Dwarf Fortress Bug Tracker - Dwarf Fortress
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0010540Dwarf FortressDwarf Mode -- Invasionspublic2018-01-21 12:162018-01-24 07:45
0010540: Closed bridge impact vastly the fps in this siege
In my fortress i had raised my bridge entrance in order to buy time for my military squads to gather near my gates.

Meanwhile the gobs/trolls/beak dogs were moving around.

While waiting for my dwarves to finish their equipment picking, i noticed oddly the fps is going down vastly, something i didn't noticed in past siege of that long lived fortress.

As soon as the bridge was lowered again, the fps went back to normal.
I know it's an old bug report but i have a good case of it that just happened in the latest 44.05 that i think is very related to this invader pathfinding problem.

Load that saved game :
http://dffd.bay12games.com/file.php?id=13450 [^]

press space to resume gameplay and wait for a few seconds so the fps get to its lower value.
Press q and select the lever located here :

You are already in front of the required lever
mg]https://i.imgur.com/hs9pCSd.gif[/img] [^]
So press q and select it

Press a then P to activate that lever. It will lower the bridge i am using as the fortress entrance.

Wait a bit until the bridge is lowered and see how the fps goes back to normal.
looking around i found this very old bug report
http://www.bay12games.com/dwarves/mantisbt/view.php?id=3164 [^]
But i have no idea if the source of the problem is related to this same buildingdestroyer tag, so i prefered opening a new one as the older one is a bit more than 7 years old.
No tags attached.
related to 0003164confirmed Footkerchief Severe lag during sieges due to buildingdestroyer pathfinding 
Issue History
2018-01-21 12:16RobsoieNew Issue
2018-01-21 14:59DetrosRelationship addedrelated to 0003164
2018-01-24 07:45LociNote Added: 0037701
2018-01-24 07:45LociAssigned To => Loci
2018-01-24 07:45LociStatusnew => confirmed
2018-04-25 16:11HuntthetrollIssue Monitored: Huntthetroll

2018-01-24 07:45   
Considering your outer defenses consist of 1 z-level wood log walls (very easy to climb), the invaders should have no trouble bypassing your raised bridge. Instead, they just wait around outside being shot with bolts and presumably repathing frequently (causing the noted FPS drain).