Constantly growing city

[TygerFish]

I'm not sure if this is -Experimental's fault of pak.German-exp's fault, but this save has a constantly growing city:

http://tygerfish.homelinux.net/simutrans/pak.German.constantgrow.sve

Should be pretty obvious which one; just put it on fast-forward... 

[jamespetts]

Might I ask - what is the current private car ownership percentage? A city unconnected to player's transport can still grow if it has a road connexion and enough people have their own car. Or is the problem not that the city is growing other than when connected to player transport, but that it is growing in some perverse sort of way? You write that it is growing constantly - what makes you think that it ought not be growing?

[TygerFish]

Might I ask - what is the current private car ownership percentage? A city unconnected to player's transport can still grow if it has a road connexion and enough people have their own car. Or is the problem not that the city is growing other than when connected to player transport, but that it is growing in some perverse sort of way? You write that it is growing constantly - what makes you think that it ought not be growing?

Definitely perverse.    Like, every calendar day the city is growing as fast as it would in a month with ideal growth conditions, despite not providing any service.

[jamespetts]

Hmm, this is very odd. The problem seems to be that the internally recorded population of the city was 0, which triggered the city building routine that is used for new cities when they are first built, which also resets the internally recorded population number to zero after it has run, expecting some other method to increase it later. I am not quite sure how it got to zero in the first place (it might, very unusually, have been created at zero), but I have applied a fix which checks at the beginning of every month (by which time a city should have more than zero population) whether a city's population is zero, and increases it if it is to prevent this from occurring. On testing, when applied to your saved game, this indeed stopped the runaway growth after the beginning of the next month.

This may equally be a problem with Standard that only occurs very, very infrequently, but it's not the sort of thing that would be easy to reproduce.

[TygerFish]

Hmm, this is very odd. The problem seems to be that the internally recorded population of the city was 0, which triggered the city building routine that is used for new cities when they are first built, which also resets the internally recorded population number to zero after it has run, expecting some other method to increase it later. I am not quite sure how it got to zero in the first place (it might, very unusually, have been created at zero), but I have applied a fix which checks at the beginning of every month (by which time a city should have more than zero population) whether a city's population is zero, and increases it if it is to prevent this from occurring. On testing, when applied to your saved game, this indeed stopped the runaway growth after the beginning of the next month.

This may equally be a problem with Standard that only occurs very, very infrequently, but it's not the sort of thing that would be easy to reproduce.

Yeah, I didn't know what the most likely cause was...

Would it be easier to put the check in the city creation routine so that it only occurs once?

[jamespetts]

Ahh, that wouldn't work, because the city creation routine sets it at zero so that the subsequent growth method, on detecting that it is zero, can grow it.

[mopoona]

May this also be related to max_walking_distance_km_tenth value? When you start a game with this setting !=0 you'll see many yellow areas on the Destinations map

[jamespetts]

This particular issue was not related to the maximum walking distance value, but I am working on (1) improving the GUI for passenger destinations (so that they differentiate in colour between passengers who can get to their destination by walking, passengers who use their private cars, and passengers for whom the journey is too long) and (2) fixing some issues with how passengers check whether they can reach their destinations by private car or walking.

[quarks]

Hi,

well, dont know if this is still relevant. I had the same problem. one or more cities would start building new houses on mass and wont stop. after a few test i found that this problem only occurs when when you start a new game. the wild growing city or cities will be allways the one with the least citizens and the unemployed and homeless count in that city information window will show 0.

have a nice day

[jamespetts]

Quarks,

firstly, welcome to the forum! Secondly, which version of Simutrans are you using when experiencing this problem?

[quarks]

firstly, thanks jamespetts.
secondly: i use 102.3 experimental 9.2 with pak.german-exp.20382. all downloaded just a couple of days ago. more questions -> fire away.

have a nice day

e: it seems that you can reproduce this behaviour. open a game (new or old doesnt matter) change to public player and open the map editor. then just decrease the citizens in a random city until at one stage you must reach the minimum possible inhabitants for this city. instead you can go further but it will increase the citizens and the city will grow like mental.

to stop this city behaviour, you just have to add people (to get over that "minimum citizen limit") and everything will go back to normal again.

looks like there is the end for the minimum missing to stop this behaviour. in pak.german and pak.128 it is not possible to go below a certain number of citizens (well, in pak.german the number of citizens in one city went to -20, but no mental building spree).

e2: looks like if the number of citizens in one town is 132 or below this behaviour will happen (unemployed and homeless = 0) but 133 is fine (unemployed and homeless = 1)

[jamespetts]

Quarks,

thank you for reporting that - I have now found and fixed the problem. The fix will be available in the next release.