Can't pickle h5py objects

[rodluger]

h5py objects in general cannot be pickled; see for instance this thread. Since multiprocessing relies on pickling to send instructions to each of the workers, the current implementation, in particular this line, will likely break things on certain platforms. I'm getting a "h5py objects cannot be pickled" error whenever I try to run several of the tests on my MacOSX laptop.

Possible fixes are to pass the name of the file to the workers and have them open it, or to convert the data into a numpy array. There may be other solutions if you google this a bit.