Add `f16` formatting and parsing by tgross35 · Pull Request #127013 · rust-lang/rust

tgross35 · 2024-06-27T04:49:47Z

Use the same algorithms as for f32 and f64 to implement f16 parsing and printing.

try-job: x86_64-gnu-aux

tgross35 · 2024-06-27T04:59:12Z

@rustbot label +rla-silenced

tgross35 · 2024-06-27T09:16:35Z

@rustbot label +F-f16_and_f128

tgross35 · 2024-07-09T19:31:19Z

This will need #127510

bors · 2024-07-15T20:16:57Z

☔ The latest upstream changes (presumably #127020) made this pull request unmergeable. Please resolve the merge conflicts.

library/core/src/num/dec2flt/number.rs

tgross35 · 2024-07-28T19:46:30Z

Update: I'm really just waiting on #128083 to bump stage0, managing #[cfg(not(bootstrap))] and always building stage1 got too painful.

bors · 2024-07-30T00:17:37Z

☔ The latest upstream changes (presumably #128360) made this pull request unmergeable. Please resolve the merge conflicts.

tgross35 · 2025-05-15T19:13:49Z

@Mark-Simulacrum the only thing that changed from the original approval should be the addition of the fallback. I double checked with Bjorn and there shouldn’t be any problems with that.

@rustbot ready

Mark-Simulacrum

r=me with nit fixed

Mark-Simulacrum · 2025-05-15T19:17:47Z

library/core/src/num/dec2flt/mod.rs

+// FIXME(f16_f128): A fallback is used when the backend+target does not support f16 well, in order
+// to avoid ICEs.
+
+// After the bootstrap bump this should be: `#[cfg(not(target_has_reliable_f16))`


If true, please write this as a pair of cfg_attrs not a comment - we have some partial automation that can find and replace cfg attrs automatically but comments are near invisible to that.

That is indeed not correct, the comment is from before the post-bump rebase. Removed.

tgross35 · 2025-05-15T20:59:46Z

@bors r=Mark-Simulacrum

bors · 2025-05-15T20:59:49Z

📌 Commit 221d7f3 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

bors · 2025-05-17T22:43:34Z

☔ The latest upstream changes (presumably #138087) made this pull request unmergeable. Please resolve the merge conflicts.

tgross35 · 2025-05-17T22:49:00Z

Rebased.

@bors r=Mark-Simulacrum

bors · 2025-05-17T22:49:02Z

📌 Commit 1c38c28 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

bors · 2025-05-18T16:39:22Z

⌛ Testing commit 1c38c28 with merge ac28adb...

tgross35 · 2025-05-18T16:42:56Z

@bors r- retry #141228 (comment)

Use the existing Lemire (decimal -> float) and Dragon / Grisu algorithms (float -> decimal) to add support for `f16`. This allows updating the implementation for `Display` to the expected behavior for `Display` (currently it prints the a hex bitwise representation), matching other floats, and adds a `FromStr` implementation. In order to avoid crashes when compiling with Cranelift or on targets where f16 is not well supported, a fallback is used if `cfg(target_has_reliable_f16)` is not true.

Extend the existing tests for `f32` and `f64` with versions that include `f16`'s new printing and parsing implementations. Co-authored-by: Speedy_Lex <alex.ciocildau@gmail.com>

This requires a fix to the subnormal test to cap the maximum allowed value within the maximum mantissa.

tgross35 · 2025-05-18T16:52:29Z

@bors try

bors · 2025-05-18T16:53:39Z

⌛ Trying commit 250869e with merge fc768c1...

bors · 2025-05-18T18:46:17Z

☀️ Try build successful - checks-actions
Build commit: fc768c1 (fc768c1d28c6ea7cd5c231c94c80f94ac5b7ee52)

tgross35 · 2025-05-18T19:00:04Z

Needed a config for Miri.

@bors r=Mark-Simulacrum rollup=iffy

bors · 2025-05-18T19:00:06Z

📌 Commit 250869e has been approved by Mark-Simulacrum

It is now in the queue for this repository.

bors · 2025-05-18T20:38:04Z

⌛ Testing commit 250869e with merge 4d051fb...

bors · 2025-05-18T23:51:57Z

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 4d051fb to master...

github-actions · 2025-05-18T23:54:46Z

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 4455c89 (parent) -> 4d051fb (this PR)

Test differences

Show 17 test diffs

Stage 0

num::dec2flt::decimal::check_fast_path_f16: [missing] -> pass (J1)
num::dec2flt::float::test_f16_consts: [missing] -> pass (J1)
num::dec2flt::float::test_f16_integer_decode: [missing] -> pass (J1)
num::dec2flt::lemire::compute_float_f16_rounding: [missing] -> pass (J1)
num::flt2dec::random::exact_f16_random_equivalence_test: [missing] -> pass (J1)
num::flt2dec::random::shortest_f16_exhaustive_equivalence_test: [missing] -> pass (J1)

Stage 1

num::dec2flt::decimal::check_fast_path_f16: [missing] -> pass (J0)
num::dec2flt::float::test_f16_consts: [missing] -> pass (J0)
num::dec2flt::float::test_f16_integer_decode: [missing] -> pass (J0)
num::dec2flt::lemire::compute_float_f16_rounding: [missing] -> pass (J0)
num::flt2dec::random::exact_f16_random_equivalence_test: [missing] -> pass (J0)
num::flt2dec::random::shortest_f16_exhaustive_equivalence_test: [missing] -> pass (J2)
num::flt2dec::random::shortest_f16_exhaustive_equivalence_test: [missing] -> ignore (J3)

Additionally, 4 doctest diffs were found. These are ignored, as they are noisy.

Job group index

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 4d051fb306e661654d088892e02e69b8c0c39d43 --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

dist-aarch64-linux: 5276.3s -> 7698.3s (45.9%)
dist-x86_64-apple: 10179.7s -> 7488.0s (-26.4%)
x86_64-apple-2: 4891.2s -> 4440.8s (-9.2%)
aarch64-apple: 3815.6s -> 4158.7s (9.0%)
x86_64-apple-1: 7586.7s -> 6936.2s (-8.6%)
dist-apple-various: 5946.6s -> 6435.1s (8.2%)
x86_64-msvc-ext1: 7033.4s -> 7521.5s (6.9%)
i686-gnu-2: 6282.8s -> 6683.9s (6.4%)
x86_64-gnu-aux: 5838.3s -> 6206.0s (6.3%)
x86_64-gnu-llvm-20-2: 6240.9s -> 5852.2s (-6.2%)

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.

tgross35 · 2025-05-18T23:56:35Z

🎉🎉🎉 just a month short of this PR’s one year anniversary, I’m very glad to have this in! Thanks @speedy-lex for all the help.

rust-timer · 2025-05-19T01:24:19Z

Finished benchmarking commit (4d051fb): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.8%	[0.4%, 1.0%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (secondary 0.2%)

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.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.7%	[0.6%, 0.9%]	3
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.7%	[-0.7%, -0.6%]	2
All ❌✅ (primary)	-	-	0

Cycles

Results (secondary 1.3%)

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.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.9%	[0.4%, 5.4%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.9%	[-2.0%, -1.9%]	3
All ❌✅ (primary)	-	-	0

Binary size

Results (primary 0.2%, secondary 0.3%)

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.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.0%, 0.5%]	16
Regressions ❌ (secondary)	0.3%	[0.0%, 0.5%]	71
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.0%, 0.5%]	16

Bootstrap: 775.321s -> 775.275s (-0.01%)
Artifact size: 365.53 MiB -> 365.57 MiB (0.01%)

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 Jun 27, 2024

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rustbot added the rla-silenced Silences rust-log-analyzer postings to the PR it's added on. label Jun 27, 2024

rustbot added the F-f16_and_f128 `#![feature(f16)]`, `#![feature(f128)]` label Jun 27, 2024

fbstj reviewed Jul 15, 2024

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library/core/src/num/dec2flt/number.rs Outdated Show resolved Hide resolved

tgross35 mentioned this pull request Jul 18, 2024

Tracking Issue for f16 and f128 float types #116909

Open

92 tasks

tgross35 force-pushed the f16-format-parse branch 2 times, most recently from 7c3f9c1 to f3ebeb3 Compare July 23, 2024 09:52

tgross35 force-pushed the f16-format-parse branch from 2eaa479 to 422c52e Compare August 6, 2024 08:47

Dylan-DPC 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 Aug 20, 2024

tgross35 force-pushed the f16-format-parse branch 6 times, most recently from 21ffabc to 2098f01 Compare August 25, 2024 07:53

rustbot added the T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) label Aug 25, 2024

tgross35 force-pushed the f16-format-parse branch 5 times, most recently from 404089f to 3636530 Compare August 30, 2024 09:04

Mark-Simulacrum reviewed May 15, 2025

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hkBst mentioned this pull request May 16, 2025

Rollup of 14 pull requests #141067

Closed

This was referenced May 18, 2025

Rollup of 6 pull requests #141208

Closed

Rollup of 10 pull requests #141228

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tgross35 and others added 2 commits May 18, 2025 16:51

float: Add tests for f16 conversions to and from decimal

977d841

Extend the existing tests for `f32` and `f64` with versions that include `f16`'s new printing and parsing implementations. Co-authored-by: Speedy_Lex <alex.ciocildau@gmail.com>

float: Add f16 to test-float-parse

250869e

This requires a fix to the subnormal test to cap the maximum allowed value within the maximum mantissa.

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fmease mentioned this pull request May 18, 2025

Rollup of 6 pull requests #141233

Closed

folkertdev mentioned this pull request May 19, 2025

avx512_target_feature is now stable on nightly rust-lang/stdarch#1802

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Test differences

Stage 0

Stage 1

Job duration changes

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rust-timer commented May 19, 2025

Overall result: ❌ regressions - no action needed

Instruction count

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Cycles

Binary size

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tgross35 commented Jun 27, 2024 •

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