0.8.0 closed the sign-absorption defect at `HistoryBuilder::mu/sigma/beta`
and at both ingestion paths. It was still open one layer down, in the
constructors those paths call. Measured, all bit identical to their
positive counterparts:
Gaussian::from_ms(25.0, -8.33) == from_ms(25.0, +8.33)
Rating::new(_, -4.17, _) == Rating::new(_, +4.17, _)
ConstantDrift(-0.0833) == ConstantDrift(+0.0833)
sigma, beta and gamma enter only as squares, so the sign vanished without
comment. Worst of the set: `Rating::new(_, NaN, _)` reached `Game::ranked`
which returned **Ok** carrying `Gaussian { pi: NaN, tau: NaN }` — no
`converge` on that path to catch it.
`from_ms` and `Rating::new` now reject. `ConstantDrift` cannot: the field
is public and positional, so there is no constructor to intercept, and
sealing it would break every `ConstantDrift(x)` for a case whose resulting
model is perfectly valid. Documented instead. Its non-finite half IS
rejected — `converge` validates the drift variance each competitor
accumulates, which also covers a custom `Drift` impl.
Two things the tests caught that I had wrong:
NaN sigma must PASS `from_ms`. My first version rejected it, and two
existing tests went red immediately: a broken fit legitimately produces a
NaN sigma from `sqrt` of a negative truncated variance, and the design is
to propagate that to `NonFiniteResult`. Rejecting it turned the reporting
path into a panic inside inference. Written as
`sigma >= 0.0 || sigma.is_nan()` so the intent is explicit rather than
hidden in a negated comparison.
Very small sigma is also not rejected, and that is deliberate: `approx`
produces small truncated sigmas legitimately. `pi = 1/sigma^2` leaves
f64's range below ~1.5e-154 and `tau = mu*pi` overflows sooner, at a
threshold that depends on mu — so there is a band where pi is finite and
only tau is not. Both land on the existing point-mass representation.
Documented, including that such a Gaussian is not equal to itself and can
make two identical declarations report as conflicting.
BREAKING CHANGE: `Gaussian::from_ms` panics on a negative sigma, and
`Rating::new` panics unless beta is finite and non-negative. `converge`
returns `InvalidParameter` for a non-finite drift variance.
Closes#61
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011hcFjNDmHXZF8URGLku5zZ
The last three unvalidated setters, beside `p_draw`, `score_sigma` and
`convergence`, which all assert eagerly. Measured before choosing bounds:
beta = 0 -> works, pi 0.0211 (vs 0.0193 at the default)
beta = -4.17 -> bit-identical to +4.17
sigma = -8.33 -> bit-identical to +8.33
sigma = 0 -> NonFiniteResult, current_skill returns tau: NaN
sigma = inf -> same
mu = NaN -> same
So the bounds are not the obvious ones. `beta = 0` is legitimate and
meaningful — performance is then exactly skill, and the fit moves
measurably rather than degenerating — so zero is allowed and a test pins
that it reaches a different answer, since "allowed" would otherwise be
indistinguishable from "unchecked".
The negative cases are the quiet ones. `sigma` and `beta` enter inference
only as squares, so a negative value behaves as its absolute value and
the sign is dropped without comment. That is the same defect
`Member::with_drift_scale` already rejects, for the reason already
written there.
The non-finite cases are detected today — `converge` reports
NonFiniteResult — but a caller who reads `current_skill` first is handed
`tau: NaN`, so rejecting at the boundary is what actually closes it.
BREAKING CHANGE: `HistoryBuilder::mu`, `sigma` and `beta` now panic on
values they previously accepted, matching the existing behaviour of
`p_draw`, `score_sigma` and `convergence`.
Refs #18
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011hcFjNDmHXZF8URGLku5zZ
`Game::ranked` and `Game::scored` validated `p_draw` and `score_sigma`
but never `convergence`. `ConvergenceOptions` has public fields and
`GameOptions` carries one, so a caller could hand the engine a set that
`HistoryBuilder`'s eager asserts never saw. Past that, the only guard
was a `debug_assert!`, which is gone in the profile users ship.
An `alpha` of zero is the bad case, and it fails silently rather than
loudly. Measured in release before the fix:
likelihoods: [[Gaussian { pi: 0.0, tau: 0.0 }],
[Gaussian { pi: 0.0, tau: 0.0 }]]
Every EP update unapplied, every likelihood uninformative, inference
returning the priors it was given — and an `OwnedGame` that looks
entirely ordinary to the caller. `HistoryBuilder::convergence` already
documents exactly this hazard; the `Game` constructors just did not
share the check.
Adds `ConvergenceOptions::validate`, called by both constructors.
Rejects `alpha` outside `(0.0, 1.0]` and negative `epsilon`; NaN fails
both comparisons and is rejected too.
`tests/validation.rs` states the release-mode guarantee for the whole
public surface, not just this hole, and CI already runs the suite in
release. Probing the other conditions #18 lists found five of eight
already enforced — ties without a draw probability, per-event score
sigma, weight/team dimensions, draw-probability range, score-sigma
range — so this closes the remaining gap rather than the whole issue.
The engine keeps its `debug_assert!`s as invariant documentation.
Refs #18
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011hcFjNDmHXZF8URGLku5zZ
logaritmiskandClaude Opus 5