Farmland can end up scanning up to 162 blocks looking for water in the worst case. This is obviously not great for huge farms where there are thousands of blocks of the stuff.
In most farms, the water won't be moved, and nor will the farmland. This means that we can avoid this costly search on random updates.
This PR implements a cache using blockstate data (only possible in PM5) which stores an index mapping to a coordinate offset where water was previously found by this farmland block. This allows the farmland to avoid water searching entirely in most cases.
This is a colossal improvement as compared to scanning the whole 9x2x9 area every time, which, on average, scans about 40 blocks to find water if the water is at the same Y coordinate. In real terms this translates into about a 8x performance improvement for farmland (see timings below).
xxhash is generally well known for its hash key properties, so this is a suitable use case.
We XOR the state data with a partial hash of xxh3(typeID), which provides sufficient hash distribution regardless of the size of state data.
The previous method started to break down as the number of bits exceeded the number of significant bits of type ID (about 10 currently).
As well as being better for hash distribution regardless of state data size, this also reduces the load factor of RuntimeBlockRegistry to 1.08 (previously around 1.24), which is a nice bonus.
fixes#5858
technically speaking, the sideways states for non-fully-grown stems shouldn't exist, but they do in Bedrock, and changing this code to split non-fully-grown stems from fully grown ones would likely require BC breaks.
This was the minimum necessary to achieve the desired functionality.
due to technical limitations, this requires separating them back into two different block types. However, this isn't too egregious since it's just one flag, and actually simplifies some code.
closes#5478
the following things are currently not implemented:
- particle/sound effects when an entity extinguishes itself
- particle/sound effects when mixing different stuff in a cauldron
- powder snow cauldron
both of these things are contingent on #5169, but for the time being, the PR is functionally complete and I want to move on to something else without being stalled by the particle+sound problem (which I haven't yet decided how to solve).
