float tests: deduplicate min, max, and rounding tests
Part of https://github.com/rust-lang/rust/issues/141726
Best reviewed commit-by-commit.
- Use `assert_biteq!` in the `mod.rs` tests. This requires some trickery to make shadowing macros with imports work.
- The min, max, minimum, maximum tests in `tests/floats/f*.rs` are entirely subsumed by what we already have in `tests/float/mod.rs`, so I just removed them.
- The rounding tests (floor etc) in `f*.rs` had more test points, so I copied them over. They didn't have `0.5` and `-0.5` though which seem like interesting points in particular regarding the sign of the resulting zero if that's what it sounds to, and they didn't max min/max/inf/nan tests, so this was really a merger of both tests.
r? ``@tgross35``
Enable Non-determinism of float operations in Miri and change std tests
Links to [#4208](https://github.com/rust-lang/miri/issues/4208) and [#3555](https://github.com/rust-lang/miri/issues/3555) in Miri.
Non-determinism of floating point operations was disabled in rust-lang/rust#137594 because it breaks the tests and doc-tests in core/coretests and std. This PR enables some of them.
This pr includes the following changes:
- Enables the float non-determinism but with a lower relative error of 4ULP instead of 16ULP
- These operations now have a fixed output based on the C23 standard, except the pow operations, this is tracked in [#4286](https://github.com/rust-lang/miri/issues/4286#issue-3010677983)
- Changes tests that made incorrect assumptions about the operations, not to make that assumption anymore (from `assert_eq!` to `assert_approx_eq!`.
- Changed the doctests of the stdlib of these operations to compare against fixed constants instead of `f*::EPSILON`, which now succeed with Miri and `-Zmiri-many-seeds`
- Added a constant `APPROX_DELTA` in `std/tests/floats/f32.rs` which is used for approximation tests, but with a different value when run in Miri. This is to make these tests succeed.
- Added tests in the float tests of Miri to test the C23 behaviour.
Fixes https://github.com/rust-lang/miri/issues/4208
float: Replace some approximate assertions with exact
As was mentioned at [1], we currently use `assert_approx_eq` for testing
some math functions that guarantee exact results. Replace approximate
assertions with exact ones for the following:
* `ceil`
* `floor`
* `fract`
* `from_bits`
* `mul_add`
* `round_ties_even`
* `round`
* `trunc`
This likely wasn't done in the past to avoid writing out exact decimals
that don't match the intuitive answer (e.g. 1.3 - 1.0 = 0.300...004),
but ensuring our results are accurate seems more important here.
[1]: https://github.com/rust-lang/rust/pull/138087#issuecomment-2842069281
The first commit is a small bit of macro cleanup.
try-job: aarch64-gnu
try-job: x86_64-gnu-aux
`assert_eq!` ignores the sign of zero, but for any tests involving zeros
we do care about this sign. Replace `assert_eq!` with `assert_biteq!`
everywhere possible for float tests to ensure we don't miss this.
`assert_biteq!` is also updated to check equality on non-NaNs, to catch
the unlikely case that bitwise equality works but our `==`
implementation is broken.
There is one notable output change: we were asserting that
`(-0.0).fract()` and `(-1.0).fract()` both return -0.0, but both
actually return +0.0.
As was mentioned at [1], we currently use `assert_approx_eq` for testing
some math functions that guarantee exact results. Replace approximate
assertions with exact ones for the following:
* `ceil`
* `floor`
* `fract`
* `from_bits`
* `mul_add`
* `round_ties_even`
* `round`
* `trunc`
This likely wasn't done in the past to avoid writing out exact decimals
that don't match the intuitive answer (e.g. 1.3 - 1.0 = 0.300...004),
but ensuring our results are accurate seems more important here.
[1]: https://github.com/rust-lang/rust/pull/138087#issuecomment-2842069281
When these functions were added in
https://github.com/rust-lang/rust/pull/138087
It made a relatively common pattern for emulating
these functions using an extension trait (which
internally uses `libm`) much more fragile.
If `core::f32` happened to be imported by the user
(to access a constant, say), then that import in
the module namespace would take precedence over
`f32` in the type namespace for resolving these
functions, running headfirst into the stability
attribute.
We ran into this in Color -
https://github.com/linebender/color - and chose to
release the remedial 0.3.1 and 0.2.4, to allow
downstream crates to build on `docs.rs`.
As these methods are perma-unstable, moving them
into a new module should not have any long-term
concerns, and ensures that this breakage doesn't
adversely impact anyone else.
The previous commit moved all test files from `std` to `core` so git
understands the move. Not all functionality is actually testable in
`core`, however, so perform move the relevant portions back. Changes
from inherent to module methods is also done since this is the form of
math operations available in `core` (as `core_float_math`).
Many float-related tests in `std` only depend on `core`, so move the
tests there. This also allows us to verify functions from
`core_float_math`.
Since the majority of test files need to be moved to `coretests`, move
the files here without any cleanup; this is done in a followup commit.
This makes git history slightly cleaner, but coretests will not build
immediately after this commit.
