Use vec![] for vector creation #26904
Merged
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| // use `resize` so that the zero filling is as efficient as possible | ||
| let len = self.inner.len(); | ||
| self.inner.resize(len + amt as usize, 0); | ||
| } |
There was a problem hiding this comment.
How come this is surrounded with an if?
There was a problem hiding this comment.
Ah great question, that's an artifact of the version I wrote first
There was a problem hiding this comment.
Other than that though this all looks good to me! r=me with this changed.
Vec::resize compiles to better code than .extend(repeat(0).take(n)) does right now.
|
Thanks for looking at it. You're quick! @bors: r=alexcrichton |
|
📌 Commit 475e0be has been approved by |
|
⌛ Testing commit 475e0be with merge ef2d987... |
|
💔 Test failed - auto-win-gnu-64-opt |
The common pattern `iter::repeat(elt).take(n).collect::<Vec<_>>()` is exactly equivalent to `vec![elt; n]`, do this replacement in the whole tree. (Actually, vec![] is smart enough to only call clone n - 1 times, while the former solution would call clone n times, and this fact is virtually irrelevant in practice.)
|
Forgot an unused import, updated. |
|
@bors: r=alexcrichton |
|
📌 Commit 836f32e has been approved by |
bors
added a commit
that referenced
this pull request
Jul 9, 2015
In a followup to PR #26849, improve one more location for I/O where we can use `Vec::resize` to ensure better performance when zeroing buffers. Use the `vec![elt; n]` macro everywhere we can in the tree. It replaces `repeat(elt).take(n).collect()` which is more verbose, requires type hints, and right now produces worse code. `vec![]` is preferable for vector initialization. The `vec![]` replacement touches upon one I/O path too, Stdin::read for windows, and that should be a small improvement. r? @alexcrichton
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
In a followup to PR #26849, improve one more location for I/O where
we can use
Vec::resizeto ensure better performance when zeroingbuffers.
Use the
vec![elt; n]macro everywhere we can in the tree. It replacesrepeat(elt).take(n).collect()which is more verbose, requires typehints, and right now produces worse code.
vec![]is preferable for vectorinitialization.
The
vec![]replacement touches upon one I/O path too, Stdin::readfor windows, and that should be a small improvement.
r? @alexcrichton