`HistoryBuilder::online(true)` is inert: it flips a flag that reaches
`Item::within_prior`, which reads `Skill.online` — a field initialised to
`N_INF` and assigned nowhere. So `log_evidence()` under that setting reports
`n * ln(0.5)`, every game scored as a coin flip. The number is finite and
plausible, which is why nothing caught it.
Issue #19 proposed populating the field during the forward pass. That does
not work, and the reason shapes the whole design. `new_forward_info` sets
`skill.forward` from the previous slice's `forward_prior_out`, which is
`skill.forward * skill.likelihood`; `History::iteration` alternates backward
and forward sweeps, so from the second iteration onward that likelihood has
already absorbed backward information. After `converge()`, `skill.forward`
is a smoothed quantity — and so is anything written from it.
The same reasoning condemns the neighbouring `forward: bool` flag, which is
a filtering quantity only on a history that was never converged. That is why
the test at history.rs:1183 can assert the two evidences are equal. Left
alone here; recorded as a follow-up.
The design is a read-only forward-only pass instead: walk slices in time
order carrying their own forward messages, and per slice build a scratch
clone whose `backward` is `N_INF`, then run the unmodified production sweep
on it. Reusing `iterate_to_convergence` rather than reimplementing inference
means a competitor playing twice at one time is handled by the same
within-slice EP that `converge()` uses, instead of being approximated the
way today's evidence paths approximate it. Nothing is stored on `Skill`,
which drops 16 bytes and helps #17 regardless.
Three methods ship — `filtered_log_evidence`, `filtered_learning_curves`,
`filtered_learning_curve` — all taking `&self`. The second consumer is
ustat, whose learning curves start already collapsed to sigma 0.9-1.6
against a prior of 6.0 because every point is smoothed; the filtered view
cannot be reconstructed from the public API today except by O(n^2) refits.
The red test brackets the issue's own fixture strictly between 5*ln(0.5) and
the batch evidence, so neither "still inert" nor "accidentally smoothed"
passes. The invariant that would have caught this bug class is that filtered
results are identical before and after `converge()` — exactly what a stored
field cannot give.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T5SYDExxL4vZgvunrcNSMc
Outcome::Scored becomes a struct variant with an Option<f64> sigma
field. None inherits HistoryBuilder::score_sigma; Some(s) overrides
per event. Resolved at ingest time so EventKind::Scored stays a plain
f64 and TimeSlice/run_chain need zero changes. New constructors
Outcome::scores_with_sigma and EventBuilder::scores_with_sigma cover
the override path; existing scores(..) keeps its signature with
sigma=None internally.
Breaking change to Outcome::Scored variant shape (tuple → struct);
acceptable in 0.1.x. Closes the last item from the T4-MarginFactor
deferred wishlist.
Closes the gap between HistoryBuilder::convergence(opts) and the
within-game inference loop. TimeSlice gains a convergence field;
History passes self.convergence at construction; the three
Game::*_with_arena callsites in time_slice.rs read it. Also renames
TimeSlice::convergence the method (now iterate_to_convergence) to
disambiguate from the new field.
Pure plumbing — no new public API, no behavioral change for users on
default options. Makes Damped EP reachable through the History path.
Smallest-scope realisation of spec §"Built-in schedules" Damped: a
ConvergenceOptions::alpha field plumbed through run_chain to a new
Gaussian::damp_natural helper applied inside TruncFactor and
MarginFactor's propagate. alpha=1.0 default keeps every existing
golden bit-equal; alpha<1.0 stabilises oscillating fixed-point loops
on hard graphs.
Defers Schedule trait integration, nat-param convergence switch,
oscillation auto-detect, Residual/OneShot, and Synergy/ScoreFactor —
each gets its own future plan.
Three independent cleanups: dedupe Game::likelihoods and likelihoods_scored
via a run_chain helper taking a make_link closure, make BuiltinFactor's
log_evidence match exhaustive, and fix stale numerics in the T4 plan doc.
logaritmiskandClaude Opus 5