non MP-safe WML

[Noyga]

The folowing functions are known to possibly cause Out of Sync errors in multiplayer :

*) Random
[variable]
name=var
random=1..X
[variable]
(Usually via the {RANDOM 1..X} macro)

You can get a pseudorandom replacement macro here, but this will not work before turn 2

*) Random_traits=yes

[unit]
type=Peasant
side=1
x=5
y=5
random_traits=yes
[/unit]

In general everything that uses randomness is evaluated with possibly different values on each computer of a multiplayer games. If this affect terrain, stats or the scenario itself it can cause Out of Sync errors.
So avoid thoses things if you make a multiplayer scenario.

*) Custom units

[units] don't travel across the network so unless you get all the player to download the same version :
- units with modified stats will have differents stats for every players if they don't have the same version ... => This can cause OOS because of the stats mismatch.
- new custom units won't be found if the player did not install it => They won't be able to play because the unit is missing.

[Elvish_Pillager]

but this will not work before turn 2

Correction: It will work after a fasion, but

PSEUDORANDOM will give the same sequence each game if you don't use the macro {GENERIC_PSEUDORANDOM_INIT} (it goes straight in your [multiplayer] tag). It will still give identical sequences when you use it before turn 2 starts.

[Boucman]

these should be filled as bug if it's not already done, thx for the list

[Elvish_Pillager]

Also - [+units] don't travel across the network, you can't use custom units in MP. (unless you get all players to download them)

[Noyga]

Thank you, i did not think about [units].
I updated the first post.

[Sapient]

Also, having any options in a multiplayer start or turn event message will cause OOS (since different players may select different options). Thanks to Roze/Flamie for pointing this one out.

[deserter]

*) Random
[variable]
name=var
random=1..X
[variable]
(Usually via the {RANDOM 1..X} macro)

You can get a pseudorandom replacement macro here, but this will not work before turn 2

I think that the 'random' function doesn't cause OoS if it is called in a prestart event. It didn't cause any problems for me in neither hotseat mode nor the actual network game. I'm glad about it!

[Rhuvaen]

Random function did cause OOS errors for me even when used in a prestart event. Hm.

I also cannot change the canrecruit status of a unit during a side turn event - it causes massive oos because the other clients don't think the unit can recruit. Is there any other event which would allow a change of canrecruit?

[deserter]

Random function did cause OOS errors for me even when used in a prestart event. Hm.

After all it did cause it for me too...

I only thought that the OOS would have appeared when the random-function was executed. Instead it appeared, when the unit that was created by using the random-function attacked another unit.

[zookeeper]

I only thought that the OOS would have appeared when the random-function was executed.

That's when the games go out of sync. It's just not detected until you actually do something with the unit (in this case, attacking).

[deserter]

I only thought that the OOS would have appeared when the random-function was executed.

That's when the games go out of sync. It's just not detected until you actually do something with the unit (in this case, attacking).

Right.

BTW, Why is the random-function causing OOS errors?
Does each client generate it's own version of the variable or something? (which should be the same variable for every client, but instead each client has it's own random variable)
Just a guess, I know next to nothing about coding.

If this, however, was the reason, couldn't the server generate the variable for all the clients? Where does the RNG get the numbers to determine hits and misses and why doesn't it cause the OOS error?

[Rhuvaen]

Two more:

[story] tags don't show across the network (only the host will see 'em).

Select events fire only for the particular client and cause OOS if they affect game-relevant data.

[qk]

events in era doesn`t work in MP. I must fix it

[Baufo]

Just for the record, random variables will work in 1.3.

[Rhuvaen]

For the record, have any of these been fixed in the new, stable 1.2?