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IDProjectCategoryView StatusDate SubmittedLast Update
0001952Zandronum[All Projects] Bugpublic2014-10-09 19:432026-05-22 23:38
ReporterTribeam213 
Assigned ToTorr Samaho 
PriorityhighSeveritycrashReproducibilityalways
StatusassignedResolutionopen 
PlatformMicrosoftOSWindowsOS VersionXP/Vista/7
Product Version1.3 
Target VersionFixed in Version 
Summary0001952: Extreme lag from an old wad
DescriptionSo I've been going through a lot of old mods lately, when I came across this lag problem in supersonicdoom

On Map28 there is a room full of fans, whenever you walk in and the fans activate, the game starts lagging to about... 0 fps...

Tried to figure out why it happens before I posted this report, but couldn't reproduce the problem in my own test map.

This happens in both 1.3 and 2.0
Does not happen in ZDoom or GZDoom
Steps To ReproduceAt the start of the map, turn on noclip, turn 90 degrees to your left, and head straight.

1. zandronum -iwad doom2.wad -file sonic_lag_03.wad -host +skill 3 +sv_cheats 1
2. Connect a client to the server and join the game.
3. Drop down onto the floor to trigger the fans spinning, it will start to lag greatly. This lag does not appear offline as of 3.2.
Attached Files? file icon sonic_lag_03.wad [^] (1,839,873 bytes) 2026-05-22 23:00
? file icon sonic_lag_gzdoom.wad [^] (386,824 bytes) 2026-05-22 23:00

- Relationships

-  Notes
User avatar (0010434)
Dusk (developer)
2014-10-09 19:55

 Without a WAD link this report is pretty much useless.
User avatar (0010435)
Tribeam213 (reporter)
2014-10-09 20:01

 'http://www.gamers.org/pub/idgames/levels/doom2/Ports/megawads/sonic.zip [^]'

Sorry about that, forgot
User avatar (0010437)
Dusk (developer)
2014-10-09 21:04
edited on: 2014-10-09 21:05

 Debugging says the culprit is the horribly inefficient P_FindFirstFreeFloorID() function. I'll optimize this function (and its twins >_>).
User avatar (0010441)
Dusk (developer)
2014-10-09 22:10

 Turns out this function has *seven* different twin functions. This is requiring rather major rework to make into anything sensible. This patch is going to be a teeny bit larger than I first anticipated as I'm going in for a full refactor.
User avatar (0010444)
Dusk (developer)
2014-10-10 01:24
edited on: 2014-10-10 01:34

 Big one incoming here:'https://bitbucket.org/crimsondusk/zandronum-stable/commits/19fbc48cc324fee30aebe5e19e9783ed8ff9e2fc [^]'

- all movers, ceilings, floors, pillars etc alike now use a single pool of 2^16 mover net IDs instead of 2^13 each (overall this increases the limit somewhat)
- new, linear-complex net ID choosing algorithm doesn't cause lock-ups in less-than-ideal scenarios, sonic map28 has a *lot* of instant movers in the fan hall, which caused the FindFreeFloorID function to spaz out
- a large amount of code duplication removed

No zandronum-history entry yet because I don't consider this changeset complete. I'm expecting something to crop up as this obviously enough needs through testing. Thus also needs a build for testing...
User avatar (0010481)
Torr Samaho (administrator)
2014-10-11 13:00

 I think it's not worth to make the code more complicated just so save a few kb of memory. If you really want to avoid using more than a bit to store a bool, I suggest to create a bit vector class that completely encapsulated all the bit shifts and index arithmetics.

Also, why do you invent a completely new network index handling algorithm when we already have one (ACTOR_GetNewNetID) and you could generalize that one instead? From a quick glance, I'd say that the existing mechanism is even more efficient. It won't necessarily slow down with the number of already used IDs while yours will go through all IDs starting from the first to find a free one (see how g_ulFirstFreeNetID is used).
User avatar (0010482)
Dusk (developer)
2014-10-11 13:24

 So you're saying we should tie the mover net IDs in with actor IDs?
User avatar (0011093)
Torr Samaho (administrator)
2014-12-27 16:38

 For the record, we discussed this on IRC a while ago. I don't mean to use the same ID list for actors and movers, just the same ID list management code. I converted the actor ID list code to a class locally, to make this possible without code duplication. Still needs some refinement though before I can push it to the stable repository.
User avatar (0011097)
Torr Samaho (administrator)
2014-12-28 13:39

 I added the ID list code to the stable sandbox. Still almost untested, but should be good enough to try this with the movers.
User avatar (0024757)
unknownna (updater)
2026-05-22 23:02

 I've been investigating this issue recently, and for what it's worth, the unplayable lag that occurred on the offending map (MAP28) has been eliminated when playing offline since 3.2-alpha-250323-2124. Something changed between 3.2-241030-1744 and 3.2-250323-2124 that caused the lag to disappear offline.

It still lags quite a bit online however, but it doesn't freeze up the server anymore compared to before. I decided to strip down the map painstakingly into its own example wad as far as possible without removing the consistent lag.

Quote from Dusk
- new, linear-complex net ID choosing algorithm doesn't cause lock-ups in less-than-ideal scenarios, sonic map28 has a *lot* of instant movers in the fan hall, which caused the FindFreeFloorID function to spaz out
- a large amount of code duplication removed


When I strip down the map too much, it stops lagging online too. The less sectors and things there are, the less lag present.

The client's tick offset seemingly makes it smoother or laggier as well.

On a separate note, when stripping down the offending part of the map too much into its own example wad, there seems to be a difference in the sector sounds between Zandronum and GZDoom 1.8.6. In Zandronum, the sector platform sounds play, but in GZDoom 1.8.6 they don't for some reason.
I decided to not keep this behavior for the main example wad since we just want to be guaranteed to reproduce the lag here, but I nonetheless uploaded the other completely stripped down wad as well so you can see the difference between the ports if you want to.

And here's link to the mod in the OP since the link posted earlier doesn't work anymore:'https://www.doomworld.com/idgames/levels/doom2/Ports/megawads/sonic [^]'

Fixing this would help eliminate even more stuttering on the client, which is always welcome.

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Supporters: unknownna
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- Issue History
Date Modified Username Field Change
2014-10-09 19:43 Tribeam213 New Issue
2014-10-09 19:55 Dusk Note Added: 0010434
2014-10-09 19:55 Dusk Assigned To => Dusk
2014-10-09 19:55 Dusk Status new => feedback
2014-10-09 19:55 Dusk Assigned To Dusk =>
2014-10-09 20:01 Tribeam213 Note Added: 0010435
2014-10-09 20:01 Tribeam213 Status feedback => new
2014-10-09 21:03 Dusk Assigned To => Dusk
2014-10-09 21:03 Dusk Status new => assigned
2014-10-09 21:04 Dusk Note Added: 0010437
2014-10-09 21:05 Dusk Note Edited: 0010437 View Revisions
2014-10-09 22:10 Dusk Note Added: 0010441
2014-10-10 01:24 Dusk Note Added: 0010444
2014-10-10 01:24 Dusk Status assigned => needs review
2014-10-10 01:34 Dusk Note Edited: 0010444 View Revisions
2014-10-10 01:34 Dusk Note Edited: 0010444 View Revisions
2014-10-11 13:00 Torr Samaho Note Added: 0010481
2014-10-11 13:01 Torr Samaho Status needs review => feedback
2014-10-11 13:24 Dusk Note Added: 0010482
2014-12-27 16:38 Torr Samaho Note Added: 0011093
2014-12-27 23:22 Dusk Assigned To Dusk => Torr Samaho
2014-12-27 23:22 Dusk Status feedback => assigned
2014-12-28 13:39 Torr Samaho Note Added: 0011097
2026-05-22 23:00 unknownna File Added: sonic_lag_03.wad
2026-05-22 23:00 unknownna File Added: sonic_lag_gzdoom.wad
2026-05-22 23:02 unknownna Note Added: 0024757
2026-05-22 23:27 unknownna Steps to Reproduce Updated View Revisions
2026-05-22 23:38 unknownna Priority normal => high




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