ZeroAllocJobScheduler

A high-performance alloc-free C# job scheduler.
Schedules and executes jobs on a set of worker threads with automatic pooling of internal handles.

Usage

public class HeavyCalculation : IJob
{
  public void Execute()
  {
    Thread.Sleep(50);  // Simulate heavy work
    Console.WriteLine("Done");
  }
}

// Create a new Scheduler, which you should keep the lifetime of your program. This is the only API call that will allocate or generate garbage.
var scheduler = new JobScheduler(new JobScheduler.Config()
{
    // Names the process "MyProgram0", "MyProgram1", etc.
    ThreadPrefixName = "MyProgram",

    // Automatically chooses threads based on your processor count
    ThreadCount = 0,

    // The amount of jobs that can exist in the queue at once without the scheduler spontaneously allocating and generating garbage.
    // Past this number, the scheduler is no longer Zero-Alloc!
    // Higher numbers slightly decrease performance and increase memory consumption, so keep this on the lowest possible end for your application.
    MaxExpectedConcurrentJobs = 64,

    // Enables or disables strict allocation mode: if more jobs are scheduled at once than MaxExpectedConcurrentJobs, it throws an error.
    // Not recommended for production code, but good for debugging allocation issues.
    StrictAllocationMode = false,
});

// You need to pool/create jobs by yourself. This will, of course, allocate, so cache and reuse the jobs.
var firstJob = new HeavyCalculation();  
var firstHandle = scheduler.Schedule(firstJob); // Schedules job locally

scheduler.Flush();                              // Dispatches all scheduled jobs to the worker threads
firstHandle.Complete();                         // Blocks the thread until the job is complete.

// Call Dispose at program exit, which shuts down all worker threads
scheduler.Dispose();                

Dependencies

To set a sequential dependency on a job, simply pass a created JobHandle to JobScheduler.Schedule(job, dependency).

var handle1 = scheduler.Schedule(job1);
var handle2 = scheduler.Schedule(job2, handle1);    // job2 will only begin execution once job1 is complete!
scheduler.Flush();

Multiple dependencies

Use Scheduler.CombineDependencies(JobHandle[] handles) to get a new handle that depends on the handles in parallel. That handle can then be passed into future Schedule call as a dependency itself!

// You must create the array of handles, and handle caching/storage yourself.
JobHandle[] handles = new JobHandle[2];

handles[0] = Scheduler.Schedule(job1);
handles[1] = Scheduler.Schedule(job2);
JobHandle combinedHandle = Scheduler.CombineDependencies(handles);          // Combines all handles into the array into one

var dependantHandle = Scheduler.Schedule(job3, combinedHandle);             // job3 now depends on job1 and job2.
                                                                            // job1 and job2 can Complete() in parallel, but job3 can only run once both are complete.

dependantHandle.Complete();                                                 // Blocks the main thread until all three tasks are complete.

Bulk complete

Rather than using CombineDependencies(), if you just need to block the main thread until a list of handles are complete, you can use this syntax:

JobHandle.CompleteAll(JobHandle[] handles);                     // Waits for all JobHandles to finish, and blocks the main thread until they each complete (in any order)
JobHandle.CompleteAll(List<JobHandle> handles);

Or, if you don't want to maintain a list or array, you can just call handle.Complete() on all your handles, in any order.