LightRNG for better entity performance

sources/src/main/java/io/akarin/api/internal/utils/random/LightRNG.java

@@ -0,0 +1,240 @@
+/*
+Written in 2015 by Sebastiano Vigna (vigna@acm.org)
+
+To the extent possible under law, the author has dedicated all copyright
+and related and neighboring rights to this software to the public domain
+worldwide. This software is distributed without any warranty.
+
+See <http://creativecommons.org/publicdomain/zero/1.0/>. */
+package io.akarin.api.internal.utils.random;
+
+/**
+ * This is a SplittableRandom-style generator, meant to have a tiny state
+ * that permits storing many different generators with low overhead.
+ * It should be rather fast, though no guarantees can be made on all hardware.
+ * <br>
+ * Benchmarking on a Windows laptop with an i7-4700MQ processor running OpenJDK 8
+ * reports generation of 64-bit random long output as 17.8x faster than generating
+ * an equivalent number of random longs with java.util.Random, and generation of
+ * 32-bit random int output as 9.8x faster. Specifically, generating 1 billion longs
+ * took about 1.28 nanoseconds per long (1.277 seconds for the whole group) with
+ * LightRNG, while java.util.Random (which is meant to produce int, to be fair) took
+ * about 22.8 nanoseconds per long (22.797 seconds for the whole group). XorRNG
+ * appears to be occasionally faster on int output than LightRNG, but it isn't clear
+ * why or what causes that (JIT or GC internals, possibly). XorRNG is slightly
+ * slower at generating 64-bit random data, including long and double, but not by
+ * a significant degree (a multiplier between 0.9 and 1.2 times). The only deciding
+ * factor then is state size, where LightRNG is as small as possible for any JVM
+ * object with even a single field: 16 bytes (on a 64-bit JVM; 8-byte objects with
+ * 4 bytes or less of non-static members may be possible on 32-bit JVMs but I can't
+ * find anything confirming that guess).
+ * <br>
+ * So yes, this should be very fast, and with only a single long used per LightRNG,
+ * it is about as memory-efficient as these generators get.
+ * <br>
+ * Written in 2015 by Sebastiano Vigna (vigna@acm.org)
+ * @author Sebastiano Vigna
+ * @author Tommy Ettinger
+ */
+public class LightRNG implements RandomnessSource, StatefulRandomness
+{
+	/** 2 raised to the 53, - 1. */
+    private static final long DOUBLE_MASK = ( 1L << 53 ) - 1;
+    /** 2 raised to the -53. */
+    private static final double NORM_53 = 1. / ( 1L << 53 );
+    /** 2 raised to the 24, -1. */
+    private static final long FLOAT_MASK = ( 1L << 24 ) - 1;
+    /** 2 raised to the -24. */
+    private static final double NORM_24 = 1. / ( 1L << 24 );
+
+	private static final long serialVersionUID = -374415589203474497L;
+
+    public long state; /* The state can be seeded with any value. */
+
+    /** Creates a new generator seeded using Math.random. */
+    public LightRNG() {
+        this((long) Math.floor(Math.random() * Long.MAX_VALUE));
+    }
+
+    public LightRNG( final long seed ) {
+        setSeed(seed);
+    }
+
+    @Override
+    public int next( int bits ) {
+        return (int)( nextLong() & ( 1L << bits ) - 1 );
+    }
+
+    /**
+     * Can return any long, positive or negative, of any size permissible in a 64-bit signed integer.
+     * @return any long, all 64 bits are random
+     */
+    @Override
+    public long nextLong() {
+        long z = ( state += 0x9E3779B97F4A7C15L );
+        z = (z ^ (z >>> 30)) * 0xBF58476D1CE4E5B9L;
+        z = (z ^ (z >>> 27)) * 0x94D049BB133111EBL;
+        return z ^ (z >>> 31);
+    }
+
+    /**
+     * Produces a copy of this RandomnessSource that, if next() and/or nextLong() are called on this object and the
+     * copy, both will generate the same sequence of random numbers from the point copy() was called. This just need to
+     * copy the state so it isn't shared, usually, and produce a new value with the same exact state.
+     *
+     * @return a copy of this RandomnessSource
+     */
+    @Override
+    public RandomnessSource copy() {
+        return new LightRNG(state);
+    }
+
+    /**
+     * Can return any int, positive or negative, of any size permissible in a 32-bit signed integer.
+     * @return any int, all 32 bits are random
+     */
+    public int nextInt() {
+        return (int)nextLong();
+    }
+
+    /**
+     * Exclusive on the upper bound.  The lower bound is 0.
+     * @param bound the upper bound; should be positive
+     * @return a random int less than n and at least equal to 0
+     */
+    public int nextInt( final int bound ) {
+        if ( bound <= 0 ) return 0;
+        int threshold = (0x7fffffff - bound + 1) % bound;
+        for (;;) {
+            int bits = (int)(nextLong() & 0x7fffffff);
+            if (bits >= threshold)
+                return bits % bound;
+        }
+    }
+    /**
+     * Inclusive lower, exclusive upper.
+     * @param lower the lower bound, inclusive, can be positive or negative
+     * @param upper the upper bound, exclusive, should be positive, must be greater than lower
+     * @return a random int at least equal to lower and less than upper
+     */
+    public int nextInt( final int lower, final int upper ) {
+        if ( upper - lower <= 0 ) throw new IllegalArgumentException("Upper bound must be greater than lower bound");
+        return lower + nextInt(upper - lower);
+    }
+
+    /**
+     * Exclusive on the upper bound. The lower bound is 0.
+     * @param bound the upper bound; should be positive
+     * @return a random long less than n
+     */
+    public long nextLong( final long bound ) {
+        if ( bound <= 0 ) return 0;
+        long threshold = (0x7fffffffffffffffL - bound + 1) % bound;
+        for (;;) {
+            long bits = nextLong() & 0x7fffffffffffffffL;
+            if (bits >= threshold)
+                return bits % bound;
+        }
+    }
+
+    /**
+     * Inclusive lower, exclusive upper.
+     * @param lower the lower bound, inclusive, can be positive or negative
+     * @param upper the upper bound, exclusive, should be positive, must be greater than lower
+     * @return a random long at least equal to lower and less than upper
+     */
+    public long nextLong( final long lower, final long upper ) {
+        if ( upper - lower <= 0 )  throw new IllegalArgumentException("Upper bound must be greater than lower bound");
+        return lower + nextLong(upper - lower);
+    }
+    /**
+     * Gets a uniform random double in the range [0.0,1.0)
+     * @return a random double at least equal to 0.0 and less than 1.0
+     */
+    public double nextDouble() {
+        return ( nextLong() & DOUBLE_MASK ) * NORM_53;
+    }
+
+    /**
+     * Gets a uniform random double in the range [0.0,outer) given a positive parameter outer. If outer
+     * is negative, it will be the (exclusive) lower bound and 0.0 will be the (inclusive) upper bound.
+     * @param outer the exclusive outer bound, can be negative
+     * @return a random double between 0.0 (inclusive) and outer (exclusive)
+     */
+    public double nextDouble(final double outer) {
+        return nextDouble() * outer;
+    }
+
+    /**
+     * Gets a uniform random float in the range [0.0,1.0)
+     * @return a random float at least equal to 0.0 and less than 1.0
+     */
+    public float nextFloat() {
+        return (float)( ( nextLong() & FLOAT_MASK ) * NORM_24 );
+    }
+
+    /**
+     * Gets a random value, true or false.
+     * Calls nextLong() once.
+     * @return a random true or false value.
+     */
+    public boolean nextBoolean() {
+        return ( nextLong() & 1 ) != 0L;
+    }
+
+    /**
+     * Given a byte array as a parameter, this will fill the array with random bytes (modifying it
+     * in-place). Calls nextLong() {@code Math.ceil(bytes.length / 8.0)} times.
+     * @param bytes a byte array that will have its contents overwritten with random bytes.
+     */
+    public void nextBytes( final byte[] bytes ) {
+        int i = bytes.length, n = 0;
+        while( i != 0 ) {
+            n = Math.min( i, 8 );
+            for ( long bits = nextLong(); n-- != 0; bits >>= 8 ) bytes[ --i ] = (byte)bits;
+        }
+    }
+
+
+
+    /**
+     * Sets the seed of this generator (which is also the current state).
+     * @param seed the seed to use for this LightRNG, as if it was constructed with this seed.
+     */
+    public void setSeed( final long seed ) {
+        state = seed;
+    }
+    /**
+     * Sets the seed (also the current state) of this generator.
+     * @param seed the seed to use for this LightRNG, as if it was constructed with this seed.
+     */
+    @Override
+    public void setState( final long seed ) {
+        state = seed;
+    }
+    /**
+     * Gets the current state of this generator.
+     * @return the current seed of this LightRNG, changed once per call to nextLong()
+     */
+    @Override
+    public long getState() {
+        return state;
+    }
+
+    /**
+     * Advances or rolls back the LightRNG's state without actually generating numbers. Skip forward
+     * or backward a number of steps specified by advance, where a step is equal to one call to nextInt().
+     * @param advance Number of future generations to skip past. Can be negative to backtrack.
+     * @return the state after skipping.
+     */
+    public long skip(long advance)
+    {
+        return state += 0x9E3779B97F4A7C15L * advance;
+    }
+
+    @Override
+    public String toString() {
+        return "LightRNG (" + state + ")"; // Akarin
+    }
+
+}

sources/src/main/java/io/akarin/api/internal/utils/random/LightRandom.java

@@ -0,0 +1,62 @@
+package io.akarin.api.internal.utils.random;
+
+import java.util.Random;
+
+/**
+ * This is a "fake" LightRandom, backed by the LightRNG.
+ * 
+ * This is useful if you want to quickly replace a Random variable with
+ * LightRNG without breaking every code.
+ */
+public class LightRandom extends Random {
+	public static LightRNG light = new LightRNG(); // LightRNG, static.
+	
+	private static final long serialVersionUID = 1L;
+
+	@Override
+	public int next(int bits) {
+		return light.next(bits);
+	}
+	
+	@Override
+	public void nextBytes(byte[] bytes) {
+		light.nextBytes(bytes);
+	}
+	
+	@Override
+	public int nextInt() {
+		return light.nextInt();
+	}
+	
+	@Override
+	public int nextInt(int n) {
+		return light.nextInt(n);
+	}
+	
+	@Override
+	public long nextLong() {
+		return light.nextLong();
+	}
+	
+	@Override
+	public boolean nextBoolean() {
+		return light.nextBoolean();
+	}
+	
+	@Override
+	public float nextFloat() {
+		return light.nextFloat();
+	}
+	
+	@Override
+	public double nextDouble() {
+		return light.nextDouble();
+	}
+	
+	// Akarin start
+	@Override
+	public void setSeed(long seed) {
+        light.setSeed(seed);
+    }
+	// Akarin end
+}

sources/src/main/java/io/akarin/api/internal/utils/random/RandomnessSource.java

@@ -0,0 +1,40 @@
+package io.akarin.api.internal.utils.random;
+
+import java.io.Serializable;
+
+/**
+ * This interface defines the interactions required of a random number
+ * generator. It is a replacement for Java's built-in Random because for
+ * improved performance.
+ *
+ * @author Eben Howard - http://squidpony.com - howard@squidpony.com
+ */
+public interface RandomnessSource extends Serializable {
+
+    /**
+     * Using this method, any algorithm that might use the built-in Java Random
+     * can interface with this randomness source.
+     *
+     * @param bits the number of bits to be returned
+     * @return the integer containing the appropriate number of bits
+     */
+    int next(int bits);
+
+    /**
+     *
+     * Using this method, any algorithm that needs to efficiently generate more
+     * than 32 bits of random data can interface with this randomness source.
+     *
+     * Get a random long between Long.MIN_VALUE and Long.MAX_VALUE (both inclusive).
+     * @return a random long between Long.MIN_VALUE and Long.MAX_VALUE (both inclusive)
+     */
+    long nextLong();
+
+    /**
+     * Produces a copy of this RandomnessSource that, if next() and/or nextLong() are called on this object and the
+     * copy, both will generate the same sequence of random numbers from the point copy() was called. This just need to
+     * copy the state so it isn't shared, usually, and produce a new value with the same exact state.
+     * @return a copy of this RandomnessSource
+     */
+    RandomnessSource copy();
+}

sources/src/main/java/io/akarin/api/internal/utils/random/StatefulRandomness.java

@@ -0,0 +1,20 @@
+package io.akarin.api.internal.utils.random;
+
+/**
+ * A simple interface for RandomnessSources that have the additional property of a state that can be re-set.
+ * Created by Tommy Ettinger on 9/15/2015.
+ */
+public interface StatefulRandomness extends RandomnessSource {
+    /**
+     * Get the current internal state of the StatefulRandomness as a long.
+     * @return the current internal state of this object.
+     */
+    long getState();
+
+    /**
+     * Set the current internal state of this StatefulRandomness with a long.
+     *
+     * @param state a 64-bit long. You should avoid passing 0, even though some implementations can handle that.
+     */
+    void setState(long state);
+}

sources/src/main/java/io/akarin/server/mixin/optimization/MixinEntity.java

@@ -21,7 +21,7 @@ public abstract class MixinEntity {
     @Overwrite // PAIL: isInLava
     public boolean au() {
         /*
-         * This is originally comes from Migot (https://github.com/Poweruser/Migot/commit/cafbf1707107d2a3aa6232879f305975bb1f0285)
+         * This originally comes from Migot (https://github.com/Poweruser/Migot/commit/cafbf1707107d2a3aa6232879f305975bb1f0285)
          * Thanks @Poweruser
          */
         int currentTick = MinecraftServer.currentTick;