Interesting Bug: Double Connection = Double Power Demand!

[zebulon_stonehenge 135]

Ahoy fellow SC4 fans. I just found an interesting bug in SC4. I was playing one of my older cities tonight, a "Big" city, developing some of its wilderness land into commercial and industrial centers. (The idea being, bring in loads of commuters from the residential city to the south.) Suddenly my power bill shot through the roof! (I'm buying power from the town to the north.) The power demand, which had crept slowly up from 30,000 to 40,000 over 50 years, suddenly jumped to 80,000 in just one month! I was suddenly having to pay a §6000/month electric bill in order to keep up with demand! I was perplexed.

But I found the problem. I discovered that I had 2 electric connections to the town to the north. (I apparently had added the extra connection the night before, not realizing that a connection already existed.) I bulldozed one, and my power demand dropped from 80,000 to 40,000! (See attached image.)

Very odd. I'm not sure if this bug will occur every time one buys power from a town with 2 connections, or if it's a sporadic bug, or a one-off fluke. I did determine, though, that having 3 connections to my power purveyor tripled my demand, so apparently BuggyDemand = N * CorrectDemand, where N is number of connections to power purveyor.

And that's bizarre, because while I can see how it would be easy for a supply bug to get in the program (buying 40,000 per connected power pole, instead of 40,000 per power purveyor), that's not what's happening; instead it's the demand that gets multiplied. How the number of power connections to a purveyor could impact demand, I have no idea. I'd love to see the source code on that.

[CorinaMarie 29,571]

That's an interesting discovery. I'll try some time to see if I can recreate what you have.

Btw, where did you get that power graph? Mine doesn't Imported and Exported listed.

[zebulon_stonehenge 135]

12 minutes ago, CorinaMarie said:

where did you get that power graph? Mine doesn't Imported and Exported listed.

I believe that's from GraphModd. I have both DataModd and GraphModd from Tropod installed. Those can be found here:

https://community.simtropolis.com/files/file/21306-dataview-modd-rh/
https://community.simtropolis.com/files/file/21317-graphmodd-v2/

[CorinaMarie 29,571]

It was easy to replicate your findings. I tried it both with and without the GraphMod and the increase upon reloading the city with the second connection in place shot up just like yours. Then bulldozing one connection and back it dropped to normal in both tests.

Next I added a wind mill power plant while both connections were in place and it doesn't blend its output with the purchased power. I bulldozed the second connection, ran more time, and still the wind mill has none of its capacity used.

 

[twalsh102 1,601]

From Prima's Official Strategy Guide for SimCity 4 Deluxe (page 314)"

"TIP
A city consumes its purchased resources before those it produces domestically. ..."  This would explain what you are seeing with the Windmill, regardless of the number of Power Neighbor Connections (if they exist).

The only reason to create a Neighbor Connection for things such as water and power is to initiate a Neighbor Deal.

(page 315)

"ONE DEAL PER RESOURCE PER NEIGHBOR
You can only have one deal (buy or sell) with any one neighbor.  ..."  I think this primarily pertains with trying to create both a buy and sell deal for the same resource.

Perhaps this isn't a bug, but a purposely-pointed reminder of the above.  Or perhaps, since a Neighbor Deal is already in place, the game assumes you want to multiply the size of the Deal by adding additional connections.  Might be interesting to see if the same thing happens with a Neighbor Deal for water

[jeffryfisher 2,176]

Electricity is buggy. I've recently had (single-grid) cities where I was buying electricity from more than one neighbor at the same time, and as I raised the purchase amount from one neighbor, my demand went up and up for as much as I could buy (to a ridiculous level). However, if I increased the other neighbor (or bought all of my electricity from either one neighbor), then supply could break clear of demand like normal.

Apparently time has to run for a month or more to redistribute electrons across the grid when there are two suppliers.

And if you want to play with water, just try selling a large amount through two connections to the same neighbor, especially if you complete a closed loop of pipe between pumps and connections (but don't save the result in a city you care about!)