BinaryHeap: Simplify sift down
Sift down was doing all too much work: it can stop directly when the
current element obeys the heap property in relation to its children.
In the old code, sift down didn't compare the element to sift down at
all, so it was maximally sifted down and relied on the sift up call to
put it in the correct location.
This should speed up heapify and .pop().
Also rename Hole::removed() to Hole::element()
Sift down was doing all too much work: it can stop directly when the
current element obeys the heap property in relation to its children.
In the old code, sift down didn't compare the element to sift down at
all, so it was maximally sifted down and relied on the sift up call to
put it in the correct location.
This should speed up heapify and .pop().
Also rename Hole::removed() to Hole::element()
sort: Fast path for already sorted data
When merging two sorted blocks `left` and `right` if the last element in
`left` is <= the first in `right`, the blocks are already in sorted order.
Add this as an additional fast path by simply copying the whole left
block into the output and advancing the left pointer. The right block is
then treated the same way by the already present logic in the merge
loop.
Can reduce runtime of .sort() to less than 50% of the previous, if the data
was already perfectly sorted. Sorted data with a few swaps are also
sorted quicker than before. The overhead of one comparison per merge
seems to be negligible.
Since commit 46068c9da, call to `reserve()` on empty vec allocates
exactly requested capacity, so unroll of first iteration may help only
with branch prediction.
When merging two sorted blocks `left` and `right` if the last element in
`left` is <= the first in `right`, the blocks are already sorted.
Add this as an additional fast path by simply copying the whole left
block into the output and advancing the left pointer. The right block is
then treated the same way by the already present logic in the merge
loop.
Reduces runtime of .sort() to less than 50% of the previous, if the data
was already perfectly sorted. Sorted data with a few swaps are also
sorted quicker than before. The overhead of one comparison per merge
seems to be negligible.
vec: Remove old comment in Vec::drop
This comment was leftover from an earlier revision of a PR, something
that never was merged. There is no ZST special casing in Vec::drop.
I think this should fix the test failures in debug mode from #29492
The assertion was written incorrectly, and I don't like the way the new assertion is written, but I _think_ it does the right thing now.
This documentation confused me when trying to use truncate on a project. Originally, it was unclear whether truncate removed the last `len` elements, or whether it cut down the vector to be exactly `len` elements long. The example was also ambiguous.
This commit stabilizes and deprecates library APIs whose FCP has closed in the
last cycle, specifically:
Stabilized APIs:
* `fs::canonicalize`
* `Path::{metadata, symlink_metadata, canonicalize, read_link, read_dir, exists,
is_file, is_dir}` - all moved to inherent methods from the `PathExt` trait.
* `Formatter::fill`
* `Formatter::width`
* `Formatter::precision`
* `Formatter::sign_plus`
* `Formatter::sign_minus`
* `Formatter::alternate`
* `Formatter::sign_aware_zero_pad`
* `string::ParseError`
* `Utf8Error::valid_up_to`
* `Iterator::{cmp, partial_cmp, eq, ne, lt, le, gt, ge}`
* `<[T]>::split_{first,last}{,_mut}`
* `Condvar::wait_timeout` - note that `wait_timeout_ms` is not yet deprecated
but will be once 1.5 is released.
* `str::{R,}MatchIndices`
* `str::{r,}match_indices`
* `char::from_u32_unchecked`
* `VecDeque::insert`
* `VecDeque::shrink_to_fit`
* `VecDeque::as_slices`
* `VecDeque::as_mut_slices`
* `VecDeque::swap_remove_front` - (renamed from `swap_front_remove`)
* `VecDeque::swap_remove_back` - (renamed from `swap_back_remove`)
* `Vec::resize`
* `str::slice_mut_unchecked`
* `FileTypeExt`
* `FileTypeExt::{is_block_device, is_char_device, is_fifo, is_socket}`
* `BinaryHeap::from` - `from_vec` deprecated in favor of this
* `BinaryHeap::into_vec` - plus a `Into` impl
* `BinaryHeap::into_sorted_vec`
Deprecated APIs
* `slice::ref_slice`
* `slice::mut_ref_slice`
* `iter::{range_inclusive, RangeInclusive}`
* `std::dynamic_lib`
Closes#27706Closes#27725
cc #27726 (align not stabilized yet)
Closes#27734Closes#27737Closes#27742Closes#27743Closes#27772Closes#27774Closes#27777Closes#27781
cc #27788 (a few remaining methods though)
Closes#27790Closes#27793Closes#27796Closes#27810
cc #28147 (not all parts stabilized)
This commit stabilizes and deprecates library APIs whose FCP has closed in the
last cycle, specifically:
Stabilized APIs:
* `fs::canonicalize`
* `Path::{metadata, symlink_metadata, canonicalize, read_link, read_dir, exists,
is_file, is_dir}` - all moved to inherent methods from the `PathExt` trait.
* `Formatter::fill`
* `Formatter::width`
* `Formatter::precision`
* `Formatter::sign_plus`
* `Formatter::sign_minus`
* `Formatter::alternate`
* `Formatter::sign_aware_zero_pad`
* `string::ParseError`
* `Utf8Error::valid_up_to`
* `Iterator::{cmp, partial_cmp, eq, ne, lt, le, gt, ge}`
* `<[T]>::split_{first,last}{,_mut}`
* `Condvar::wait_timeout` - note that `wait_timeout_ms` is not yet deprecated
but will be once 1.5 is released.
* `str::{R,}MatchIndices`
* `str::{r,}match_indices`
* `char::from_u32_unchecked`
* `VecDeque::insert`
* `VecDeque::shrink_to_fit`
* `VecDeque::as_slices`
* `VecDeque::as_mut_slices`
* `VecDeque::swap_remove_front` - (renamed from `swap_front_remove`)
* `VecDeque::swap_remove_back` - (renamed from `swap_back_remove`)
* `Vec::resize`
* `str::slice_mut_unchecked`
* `FileTypeExt`
* `FileTypeExt::{is_block_device, is_char_device, is_fifo, is_socket}`
* `BinaryHeap::from` - `from_vec` deprecated in favor of this
* `BinaryHeap::into_vec` - plus a `Into` impl
* `BinaryHeap::into_sorted_vec`
Deprecated APIs
* `slice::ref_slice`
* `slice::mut_ref_slice`
* `iter::{range_inclusive, RangeInclusive}`
* `std::dynamic_lib`
Closes#27706Closes#27725
cc #27726 (align not stabilized yet)
Closes#27734Closes#27737Closes#27742Closes#27743Closes#27772Closes#27774Closes#27777Closes#27781
cc #27788 (a few remaining methods though)
Closes#27790Closes#27793Closes#27796Closes#27810
cc #28147 (not all parts stabilized)
{BTree,Hash}{Map,Set} will not update their key if it already exists, which
can matter with more complex keys. This behavior is now documented.
Fixes#26888
{BTree,Hash}{Map,Set} will not update their key if it already exists, which
can matter with more complex keys. This behavior is now documented.
Fixes#26888
This is a WIP PR for my implementation of drain over the VecDeque data structure supporting ranges. It brings the VecDeque drain implementation in line with Vec's.
Tests haven't been written for the new function yet.
I needed it in `RawVec`, `Vec`, and `TypedArena` for `rustc` to
bootstrap; but of course that alone was not sufficient for `make
check`.
Later I added `unsafe_destructor_blind_to_params` to collections, in
particular `LinkedList` and `RawTable` (the backing representation for
`HashMap` and `HashSet`), to get the regression tests exercising
cyclic structure from PR #27185 building.
----
Note that the feature is `dropck_parametricity` (which is not the same
as the attribute's name). We will almost certainly vary our strategy
here in the future, so it makes some sense to have a not-as-ugly name
for the feature gate. (The attribute name was deliberately selected to
be ugly looking.)
Our docs were very basic for the various versions of from_utf8, so
this commit beefs them up.
It also improves docs for the &str variant's error, Utf8Error.
