Fix Uniform::new_inclusive overflow on large finite float ranges - #1821
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Dividing high - low by 1 - EPSILON can round to infinity even when the range itself is finite (e.g. 0.0..=f64::MAX), yielding a spurious NonFinite error while Uniform::new and sample_single_inclusive both accept the same range. Clamp infinite lanes to the largest finite value and let new_bounded reduce scale as usual, so that samples still cannot exceed high. Noted by dhardy in #1603.
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Pull request overview
This PR fixes Uniform::new_inclusive for floating-point ranges where (high - low) / (1 - ε) can round to infinity even though (high - low) is finite (e.g. 0.0..=f64::MAX), aligning behavior with sample_single_inclusive and avoiding spurious Error::NonFinite.
Changes:
- Adjust
UniformFloat::new_inclusiveto validate(high - low)for finiteness before scaling, allowing large finite inclusive ranges that previously overflowed during scaling. - Update the
new_boundedscale-reduction loop to use<=masking plusall()(instead of>plusany()), and add targeted tests fordecrease_masked(including infinity cases). - Add a
CHANGELOG.mdentry documenting the fix.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
src/distr/utils.rs |
Renames/adjusts float mask utilities and adds tests for decrease_masked, including infinity handling. |
src/distr/uniform_float.rs |
Fixes new_inclusive overflow-to-infinity rejection for large finite float ranges and extends test coverage for those bounds. |
CHANGELOG.md |
Documents the Uniform::new_inclusive large-range fix in Unreleased notes. |
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To avoid stalling this fix further I will now merge it without third-party review. |
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CHANGELOG.mdentrySummary
Replaces #1809, allowing
Uniform::new_inclusiveto accept ranges like0.0..=f64::MAXwhich overflow-to-infinity, without extra code.Details
This allows
UniformFloat::new_inclusive(0.0, f64::MAX)to return a valid sampler, though in practice the largest value which may be sampled remains1.next_down() * MAX = MAX.next_down().This is slightly more consistent with
sample_single_inclusivewhich also accepts this range and also does not actually ever emit the largest value.