将交错的NumPy整数数组转换为complex64的最快方法是什么？

import numpy as np

a = np.zeros(1000000, dtype=np.int16)
b = np.complex64(a[::2]) + np.complex64(1j) * np.complex64(a[1::2])

[~]
|1> import numpy as np

[~]
|2> a = np.zeros(1000000, dtype=np.int16)

[~]
|3> b = a.astype(np.float32).view(np.complex64)

[~]
|4> b.shape
(500000,)

[~]
|5> b.dtype
dtype(\'complex64\')