wiJobSystem.h

#pragma once

#include <functional>
#include <atomic>

namespace wi::jobsystem
{
	void Initialize(uint32_t maxThreadCount = ~0u);
	void ShutDown();

	struct JobArgs
	{
		uint32_t jobIndex;		// job index relative to dispatch (like SV_DispatchThreadID in HLSL)
		uint32_t groupID;		// group index relative to dispatch (like SV_GroupID in HLSL)
		uint32_t groupIndex;	// job index relative to group (like SV_GroupIndex in HLSL)
		bool isFirstJobInGroup;	// is the current job the first one in the group?
		bool isLastJobInGroup;	// is the current job the last one in the group?
		void* sharedmemory;		// stack memory shared within the current group (jobs within a group execute serially)
	};

	uint32_t GetThreadCount();

	// Defines a state of execution, can be waited on
	struct context
	{
		std::atomic<uint32_t> counter{ 0 };
	};

	// Add a task to execute asynchronously. Any idle thread will execute this.
	void Execute(context& ctx, const std::function<void(JobArgs)>& task);

	// Divide a task onto multiple jobs and execute in parallel.
	//	jobCount	: how many jobs to generate for this task.
	//	groupSize	: how many jobs to execute per thread. Jobs inside a group execute serially. It might be worth to increase for small jobs
	//	task		: receives a JobArgs as parameter
	void Dispatch(context& ctx, uint32_t jobCount, uint32_t groupSize, const std::function<void(JobArgs)>& task, size_t sharedmemory_size = 0);

	// Returns the amount of job groups that will be created for a set number of jobs and group size
	uint32_t DispatchGroupCount(uint32_t jobCount, uint32_t groupSize);

	// Check if any threads are working currently or not
	bool IsBusy(const context& ctx);

	// Wait until all threads become idle
	//	Current thread will become a worker thread, executing jobs
	void Wait(const context& ctx);
}