c3b67f45bd
Song separation went from not computable — the reference sat below the floor — to 0.38, with the floor falling from 0.1449 to 0.1185 and the gap widening. Every structural block moved: scale 40 to 59%, orient 65 to 89%, layout 60 to 111%, texture 89 to 81%, motion 53 to 65% of the reference. Container variety rose throughout, 0.0557 to 0.0815 to 0.0901, which is the stop condition holding: the library did not homogenise as it converged on shared content. Coupling did not move and is recorded as such. Whether a song looks different in proportion to how it sounds different is still unsolved, and the migration was never aimed at it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
249 lines
8.9 KiB
Markdown
249 lines
8.9 KiB
Markdown
# Migrating a scene onto the identity artifacts
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The recipe `tools/migration-status.js` reports progress against. Sixty-one
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scenes is too many to convert from taste, so this is written to be followed
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mechanically and to produce the same result twice.
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Background is EPIC-3.md. The one-line version: a scene draws its own content, a
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migrated scene draws the *song's* content — its cast, in its ink, on its lattice
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— and the measured payoff is additive with everything the scene already did.
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```bash
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node tools/migration-status.js # the queue, and what each scene needs
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node tools/migration-status.js --all # every scene and its tier
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```
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---
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## The rule that decides everything
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> **An artifact is content a scene could not have invented for itself.**
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If the scene still looks right with the identity switched off, it has used the
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artifact as a modifier and the migration has not happened. That is not a style
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preference — it is the exact failure mode of `u_sigSides`, which thirty scenes
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declare and most quietly ignore, and it is why the gate below exists.
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---
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## The four tiers
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The classifier assigns these from the shader source. Check its answer, don't
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trust it: it reads patterns, and a scene that places elements in an unusual way
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will be misfiled.
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| tier | what it looks like | consumes |
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|---|---|---|
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| **drawn** | loops over discrete elements at computed positions | `cast, ink, staging` |
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| **figure** | one or a few forms, its own composition | `cast, ink` |
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| **field** | a continuous surface — noise, flow, terrain | `ink` |
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| **treatment** | an effect over an image rather than an image | `ink` |
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Accents are excluded. They are mostly-empty depth passes, not subjects.
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---
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## Recipe: `drawn`
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The highest payoff and the least invention. Four edits.
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**1. Declare it.** Add to the module, above `params`:
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```js
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consumes: ['cast', 'ink', 'staging'],
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```
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**2. Replace the primitive with the cast.** Whatever the loop was drawing —
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a circle, a box, `sigShape`, a bespoke SDF — becomes one of:
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```glsl
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float d = castMain(q) * size; // the protagonist: large, few
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float d = castChorus(q) * size; // the chorus: small, many
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```
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`q` is the element-local coordinate, `(p - pos) / size`. Multiplying the result
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back by `size` restores it to scene units, which is what the ink expects.
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Use `castMain` when the scene draws a handful of things and `castChorus` when it
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draws a crowd. A scene that draws both should use both — that is what the two
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members are for.
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**3. Replace the placement with the lattice.**
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```glsl
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vec3 node = stageNode(fi, float(u_count)); // xy position, z scale multiplier
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vec2 pos = node.xy;
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float size = u_size * node.z;
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```
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Keep whatever the scene did that was *motion* — a drift, an orbit, a wander, a
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march. Give up what was *composition*. The split is the point: identity owns
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where things are, the scene owns what they do.
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A scene whose composition IS its identity — a spiral that must be a spiral — can
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keep it and take `stageScale()` alone, which is the song's element size. Declare
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`staging` either way.
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**4. Replace the edge with the ink.**
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```glsl
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col = mix(col, pal(i + 1), inkMask(d, uv));
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```
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`inkMask` does fill, fill treatment (hatch, stipple, halftone), outline and edge
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hardness in one call. Delete the scene's own `smoothstep(soft, -soft, d)` and
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its `sigEdge` — the ink supersedes both.
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Then wrap the return:
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```glsl
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return vec4(inkValue(col), 1.0);
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```
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**Do not** delete `sigCamera`, `sigGrain`, `sigHorizonY` or `sigAir`. Traits and
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artifacts are different layers and both still apply.
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---
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## Recipe: `figure`
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Steps 1, 2 and 4, skipping the lattice. Declare `consumes: ['cast', 'ink']`.
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Take `stageScale()` if the figure has a size worth scaling and add `staging` if
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you do.
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---
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## Recipe: `field` and `treatment`
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There are no elements to replace, so this is one edit plus a judgement.
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```js
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consumes: ['ink'],
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```
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```glsl
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return vec4(inkValue(col), 1.0);
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```
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If the field already dithers, hatches or posterises internally, replace that
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with `inkPattern(uv)` so the treatment is the song's rather than the scene's.
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If it does not, `inkValue` alone is the whole migration — a value structure
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shared across every scene in a video is worth having and costs one line.
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Be honest about `treatment` scenes. Most of them are effects wearing a scene's
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clothes, and EPIC-3 §8 argues they should move into the identity's EFFECTS
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register rather than compete for screen time as subjects. Migrating one is a
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holding action, not the answer.
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---
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## Verifying — the part that makes this reproducible
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A migration is not done when the code looks right. It is done when the gate
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passes:
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```
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checks.html?scene=<Scene%20Name>
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```
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Every artifact in `consumes` must show a passing line:
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```
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PASS consumes: cast delta 255/255 (floor 24)
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PASS consumes: ink delta 255/255 (floor 24)
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PASS consumes: staging delta 255/255 (floor 24)
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```
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That check renders the scene twice under two deliberately distant identities and
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requires the picture to change. A scene that declares `cast` and ignores it
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fails here, which is the only reason `consumes` can be trusted at library scale.
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`npm run lint:scenes` enforces the other half in both directions: declaring an
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artifact without calling it, and calling one without declaring it. The second
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matters more than it looks — an undeclared artifact hides the scene from this
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report and from anything that later selects scenes on capability.
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Then the usual battery still applies. `renders something`, `animates`,
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`deterministic`, `distinct`, `param sweep`, `flash rate` and every declared
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trait must all still pass. A migration that breaks `distinct` has made the scene
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into one of its neighbours, which is a real risk here: the more scenes share a
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cast, the more two weakly-composed ones converge.
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---
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## Measuring the payoff
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Per scene, the gate. Across the library, two numbers:
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```
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checks.html?decompose=1 identity against container, measured apart
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checks.html?experiment=1 stages against legacy, with error bars
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```
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`decompose` is the one to watch. Before the migration, over the four purpose-
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built stages:
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```
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identity only 0.0299 container only 0.0557 identity = 54% of container
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```
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After the first eighteen scenes, over the eight that consumed the cast:
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```
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identity only 0.1287 container only 0.0815 identity = 158% of container
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```
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Complete, over all thirty-two:
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```
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identity only 0.1054 container only 0.0901 identity = 117% of container
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```
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The number that matters in that row is `container only`, which went 0.0557 →
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0.0815 → 0.0901 as the migration progressed. That is the stop condition below
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holding: the library did not homogenise. `identity only` is noisier than it
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looks because the scene it probes is picked from the migrated set and changes
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between runs — Constellation, then Metaballs, then Floating Geometry — so read
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it as "comparable to the container" rather than as a precise ratio.
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End to end, song variety across twelve songs before and after the epic:
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```
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floor observed separation
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before 0.1449 0.1508 not computable (the reference sat below the floor)
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after 0.1185 0.1376 0.38
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```
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The floor fell and the gap widened, which is both halves of what the inversion
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was supposed to buy. Every structural block moved with it — scale 40→59%,
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orient 65→89%, layout 60→111%, texture 89→81%, motion 53→65% of reference.
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Coupling did not move: -0.09, still indistinguishable from zero. Whether a song
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LOOKS different in proportion to how it SOUNDS different remains unsolved, and
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nothing in the migration addressed it.
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Read that with its caveat: the stage set changed underneath the measurement, so
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part of the jump is that Metaballs expresses a cast more strongly than
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Constellation did rather than that the migration itself moved anything. What it
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does establish is the thing worth knowing — a migrated LIBRARY scene carries the
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identity better than a stage written from scratch to carry it. The bespoke
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stages were the wrong shape of effort. As scenes migrate, the
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`identity only` number should climb while `container only` holds — because the
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whole point of the correction in EPIC-3 §9b is that these add rather than trade.
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If `container only` falls as scenes migrate, the migration is homogenising the
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library and should stop.
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---
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## A caution learned the expensive way
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This harness's noise floor is large enough to invent findings. Three claims in
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this epic were made from single runs and withdrawn after repeats: that roster
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size was the dominant lever, that stages beat legacy by 14%, and that the
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identity's range was the bottleneck. Anything under about 0.01 of spread needs
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`&repeats=3` before it is believed, and a difference that changes sign with the
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sample size is not a difference.
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Migrate in batches, measure after each batch, and expect the per-batch effect to
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be inside the noise. The trend across batches is the signal.
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