importing blaze starts cpu_count() + 3 threads

[richafrank]

Not exactly a bug, but maybe an improvement request -

In debugging some context switching in our app, I was surprised to see a number of extra python Threads running. It turned out they are started by the import of blaze, because blaze/__init__.py imports blaze/utils.py, which instantiates a multiprocessing.ThreadPool at module scope. The pool starts 3 helper threads plus 1 thread per cpu.

I think this pool is only used by h5py. Is its creation something that could be made lazy, such that apps don't need to run the extra threads just to import blaze, especially if they don't compute with h5py?

[richafrank]

Thanks!