pickle is just very slow...

pickle_numpy_benchmark.py

import pickle
import numpy as np


img = np.random.rand(3, 1000, 1000)
data = img.tobytes()


def dump(arr):
    return pickle.dumps((arr.tobytes(), arr.dtype, arr.shape))

  def load(data):
    byte, dt, shape = pickle.loads(data)
    arr = np.frombuffer(byte, dtype=dt)
    arr.resize(shape)
    return arr

%timeit pickle.loads(pickle.dumps(img))
# 17.9 ms ± 100 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
%timeit load(dump(img))
# 18.8 ms ± 286 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
%timeit pickle.dumps(img)
# 12.3 ms ± 101 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
%timeit dump(img)
# 12.5 ms ± 255 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
%timeit pickle.dumps(data)
# 6.63 ms ± 179 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)
%timeit img.tobytes()
# 5.87 ms ± 120 µs per loop (mean ± std. dev. of 7 runs, 100 loops each)