nidan]

it is tricky to understand when a train would pass through a waypoint without stopping even if it has a condition, like "cargo empty"

It's very simple: A stop is a waypoint if, and only if, its schedule entry has no wait conditions; the train will not stop, except for "no path" situations. If there's at least one wait condition (it doesn't matter which kind), that stop is not a waypoint and the train must stop.

[mmmPI]

It's very simple: A stop is a waypoint if, and only if, its schedule entry has no wait conditions; the train will not stop, except for "no path" situations. If there's at least one wait condition (it doesn't matter which kind), that stop is not a waypoint and the train must stop.

Mmmm about the semantic a waypoint is whatever you want it to be, it can have condition it doesn't matter you can still call it a waypoint for me.

But this aside, it's not that simple you can have trains that behave differently at "waypoint" stations and not only the thing OP mentionned that is a bug :

waypoint.zip

(5.89 MiB) Downloaded 11 times

Setup are the same, in one case the train is stuck , in the other not.