Pickle is significantly slower than a memory copy #7544
Description
My machine copies memory at 5GB/s
In [1]: b = b'0' * 1000000000
In [2]: %time len(b[1:])
CPU times: user 139 ms, sys: 63.3 ms, total: 202 ms
Wall time: 202 ms
Out[2]: 999999999But NumPy arrays only serialize at 2.5 GB/s
In [4]: import numpy as np
In [5]: x = np.random.randint(0, 255, dtype='u1', size=1000000000) # 1GB
In [6]: import pickle
In [7]: %time len(pickle.dumps(x, protocol=-1))
CPU times: user 309 ms, sys: 96.2 ms, total: 405 ms
Wall time: 404 ms
Out[7]: 1000000161Why the extra time?
Versions
Python 3.4, Linux, NumPy 1.11.0