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gschup / ggrs

GGRS is a reimagination of GGPO, enabling P2P rollback networking in Rust. Rollback to the future!

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Desync Detection Mode not behaving as expected

PraxTube opened this issue · comments

commented

Describe the bug
I would have expected the with_desync_detection_mode to rollback every second or some specific time interval, however in my case it only rollsback at the very start and then it just stops. I am not sure if this is the intended behaviour, but from what I can understand from the docs it should rollback in intervals?

It's a bit hard to see in the picture below, but the console output indicates no syncing errors even though the two peers are clearly desynced.

No sync issues even though we are cleary desynced

To Reproduce
I followed the example as best as I could, essentially

  • Add with_desync_detection_mode
  • Add print_events_system to Update
  • Trigger desync on purpose to get error messages (which didn't happen)

It's likely that I forgot something.
I also tried to get desyncs in the example game, but that didn't work.

Expected behavior
I expected for the desync to run continuously. I am also not really sure what the difference between start_synctest_session and with_desync_detection_mode is. Shouldn't they both test checksums for equality and report errors?

Desktop
OS: Zorin OS 16.3 x86_64 (Ubuntu 16 based)

Also this isn't really a bug report, but rather a what the hell is happening, please help me report, but that label doesn't exist unfortunately.

commented

Usually, GGRS only sends inputs between clients. If your gamestate evolves deterministically with given inputs, this should keep the clients in sync.

The desync detection mode does not force rollbacks, but it sends checksums of gamestates between clients in addition to the inputs. If the checksums don't match, it will notify you through an event. For this, you need to compute a checksum of your gamestate when saving the state.

If you want to force your setup to go through regular save and load actions, I recommend using the SyncTestSession.

commented

Thanks for the fast reply. I thought my gamestate is deterministic, but that isn't the case. So now I need to figure out what the issue is. What would you recommend how I do this? Should I use desync detecion mode, or SyncTestSession or something else?

commented

I recommend starting by setting up a SyncTestSession. It will rollback a predetermined number of frames every frame, so you can really test if everything is working properly there.

commented

Alright will do that, thank you very much 👍