The Icemark was indeed a changed place

An interesting thing came from fixing the battle code in Doomdark’s Revenge, it highlighted a bug that is in the original code, that I can’t tell if ever caused an outward problem.

It is all to do with loyalty.

Loyalty in DDR is about race. Which race are you loyal to: Giants, Dwarves, Hearstealer, Moonprince… etc. When a lord recruits another lord, they become their liege and the new vassal becomes loyal to the same loyalty race.

When a AI lord moves in to a location, they check the loyalty of any lords present and if there is a difference in loyalty, they may attempt to recruit.

The problem is – if a lord who has vassals is recruited the loyalty of the vassals does not change, but the loyalty of the lord does. The liege of the vassals does not change either. So these lords have a liege of a lord who is not loyal to the same race as them. And they will potentially attempt to follow them or follow the same instructions. Even though they are technically the enemy.

Should the vassals ever find themselves in the same location as their liege, they are no longer the same loyalty so they will attempt to recruit them. In this instance the, the vassals becomes the liege of their liege, but their own liege does not change. Confused yet?

What we have here, is circular lieges.

Example:

Glormeon the Giant’s liege is Imagrorn the Giant, and Imagrorn’s liege is Varagrim. But let’s say Imagrorn is recruited by Carormand the Barbarian, then Imagorn’s liege is now Carormand, and his loyalty is to the Barbarians. But Glormeon’s liege is still Imagrorn, however his loyalty is still to the Giants.

The first problem here is that these two lords now see themselves as enemies or potential recruits. So they could fight or recruit. But also Glormeon will follow orders of Imagrorn even though they are enemies. Which may be tracking him down or following his enemies, or liege… and should Glormeon enter a location with Imagrorn he may attempt to recruit them. If this is successful then Glormeon’s liege would be Imagrorn and Imagrorn’s liege would be Glormeon.

In the original this situation would occur. Which I think really just messes with the AI. But in the remake, I traverse the liege tree to work out who is the overall lord in charge, and if we have a circular liege then the game crashes!

So the question is – how to fix.

So I remove the liege traversal and allow the original messy AI or do I break the liege link as soon as recruitment happens… ie: When Imagrorn is recruited and his liege changes to Carormand, then Glormeon’s new liege becomes Varagrim. Or should Glormeon remain loyal to Imagrorn and change his race loyalty to the Barbarians?

As a bug fix the first seems the quickest and keeps the gameplay the same. The other two options the potentially becomes gameplay rules.

This also doesn’t take in to account that the human player, ultimately The Moonprince, may be the loyalty race of some of these lords.

I am tracking the bug here on the GitHub repos for anyone interested.

Many battles fought again by tongue

Strange day today. Not just because it would have been Mike’s birthday, but because for some reason I found myself fixing a bug in Doomdark’s Revenge. Back in January I had a bug reported to me by Simon Foston, I managed to get some save games from him and just needed to find some time to look at it. Now, it’s taken a little while for me to find that time, but for some reason I looked at it today. It wasn’t a conscious decision, I was just looking through some emails that needed dealing with and noticed Simon’s bug report.
A quick look through the code and with a tip off from Simon’s report, it became apparent that the ghosts of dead lords were continuing to take part in battles. I checked the original code and it looked as if the bug was there too, however, I then found that the isDead check was happening later in the process. Strangely what it means is that battles at a dead lords location are processed as part of a dead characters turn, and not as part of other characters in the location. In my case, I’d missed the later isDead check and therefore the dead lord actually took part in the battle.

 

So, it seemed strange to be working on a bug in Doomdark’s Revenge that included the dearly departed, today of all days. I’m sure Mike had a wry smile..

To Luxor, everything now grew clear

Clumping together...I’ve spent some more time looking at the AI for Doomdark’s Revenge, trying to work out why it doesn’t quite appear to be playing like the original. One thing I noticed is that I have completely misunderstood the recruiting logic when it comes to Loyalty and Treachery. I made changes in the last version, but I am going to need to revert them.

The approach algorithm

  • compare the the attributes of the lords and looking for matches gain +1 for each match.
  • If the character being approached is not loyal then +1
  • If the character being approached is treacherous then * 2
  • if the recruiting character is the liege of the character being approached then +3
  • If the recruiting character carries a crown of persuasion then +2
  • If the score is greater than 3 then the approach will succeed.

The basic concept that I have misunderstood is: Loyal characters are less likely to be recruited away form their current liege and un-loyal characters are more likely, therefore the algorithm gets a +1 for none loyal characters. And that treacherous characters are more likely to leave and thus the *2

The next thing I have missed is the lords following the objectives of their lieges.

It works like this.

If the lord has a liege and that liege is following their liege or their foe, then we must follow our liege. Otherwise pick a new objective.

There is a 32% chance that we will pick a new objective. Although that should be 25% because we could pick the objective we already have. That leaves a 68%/75% chance that we continue doing what they were already doing.

The problem for me is the first check. If we use Shareth as an example. She has a 12.5% chance that she will choose to follow either her foe or leader. As she has no leader she reverts to Luxor, which is her foe. So she has a 12.5% chance that she will follow Luxor. All the lords that follow her now have a 100% chance of following Shareth, and this ripples all the way down the stack of lords. Which at the start of the game means that 47 Icelords will disregard what they are doing and follow her.

The mistake I had made is that I had made the following lords take the objectives of their liege when their liege was following their liege or foe. What this means is that when the liege is following their foe the lord follows their own foe. So using Shareth again as the example, when she is following her liege ( Luxor by default ) then all her minions will head to her location, but when she is following her foe ( Luxor ), then all her minions are heading to their foe and not to her location. So as an example, Imgaril the Icelord would be heading to Imgorthand the Fey, who, is likely the the other direction of Shareth.

Hopefully this fix should make the game more like the original, but it bothers me that it is a flawed AI. I ran the game for the first ten days, up until the first battle took place, I ran it on the emulator too to compare notes. Here is what Shareth did over those days.

  1. Head Home
  2. Head Home
  3. Head Home
  4. Follow Luxor
  5. Head Home
  6. Follow Luxor
  7. Follow Luxor
  8. Follow Luxor
  9. Search for object
  10. Head home

Now Talormane does this

  1. Head Home
  2. Head Home
  3. Search for object
  4. Search for object
  5. Follow Lorelorn
  6. Follow Lorelorn
  7. Follow Lorelorn
  8. Follow Lorelorn
  9. Follow Lorelorn
  10. Follow Asorthane

The reason for the delayed follow on day 4 is because Talormane is following Lorelorn who is following Shareth, but Lorelorn is lower in the processing order than Talormane, and thus Talormane doesn’t know that Lorelorn is going to follow Shareth in that turn.

The final thing that I changed was that there is a 6.25% chance that the change of objective will be DO NOTHING. This is especially important for being in a battle with someone who is not the lords foe, because it means that without this the lord will always leave the battlefield. The mistake I had made was that I persisted the do nothing as an objective, i.e.. The lords objective becomes do nothing. But it shouldn’t, it should stay the same as the previous objective, and this turn that objective is ignored.

Going back to Shareth. If she chose to DO NOTHING then her objective would no longer be follow liege or foe, which means that her followers would be able to perform whichever objective they chose. However, if her previous objective had have been follow liege or foe, then her followers should still be heading towards her when she chooses to do nothing. This would have the affect of allowing them to catch up on her.