Fibers in BHL

Fibers in BHL provide a lightweight concurrency mechanism for managing coroutines and parallel execution. They are the underlying mechanism that powers BHL's parallel execution features.

Basic Concepts

Starting Fibers

start() launches a coroutine as an independent fiber and returns a FiberRef:

coro func foo() { yield() }

FiberRef fb = start(foo)

// anonymous coroutine
start(coro func() { yield() })

// with arguments
coro func bar(int value) { yield() }
start(bar, 42)

Fiber Hierarchy

Parent-Child Relationships

Fibers can create child fibers, forming a hierarchy:

coro func parent() {
    // These become child fibers
    start(child1)
    start(child2)
    yield()
}

coro func child1() {
    yield()
}

coro func child2() {
    yield()
}

Stopping Fibers

Use stop(FiberRef) to stop a running fiber. FiberRef.IsRunning tells you whether the fiber is still active:

coro func manager() {
    FiberRef w1 = start(worker1)
    FiberRef w2 = start(worker2)

    yield wait(1000)
    if(w1.IsRunning) { stop(w1) }
}

Function Pointers and Fibers

Storing Function References

Fibers can work with function pointers for dynamic execution:

coro func example() {
    // Store coroutine reference
    func coro void ptr = worker
    
    // Start using function pointer
    start(ptr)
}

coro func worker() {
    yield()
}

Lambda Functions

Fibers can execute lambda functions with captured variables:

func example() {
    int counter = 0
    
    // Start lambda that captures counter
    start(coro func() {
        counter = counter + 1
        yield()
        trace((string)counter)
    })
}

Advanced Features

Deferred Execution

Fibers support deferred execution using defer:

coro func example() {
    defer {
        // This runs when the fiber stops
        cleanup()
    }
    
    start(worker)
    yield()
}