Tensorflow: Passing a session to a python multipro

Question

I'm using tensorflow to preprocess some large images. I was having a problem where the memory was rapidly collapsing. I turned to use multiprocessing in python so the memory would free up entirely whenever I want.

The thing is, I'm using python's multiprocess queues and for some reason unknown I can't pass my tensorflow session from my parent process to the children. Using some advanced debugging techniques (i.e. printing something every few lines) I noticed that python just goes idle inside the line where I make use of the session, it doesn't throw an error message.

My code looks something like this:

def subprocess(some_image, sess, q):
    with sess.as_default():
        # ... use sess and q ...
        print "All good and well" #This is printed
        some_image.eval() #Nothing happens here in console
        print "Still all good and well" #This is not printed

if __name__ == '__main__':
    # ... some initial operations ...
    some_image = read_some_image()

    sess = tf.Session()

    q = Queue()
    q.put(something)
    p = Process(target=subprocess, args=(some_image, sess, q))
    p.start()
    p.join()

What could be the problem? Many thanks!

Answer 1

All you need is distributed tensorflow.

1. Create the graph and session in the parent process. Place some of the operators(especially, variables) to workers while constructing graph.
2. Create child processes, and run them

Answer 2

I don't think you can share "state" as in the tf.Session() between processes like that. I would think that each process needed it's own session.