Walls still work in cities

[DaveMcW]

Tacit_Exit of CFC ran some tests on city walls. It seems that walls still give their defense bonus in cities even though you can't build them anymore!

Test: 5000 Warriors vs. 5000 Warriors

Defense           Attacker Wins
Town/None/None    0.4616 
Town/Wall/None    0.2816
Town/None/GWall   0.4532
Town/Wall/GWall   0.1868
City/None/None    0.2870
City/Wall/None    0.1852
City/None/GWall   0.2822
City/Wall/GWall   0.1360


Combat Calc: Warrior vs. Warrior

Defense   Attacker Wins
10%       0.456
60%       0.291
110%      0.194
160%      0.134

[Konquest02]

Interresting result... I might build the GW once in a while after all!

Is it a bug or a feature?

--Kon--

[Theseus]

I build a lot of walls.

This is good.

[Dis]

hmm

I once tried building walls. But my vet spearman were still defeated by archers.

[alexman]

Woa! Thanks for the heads up!

This is definitely a bug, probably introduced when they added the civil defense for PTW.

[Brizey]

Hmmm. I've wondered about this. I can recall a few cities that just seemed unnaturally tough to take.

[Catt]

Originally posted by alexman
This is definitely a bug, probably introduced when they added the civil defense for PTW.

I agree - definitely a bug. I have no quarrel with the concept, but, unless I am hopelessly mistaken, the game materials (manual and civilopedia) and a Firaxian quite clearly stated that walls meant nothing to a City.

Firaxis should either fix the bug or clarify when Walls are effective.

Catt

[vmxa1]

Get the testers to run the test with 1.29f no PTW and see if it still behaves the same way (I suspect not).

[Ribannah]

We'll have to redo all the Tank v Spearman calculations ....

While it is probably a bug, the walls of the city of Paris protected them well in the Middle Ages.

[Hurricane]

City/None/None    0.2870
City/Wall/None    0.1852
City/None/GWall   0.2822
City/Wall/GWall   0.1360

Now this is strange. Look at the effect of the Great Wall in cities. A city without walls but with the GW gets no bonus, but a city with both walls and GW get a higher bonus than a city with walls only. In other words, the GW works in cities only if they also have city walls.

[theNiceOne]

Originally posted by Hurricane
Now this is strange. Look at the effect of the Great Wall in cities. A city without walls but with the GW gets no bonus, but a city with both walls and GW get a higher bonus than a city with walls only. In other words, the GW works in cities only if they also have city walls.

But this is as expected. The Great Wall has two effects. One is to increase your effectiveness against barbarians, and the other is to increase the effectiveness of walls. If you don't have any walls in a city, then there's nothing to improve either.

[Arrian]

Interesting.

It should be fixed. Either that, or one should be able to build walls at any time, instead of only before the city hits size 7.

-Arrian

[CerberusIV]

What prevents a player from building walls in a size 7 city? The reason I ask is that I once tried to add bombardment defence to the civil defence improvement and found I could not build it in cities above size 6. If bombardment defence is removed from walls does this allow them to be built in size 7 and above cities?

I actually changed the Great Wall to give walls in all cities on the same continent. I am now beginning to question if this was as good an idea as it first looked, as those walls disappear with metallurgy. I thought they would be obsolete by that time but it seems not.

[Hurricane]

Ok, I did a small test scenario. 4 cities (size 9)

Antium: no walls, no GW
Cumae: walls, no GW
Memphis: no walls, GW
Heliopolis: walls, GW

Each city was defended by 2 units. I attacked the first city with 2 swordsmen (all regs), noted the exact combat (for example hit, hit, wound, hit and wound, hit, wound, hit, wound). I then reloaded and did the same for the next city. With random seed on, the combat outcomes should be EXACTLY the same, no matter which city you attack, IF the walls and GW work like inteded. BTW, this is in 4000bc, so the GW is not obsolete.

I did the test 5 times (each with 4 reloads), and each and every reload had identical results. The effect of the GW should definitely appear. I don't know what Tacit_Exit did, but my game sure as hell works like it should.

My test is attached. Play as Greeks.

EDIT. This is on v1.29. Maybe it's a PTW bug?

[Hurricane]

Originally posted by vmxa1
Get the testers to run the test with 1.29f no PTW and see if it still behaves the same way (I suspect not).

[vulture]

I'm not sure that that's enough of a test Hurricane. Firstly, how sure are you that the 5 tests are independent, or is there are a chance that each test also has the same random seed (so you are doing 20 sets of combats all with the same random seed)? Secondly, what is the defensive unit? Not that it makes much difference, but I'm curious.

Thirdly, the presence or absence of walls in a city only makes a difference if the PRNG throws up a random number in the narrow(ish) range where it makes a difference. For swordsmen attacking spearmen in a city without walls (or as the game is supposed to work) the swordsman wins when the PRNG is < 0.4829 (if it returns values in the range 0...1), whereas with walls (if this bug is real) the swordsman wins when the PRNG is < 0.4167. So only PRNG values that fall in the range 0.4167...0.4829 are going to give different results in the two cases - the rest of the time the result of that round of combat is the same regardless. With a small number of rounds of combat - worst case scenario you have 2 combats, with around 8 random numbers - it is quite plausible (55%) that the PRNG never throws up a number in the relevant range, so the combat results should be the same. If you saw the same sequence in each case with 20 swordsmen in each attack against 20 spearmen (with around 80 rounds of combat) then the odds that none of them fall in the significant range are more like 0.3%, which would be a significant result. If you can do it with a greater number of combats I'd be interested to see what turns up (not in a position to do it myself right now).

[Hurricane]

I wrote down the combat results from the different saves, and they were different. So the seed had changed.

The defender was a spearman.

Thirdly, the presence or absence of walls in a city only makes a difference if the PRNG throws up a random number in the narrow(ish) range where it makes a difference. For swordsmen attacking spearmen in a city without walls (or as the game is supposed to work) the swordsman wins when the PRNG is < 0.4829 (if it returns values in the range 0...1), whereas with walls (if this bug is real) the swordsman wins when the PRNG is < 0.4167. So only PRNG values that fall in the range 0.4167...0.4829 are going to give different results in the two cases - the rest of the time the result of that round of combat is the same regardless. With a small number of rounds of combat - worst case scenario you have 2 combats, with around 8 random numbers - it is quite plausible (55%) that the PRNG never throws up a number in the relevant range, so the combat results should be the same. If you saw the same sequence in each case with 20 swordsmen in each attack against 20 spearmen (with around 80 rounds of combat) then the odds that none of them fall in the significant range are more like 0.3%, which would be a significant result. If you can do it with a greater number of combats I'd be interested to see what turns up (not in a position to do it myself right now).

This is a good comment, and I also thought about it. The 5 different games were unique, so I think it was enough. As you probably noted in Tacit_Exit's test, a city with both walls and the GW would give an even higher defence than a city with just walls, so the change should show up in more cases than you mention. But if anybody feels they need more confirmation, please try out the test map I made.

[Hurricane]

It was actually 44 rounds of combat. I'm not statistics expert, but what is the chance that none of 44 rounds fall into the gap 0.4167...0.4829 ?

Here is the actual combat results, BTW. H means that the attacker scored a hit, w that the defender scored a hit.

[MrWhereItsAt]

Assuming that inteval is out of a potential 1, the chance of no favourable results is nearly 5%. Not infinitesimal by any stretch, but still relatively unlikely. I think the key is that all your results were EXACTLY the same. That smells a bit fishy to me.

[Hurricane]

Originally posted by MrWhereItsAt
Assuming that inteval is out of a potential 1, the chance of no favourable results is nearly 5%. Not infinitesimal by any stretch, but still relatively unlikely. I think the key is that all your results were EXACTLY the same. That smells a bit fishy to me.

Yes, 5% for ONE roll. But now we have 44 rounds. So shouldn't it be 0,95^44, which is roughly 1%?

And the point is that the expected result is that the results are exactly the same. That happens if the walls and GW work like they are supposed to. That is that they don't work at all in cities.

[theNiceOne]

You're right Hurricane - it's less than 1% for the 44 rounds.

Assuming that both Hurricane and Tacit_Exit have done their calculations right (and I have no reson to doubt that), it means that this has been changed from civ 1.29 to ptw, and my guess is that it is a bug.

[vulture]

Actually MrWIA is right with the 5% value - the probability that you see no difference even though the odds are different, is the probability that none of the random numbers fall in the specified range 0.4167...0.4829, which is 0.9338^44 = 0.049, or pretty close to 5% (0.95^44 is around 10%, not 1%).

For regular swordsmen attacking regular spearmen in a city with walls, great wall, and bug, the chance of the swordsman winning a round of combat is 0.3659. The odds in the other extreme (no walls) are 0.4839 (I mis-typed earlier). The 'sensitive' range is 0.118, and the odds that none of the 44 rounds of combat have a random number in this range is 0.0040, or 0.4%. So this is pretty strong evidence that the bug isn't present in Hurricane's version, which is 1.29f, not PtW (if I recall correctly).

[Hurricane]

Thanks vulture. Like I said, I suck at statistics. Maybe I'll run the test a few more times when I get home, just to make sure. And yes, it is v1.29f, not PTW.