Fr0zka
f3faa3b5c2
Jahni measured what I had only flagged: generation is slower on the op-stack path. Two compounding causes. The memo was keyed on InstanceId, which changes on every stack rebuild — every chunk. GSurfColCache, the cache this path replaced, is keyed on (XY box, StrateKey, Seed, LayoutVersion) with no ChunkZ, deliberately shared down the whole vertical strate stack. So a 4-chunk strate recomputed every column four times, including the cliff's four extra structural samples per column. And the table held 256 entries where a chunk is CHUNK_SIZE^2 = 1024 columns, so it thrashed against itself within a single tile before any cross-chunk question arose. PrepareChunk now derives a shared ColumnKey from (StrateBottomWorldZ, LayoutVersion, Seed) — the same identity GSurfColCache uses — and the table is 4096 entries (~150 KB/worker, in line with GSurfColCache's 6 x 59 KB). The memo is thread_local so it already survived rebuilds; only the key was discarding the contents. Sharing across chunk Z is sound because heights are XY-pure by type and the biome field is documented Z-independent — the same justification GSurfColCache rests on. ColumnKey starts at InstanceId rather than 0: slots initialise to Key = 0, so a zero key would falsely hit the pristine slot at (0,0). Without PrepareChunk you get per-instance caching, which is less sharing but still correct. This may not close the gap entirely and I am not claiming it does. Virtual dispatch and the hashed lookup vs a direct-indexed box both remain; they are smaller than a 4x column recompute, but "smaller" is a guess until measured. UNVERIFIED: not compiled. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>