Improve .assume_init() and use Array::maybe_uninit instead of Array::uninitialized #876
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Fix up the way we implement .assume_init() - use a mapping of the data storage type instead of transmute. The end result is similar anyway but easier to verify that it is correct. See docs for Arc::from_raw for its requirements - which we should now adhere to.
Avoid Array::uninitialized and use maybe_uninit.
bluss
commented
Dec 29, 2020
| /// ## Safety | ||
| /// | ||
| /// Caller must ensure the two types have the same representation. | ||
| unsafe fn data_subst(self) -> Self::Output; | ||
| } |
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Note that the data storage types are never publically available so the user of ndarray can never reach this method and call it.
bluss
changed the title
This was referenced Jan 25, 2021
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Improve
.assume_init()so that we can see that it is on sound ground (and not transmuting wildly).Then the remaining internal uses of
Array::uninitializedare removed and replaced withArray::maybe_uninit.Fixes part of #796
Prerequisite of #804
This pull request demonstrates two different ways of working with
maybe_uninit. In concatenate and stack,we can see how we're using the more "Rust-level" approach of using regular array traversal and interacting with
elements of type
MaybeUninit<A>(by just assigning to them, but still).In the implementation of
dotand the benchmark, we instead use raw array views -RawArrayViewMut,cast the raw view from element type
MaybeUninit<A>toA, and handle the resulting raw view andraw pointers carefully. We have some power in the ndarray abstractions because we can use
Zipto traverse raw views just like regular arrays.