@jeremy_k said in Console App how to populate a 10.000*10.000 Grid efficiently?: A easy optimization for setting a quadrant or an entire 2d space as a single color is to remove all subtrees of that tree, Absolutely. If that's the sort of thing you want to do. Doesn't seem to relate to toggling the state of 100,000 adjacent bits in 5 million. it stores all squares that shall be changed in a vector. The squares changed can be anywhere in this big map, eventually reaching many millions of squares needed to be changed at onces. If that is what you need to do, again I'm not sure I see any use of these quadtrees. But only you need the exact situation.