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fix!: apply competitor configuration whenever it is supplied

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`Member::with_prior` and `with_drift_scale` were consumed only on the
branch that *creates* a competitor — `priors.remove` sat inside
`if !self.agents.contains(..)`. Supplying either for a key the history
already knew did nothing at all: no error, no warning, and output
computed from the default prior. A prior applied on a competitor's very
first event and was silently discarded ever after.

Configuration now applies whenever supplied. Two details this forced:

Configuration is tracked per *field* rather than as a merged `Rating`.
A member setting only `drift_scale` must not also assert the default
prior, or it would silently undo a prior seeded on an earlier event.

Slice state has to be refreshed. `drift_scale` is re-derived on every
forward pass, but a prior is written into the competitor's earliest
slice once, at ingestion, and `iteration` refreshes only slices after
the first. Without the refresh a late prior would reach the drift terms
and nothing else — a subtler version of the drop being fixed. This was
caught by a test, not by reading the code.

Conflicting values for one competitor within a single batch are now
`ConflictingCompetitorConfig` rather than resolved by iteration order.
Events in a batch are unordered, so "last one wins" would make the
result depend on traversal — and `tests/ingestion_equivalence.rs` exists
to rule exactly that out. Repeating the same value stays inert, which is
the shape callers get when configuration is a property of the domain.

That invariant turned out to be tested only for *unconfigured*
competitors: every helper in that file built members with `Member::new`.
Extended to cover configured ones, including a check that configuration
changes the fit at all, so the order tests cannot pass vacuously.

`with_prior` had no coverage under `tests/` whatsoever, which is how
this survived. Adds `tests/competitor_config.rs`.

`drift_scale_is_ignored_after_first_appearance` asserted the old
behaviour and now asserts the new one. It was written as a deliberate
change-detector — "moving the capture would be a visible break, not a
silent one" — so it inverted rather than being deleted.

Also removes `InferenceError::ConvergenceFailed` and `NegativePrecision`,
which no code path ever constructed: public variants advertising failure
modes no caller could observe. Partial #20 — its other items were
already resolved, except `Outcome::winner` still panicking.

BREAKING CHANGE: `prior` and `drift_scale` now take effect for
competitors the history already knows, where they were previously
ignored; a batch supplying conflicting values for one competitor is now
an error. `InferenceError::ConvergenceFailed` and
`InferenceError::NegativePrecision` are removed.

Closes #10. Refs #20.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011hcFjNDmHXZF8URGLku5zZ
This commit is contained in:
logaritmisk
2026-09-07 15:42:31 +02:00
co-authored by Claude Opus 5
parent 7341669d1a
commit 8c087ad015
6 changed files with 534 additions and 55 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tests/drift_scale.rs
+112 -15
View File
@@ -341,13 +341,20 @@ fn zero_scale_pins_a_competitor_in_the_filtered_pass() {
);
}
/// `drift_scale` is competitor configuration captured at first appearance, the
/// same as `prior` — a later `with_drift_scale` on a key the history already
/// knows is ignored. This guards that decision rather than driving it: the
/// behaviour falls out of where the capture happens, and the point of the test
/// is that moving the capture would be a visible break, not a silent one.
/// `drift_scale` is competitor configuration, and configuration supplied for a
/// competitor the history already knows is now *applied* rather than dropped.
///
/// This test previously asserted the opposite. It was written as a deliberate
/// change-detector — "moving the capture would be a visible break, not a silent
/// one" — and that is exactly what happened: the capture moved, and the
/// assertion inverted rather than being deleted.
///
/// Because configuration lives on the competitor and `converge` refits from
/// competitor state, a late pin applies to the *whole* history, not just to
/// events after it. So a scale set on the second batch must reach the same fit
/// as one set from the very first event.
#[test]
fn drift_scale_is_ignored_after_first_appearance() {
fn drift_scale_applies_when_set_after_first_appearance() {
let mut late = History::builder()
.mu(25.0)
.sigma(25.0 / 3.0)
@@ -368,7 +375,7 @@ fn drift_scale_is_ignored_after_first_appearance() {
}])
.unwrap();
// Second batch asks for a pin. Too late: the competitor already exists.
// Second batch asks for a pin. No longer too late.
late.add_events(vec![Event {
time: 1000,
teams: smallvec![
@@ -380,23 +387,113 @@ fn drift_scale_is_ignored_after_first_appearance() {
.unwrap();
late.converge().unwrap();
let ignored = curve(&late, "anchor");
let drifting = curve(&fit(distant_pair(None), 25.0 / 300.0), "anchor");
let applied = curve(&late, "anchor");
let pinned_from_the_start = curve(&fit(distant_pair(Some(0.0)), 25.0 / 300.0), "anchor");
let never_pinned = curve(&fit(distant_pair(None), 25.0 / 300.0), "anchor");
for ((t_l, g_l), (t_r, g_r)) in ignored.iter().zip(drifting.iter()) {
for ((t_l, g_l), (t_r, g_r)) in applied.iter().zip(pinned_from_the_start.iter()) {
assert_eq!(t_l, t_r);
assert!(
(g_l.sigma() - g_r.sigma()).abs() < 1e-9,
"a scale set after first appearance must be ignored, leaving the fit \
identical to one that never set it: t={t_l}, {} vs {}",
"a late pin should refit the whole history: t={t_l}, {} vs {}",
g_l.sigma(),
g_r.sigma()
);
}
let pinned = curve(&fit(distant_pair(Some(0.0)), 25.0 / 300.0), "anchor");
// And it must actually have done something.
assert!(
(ignored[1].1.sigma() - pinned[1].1.sigma()).abs() > 1e-6,
"sanity: the pinned fit must actually differ, or the assertion above is vacuous"
applied
.iter()
.zip(never_pinned.iter())
.any(|((_, a), (_, b))| (a.sigma() - b.sigma()).abs() > 1e-9),
"the pin had no effect at all — the silent drop is back"
);
}
/// Re-declaring the same configuration must be inert. This is the shape a
/// caller gets when the configuration is a property of the domain — "layouts
/// are static" — so every ingestion path repeats it on every event.
///
/// Both histories see exactly the same events; only how many times the scale
/// is declared differs.
#[test]
fn repeating_the_same_configuration_changes_nothing() {
let events = |declare_every_time: bool| {
let anchor = |first: bool| {
if first || declare_every_time {
Member::new("anchor").with_drift_scale(0.0)
} else {
Member::new("anchor")
}
};
vec![
Event {
time: 0,
teams: smallvec![
Team::with_members([anchor(true)]),
Team::with_members([Member::new("player")]),
],
outcome: Outcome::winner(0, 2),
},
Event {
time: 1000,
teams: smallvec![
Team::with_members([anchor(false)]),
Team::with_members([Member::new("player")]),
],
outcome: Outcome::winner(1, 2),
},
]
};
let once = curve(&fit(events(false), 25.0 / 300.0), "anchor");
let every_time = curve(&fit(events(true), 25.0 / 300.0), "anchor");
for ((t_l, a), (t_r, b)) in once.iter().zip(every_time.iter()) {
assert_eq!(t_l, t_r);
assert!(
(a.sigma() - b.sigma()).abs() < 1e-12,
"t={t_l}: declaring the same scale repeatedly changed the fit, {} vs {}",
a.sigma(),
b.sigma()
);
}
}
#[test]
fn a_batch_that_contradicts_itself_is_rejected() {
let mut h = History::builder().convergence(CONVERGENCE).build();
let err = h
.add_events(vec![
Event {
time: 0,
teams: smallvec![
Team::with_members([Member::new("anchor").with_drift_scale(0.0)]),
Team::with_members([Member::new("player")]),
],
outcome: Outcome::winner(0, 2),
},
Event {
time: 1,
teams: smallvec![
Team::with_members([Member::new("anchor").with_drift_scale(1.0)]),
Team::with_members([Member::new("player")]),
],
outcome: Outcome::winner(0, 2),
},
])
.expect_err("two different scales for one competitor in one batch");
assert!(
matches!(
err,
InferenceError::ConflictingCompetitorConfig {
field: "drift_scale",
..
}
),
"got {err:?}"
);
}