Parallel planning primitives

- Engines/InstanceManagers now provide Plans for frames/ticks
- TODO: batching is broken
- TODO: plan caching
- Add Plan interface which can be used to compose complex systems
  of parallel execution
- Add Synchronizer to facilitate barriering
- Remove WorkGroup
- Summary of different primitives below, names need work :ioa:
  - BarrierPlan: executes one plan then another
  - NestedPlan: executes many plans at once
  - OnMainThreadPlan: waits for a syncPoint to execute
  - RunOnAllPlan: dispatches work over a Supplier<List>
  - SimplePlan: executes many Runnables at once
  - UnitPlan: does nothing

src/main/java/com/jozufozu/flywheel/api/backend/Engine.java

@@ -5,6 +5,7 @@ import java.util.List;
 import com.jozufozu.flywheel.api.event.RenderContext;
 import com.jozufozu.flywheel.api.event.RenderStage;
 import com.jozufozu.flywheel.api.instancer.InstancerProvider;
+import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.api.task.TaskExecutor;
 
 import net.minecraft.client.Camera;
@@ -28,4 +29,6 @@ public interface Engine extends InstancerProvider {
 	void addDebugInfo(List<String> info);
 
 	void delete();
+
+	Plan planThisFrame(RenderContext context);
 }

src/main/java/com/jozufozu/flywheel/api/task/Plan.java

@@ -0,0 +1,42 @@
+package com.jozufozu.flywheel.api.task;
+
+import com.jozufozu.flywheel.lib.task.BarrierPlan;
+
+public interface Plan {
+	/**
+	 * Submit this plan for execution.
+	 * <p>
+	 * You <em>must</em> call {@code onCompletion.run()} when the plan has completed execution.
+	 *
+	 * @param taskExecutor The executor to use for submitting tasks.
+	 * @param onCompletion A callback to run when the plan has completed execution, useful for chaining plans.
+	 */
+	void execute(TaskExecutor taskExecutor, Runnable onCompletion);
+
+	default void execute(TaskExecutor taskExecutor) {
+		execute(taskExecutor, () -> {
+		});
+	}
+
+	/**
+	 * Create a new plan that executes this plan, then the given plan.
+	 *
+	 * @param plan The plan to execute after this plan.
+	 * @return The new, composed plan.
+	 */
+	default Plan then(Plan plan) {
+		// TODO: AbstractPlan?
+		return new BarrierPlan(this, plan);
+	}
+
+	/**
+	 * If possible, create a new plan that accomplishes everything
+	 * this plan does but with a simpler execution schedule.
+	 *
+	 * @return A simplified plan, or this.
+	 */
+	default Plan maybeSimplify() {
+		// TODO: plan caching/simplification
+		return this;
+	}
+}

src/main/java/com/jozufozu/flywheel/api/task/TaskExecutor.java

@@ -9,4 +9,6 @@ public interface TaskExecutor extends Executor {
 	void syncPoint();
 
 	int getThreadCount();
+
+	void scheduleForMainThread(Runnable runnable);
 }

src/main/java/com/jozufozu/flywheel/backend/engine/batching/BatchingEngine.java

@@ -9,7 +9,9 @@ import com.jozufozu.flywheel.api.instancer.Instancer;
 import com.jozufozu.flywheel.api.model.Model;
 import com.jozufozu.flywheel.api.struct.InstancePart;
 import com.jozufozu.flywheel.api.struct.StructType;
+import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.api.task.TaskExecutor;
+import com.jozufozu.flywheel.lib.task.PlanUtil;
 import com.jozufozu.flywheel.util.FlwUtil;
 import com.mojang.blaze3d.vertex.PoseStack;
 
@@ -32,17 +34,34 @@ public class BatchingEngine implements Engine {
 	public void beginFrame(TaskExecutor executor, RenderContext context) {
 		transformManager.flush();
 
-		Vec3 cameraPos = context.camera().getPosition();
+		Vec3 cameraPos = context.camera()
+				.getPosition();
 		var stack = FlwUtil.copyPoseStack(context.stack());
 		stack.translate(-cameraPos.x, -cameraPos.y, -cameraPos.z);
 
-		// TODO: async task executor barriers
 		executor.syncPoint();
 		submitTasks(executor, stack.last(), context.level());
 	}
 
+	@Override
+	public Plan planThisFrame(RenderContext context) {
+		return PlanUtil.of(transformManager::flush)
+				.then(planTransformers(context));
+	}
+
+	private Plan planTransformers(RenderContext context) {
+		Vec3 cameraPos = context.camera()
+				.getPosition();
+		var stack = FlwUtil.copyPoseStack(context.stack());
+		stack.translate(-cameraPos.x, -cameraPos.y, -cameraPos.z);
+
+		// TODO: planify batching engine
+		return PlanUtil.of();
+	}
+
 	private void submitTasks(TaskExecutor executor, PoseStack.Pose matrices, ClientLevel level) {
-		for (var transformSetEntry : transformManager.getTransformSetsView().entrySet()) {
+		for (var transformSetEntry : transformManager.getTransformSetsView()
+				.entrySet()) {
 			var stage = transformSetEntry.getKey();
 			var transformSet = transformSetEntry.getValue();
 

src/main/java/com/jozufozu/flywheel/backend/engine/indirect/IndirectEngine.java

@@ -11,9 +11,11 @@ import com.jozufozu.flywheel.api.instancer.Instancer;
 import com.jozufozu.flywheel.api.model.Model;
 import com.jozufozu.flywheel.api.struct.InstancePart;
 import com.jozufozu.flywheel.api.struct.StructType;
+import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.api.task.TaskExecutor;
 import com.jozufozu.flywheel.gl.GlStateTracker;
 import com.jozufozu.flywheel.gl.GlTextureUnit;
+import com.jozufozu.flywheel.lib.task.PlanUtil;
 import com.mojang.blaze3d.systems.RenderSystem;
 
 import net.minecraft.client.Camera;
@@ -40,7 +42,16 @@ public class IndirectEngine implements Engine {
 
 	@Override
 	public void beginFrame(TaskExecutor executor, RenderContext context) {
-		try (var restoreState = GlStateTracker.getRestoreState()) {
+		flushDrawManager();
+	}
+
+	@Override
+	public Plan planThisFrame(RenderContext context) {
+		return PlanUtil.onMainThread(this::flushDrawManager);
+	}
+
+	private void flushDrawManager() {
+		try (var state = GlStateTracker.getRestoreState()) {
 			drawManager.flush();
 		}
 	}

src/main/java/com/jozufozu/flywheel/backend/engine/instancing/InstancingEngine.java

@@ -12,6 +12,7 @@ import com.jozufozu.flywheel.api.instancer.Instancer;
 import com.jozufozu.flywheel.api.model.Model;
 import com.jozufozu.flywheel.api.struct.InstancePart;
 import com.jozufozu.flywheel.api.struct.StructType;
+import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.api.task.TaskExecutor;
 import com.jozufozu.flywheel.backend.Pipelines;
 import com.jozufozu.flywheel.backend.compile.FlwCompiler;
@@ -19,6 +20,7 @@ import com.jozufozu.flywheel.backend.engine.UniformBuffer;
 import com.jozufozu.flywheel.gl.GlStateTracker;
 import com.jozufozu.flywheel.gl.GlTextureUnit;
 import com.jozufozu.flywheel.lib.material.MaterialIndices;
+import com.jozufozu.flywheel.lib.task.PlanUtil;
 import com.mojang.blaze3d.systems.RenderSystem;
 
 import net.minecraft.client.Camera;
@@ -47,7 +49,16 @@ public class InstancingEngine implements Engine {
 
 	@Override
 	public void beginFrame(TaskExecutor executor, RenderContext context) {
-		try (var state = GlStateTracker.getRestoreState()) {
+		flushDrawManager();
+	}
+
+	@Override
+	public Plan planThisFrame(RenderContext context) {
+		return PlanUtil.onMainThread(this::flushDrawManager);
+	}
+
+	private void flushDrawManager() {
+		try (var restoreState = GlStateTracker.getRestoreState()) {
 			drawManager.flush();
 		}
 	}

src/main/java/com/jozufozu/flywheel/backend/task/ParallelTaskExecutor.java

@@ -3,7 +3,9 @@ package com.jozufozu.flywheel.backend.task;
 import java.util.ArrayList;
 import java.util.Deque;
 import java.util.List;
+import java.util.Queue;
 import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.atomic.AtomicBoolean;
 
 import org.jetbrains.annotations.Nullable;
@@ -34,6 +36,7 @@ public class ParallelTaskExecutor implements TaskExecutor {
 
 	private final List<WorkerThread> threads = new ArrayList<>();
 	private final Deque<Runnable> taskQueue = new ConcurrentLinkedDeque<>();
+	private final Queue<Runnable> mainThreadQueue = new ConcurrentLinkedQueue<>();
 
 	private final Object taskNotifier = new Object();
 	private final Object tasksCompletedNotifier = new Object();
@@ -118,10 +121,19 @@ public class ParallelTaskExecutor implements TaskExecutor {
 		}
 
 		synchronized (taskNotifier) {
-			taskNotifier.notify();
+			taskNotifier.notifyAll();
 		}
 	}
 
+	@Override
+	public void scheduleForMainThread(Runnable runnable) {
+		if (!running.get()) {
+			throw new IllegalStateException("Executor is stopped");
+		}
+
+		mainThreadQueue.add(runnable);
+	}
+
 	/**
 	 * Wait for all running tasks to finish.
 	 */
@@ -130,7 +142,7 @@ public class ParallelTaskExecutor implements TaskExecutor {
 		Runnable task;
 
 		// Finish everyone else's work...
-		while ((task = taskQueue.pollLast()) != null) {
+		while ((task = pollForSyncPoint()) != null) {
 			processTask(task);
 		}
 
@@ -146,6 +158,15 @@ public class ParallelTaskExecutor implements TaskExecutor {
 		}
 	}
 
+	@Nullable
+	private Runnable pollForSyncPoint() {
+		Runnable task = mainThreadQueue.poll();
+		if (task != null) {
+			return task;
+		}
+		return taskQueue.pollLast();
+	}
+
 	public void discardAndAwait() {
 		// Discard everyone else's work...
 		while (taskQueue.pollLast() != null) {

src/main/java/com/jozufozu/flywheel/backend/task/SerialTaskExecutor.java

@@ -13,6 +13,11 @@ public class SerialTaskExecutor implements TaskExecutor {
 		task.run();
 	}
 
+	@Override
+	public void scheduleForMainThread(Runnable runnable) {
+		runnable.run();
+	}
+
 	@Override
 	public void syncPoint() {
 	}

src/main/java/com/jozufozu/flywheel/impl/instancing/InstanceWorld.java

@@ -11,6 +11,7 @@ import com.jozufozu.flywheel.api.event.RenderStage;
 import com.jozufozu.flywheel.api.instance.DynamicInstance;
 import com.jozufozu.flywheel.api.instance.TickableInstance;
 import com.jozufozu.flywheel.api.instance.effect.Effect;
+import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.backend.task.FlwTaskExecutor;
 import com.jozufozu.flywheel.backend.task.ParallelTaskExecutor;
 import com.jozufozu.flywheel.config.FlwCommands;
@@ -19,6 +20,7 @@ import com.jozufozu.flywheel.impl.instancing.manager.BlockEntityInstanceManager;
 import com.jozufozu.flywheel.impl.instancing.manager.EffectInstanceManager;
 import com.jozufozu.flywheel.impl.instancing.manager.EntityInstanceManager;
 import com.jozufozu.flywheel.impl.instancing.manager.InstanceManager;
+import com.jozufozu.flywheel.lib.task.PlanUtil;
 
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.level.LevelAccessor;
@@ -68,9 +70,12 @@ public class InstanceWorld implements AutoCloseable {
 	 * </p>
 	 */
 	public void tick(double cameraX, double cameraY, double cameraZ) {
-		blockEntities.tick(taskExecutor, cameraX, cameraY, cameraZ);
-		entities.tick(taskExecutor, cameraX, cameraY, cameraZ);
-		effects.tick(taskExecutor, cameraX, cameraY, cameraZ);
+		var blockEntityPlan = blockEntities.planThisTick(cameraX, cameraY, cameraZ);
+		var entityPlan = entities.planThisTick(cameraX, cameraY, cameraZ);
+		var effectPlan = effects.planThisTick(cameraX, cameraY, cameraZ);
+
+		PlanUtil.of(blockEntityPlan, entityPlan, effectPlan)
+				.execute(taskExecutor);
 	}
 
 	/**
@@ -82,17 +87,16 @@ public class InstanceWorld implements AutoCloseable {
 	 * </p>
 	 */
 	public void beginFrame(RenderContext context) {
-		boolean originChanged = engine.updateRenderOrigin(context.camera());
-
-		if (originChanged) {
-			blockEntities.recreateAll();
-			entities.recreateAll();
-			effects.recreateAll();
-		}
-
 		taskExecutor.syncPoint();
 
-		if (!originChanged) {
+		getManagerPlan(context).then(engine.planThisFrame(context))
+				.execute(taskExecutor);
+	}
+
+	private Plan getManagerPlan(RenderContext context) {
+		if (engine.updateRenderOrigin(context.camera())) {
+			return PlanUtil.of(blockEntities::recreateAll, entities::recreateAll, effects::recreateAll);
+		} else {
 			var cameraPos = context.camera()
 					.getPosition();
 			double cameraX = cameraPos.x;
@@ -100,12 +104,8 @@ public class InstanceWorld implements AutoCloseable {
 			double cameraZ = cameraPos.z;
 			FrustumIntersection culler = context.culler();
 
-			blockEntities.beginFrame(taskExecutor, cameraX, cameraY, cameraZ, culler);
-			entities.beginFrame(taskExecutor, cameraX, cameraY, cameraZ, culler);
-			effects.beginFrame(taskExecutor, cameraX, cameraY, cameraZ, culler);
+			return PlanUtil.of(blockEntities.planThisFrame(cameraX, cameraY, cameraZ, culler), entities.planThisFrame(cameraX, cameraY, cameraZ, culler), effects.planThisFrame(cameraX, cameraY, cameraZ, culler));
 		}
-
-		engine.beginFrame(taskExecutor, context);
 	}
 
 	/**

src/main/java/com/jozufozu/flywheel/impl/instancing/manager/InstanceManager.java

@@ -1,22 +1,21 @@
 package com.jozufozu.flywheel.impl.instancing.manager;
 
-import java.util.List;
 import java.util.Queue;
 import java.util.concurrent.ConcurrentLinkedQueue;
-import java.util.function.Consumer;
 
 import org.joml.FrustumIntersection;
 
 import com.jozufozu.flywheel.api.instance.DynamicInstance;
 import com.jozufozu.flywheel.api.instance.Instance;
 import com.jozufozu.flywheel.api.instance.TickableInstance;
-import com.jozufozu.flywheel.api.task.TaskExecutor;
+import com.jozufozu.flywheel.api.task.Plan;
 import com.jozufozu.flywheel.config.FlwConfig;
 import com.jozufozu.flywheel.impl.instancing.ratelimit.BandedPrimeLimiter;
 import com.jozufozu.flywheel.impl.instancing.ratelimit.DistanceUpdateLimiter;
 import com.jozufozu.flywheel.impl.instancing.ratelimit.NonLimiter;
 import com.jozufozu.flywheel.impl.instancing.storage.Storage;
 import com.jozufozu.flywheel.impl.instancing.storage.Transaction;
+import com.jozufozu.flywheel.lib.task.PlanUtil;
 
 public abstract class InstanceManager<T> {
 	private final Queue<Transaction<T>> queue = new ConcurrentLinkedQueue<>();
@@ -115,21 +114,10 @@ public abstract class InstanceManager<T> {
 		}
 	}
 
-	/**
-	 * Ticks the InstanceManager.
-	 *
-	 * <p>
-	 *     {@link TickableInstance}s get ticked.
-	 *     <br>
-	 *     Queued updates are processed.
-	 * </p>
-	 */
-	public void tick(TaskExecutor executor, double cameraX, double cameraY, double cameraZ) {
+	public Plan planThisTick(double cameraX, double cameraY, double cameraZ) {
 		tickLimiter.tick();
 		processQueue();
-
-		var instances = getStorage().getTickableInstances();
-		distributeWork(executor, instances, instance -> tickInstance(instance, cameraX, cameraY, cameraZ));
+		return PlanUtil.runOnAll(getStorage()::getTickableInstances, instance -> tickInstance(instance, cameraX, cameraY, cameraZ));
 	}
 
 	protected void tickInstance(TickableInstance instance, double cameraX, double cameraY, double cameraZ) {
@@ -138,12 +126,10 @@ public abstract class InstanceManager<T> {
 		}
 	}
 
-	public void beginFrame(TaskExecutor executor, double cameraX, double cameraY, double cameraZ, FrustumIntersection frustum) {
+	public Plan planThisFrame(double cameraX, double cameraY, double cameraZ, FrustumIntersection frustum) {
 		frameLimiter.tick();
 		processQueue();
-
-		var instances = getStorage().getDynamicInstances();
-		distributeWork(executor, instances, instance -> updateInstance(instance, cameraX, cameraY, cameraZ, frustum));
+		return PlanUtil.runOnAll(getStorage()::getDynamicInstances, instance -> updateInstance(instance, cameraX, cameraY, cameraZ, frustum));
 	}
 
 	protected void updateInstance(DynamicInstance instance, double cameraX, double cameraY, double cameraZ, FrustumIntersection frustum) {
@@ -153,21 +139,4 @@ public abstract class InstanceManager<T> {
 			}
 		}
 	}
-
-	private static <I> void distributeWork(TaskExecutor executor, List<I> instances, Consumer<I> action) {
-		final int size = instances.size();
-		final int threadCount = executor.getThreadCount();
-
-		if (threadCount == 1) {
-			executor.execute(() -> instances.forEach(action));
-		} else {
-			final int stride = Math.max(size / (threadCount * 2), 1);
-			for (int start = 0; start < size; start += stride) {
-				int end = Math.min(start + stride, size);
-
-				var sub = instances.subList(start, end);
-				executor.execute(() -> sub.forEach(action));
-			}
-		}
-	}
 }

src/main/java/com/jozufozu/flywheel/lib/light/LightUpdater.java

@@ -1,13 +1,9 @@
 package com.jozufozu.flywheel.lib.light;
 
-import java.util.Queue;
 import java.util.Set;
-import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.stream.Stream;
 
-import com.jozufozu.flywheel.backend.task.FlwTaskExecutor;
 import com.jozufozu.flywheel.lib.box.ImmutableBox;
-import com.jozufozu.flywheel.lib.task.WorkGroup;
 import com.jozufozu.flywheel.util.FlwUtil;
 import com.jozufozu.flywheel.util.WorldAttached;
 
@@ -57,19 +53,6 @@ public class LightUpdater {
 		}
 	}
 
-	private void tickParallel() {
-		Queue<LightListener> listeners = new ConcurrentLinkedQueue<>();
-
-		WorkGroup.builder()
-				.addTasks(tickingListeners.stream(), listener -> {
-					if (listener.tickLightListener()) {
-						listeners.add(listener);
-					}
-				})
-				.onComplete(() -> listeners.forEach(this::addListener))
-				.execute(FlwTaskExecutor.get());
-	}
-
 	/**
 	 * Add a listener.
 	 *

src/main/java/com/jozufozu/flywheel/lib/task/BarrierPlan.java

@@ -0,0 +1,11 @@
+package com.jozufozu.flywheel.lib.task;
+
+import com.jozufozu.flywheel.api.task.Plan;
+import com.jozufozu.flywheel.api.task.TaskExecutor;
+
+public record BarrierPlan(Plan first, Plan second) implements Plan {
+	@Override
+	public void execute(TaskExecutor taskExecutor, Runnable onCompletion) {
+		first.execute(taskExecutor, () -> second.execute(taskExecutor, onCompletion));
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/NestedPlan.java

@@ -0,0 +1,29 @@
+package com.jozufozu.flywheel.lib.task;
+
+import java.util.List;
+
+import com.jozufozu.flywheel.api.task.Plan;
+import com.jozufozu.flywheel.api.task.TaskExecutor;
+
+public record NestedPlan(List<Plan> parallelPlans) implements Plan {
+	@Override
+	public void execute(TaskExecutor taskExecutor, Runnable onCompletion) {
+		if (parallelPlans.isEmpty()) {
+			onCompletion.run();
+			return;
+		}
+
+		var size = parallelPlans.size();
+
+		if (size == 1) {
+			parallelPlans.get(0)
+					.execute(taskExecutor, onCompletion);
+			return;
+		}
+
+		var wait = new Synchronizer(size, onCompletion);
+		for (Plan plan : parallelPlans) {
+			plan.execute(taskExecutor, wait::decrementAndEventuallyRun);
+		}
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/OnMainThreadPlan.java

@@ -0,0 +1,15 @@
+package com.jozufozu.flywheel.lib.task;
+
+import com.jozufozu.flywheel.api.task.Plan;
+import com.jozufozu.flywheel.api.task.TaskExecutor;
+
+public record OnMainThreadPlan(Runnable task) implements Plan {
+	@Override
+	public void execute(TaskExecutor taskExecutor, Runnable onCompletion) {
+		// TODO: detect if we're already on the render thread and just run the task directly
+		taskExecutor.scheduleForMainThread(() -> {
+			task.run();
+			onCompletion.run();
+		});
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/PlanUtil.java

@@ -0,0 +1,29 @@
+package com.jozufozu.flywheel.lib.task;
+
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+import com.jozufozu.flywheel.api.task.Plan;
+
+public class PlanUtil {
+	public static <T> Plan runOnAll(Supplier<List<T>> iterable, Consumer<T> forEach) {
+		return new RunOnAllPlan<>(iterable, forEach);
+	}
+
+	public static Plan of() {
+		return UnitPlan.INSTANCE;
+	}
+
+	public static Plan of(Plan... plans) {
+		return new NestedPlan(List.of(plans));
+	}
+
+	public static Plan of(Runnable... tasks) {
+		return new SimplePlan(List.of(tasks));
+	}
+
+	public static Plan onMainThread(Runnable task) {
+		return new OnMainThreadPlan(task);
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/RunOnAllPlan.java

@@ -0,0 +1,57 @@
+package com.jozufozu.flywheel.lib.task;
+
+import java.util.List;
+import java.util.function.Consumer;
+import java.util.function.Supplier;
+
+import com.jozufozu.flywheel.api.task.Plan;
+import com.jozufozu.flywheel.api.task.TaskExecutor;
+
+public record RunOnAllPlan<T>(Supplier<List<T>> listSupplier, Consumer<T> action) implements Plan {
+	@Override
+	public void execute(TaskExecutor taskExecutor, Runnable onCompletion) {
+		taskExecutor.execute(() -> {
+			var list = listSupplier.get();
+			final int size = list.size();
+
+			if (size == 0) {
+				onCompletion.run();
+			} else if (size <= getChunkingThreshold(taskExecutor)) {
+				processList(list, onCompletion);
+			} else {
+				dispatchChunks(list, taskExecutor, onCompletion);
+			}
+		});
+	}
+
+	private void dispatchChunks(List<T> suppliedList, TaskExecutor taskExecutor, Runnable onCompletion) {
+		final int size = suppliedList.size();
+		final int threadCount = taskExecutor.getThreadCount();
+
+		final int chunkSize = (size + threadCount - 1) / threadCount; // ceiling division
+		final int chunkCount = (size + chunkSize - 1) / chunkSize; // ceiling division
+
+		var synchronizer = new Synchronizer(chunkCount, onCompletion);
+		int remaining = size;
+
+		while (remaining > 0) {
+			int end = remaining;
+			remaining -= chunkSize;
+			int start = Math.max(remaining, 0);
+
+			var subList = suppliedList.subList(start, end);
+			taskExecutor.execute(() -> processList(subList, synchronizer::decrementAndEventuallyRun));
+		}
+	}
+
+	private void processList(List<T> suppliedList, Runnable onCompletion) {
+		for (T t : suppliedList) {
+			action.accept(t);
+		}
+		onCompletion.run();
+	}
+
+	private static int getChunkingThreshold(TaskExecutor taskExecutor) {
+		return 512;
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/SimplePlan.java

@@ -0,0 +1,24 @@
+package com.jozufozu.flywheel.lib.task;
+
+import java.util.List;
+
+import com.jozufozu.flywheel.api.task.Plan;
+import com.jozufozu.flywheel.api.task.TaskExecutor;
+
+public record SimplePlan(List<Runnable> parallelTasks) implements Plan {
+	@Override
+	public void execute(TaskExecutor taskExecutor, Runnable onCompletion) {
+		if (parallelTasks.isEmpty()) {
+			onCompletion.run();
+			return;
+		}
+
+		var synchronizer = new Synchronizer(parallelTasks.size(), onCompletion);
+		for (Runnable task : parallelTasks) {
+			taskExecutor.execute(() -> {
+				task.run();
+				synchronizer.decrementAndEventuallyRun();
+			});
+		}
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/Synchronizer.java

@@ -0,0 +1,19 @@
+package com.jozufozu.flywheel.lib.task;
+
+import java.util.concurrent.atomic.AtomicInteger;
+
+public class Synchronizer {
+	private final AtomicInteger countDown;
+	private final Runnable onCompletion;
+
+	public Synchronizer(int countDown, Runnable onCompletion) {
+		this.countDown = new AtomicInteger(countDown);
+		this.onCompletion = onCompletion;
+	}
+
+	public void decrementAndEventuallyRun() {
+		if (countDown.decrementAndGet() == 0) {
+			onCompletion.run();
+		}
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/UnitPlan.java

@@ -0,0 +1,16 @@
+package com.jozufozu.flywheel.lib.task;
+
+import com.jozufozu.flywheel.api.task.Plan;
+import com.jozufozu.flywheel.api.task.TaskExecutor;
+
+public class UnitPlan implements Plan {
+	public static final UnitPlan INSTANCE = new UnitPlan();
+
+	private UnitPlan() {
+	}
+
+	@Override
+	public void execute(TaskExecutor taskExecutor, Runnable onCompletion) {
+		onCompletion.run();
+	}
+}

src/main/java/com/jozufozu/flywheel/lib/task/WorkGroup.java

@@ -1,72 +0,0 @@
-package com.jozufozu.flywheel.lib.task;
-
-import java.util.Iterator;
-import java.util.concurrent.Executor;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.function.Consumer;
-import java.util.stream.Stream;
-
-import org.jetbrains.annotations.Nullable;
-
-public final class WorkGroup {
-	public static void run(Iterator<Runnable> tasks, Executor executor) {
-		tasks.forEachRemaining(executor::execute);
-	}
-
-	public static void run(Iterator<Runnable> tasks, @Nullable Runnable finalizer, Executor executor) {
-		if (finalizer == null) {
-			run(tasks, executor);
-			return;
-		}
-
-		AtomicInteger incompleteTaskCounter = new AtomicInteger(0);
-		tasks.forEachRemaining(task -> {
-			incompleteTaskCounter.incrementAndGet();
-			executor.execute(() -> {
-				task.run();
-				if (incompleteTaskCounter.decrementAndGet() == 0) {
-					executor.execute(finalizer);
-				}
-			});
-		});
-	}
-
-	public static Builder builder() {
-		return new Builder();
-	}
-
-	public static class Builder {
-		@Nullable
-		private Runnable finalizer;
-		private Stream<Runnable> tasks;
-
-		public Builder() {
-		}
-
-		public <T> Builder addTasks(Stream<T> iterable, Consumer<T> consumer) {
-			return addTasks(iterable.map(it -> () -> consumer.accept(it)));
-		}
-
-		public Builder addTasks(Stream<Runnable> tasks) {
-			if (this.tasks == null) {
-				this.tasks = tasks;
-			} else {
-				this.tasks = Stream.concat(this.tasks, tasks);
-			}
-			return this;
-		}
-
-		public Builder onComplete(Runnable runnable) {
-			this.finalizer = runnable;
-			return this;
-		}
-
-		public void execute(Executor executor) {
-			if (tasks == null) {
-				return;
-			}
-
-			run(tasks.iterator(), finalizer, executor);
-		}
-	}
-}