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GaelVaroquaux opened this issue Sep 30, 2012 · 5 comments
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Offset is not updated when slicing memmaps #471

GaelVaroquaux opened this issue Sep 30, 2012 · 5 comments
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00 - Bug 57 - Close? Issues which may be closable unless discussion continued component: numpy._core

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@GaelVaroquaux
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>>> import numpy as np
>>> a = np.ones((10, 10))
>>> np.save('a.npy', a)
>>> b = np.load('a.npy', mmap_mode='r')
>>> c = b[3:]
>>> c.offset
80
>>> b.offset
80

The offset of c is wrong: it does not take in account the fact that the slicing has changed the offset.
@GaelVaroquaux GaelVaroquaux mentioned this issue Sep 30, 2012
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@charris
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charris commented Feb 16, 2014

Still true in 1.9-devel.

@Nodd
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Nodd commented Feb 8, 2018

Still true in 1.14.0, but I think it's fine: in the code offset is the offset on the underlying mmap object in the file, it's normal that it doesn"t change in a view.
Otherwise what would the offset for d=b[9:5:-1] be ?
I think this issue should be closed.

@mattip
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mattip commented Aug 8, 2018

@GaelVaroquaux do you agree the offset should remain unchanged?

@mattip mattip added 00 - Bug component: numpy._core 57 - Close? Issues which may be closable unless discussion continued labels Aug 8, 2018
@GaelVaroquaux
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I don't know :).

@mattip
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mattip commented Jan 16, 2019

Closing. offset is documented at the bottom of the link as "Offset position in the file". Perhaps that could be "Offset position in the underlying file" but I think it is good enough as-is.

@mattip mattip closed this as completed Jan 16, 2019
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@charris @GaelVaroquaux @Nodd @mattip