From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Martijn Muijsers Date: Mon, 21 Aug 2023 21:46:10 +0200 Subject: [PATCH] Pre-compute VarLong sizes License: GPL-3.0 (https://www.gnu.org/licenses/gpl-3.0.html) Gale - https://galemc.org This patch is based on the following commit: "Reapply "Optimize varint writing"" By: Andrew Steinborn As part of: Velocity (https://github.com/PaperMC/Velocity) Licensed under: GPL-3.0 (https://www.gnu.org/licenses/gpl-3.0.html) * Velocity description * Inspired by the approach described at the bottom of https://richardstartin.github.io/posts/dont-use-protobuf-for-telemetry Given that we do a lot of varint writing as well, this should provide a small performance boost for larger/complex packets whilst not regressing hard on smaller packets. This includes a test to ensure that the behavior is as expected and fixes the initialization loop so that the correct results will be given. Much thanks to @octylFractal for acting as my duck while trying to figure this out. diff --git a/src/main/java/net/minecraft/network/VarLong.java b/src/main/java/net/minecraft/network/VarLong.java index c4fd722f4203e3f4de7b41de9d6ef47b5cfaed10..11339185fc70b1a34130c92d28c397d4b05569cb 100644 --- a/src/main/java/net/minecraft/network/VarLong.java +++ b/src/main/java/net/minecraft/network/VarLong.java @@ -9,6 +9,18 @@ public class VarLong { private static final int DATA_BITS_PER_BYTE = 7; public static int getByteSize(long l) { + // Gale start - Velocity - pre-compute VarInt and VarLong sizes + return VARLONG_EXACT_BYTE_LENGTHS[Long.numberOfLeadingZeros(l)]; + } + private static final int[] VARLONG_EXACT_BYTE_LENGTHS = new int[65]; + static { + for (int i = 0; i < 64; ++i) { + VARLONG_EXACT_BYTE_LENGTHS[i] = (int) Math.ceil((63d - (i - 1)) / 7d); + } + VARLONG_EXACT_BYTE_LENGTHS[64] = 1; // Special case for the number 0 + } + static int getByteSizeOld(long l) { // public -> package-private + // Gale end - Velocity - pre-compute VarInt and VarLong sizes for (int i = 1; i < 10; i++) { if ((l & -1L << i * 7) == 0L) { return i; diff --git a/src/test/java/net/minecraft/network/VarIntLongTest.java b/src/test/java/net/minecraft/network/VarIntLongTest.java new file mode 100644 index 0000000000000000000000000000000000000000..bbea09ffc2180c3c62e15d7dff51f8c220425bfe --- /dev/null +++ b/src/test/java/net/minecraft/network/VarIntLongTest.java @@ -0,0 +1,159 @@ +// Gale - Velocity - VarInt and VarLong optimizations + +package net.minecraft.network; + +import it.unimi.dsi.fastutil.ints.IntOpenHashSet; +import it.unimi.dsi.fastutil.ints.IntSet; +import it.unimi.dsi.fastutil.longs.LongOpenHashSet; +import it.unimi.dsi.fastutil.longs.LongSet; +import org.junit.jupiter.api.Assertions; +import org.junit.jupiter.api.Test; + +public class VarIntLongTest { + + private static String padStringWithLeadingZeros(String string, int length) { + if (string.length() >= length) { + return string; + } + return "0".repeat(length - string.length()) + string; + } + + private static final IntSet integerCases; + static { + integerCases = new IntOpenHashSet(); + { + integerCases.add(0); + integerCases.add(-1); + } + { + for (int i = 0; i < 32; i++) { + integerCases.add(1 << i); + } + } + { + for (int factor = 1; factor <= 7; factor++) { + int all = 0; + for (int i = 0; i <= 4; i++) { + int shifted = 1 << (i * factor); + all |= shifted; + integerCases.add(shifted); + integerCases.add(shifted - 1); + integerCases.add(~shifted); + integerCases.add(-shifted); + integerCases.add((~shifted) & (0x80000000)); + integerCases.add(all); + integerCases.add(all - 1); + integerCases.add(~all); + integerCases.add(-all); + integerCases.add((~all) & (0x80000000)); + } + } + } + { + var newCases = new IntOpenHashSet(); + for (int shiftSize = 2; shiftSize <= 6; shiftSize++) { + for (int offset = 0; offset < shiftSize; offset++) { + int striped = 0; + for (int i = offset; i < 32; i += shiftSize) { + striped |= 1 << i; + } + final var finalStriped = striped; + integerCases.forEach(existing -> { + newCases.add(existing | finalStriped); + newCases.add(existing | (~finalStriped)); + newCases.add(existing & finalStriped); + newCases.add(existing & (~finalStriped)); + newCases.add(existing - finalStriped); + newCases.add(existing - (~finalStriped)); + }); + } + } + integerCases.addAll(newCases); + } + } + + private static final LongSet longCases; + static { + longCases = new LongOpenHashSet(); + { + longCases.add(0); + longCases.add(-1); + } + { + for (int i = 0; i < 64; i++) { + longCases.add(1L << i); + } + } + { + for (int factor = 1; factor <= 7; factor++) { + long all = 0; + for (int i = 0; i <= 9; i++) { + long shifted = 1L << (i * factor); + all |= shifted; + longCases.add(shifted); + longCases.add(shifted - 1); + longCases.add(~shifted); + longCases.add(-shifted); + longCases.add((~shifted) & (0x8000000000000000L)); + longCases.add(all); + longCases.add(all - 1); + longCases.add(~all); + longCases.add(-all); + longCases.add((~all) & (0x8000000000000000L)); + } + } + } + { + var newCases = new LongOpenHashSet(); + for (int shiftSize = 2; shiftSize <= 6; shiftSize++) { + for (int offset = 0; offset < shiftSize; offset++) { + long striped = 0; + for (int i = offset; i < 64; i += shiftSize) { + striped |= 1L << i; + } + final var finalStriped = striped; + longCases.forEach(existing -> { + newCases.add(existing | finalStriped); + newCases.add(existing | (~finalStriped)); + newCases.add(existing & finalStriped); + newCases.add(existing & (~finalStriped)); + newCases.add(existing - finalStriped); + newCases.add(existing - (~finalStriped)); + }); + } + } + longCases.addAll(newCases); + } + } + + // Gale start - Velocity - pre-compute VarInt and VarLong sizes + @Test + public void testGetVarIntSizeComparedToOld() { + integerCases.forEach(value -> { + // given + int originalSize = VarInt.getByteSizeOld(value); + + // when + int size = VarInt.getByteSize(value); + + // then + Assertions.assertEquals(originalSize, size, "Optimized size (" + size + ") is not equal to original size (" + originalSize + ") for test case value " + value + " (binary: " + padStringWithLeadingZeros(Integer.toBinaryString(value), 32) + ")"); + }); + } + + @Test + public void testGetVarLongSizeComparedToOld() { + longCases.forEach(value -> { + // given + int originalSize = VarLong.getByteSizeOld(value); + + // when + int size = VarLong.getByteSize(value); + + // then + Assertions.assertEquals(originalSize, size, "Optimized size (" + size + ") is not equal to original size (" + originalSize + ") for test case value " + value + " (binary: " + padStringWithLeadingZeros(Long.toBinaryString(value), 64) + ")"); + }); + } + // Gale end - Velocity - pre-compute VarInt and VarLong sizes + +}