"""
Execute a process in parallel where individual runs
may spawn more runs.
"""

def parallel(fn, start, processes=6):
    with multiprocessing.Manager() as manager:
        results = manager.dict()
        unchecked = manager.dict({key: None for key in start })

        with multiprocessing.Pool(processes) as pool:
            pool.map(execute_process, [(results, unchecked, fn) for _ in range(processes)])

        return dict(results)

def execute_process(args):
    results, unchecked, fn = args

    while len(unchecked) != 0:
        key, _ = unchecked.popitem()

        try:
            results[key], unchecked_ = fn(key, results=results, unchecked=unchecked)

            for k in unchecked_:
                if k not in results:
                    unchecked[k] = None
        except Exception as e:
            continue