Alignment issue when passing arrays though mmap #563
Description
Arrays that are transfered to subprocesses though mmap appear not always to be aligned:
import joblib
import numpy as np
def func(x):
print(type(x))
print(x.flags)
print(x.ctypes.data / 8)
if __name__ == '__main__':
# Make the array larger than 1Mbyte so that mmap is used
n = 1024 ** 2 // 8 + 1
x = np.random.randn(n)
jobs = joblib.Parallel(2)
print(x.nbytes)
res = jobs([joblib.delayed(func)(x), joblib.delayed(func)(x)])This returns
<class 'numpy.core.memmap.memmap'>
1048584
C_CONTIGUOUS : True
F_CONTIGUOUS : True
OWNDATA : False
WRITEABLE : False
ALIGNED : False
UPDATEIFCOPY : False
570054683.375
Note the last line, the address of the first element of the array is indeed not aligned.
I'm using version 0.11, on OSx sierra.
This came up in pymc-devs/pymc#2640, and seems to happen on several OSs.