ComponentPool ISortable.Sort - Wrong if- / else-if conditions

Hi Doraku,

I noticed a problem in our game where entities with components assigned with SetSameAs<T>() suddenly took the wrong component after running world.Optimize().

After some debugging, I think I found the cause of this. In the ComponentPool class there is a function ISortable.Sort which contains the following code in lines 334 - 353:

if (_links[_sortedIndex].ReferenceCount > 1 || tempLink.ReferenceCount > 1)
 {
     for (int i = 0; i < _mapping.Length; ++i)
     {
         if (_mapping[i] == minEntityId) // <--- Wrong condition.
         {
             _mapping[i] = _sortedIndex;
         }
         else if (_mapping[i] == tempLink.EntityId) // <--- Wrong condition.
         {
             _mapping[i] = minIndex;
         }
     }
 }
 else
 {
     _mapping[minEntityId] = _sortedIndex;
     _mapping[tempLink.EntityId] = minIndex;
 }

The else branch is correct, so sorting components without additional references is handled correctly. However, if there are multiple references, you are iterating over the entire mapping table. There you want to update the outdated references into the component array. The if and else-if clause for this is wrong. I think the corrected code should read:

if (_links[_sortedIndex].ReferenceCount > 1 || tempLink.ReferenceCount > 1)
 {
     for (int i = 0; i < _mapping.Length; ++i)
     {
         if (_mapping[i] == minIndex) // <--- The mapping table stores the index into the component array and not the entity id.
         {
             _mapping[i] = _sortedIndex;
         }
         else if (_mapping[i] == _sortedIndex) // <--- Same issue here.
         {
             _mapping[i] = minIndex;
         }
     }
 }
 else
 {
     _mapping[minEntityId] = _sortedIndex;
     _mapping[tempLink.EntityId] = minIndex;
 }

I hope you can have a look at it. Thanks a lot for your ECS system, we really enjoy working with it. Keep up the good work!

[Doraku]

I should create a new version soon, I just want to do some documentation update before to close a couple more issues (no promise but hopefully tonight or tomorrow). In the meantime you could use the latest CI version from the github registry https://github.com/Doraku/DefaultEcs/packages/26448 if you prefer it instead of directly including the project 😃

[KaiHelli]

Perfect, that would be great. I wrote up a minimal example, so you are able to reproduce the issue.

World world = new World();

Entity entity1 = world.CreateEntity();
Entity entity2 = world.CreateEntity();
Entity entity3 = world.CreateEntity();

entity3.Set("Something else");
entity2.Set("Hi there!");
entity1.SetSameAs<string>(entity2);

Debug.Print(entity1 + ": " + entity1.Get<string>());
Debug.Print(entity2 + ": " + entity2.Get<string>());
Debug.Print(entity3 + ": " + entity3.Get<string>());

Debug.Print("--------");
world.Optimize();

Debug.Print(entity1 + ": " + entity1.Get<string>());
Debug.Print(entity2 + ": " + entity2.Get<string>());
Debug.Print(entity3 + ": " + entity3.Get<string>());

Which produces the output:

Entity 1:1.0: Hi there!
Entity 1:2.0: Hi there!
Entity 1:3.0: Something else
--------
Entity 1:1.0: Something else
Entity 1:2.0: Something else
Entity 1:3.0: Hi there!