The staged interactive-edit latency bench: reduce / engrave / scene-build /
paint measured separately, gating the core's portion against
req:perf:single-system-edit-latency's 16.7 ms frame. Criterion 2 asserts that a
toolkit verdict is uninformative while reduction dominates, and that sentence
had never been measured; the sequencing question it governs -- T4's spike now,
or T4b's incrementality first -- was resting on it.
The stage split is not invented here. It is the seam EditorSession::materialize
already walks, read off its private render_score and reproduced stage for
stage, so the bench measures the pipeline rather than a model of it. Only reduce
and engrave are gated: the requirement bounds "the core's portion" and says in
its own words that edit-to-pixel latency is a product-layer obligation, so
charging the SVG serializer and resvg against a core budget would be a category
error. They are measured and printed because the ruling asks for the stages
separately, and because today's is the path Ruling A demotes -- the number is
the baseline a canvas must beat, not a budget to defend.
Four findings, in the order they matter. Reduce is the only stage that scales
with log depth, near-linearly, and it breaks the frame at roughly ten thousand
edits -- 17.26 ms against 16.7, a three percent miss, so an order of magnitude
rather than a threshold. Engrave is flat and small at ~280 microseconds, and at
shallow depth it is the larger half of the core's portion, which qualifies
criterion 2 rather than confirming it: reduction does not dominate until about
depth five hundred. Paint is the largest single cost at every realistic depth --
2.12 ms at depth one hundred is four and a half times the entire core portion.
And scene-build is 3.5 microseconds of IR work plus about 130 of SVG
serialization, which the no-feature run separates: a canvas consuming the IR
directly skips some ninety-eight percent of today's per-edit cost, none of it in
the core.
The sequencing answer is therefore that T4 before T4b stands, for the opposite
reason to the one assumed. The dominant cost at the depths real sessions reach
is the render path Ruling A already demoted, not reduction. T4b's trigger is a
session ten thousand edits deep, and the bench now watches for it as the one
Xfail row.
Two things the bench had to survive being wrong about, both mine. The depth-1000
row was drafted Xfail on the assumption Fact 8 would already bite; it passes
with eightfold margin, the gate's XPASS notice said so, and the row is promoted
here rather than left stale -- which is the whole point of that mechanism. And
the first edit log alternated transposition direction per operation, which is
degenerate when the pitch-list length is even: every edit to a given pitch
pushed the same way, drifting it twenty-five semitones by depth 1000 and would
have been two hundred and fifty by depth 10000. That inflated engrave by a
factor of two and paint by nearly three -- a score-content change wearing a
log-depth costume. Alternating per pass instead bounds drift to one semitone.
The residual content effect is documented rather than hidden: paint is
non-monotonic in depth because pass-count parity decides how many accidentals
the score carries, and reading its dip at depth 10000 as a scaling win would be
a mistake.
Stated limitation: the testkit's largest fixture is three staves by ten
measures, so the engrave and scene-build columns are lower bounds and this
cannot prove the budget holds on the hundred-page orchestral score the
requirement contemplates. It shows where the time goes at the scale we can
build, and a row that misses at this size misses by more at a real one.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RSX4zSLgKvtiXaPjnMqLGz
The audit's fourth push: the biggest outstanding Phase-2 item plus the
performance gate. 793 workspace tests pass; clippy -D warnings, fmt,
and rustdoc (deny-warnings) clean; all three spec documents build with
zero undefined references.
Binary Format companion (spec/binary_format.tex, v0.1.0 — Agent J's
deliverable, 43 pages):
- Twelve chapters transcribed from the golden-locked implementation:
encoding conventions (the three prefix/endianness regimes, a
normative no-varint rule, reject-never-normalize decode discipline),
identifiers imported from the core spec's Canonical Byte-Layout
Reference, primitive value encodings, the whole-Score positional
codec ratified as the schema-major-0 wire form, operation wire
forms (envelope field order with the normative id-leads property,
the OperationPayload 0..=3 and OperationKind 0..=23 tables,
effects/conflict/anomaly/MaterializedState vocabulary), the bundle
physical layout (64-byte header, 256-byte superblock, chunk
preimages and framing, ChunkRef, manifest body order), the
operation-index payload, and the extension-blob/edit-barrier byte
forms.
- Ratifies P12-D1 (req:binfmt:opindex), P12-E1 (req:binfmt:ext-blobs),
P12-E2 (req:binfmt:condition-depth, MAX_CONDITION_DEPTH = 64
normative), and P12-E3 (req:binfmt:object-kind-open) — batch rows
struck through; discharges the provisional-codec notes in core
(P11-4), ops, and bundle (P11-D2/D4/D5) DECISIONS with ratification
cross-references.
- Pins the frozen-layout schema-evolution keystone: within schema
major 0 every positional struct layout is frozen; a field-set change
is a schema-major change with migration — formally grounding the
data-model-expansion staging decision. Open questions kept honest
in-document: SnapshotId derivation, index-refresh threshold, u64/u32
prefix unification at the next major.
- Not yet delivered from J's charter: the cross-implementation decoder
test and the wire-format fuzzer (follow-up harnesses).
F1 benches (crates/epiphany-testkit/benches/, per the F0 decision):
- criterion 0.5.1 (workspace dev-dependency; MSRV 1.77 respected with
documented transitive pins: clap 4.5.53, half 2.4.1).
- reduction bench at 1K/10K/50K envelopes with the Chapter-10 budget
(>10,000 envelopes/second cold) written in the bench as a Pass/Xfail
gate; bundle benches for the typical-edit commit (<=50 ms; measured
~14.7 ms on real disk after catching that tmpfs neuters fsync) and
the open/bootstrap read (<=200 ms; measured ~60 us).
- CI: quick budget gates in the conformance job, full gates nightly.
Subquadratic canonical_reduction_order (the F-surfaces/K-fixes
handshake, closing K's 10K-envelope acceptance gate):
- The bench documented the failure (50K at ~1.7K env/s, a 29 s cold
reduction; two O(n^2) loops); the fix replaces pair enumeration with
threshold/frontier readiness per replica plus explicit-dot dependent
lists and a stamp-tuple binary heap — O((n + sum(context)) log n),
never materializing covered pairs.
- Byte-identical order: same edge relation, same ready predicate, same
total order; the old implementation is retained as a test-only
oracle with element-for-element order-equality property tests over
fuzz sets, adversarial sets, and directed shapes (2,000-envelope
full-coverage chains, dot cycles, duplicate-id stamp ties),
mutation-tested for sensitivity.
- Measured: 1K 155K->674K env/s, 10K 12.5K->257K, 50K 1.7K->87K; all
three scale points now pass and the 50K row is promoted from Xfail.
Also: fixed nine rustdoc private/unresolved intra-doc links that had
accumulated across the pushes (the CI deny-doc-warnings job would have
failed on them).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NEs4aYiu8MXjdYdMxw8PTd
Levi Neuwirth