301 Days (redux)

Day 17 - A pool for NPCs

by Joe Threeohone

Simple NPC pooling.

Wasteful behavior

We’re no longer leaking huge amounts of data updating the NPCs, and we’re tidying up the corpses, but we’re still wasting both CPU time and memory. Old defunct NPC objects are kept around, while a new NPC will always have to be instantiated. First we’ll convert to using SetActive instead of my homemade solution for deactivating NPCs, and add some stats to track our instances.

Assets/Managers/GUIManager.cslink
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void OnGUI(){
    GUI.Box (new Rect (0,0,100,50), "# of cells\n" + mapManager.num_cells);
    GUI.Box (new Rect (100,0,100,50), "NPC Instances\n" + npcManager.NumNpcScripts);
    GUI.Box (new Rect (200,0,100,50), "Active NPC Insts\n" + npcManager.NumActiveNpcScripts);
    GUI.Box (new Rect (300,0,100,50), "NPCs in DB\n" + npcManager.NumNpcsInDb);

We’ll get rid of this old UI stuff soon, I hope.

Assets/Managers/NpcManager.cslink
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public int NumNpcScripts {
    get { return this.npcScripts.Count; }
}
public int NumActiveNpcScripts {
    get {
        int i = 0;
        foreach (KeyValuePair<int,NpcScript> kvp in this.npcScripts) {
            GameObject npc = kvp.Value.gameObject;
            if (npc.activeSelf) i++;
        }
        return i;
    }
}
int numNpcsInDb;
public int NumNpcsInDb {
    get { return numNpcsInDb; }
}
Assets/Managers/NpcManager.cslink
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void UpdateAllNpcs() {
    List<NPCLite> npcs = DragonsSpine.DAL.DBNPC.GetAllNpcs();
    print("I found " + npcs.Count + " NPCs");
    numNpcsInDb = npcs.Count;
    foreach (NPCLite npc in npcs) {
        if (npc.lastActiveRound > maxGameRound) maxGameRound = npc.lastActiveRound;
    }
    foreach (NPCLite npc in npcs) {
        // skip inactive NPCs, and make sure they know they are inactive
        if (npc.lastActiveRound < maxGameRound - 10) {
            if (npcScripts.ContainsKey(npc.worldNpcID)) {
                npcScripts[npc.worldNpcID].gameObject.SetActive(false);
            }

58 NPCs have been cleaned up, but we still have an instance for every one that ever existed. Tsk, tsk.

Reanimator

So let’s make a simple mechanism to re-use those old NPC objects.

Assets/Managers/NpcManager.cslink
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if (!npcScripts.ContainsKey(npc.worldNpcID)) {
    // Try to find an inactive one to re-use
    NpcScript tempNpc = null;
    int tempNpcId = 0;
    foreach (KeyValuePair<int,NpcScript> kvp in npcScripts) {
        if (!kvp.Value.gameObject.activeSelf) {
            tempNpc = kvp.Value;
            tempNpcId = kvp.Key;
            break;
        }
    }
    if (tempNpc != null) {
        print ("Found inactive NPC " + tempNpcId + " and am reusing it!");
        npcScripts.Remove(tempNpcId);
        tempNpc.Reset();
    } else {
        print ("Could not find an inactive NPC for " + npc.worldNpcID + " so am instantiating it!");
        tempNpc = (NpcScript) Instantiate(npcScript);
    }
    tempNpc.npcId = npc.worldNpcID;
    tempNpc.name = npc.Name;
    SetMaterials(tempNpc);
    tempNpc.toBeSeen = (position.z <= mapManager.zTop + 1);
    tempNpc.gameObject.SetActive(true);
    npcScripts[npc.worldNpcID] = tempNpc;
}
Assets/NpcScript.cslink
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void Start () {
    Reset();
}

public void Reset() {
    oldPosition = newPosition = transform.position;
    oldScale = newScale = transform.localScale;
    timeSinceStable = 0f;
    toBeSeen = true;
    npcId = 0;
    name = "undefined";
    lastActiveRound = 0;
    hitsFull = hits = 1;
    health = 1f;
    presumedDead = false;
}

Not that the extra objects were taking up so much, really, but we’ll want to be pooling things in the near future as we display more of the action.

Day 17 code - client