[Numpy-discussion] Preserving NumPy views when pickling

[Stephan Hoyer]

On Tue, Oct 25, 2016 at 1:07 PM, Nathaniel Smith <njs at pobox.com> wrote:

> Concretely, what do would you suggest should happen with:
>
> base = np.zeros(100000000)
> view = base[:10]
>
> # case 1
> pickle.dump(view, file)
>
> # case 2
> pickle.dump(base, file)
> pickle.dump(view, file)
>
> # case 3
> pickle.dump(view, file)
> pickle.dump(base, file)
>
> ?
>

I see what you're getting at here. We would need a rule for when to include
the base in the pickle and when not to. Otherwise, pickle.dump(view, file)
always contains data from the base pickle, even with view is much smaller
than base.

The safe answer is "only use views in the pickle when base is already being
pickled", but that isn't possible to check unless all the arrays are
together in a custom container. So, this isn't really feasible for NumPy.
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