Change output normalization logic to be linear against size of output #128200
Conversation
This file contains 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
rustbot
added
S-waiting-on-review
|
Seeing if this is the culprit of the perf regression requiring the #128179 revert. @bors try @rust-timer queue |
This comment has been minimized.
This comment has been minimized.
rustbot
added
the
S-waiting-on-perf
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Jul 25, 2024
[perf] Change output normalization logic to be linear against size of output I believe the previous code was accidentally quadratic. Let's perf it.
compiler/rustc_errors/src/emitter.rs
Outdated
| s = s.replace(*c, replacement); | ||
| } | ||
| s | ||
| // We replace some characters so the CLI output is always consistent and underlines aligned. |
There was a problem hiding this comment.
Can you put this in a LazyCell or whatever?
There was a problem hiding this comment.
sorting it and using binary search would be another option
There was a problem hiding this comment.
Yeah, did this just to smoke test if I was right that this is the actual problem.
Does anyone have thoughts about how to avoid the String allocation? Doubt it actually affects performance that much... but still.
There was a problem hiding this comment.
You can return a borrowed Cow if no substitutions happened and an owned one if one does happen.
There was a problem hiding this comment.
And a big match might be even simpler.
There was a problem hiding this comment.
@the8472 what do you think of the following?
str.chars()
.flat_map(|c| match output_replacements.binary_search_by_key(&c, |(k, _)| *k) {
Ok(i) => Either::Left(output_replacements[i].1.chars()),
_ => Either::Right([c].into_iter()),
})
.collect()There would be a single heap allocation by collect and nothing else, right?
There was a problem hiding this comment.
Well, it doesn't know the length so it'd still do the amortized growth thing, so O(log(l)) allocations.
And it wouldn't avoid an allocation if nothing changed.
But it's better than what's currently in the PR.
the8472
reviewed
Jul 25, 2024
compiler/rustc_errors/src/emitter.rs
Outdated
Comment on lines
2611
to
2621
| str.chars() | ||
| .map(|c| output_replacements.get(&c).map_or(c.to_string(), |s| s.to_string())) | ||
| .collect() |
There was a problem hiding this comment.
Those to_string are going to cause a lot of tiny allocations. Try using fold and appending to a String instead.
compiler/rustc_errors/src/emitter.rs
Outdated
| s = s.replace(*c, replacement); | ||
| } | ||
| s | ||
| // We replace some characters so the CLI output is always consistent and underlines aligned. |
There was a problem hiding this comment.
sorting it and using binary search would be another option
|
☀️ Try build successful - checks-actions |
This comment has been minimized.
This comment has been minimized.
|
Finished benchmarking commit (ee7d1a7): comparison URL. Overall result: ❌✅ regressions and improvements - no action neededBenchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf. @bors rollup=never Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)This benchmark run did not return any relevant results for this metric. CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 769.861s -> 770.138s (0.04%) |
rustbot
removed
the
S-waiting-on-perf
estebank
force-pushed
the
normalize-whitespace
branch
from
cd8ef40
to
e35d147
Compare
|
These commits modify the If this was unintentional then you should revert the changes before this PR is merged. |
estebank
changed the title
|
Given that there's no improvement, I'm guessing that the previous version of this PR didn't do what I wanted it to. Trying this other version, but we might have to go ahead with the revert :-/ @bors try @rust-timer queue |
This comment has been minimized.
This comment has been minimized.
rustbot
added
the
S-waiting-on-perf
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Jul 26, 2024
Change output normalization logic to be linear against size of output I believe the previous code was accidentally quadratic. Let's perf it.
|
☀️ Try build successful - checks-actions |
This comment has been minimized.
This comment has been minimized.
|
Finished benchmarking commit (c7620ca): comparison URL. Overall result: ✅ improvements - no action neededBenchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf. @bors rollup=never Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)This benchmark run did not return any relevant results for this metric. CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 772.066s -> 771.597s (-0.06%) |
rustbot
removed
the
S-waiting-on-perf
Scan strings to be normalized for printing in a linear scan and collect the resulting `String` only once. Use a binary search when looking for chars to be replaced, instead of a `HashMap::get`.
estebank
force-pushed
the
normalize-whitespace
branch
from
e35d147
to
4790f32
Compare
lqd
reviewed
Jul 31, 2024
| @@ -2559,22 +2559,13 @@ fn num_decimal_digits(num: usize) -> usize { | |||
|
|
|||
| // We replace some characters so the CLI output is always consistent and underlines aligned. | |||
| // Keep the following list in sync with `rustc_span::char_width`. | |||
| // ATTENTION: keep lexicografically sorted so that the binary search will work | |||
There was a problem hiding this comment.
Suggested change
| // ATTENTION: keep lexicografically sorted so that the binary search will work | |
| // ATTENTION: keep lexicographically sorted so that the binary search will work |
Comment on lines
+2614
to
+2616
| // Scan the input string for a character in the ordered table above. If it's present, replace | ||
| // it with it's alternative string (it can be more than 1 char!). Otherwise, retain the input | ||
| // char. At the end, allocate all chars into a string in one operation. |
There was a problem hiding this comment.
This comment seems to be a bit inaccurate.
There was a problem hiding this comment.
Oh, it was accurate, before I changed it to the current algo. Given this is already r+d, I'll do a follow up (unless you want to do that as part of your draft PR).
There was a problem hiding this comment.
I've already included it in the draft, yes, so I guess we can do it as a part of it then.
There are two drafts actually. One adding const asserts (#128465) and one using perfect hashing (#128463). They both need this one to land first, after which I guess the former can be reviewed independently of the latter, which needs some additional benchmarking.
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Aug 2, 2024
…felix Change output normalization logic to be linear against size of output Modify the rendered output normalization routine to scan each character *once* and construct a `String` to be printed out to the terminal *once*, instead of using `String::replace` in a loop multiple times. The output doesn't change, but the time spent to prepare a diagnostic is now faster (or rather, closer to what it was before rust-lang#127528).
|
The job Click to see the possible cause of the failure (guessed by this bot) |
|
💔 Test failed - checks-actions |
bors
added
S-waiting-on-review
|
Looks like a spurious failure. (I think I do not have enough rights to @bors retry) |
|
@bors retry |
bors
added
S-waiting-on-bors
|
☀️ Test successful - checks-actions |
|
Finished benchmarking commit (8c7e0e1): comparison URL. Overall result: ❌✅ regressions and improvements - ACTION NEEDEDNext Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)Results (primary -2.8%)This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 762.407s -> 760.794s (-0.21%) |
|
More improvements than regressions, and this fixed an earlier regression. @rustbot label: +perf-regression-triaged |
rustbot
added
the
perf-regression-triaged
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Aug 6, 2024
rustc_errors: use perfect hashing for character replacements The correctness of code in rust-lang#128200 relies on an array being sorted (so that it can be used in binary search later), which is currently enforced with `// tidy-alphabetical` (and characters being written in `\u{XXXX}` form), as well as lack of duplicate entries with conflicting keys, which is not currently enforced. A const assert or a test can be added checking that (implemented in rust-lang#128465). But this PR tries to use [perfect hashing](https://en.wikipedia.org/wiki/Perfect_hash_function) instead. The performance implications are unclear. Asymptotically it's faster, but in reality we should just benchmark. Plus if there are no significant performance wins, this entire things is probably not even worse the additional dependencies it brings. UPD: funnily enough, there's a PR optimizing the binary search implementation (rust-lang#128254) in the queue right now. So I guess we have to wait until that is merged too before benchmarking this.
matthiaskrgr
added a commit
to matthiaskrgr/rust
that referenced
this pull request
Aug 8, 2024
Some `const { }` asserts for rust-lang#128200
The correctness of code in rust-lang#128200 relies on an array being sorted (so that it can be used in binary search later), which is currently enforced with `// tidy-alphabetical` (and characters being written in `\u{XXXX}` form), as well as lack of duplicate entries with conflicting keys, which is not currently enforced.
This PR changes it to using a `const{ }` assertion (and also checks for duplicate entries). Sadly, we cannot use the recently-stabilized `is_sorted_by_key` here, because it is not const (but it would not allow us to check for uniqueness anyways). Instead, let's write a manual loop.
Alternative approach (perfect hash function): rust-lang#128463
r? `@ghost`
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Aug 8, 2024
…iaskrgr Rollup of 2 pull requests Successful merges: - rust-lang#128465 (Some `const { }` asserts for rust-lang#128200 ) - rust-lang#128795 (Update E0517 message to reflect RFC 2195.) r? `@ghost` `@rustbot` modify labels: rollup
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Aug 8, 2024
Some `const { }` asserts for rust-lang#128200
The correctness of code in rust-lang#128200 relies on an array being sorted (so that it can be used in binary search later), which is currently enforced with `// tidy-alphabetical` (and characters being written in `\u{XXXX}` form), as well as lack of duplicate entries with conflicting keys, which is not currently enforced.
This PR changes it to using a `const{ }` assertion (and also checks for duplicate entries). Sadly, we cannot use the recently-stabilized `is_sorted_by_key` here, because it is not const (but it would not allow us to check for uniqueness anyways). Instead, let's write a manual loop.
Alternative approach (perfect hash function): rust-lang#128463
r? `@ghost`
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.
Modify the rendered output normalization routine to scan each character once and construct a
Stringto be printed out to the terminal once, instead of usingString::replacein a loop multiple times. The output doesn't change, but the time spent to prepare a diagnostic is now faster (or rather, closer to what it was before #127528).