perf: make Random splittable

Author: Christopher-Chianelli

core/src/main/java/ai/timefold/solver/core/impl/solver/random/DefaultRandomFactory.java

@@ -32,7 +32,7 @@ public DefaultRandomFactory(RandomType randomType, Long randomSeed) {
     public RandomGenerator createRandom() {
         switch (randomType) {
             case JDK:
-                return randomSeed == null ? new Random() : new Random(randomSeed);
+                return randomSeed == null ? new DelegatingSplittableRandomGenerator(new Random().nextLong()) : new DelegatingSplittableRandomGenerator(randomSeed);
             case MERSENNE_TWISTER:
                 return new RandomAdaptor(randomSeed == null ? new MersenneTwister() : new MersenneTwister(randomSeed));
             case WELL512A:

core/src/main/java/ai/timefold/solver/core/impl/solver/random/DelegatingSplittableRandomGenerator.java

@@ -0,0 +1,99 @@
+package ai.timefold.solver.core.impl.solver.random;
+
+import java.util.SplittableRandom;
+import java.util.random.RandomGenerator;
+
+public final class DelegatingSplittableRandomGenerator implements RandomGenerator {
+    RandomGenerator.SplittableGenerator delegate;
+
+    DelegatingSplittableRandomGenerator(long seed) {
+        this.delegate = new SplittableRandom(seed);
+    }
+
+    public RandomGenerator.SplittableGenerator split() {
+        return delegate.split();
+    }
+
+    public void setDelegate(RandomGenerator.SplittableGenerator delegate) {
+        this.delegate = delegate;
+    }
+
+    // *****************************************
+    // RandomGenerator methods
+    // *****************************************
+
+    @Override
+    public long nextLong() {
+        return delegate.nextLong();
+    }
+
+    @Override
+    public int nextInt() {
+        return delegate.nextInt();
+    }
+
+    @Override
+    public int nextInt(int bound) {
+        return delegate.nextInt(bound);
+    }
+
+    @Override
+    public int nextInt(int origin, int bound) {
+        return delegate.nextInt(origin, bound);
+    }
+
+    @Override
+    public long nextLong(long bound) {
+        return delegate.nextLong(bound);
+    }
+
+    @Override
+    public long nextLong(long origin, long bound) {
+        return delegate.nextLong(origin, bound);
+    }
+
+    @Override
+    public double nextDouble() {
+        return delegate.nextDouble();
+    }
+
+    @Override
+    public double nextDouble(double bound) {
+        return delegate.nextDouble(bound);
+    }
+
+    @Override
+    public double nextDouble(double origin, double bound) {
+        return delegate.nextDouble(origin, bound);
+    }
+
+    @Override
+    public float nextFloat() {
+        return delegate.nextFloat();
+    }
+
+    @Override
+    public float nextFloat(float bound) {
+        return delegate.nextFloat(bound);
+    }
+
+    @Override
+    public float nextFloat(float origin, float bound) {
+        return delegate.nextFloat(origin, bound);
+    }
+
+    @Override
+    public double nextGaussian() {
+        return delegate.nextGaussian();
+    }
+
+    @Override
+    public boolean nextBoolean() {
+        return delegate.nextBoolean();
+    }
+
+    @Override
+    public void nextBytes(byte[] bytes) {
+        delegate.nextBytes(bytes);
+    }
+}

core/src/main/java/module-info.java

@@ -202,6 +202,7 @@
     exports ai.timefold.solver.core.impl.neighborhood to ai.timefold.solver.enterprise.core;
     exports ai.timefold.solver.core.impl.partitionedsearch to ai.timefold.solver.enterprise.core;
     exports ai.timefold.solver.core.impl.phase to ai.timefold.solver.enterprise.core;
+    exports ai.timefold.solver.core.impl.solver.random to ai.timefold.solver.enterprise.core;
     exports ai.timefold.solver.core.impl.solver.recaller to ai.timefold.solver.enterprise.core;
     exports ai.timefold.solver.core.impl.solver.event to ai.timefold.solver.enterprise.core;