Help with concurrency - traversing a DAG

[tbttfox]

So I've got a project in mind, and at the core of that project is 
a DAG with lots of nodes. This seems to be a great candidate for 
concurrent evaluation. The problem is that a node can only be 
evaluated after all of its parents have.

I'm really new to D and static typing in general (coming from 
Python-it was way too slow for this), and I'm having trouble 
navigating the shared/const/immutables and keeping within the 
concurrency structure in D.


The actual question: Will the following strategy work? I've tried 
coding this a couple times, and it just doesn't seem to be 
working. Is there something wrong with my logic?

I make a shared list of linked nodes and pass that to each thread 
on spawn. Then the indexes of any node without a parent go into a 
queue.  The main thread then passes list indexes to the worker 
threads from that queue. When a worker thread gets an index, it 
makes a local copy of that node, evaluates it, and stores the 
data it computes with the node.

Then every child of that node is checked to see if its parents 
have all been processed.  If so, that child is added to the queue 
and the thread requests another item from the queue. When the 
queue is empty, the job is done.