Factorio Forums

When playing on my server, a desync can happen randomly.
When it happens, it tends to persist for some time - attempts to reconnect sometimes succeed, sometimes consistently desync as soon as I attempt to join.
But other times, I can join fine and then play for hours before it happens again.
This started happening a few hours after upgrading to 0.16.7.

Other players don't seem to be having this issue on this server, just me (admittedly, my sample size here is very small - one other player for an hour or two). I have verified my steam files. It's worth noting that I'm playing on loopback - I have a headless server running and I am connecting to it from the same machine.
This save was continued from 0.15 so might involve some upgrade weirdness.
I can't identify anything in particular I'm doing when the desync occurs.

Here's a GDrive folder with a range of desync reports over a few hours:
https://drive.google.com/drive/folders/ ... sp=sharing

Ok man, looking into it. But the save is huge :-/

Yeah, sorry. Long-term megabase. I might try over the weekend deleting most of the contents and seeing if I can still repro.

EDIT3: Ok, disregard all this. Looks like desync still occurs even without the circuit. Maybe less often?



Ok, I've made some progress. As far as I can tell, desyncs only occur while this circuit is active:
It's a rolling average calculator to measure item throughputs. Belts in pulse mode send signals to the input, where it's multiplied to avoid rounding in later steps. This input is replicated over 4 delay ticks so every input signal lasts for 4 ticks.
The signals feed into a feedback circuit which does the following:
out = (saved + input) / (A+1)
saved = out * A

ie. every 4 ticks (because the multiply and divide circuits both need to have their A value filtered out before being fed back), it takes the average of the current input and previous value in a ratio 1:A. This produces a rolling average where A is configurable.

Every desync I've encountered has been while this circuit is:
* fully hooked up (I did not get desyncs when the out value was disconnected from the saved value)
* contains at least one non-zero value besides A.

I'll attempt to reproduce on a blank map with just this circuit in it.

EDIT: One more bit of info, this happens for many values of A. I've tested: 3k, 100.

EDIT2: Very interestingly, this seems to happen even if the circuit is unpowered, but does contain values. Link for the desync report for this specific scenario: https://drive.google.com/file/d/1mZWxVZ ... sp=sharing

Hi,
there is quite good chance that the desync is connected to a bug with electric poles that was present in this version. With the size of the save, I can't realistically confirm it though, so if possible, upgrade to the current version and file a new report if a desync occurs after that.
Thanks

We haven't had the desync since upgrading, so yeah, that makes sense.