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: aarch64-gnu

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.

src/etc/test-float-parse/src/gen/subnorm.rs

tgross35 · 2025-03-04T02:41:04Z

Edit: Could you try add test-float-parse to x.py suggest?

I don't think I've ever used this and I have no idea how it works 😆 any improvements to running test-float-parse via bootstrap are welcome though, I wired it up just enough to run tests in CI.

speedy-lex · 2025-03-04T11:25:01Z

I'm not very familiar with the CI system; can you link me to where you wired it up?
I've added it to suggest with speedy-lex@e0ca633 but I'm not sure how to get suggest to run ./test-float-parse --skip-huge

jieyouxu · 2025-03-04T11:29:20Z

./x suggest is mostly stale as I don't think anyone actually uses it.

speedy-lex · 2025-03-04T11:31:15Z

Doesn't CI use it?

jieyouxu · 2025-03-04T11:37:50Z

It does not AFAIK. It was mostly added to help local developers. #109933

I don't think it's been worked on for a while.

speedy-lex · 2025-03-04T12:17:04Z

What's the system for registering CI commands?
Where is it? I've searched through the many.sh files and I can't find anything.

jieyouxu · 2025-03-04T12:18:44Z

The CI goes through some shell wrappers x.ps1 or x.sh to invoke the x.py python wrapper¹ which in turn invokes the bootstrap python wrapper bootstrap.py to build the bootstrap crate (incl. the bootstrap binary) itself, which is the build system.

What do you want to do with "registering CI commands"? CI also goes through bootstrap.

they are to facade away platform shell/python differences. ↩

tgross35 · 2025-03-07T11:18:34Z

Thanks @speedy-lex for the tests, almost everything is passing (including test-float-parse!). I have a few todos to address before the final cleanup.

What's the system for registering CI commands? Where is it? I've searched through the many.sh files and I can't find anything.

Bootstrap can be set up to build a path as a crate, ./x t --stage src/etc/test-float-parse and (I think) ./x t --stage test-float-parse should work. If you search for test-float-parse within src/bootstrap it should point you to the right place, something like impl Step for TestFloatParse. These specific CI invocation is here

rust/src/bootstrap/mk/Makefile.in

Lines 51 to 55 in 91a0e16

    
           $(Q)$(BOOTSTRAP) test --stage 2 \ 
        
           	src/tools/cargo \ 
        
           	src/tools/cargotest \ 
        
           	src/etc/test-float-parse \ 
        
           	$(BOOTSTRAP_ARGS)

speedy-lex · 2025-03-07T14:32:06Z

@tgross35, I've figured out CI on my own already but thanks for commenting.

Also, what else needs to be done before this is finished?

tgross35 · 2025-03-07T20:15:07Z

There are a few small places where I added tests for consistency but didn’t yet update them, labeled todo:. I’ll get to them tonight, but feel free to beat me to it :)

After that this should be review-ready

tgross35 · 2025-03-08T03:33:47Z

library/coretests/tests/num/flt2dec/mod.rs

+    check_exact!(f(f16::MIN_POSITIVE) => b"6103515625       ", -4);
+    check_exact!(f(minf16)            => b"59604644775390625", -7);
+
+    // todo: add tables from f32 and f64


This is the last thing remaining to do, I think it might take a bit of work to apply the algorithms from the Paxson paper to binary16. @speedy-lex have you touched this at all?

(I'm working on it, thinking the described algorithm would be good in test-float-parse)

I haven't really looked at it since everything was so hard to find. Have you made any progress on it so far?

I made some progress but wasn't getting very good results with basically a direct implementation of the described algorithm. It's pretty complex and probably needs some thought put into it to figure out what is wrong, but I think we should be okay just leaving this as a FIXME for now.

My scratch work for reference https://github.com/tgross35/float-paxson-format-test

speedy-lex

@tgross35, you missed some func calls when you added the target_arch stuff.

library/coretests/tests/num/flt2dec/strategy/dragon.rs

library/coretests/tests/num/flt2dec/strategy/grisu.rs

bors · 2025-04-02T07:12:59Z

☔ The latest upstream changes (presumably #139229) 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) and adds a `FromStr` implementation.

tgross35 · 2025-04-02T21:15:19Z

I didn't manage to get the last group of tests implemented yet #127013 (comment), but everything else is passing so I think this should be mergable.

r? libs

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 · 2025-04-03T06:51:00Z

@bors try

Add `f16` formatting and parsing Use the same algorithms as for `f32` and `f64` to implement `f16` parsing and printing. try-job: aarch64-gnu

bors · 2025-04-03T06:52:11Z

⌛ Trying commit 6f07075 with merge cbb26c3...

bors · 2025-04-03T08:49:53Z

☀️ Try build successful - checks-actions
Build commit: cbb26c3 (cbb26c3f0959f14f1046f01715cb0dd6a506a8cd)

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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tgross35 mentioned this pull request Jul 18, 2024

Tracking Issue for f16 and f128 float types #116909

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

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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

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

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tgross35 force-pushed the f16-format-parse branch 2 times, most recently from 0c4ca7c to ddeae7b Compare April 2, 2025 20:56

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tgross35 force-pushed the f16-format-parse branch from ddeae7b to db05f28 Compare April 2, 2025 22:50

tgross35 and others added 2 commits April 3, 2025 05:34

float: Add tests for f16 conversions to and from decimal

07c145d

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

6f07075

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 db05f28 to 6f07075 Compare April 3, 2025 05:34

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Add `f16` formatting and parsing #127013

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Add `f16` formatting and parsing #127013

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