def parallel_townsend_lsp_sharedarray(times, mags, startp, endp,<EOL>stepsize=<NUM_LIT>,<EOL>nworkers=<NUM_LIT:16>):
This is a version of the above which uses shared ctypes arrays for the times
and mags arrays so as not to copy them to each worker process.

TODO: we'll need to pass a single argument to the worker so make a 2D array
and wrap the worker function with partial?

FIXME: implement this later.