Paper/patches/server/0862-Optimize-nearest-structure-border-iteration.patch
Spottedleaf 8c5b837e05 Rework async chunk api implementation
Firstly, the old methods all routed to the CompletableFuture method.
However, the CF method could not guarantee that if the caller
was off-main that the future would be "completed" on-main. Since
the callback methods used the CF one, this meant that the callback
methods did not guarantee that the callbacks were to be called on
the main thread.

Now, all methods route to getChunkAtAsync(x, z, gen, urgent, cb)
so that the methods with the callback are guaranteed to invoke
the callback on the main thread. The CF behavior remains unchanged;
it may still appear to complete on main if invoked off-main.

Secondly, remove the scheduleOnMain invocation in the async
chunk completion. This unnecessarily delays the callback
by 1 tick.

Thirdly, add getChunksAtAsync(minX, minZ, maxX, maxZ, ...) which
will load chunks within an area. This method is provided as a helper
as keeping all chunks loaded within an area can be complicated to
implement for plugins (due to the lacking ticket API), and is
already implemented internally anyways.

Fourthly, remove the ticket addition that occured with getChunkAt
and getChunkAtAsync. The ticket addition may delay the unloading
of the chunk unnecessarily. It also fixes a very rare timing bug
where the future/callback would be completed after the chunk
unloads.
2024-11-18 23:00:59 -08:00

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Diff

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Martijn Muijsers <martijnmuijsers@live.nl>
Date: Mon, 21 Aug 2023 21:05:09 +0200
Subject: [PATCH] Optimize nearest structure border iteration
Getting the nearest generated structure contains a nested set of loops that
iterates over all chunks at a specific chessboard distance. It does this by
iterating over the entire square of chunks within that distance, and checking
if the coordinates are at exactly the right distance to be on the border.
This patch optimizes the iteration by only iterating over the border chunks.
This evaluated chunks are the same, and in the same order, as before, to
ensure that the returned found structure (which may for example be a buried
treasure that will be marked on a treasure map) is the same as in vanilla.
diff --git a/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java b/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
index 31c5f54c90d6e35875f762747f8618e58e2eed91..582065b2d4e818c0edec36b2e9847f8ed3266b10 100644
--- a/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
+++ b/src/main/java/net/minecraft/world/level/chunk/ChunkGenerator.java
@@ -265,12 +265,15 @@ public abstract class ChunkGenerator {
int i1 = placement.spacing();
for (int j1 = -radius; j1 <= radius; ++j1) {
- boolean flag1 = j1 == -radius || j1 == radius;
+ // Paper start - Perf: iterate over border chunks instead of entire square chunk area
+ boolean flag1 = j1 == -radius || j1 == radius; final boolean onBorderAlongZAxis = flag1; // Paper - OBFHELPER
- for (int k1 = -radius; k1 <= radius; ++k1) {
- boolean flag2 = k1 == -radius || k1 == radius;
+ for (int k1 = -radius; k1 <= radius; k1 += onBorderAlongZAxis ? 1 : radius * 2) {
+ // boolean flag2 = k1 == -radius || k1 == radius;
- if (flag1 || flag2) {
+ // if (flag1 || flag2) {
+ if (true) {
+ // Paper end - Perf: iterate over border chunks instead of entire square chunk area
int l1 = centerChunkX + i1 * j1;
int i2 = centerChunkZ + i1 * k1;
ChunkPos chunkcoordintpair = placement.getPotentialStructureChunk(seed, l1, i2);