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Comment by ninetyninenine | Hacker News Reader

One efficiency update you can make is that if background objects don’t move, then you don’t need to recalculate the path. So check if anything moved before recalculating.

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Sure, but in games sometimes improving the average case is less important than the worst case.

So you're saying everything always moves all the time so it's more efficient to just never check and have the algorithm assume something moved always.

For most real time systems, including many games, it doesn't matter if one is more efficient than another because what matters is the predictability that comes from always rendering a complete frame in 1/60th of a second.

In many cases checking if absolutely nothing changed in a system isn't trivial either. You either have very fine grained tracking which involves a great deal of complexity and increased memory cost, or very broad tracking which results in a lot of false positives.

No, if it takes 1 ms to check if things have moved, and 5 ms to do the pathfinding then the worst case is 6ms when something moves. A guarantied 5 makes for a more stable frame rate than a sometimes 1ms, sometimes 6ms calculation. Often times 60 FPS average with high variability feels worse than 30 FPS with low variability.

That's true until the map itself changes, eg other objects moving around in the calculated path

Yeah I said that. If nothing moves. No need to change.

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