Rounding issue on Python 3

[terriyu]

Apparently, there is an issue with rounding in Python 3. This comes up in the implementation of shr_pitch():

# "time locations rounded to nearest ms"
#
# XXX numpy uses round-half-even, while matlab appears to use
# round-away-from-zero.  We can emulate this in python2 by using
# python2 round function instead of numpy's, but in python3 the
# rounding will have to take a detour through the Decimal module,
# which fortunately in python3 has a C accelerator.  Or perhaps
# we can ultimately just use round-half-even, if it turns out
# not to affect the results.  (This matters here because the time
# intervals produced by shrp are normally x.5 values.)
import sys
if sys.version_info.major > 2:
    raise NotImplementedError("python3 rounding will produce bad results")
t = np.vectorize(round)(f0_time)

Quoted from this commit: 7dcb050#diff-7953eb3de436b3d0e74a60971a8b027aR78

Currently, the code passes all tests except for anything involving shr_pitch() because of this rounding problem.

[terriyu]

The solution is to write our own rounding function using NumPy functions. Since it uses NumPy, it works in both Python2 and Python3.

See this commit for the solution f2cfe4a