Potentially bad news coming in the 1.5 patch, bros.
https://forum.paradoxplaza.com/forum/threads/anatomy-of-a-game-simulation-optimization.1484301/
One thing that was a small chunk of the time but showed up proportionally hugely more than it should have was how much time we spent applying and removing the modifiers for when characters gained and lost weight and were considered obese or malnourished. This was a primary example of the slowness of the script system compared to code.
Every couple of years we’d update the weight of a character and trigger an on action that their weight changed, from there we’d trigger events to add or remove the obese and malnourished modifiers based on two constant values we’d compare against. A very simple operation, but because of how many characters we have and all of them going into the script system it was actually showing up as a large part of a character’s yearly update.
My solution was to simply move this to be done in code, the events and on action is now removed and instead there are two defines for the thresholds of gaining and losing the modifiers. As an upside to this by doing it in code we would now always correctly update and apply the modifiers automatically when the change_current_weight is used so it feels more responsive to special events.