snap_hysteresis's tolerance band is asymmetric at two of its eight edges
まだ誰も着手していません。
評価
- 難易度
- 5/5
- 見積もり時間
- 1週間以上
- 初心者へのやさしさ
- 35/100
- issue の種類
- バグ
- 明瞭さ
- おおむね明確
- 活発さ
- 活発
- 技術スタック
- rust
- 領域
- embedded-iot
調査の方向性
Start with src/lib.rs and run ops_tests::hysteresis::the_band_edges_are_asymmetric, which records the current behavior. Decide whether the tolerance policy should remain approximate or change to midpoint, scaled tolerance, or inclusive slack. Done means a deliberate behavior choice, updated tests, and a changelog-visible commit if behavior changes.
索引モデルが issue の本文から書いたものです。
説明
ops::snap_hysteresis (src/lib.rs) rejects an input further than
HYSTERESIS_TOLERANCE from the nearest legal setting. The constant is
0.05f32, whose exact value is 0.05000000074505805969, and the
comparison is against a subtraction whose result depends on which side
of its decimal value each f32 literal rounded to.
Measured
Both functions were transcribed verbatim into a scratch binary and run
under rustc -O rather than reasoned about on paper:
| Setting | −0.05 edge | diff | +0.05 edge | diff |
|---|---|---|---|---|
| 0 °C | accepted | 0.05 |
accepted | 0.05 |
| 1 °C | rejected | 0.050000012 |
accepted | 0.049999952 |
| 2 °C | accepted | 0.049999952 |
accepted | 0.049999952 |
| 4 °C | accepted | 0.049999952 |
rejected | 0.05000019 |
Six of eight edges are accepted, and the two rejections fall on
opposite sides — the low edge at 1 °C, the high edge at 4 °C. No
single description of the band is correct for all four settings.
So a caller asking for 0.95 °C of hysteresis gets InvalidInput, while
one asking for 1.05 °C gets Hysteresis::OneC. Both are the same
distance from 1 °C as written; only their f32 representations differ.
Status
Pinned as measured by
ops_tests::hysteresis::the_band_edges_are_asymmetric, added while
closing #66, so any change to it is deliberate rather than silent.
Whether it should change is this issue.
Note the ±0.05 °C band is driver policy, not a datasheet tolerance —
SBOS663A §7.5.3.1 Table 9 specifies the four discrete encodings and
says nothing about how an arbitrary float should reach one. #66 Part 2
records the band as a legal choice.
Options
Roughly in increasing order of disruption:
- Leave it. Document the band as approximate. A caller sitting
within 0.05 °C of an edge is already asking for a setting it did not
name, and the four settings are 1 °C apart. - Compare against the midpoint between adjacent settings, or
against a tolerance scaled per setting, so the decision does not
turn on one constant's representation. - Make the comparison inclusive with slack — e.g.
>against
HYSTERESIS_TOLERANCE + f32::EPSILON, making all eight edges
accept.
Any of 2 or 3 changes behaviour for callers currently on the rejected
side of an edge, so it needs a changelog-visible commit.
Provenance
Raised while closing #66. Not a regression — the behaviour predates
that work; it was simply never asserted.
- 主要言語
- Rust
- スター
- 2
- フォーク
- 7
- PR マージ指標
- 30日以内にマージされた PR はありません
環境構築
- Dockerfile・Docker Compose ファイルなし
- プルリクエストのテンプレートなし
- コントリビューションガイドを読む
はじめの一歩
- issue を最後まで読み、次にプロジェクトのコントリビューションガイドを読みます。
- 着手することを issue にコメントします — 二人が同じ作業をするのを防げます。
- リポジトリをフォークし、ブランチを切って変更します。
- issue 番号を参照したプルリクエストを送ります。
OpenDevicePartnership/tmp108 のほかの issue
-
audit:SBOS663A bug impact:field-visible
難易度 2/5 1〜3時間 初心者へのやさしさ 84/100
-
audit:SBOS663A bug documentation impact:field-visible verdict:contradicts
難易度 1/5 1時間未満 初心者へのやさしさ 95/100
-
audit:SBOS663A bug enhancement impact:documentation
難易度 3/5 1〜2日 初心者へのやさしさ 74/100
-
audit:SBOS663A impact:latent question verdict:unsupported
難易度 4/5 3〜5日 初心者へのやさしさ 25/100
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