core: implement bounded random sampling by joboet · Pull Request #159592 · rust-lang/rust

joboet · 2026-07-20T08:21:35Z

Tracking issue: #130703

This PR implements the Distribution trait for RangeInclusive, allowing random sampling from within a range. I chose Lemire's algorithm, which is also used in FreeBSD's arc4random_uniform.

I've only implemented this for core::range::RangeInclusive to prevent typo-errors. Perhaps it makes sense though to extend the support to core::ops::RangeInclusive?

rustbot · 2026-07-20T08:21:40Z

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JohnTitor · 2026-07-27T21:56:12Z

Perhaps it makes sense though to extend the support to core::ops::RangeInclusive?

I guess we should, IIRC 1..=n is implemented by core::ops::RangeInclusive so it'd need that support (not confirmed on my end though)

JohnTitor

Overall LGTM! I'll leave you whether adding the support for core::ops::RangeInclusive in this PR or not (it'd be sweet though!). r=me with or without it

View changes since this review

joboet · 2026-07-29T15:55:22Z

I think I'll leave the ops::RangeInclusive implementation for another PR, it's just not as clear to me whether we want it.

@bors r=@JohnTitor

rust-bors · 2026-07-29T15:55:26Z

📌 Commit 8364216 has been approved by JohnTitor

It is now in the queue for this repository.

…itor core: implement bounded random sampling Tracking issue: rust-lang#130703 This PR implements the `Distribution` trait for `RangeInclusive`, allowing random sampling from within a range. I chose [Lemire's algorithm](https://doi.org/10.1145/3230636), which is also used in [FreeBSD's `arc4random_uniform`](https://cgit.freebsd.org/src/tree/lib/libc/gen/arc4random_uniform.c). I've only implemented this for `core::range::RangeInclusive` to prevent typo-errors. Perhaps it makes sense though to extend the support to `core::ops::RangeInclusive`?

Rollup of 17 pull requests Successful merges: - #159014 ([rustdoc] Do not take `doc(cfg())` into account when filtering doctests) - #159130 (a bit optimize four-digit chunks in integer formatting) - #159592 (core: implement bounded random sampling) - #159898 (Add intrinsic-test alias and set sample rate) - #158247 (hermit/fs: Return `unsupported()` instead of `from_raw_os_error(22)`) - #158649 (Hermit: fix `readdir()` ) - #159049 (Avoid ICE in From/TryFrom cast suggestion when encountering HRTBs) - #160053 (test: add test suite for the 85681 issue) - #160087 (Add regression test for nested associated-type projection ICE) - #160090 (rustc_resolve: Further reduce mutability in resolver) - #160099 (Resolver: split module resolutions into local and external resolutions) - #160106 (Add suggestions for `must_implement_one_of`) - #160117 (Remove unnecessary format usage) - #160134 (Work around Wine bug 60084 by calling WSAStartup at most once) - #160142 (bootstrap: remove use-lld config alias) - #160148 (Rename `errors.rs` file to `diagnostics.rs` (15/N)) - #160151 (Mark a doctest as requiring unwinding)

…itor core: implement bounded random sampling Tracking issue: rust-lang#130703 This PR implements the `Distribution` trait for `RangeInclusive`, allowing random sampling from within a range. I chose [Lemire's algorithm](https://doi.org/10.1145/3230636), which is also used in [FreeBSD's `arc4random_uniform`](https://cgit.freebsd.org/src/tree/lib/libc/gen/arc4random_uniform.c). I've only implemented this for `core::range::RangeInclusive` to prevent typo-errors. Perhaps it makes sense though to extend the support to `core::ops::RangeInclusive`?

Rollup of 18 pull requests Successful merges: - #159130 (a bit optimize four-digit chunks in integer formatting) - #159592 (core: implement bounded random sampling) - #159898 (Add intrinsic-test alias and set sample rate) - #158247 (hermit/fs: Return `unsupported()` instead of `from_raw_os_error(22)`) - #158649 (Hermit: fix `readdir()` ) - #159049 (Avoid ICE in From/TryFrom cast suggestion when encountering HRTBs) - #160053 (test: add test suite for the 85681 issue) - #160087 (Add regression test for nested associated-type projection ICE) - #160090 (rustc_resolve: Further reduce mutability in resolver) - #160099 (Resolver: split module resolutions into local and external resolutions) - #160106 (Add suggestions for `must_implement_one_of`) - #160117 (Remove unnecessary format usage) - #160134 (Work around Wine bug 60084 by calling WSAStartup at most once) - #160139 (iter: specialize Take::count using advance_by) - #160142 (bootstrap: remove use-lld config alias) - #160148 (Rename `errors.rs` file to `diagnostics.rs` (15/N)) - #160151 (Mark a doctest as requiring unwinding) - #160166 (Use correct feature gates for `f16`/`f128` `From` impls)

rust-bors · 2026-07-29T21:45:02Z

☀️ Test successful - CI
Approved by: JohnTitor
Duration: 3h 16m 28s
Pushing 1a833e1 to main...

github-actions · 2026-07-29T21:48:10Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing b5be620 (parent) -> 1a833e1 (this PR)

Test differences

Show 26 test diffs

26 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 1a833e16546c2eb012758ddd499964fd8afee29e --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

armhf-gnu: 1h 5m -> 1h 28m (+35.8%)
x86_64-msvc-2: 2h 30m -> 1h 38m (-34.3%)
x86_64-gnu-stable: 1h 44m -> 2h 19m (+33.5%)
pr-check-1: 21m 2s -> 28m 2s (+33.2%)
dist-arm-linux-musl: 1h 22m -> 1h 49m (+33.2%)
dist-loongarch64-musl: 1h 54m -> 1h 24m (-26.6%)
test-various: 2h 1m -> 1h 31m (-24.6%)
arm-android: 1h 18m -> 1h 36m (+23.3%)
dist-x86_64-linux-alt: 2h 27m -> 1h 54m (-22.3%)
dist-x86_64-llvm-mingw: 2h -> 1h 36m (-20.5%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2026-07-29T22:49:26Z

Finished benchmarking commit (1a833e1): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.3%	[0.3%, 0.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -0.5%, secondary -0.5%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.4%	[0.4%, 0.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.4%	[-2.4%, -0.4%]	2
Improvements ✅ (secondary)	-0.5%	[-0.7%, -0.4%]	3
All ❌✅ (primary)	-0.5%	[-2.4%, 0.4%]	4

Cycles

Results (primary -0.5%, secondary -1.4%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.8%	[0.8%, 0.9%]	2
Regressions ❌ (secondary)	1.2%	[0.4%, 3.2%]	4
Improvements ✅ (primary)	-0.9%	[-2.5%, -0.4%]	7
Improvements ✅ (secondary)	-3.4%	[-12.3%, -0.5%]	5
All ❌✅ (primary)	-0.5%	[-2.5%, 0.9%]	9

Binary size

Results (secondary 0.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.0%	[0.0%, 0.0%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Bootstrap: 489.76s -> 497.309s (1.54%)
Artifact size: 390.94 MiB -> 390.20 MiB (-0.19%)

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jul 20, 2026

rustbot assigned JohnTitor Jul 20, 2026

joboet added the A-random Area: random data generation support label Jul 20, 2026

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joboet mentioned this pull request Jul 20, 2026

Tracking Issue for secure random data generation in std #130703

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joboet added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Jul 20, 2026

joboet force-pushed the range_distribution branch from 7cf121f to d3e55bf Compare July 20, 2026 08:35

JohnTitor approved these changes Jul 27, 2026

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Comment thread library/core/src/random.rs

Comment thread library/core/src/random.rs

JohnTitor added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 27, 2026

core: implement bounded random sampling

8364216

joboet force-pushed the range_distribution branch from d3e55bf to 8364216 Compare July 29, 2026 14:11

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 29, 2026

jhpratt mentioned this pull request Jul 29, 2026

Rollup of 17 pull requests #160168

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jhpratt mentioned this pull request Jul 29, 2026

Rollup of 18 pull requests #160174

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rust-bors Bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 29, 2026

rust-bors Bot merged commit 1a833e1 into rust-lang:main Jul 29, 2026
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rustbot added this to the 1.99.0 milestone Jul 29, 2026

rust-bors Bot mentioned this pull request Jul 29, 2026

add RandomSource::next_u{32,64} methods #157193

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core: implement bounded random sampling - #159592

core: implement bounded random sampling#159592
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Overall result: ❌ regressions - no action needed

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