Add `f16` formatting and parsing #127013

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.

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.

Add `f16` formatting and parsing Use the same algorithms as for `f32` and `f64` to implement `f16` parsing and printing. try-job: x86_64-gnu-aux

Extend the existing tests for `f32` and `f64` with versions that include `f16`'s new printing and parsing implementations. Co-authored-by: Speedy_Lex <[email protected]>

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

Add `f16` formatting and parsing Use the same algorithms as for `f32` and `f64` to implement `f16` parsing and printing. try-job: x86_64-gnu-aux

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.

…Simulacrum Add `f16` formatting and parsing Use the same algorithms as for `f32` and `f64` to implement `f16` parsing and printing. try-job: x86_64-gnu-aux

Rollup of 6 pull requests Successful merges: - rust-lang#127013 (Add `f16` formatting and parsing) - rust-lang#130887 (Safer implementation of RepeatN) - rust-lang#140154 (Cygwin support in rustc) - rust-lang#140874 (make `rustc_attr_parsing` less dominant in the rustc crate graph) - rust-lang#141094 (add regression test for rust-lang#101650) - rust-lang#141110 ([std] fix the presentation of `split_off_mut` and `split_off` documentation) r? `@ghost` `@rustbot` modify labels: rollup

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

View reviewed changes

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

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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 <[email protected]>

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.

tgross35 force-pushed the f16-format-parse branch from 1c38c28 to 250869e Compare May 18, 2025 16:51

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fmease mentioned this pull request May 18, 2025

Rollup of 6 pull requests #141233

Closed

bors added the merged-by-bors This PR was explicitly merged by bors. label May 18, 2025

bors merged commit 4d051fb into rust-lang:master May 18, 2025
7 checks passed

rustbot added this to the 1.89.0 milestone May 18, 2025

tgross35 deleted the f16-format-parse branch May 18, 2025 23:56

folkertdev mentioned this pull request May 19, 2025

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

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Add `f16` formatting and parsing #127013

Add `f16` formatting and parsing #127013

tgross35 commented Jun 27, 2024 •

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Stage 0

Stage 1

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Add f16 formatting and parsing #127013

Add f16 formatting and parsing #127013

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Test differences

Stage 0

Stage 1

Job duration changes

tgross35 commented May 18, 2025

rust-timer commented May 19, 2025

Overall result: ❌ regressions - no action needed

Instruction count

Max RSS (memory usage)

Cycles

Binary size

Add `f16` formatting and parsing #127013

Add `f16` formatting and parsing #127013

tgross35 commented Jun 27, 2024 •

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