lading-optimize-find-target - SKILL.md Agent Skill

name: lading-optimize-find-target description: Finds a valid optimization target in lading. Returns a filled target.yaml template with pattern, technique, target, file, bench, and fingerprint. Use before /lading-optimize-hunt or when selecting a new optimization target. allowed-tools: Bash Read Glob Grep context: fork

Phase 1: Discover Benchmark-Eligible Modules

A module is eligible if it has a Criterion benchmark in lading_payload/benches/.

List benchmarks: Glob lading_payload/benches/*.rs — each filename (minus .rs) is a bench name
Resolve sources: For each bench name, find the corresponding source file(s) under lading_payload/src/. Check single-file modules ({name}.rs), directory modules ({name}/), and parent-module patterns (e.g., opentelemetry_log → opentelemetry/log.rs)
Match fingerprints: Glob ci/fingerprints/*/lading.yaml — each directory name is a fingerprint. Match fingerprints to modules by reading the variant: key from each config

The result is a set of (bench, source_files, fingerprint_or_none) triples.

Phase 2: Profile Allocation Intensity

Run the profiling script:

.claude/skills/lading-optimize-find-target/scripts/profile-modules

Output is TSV: module, allocations, total_bytes, peak_live_bytes. Record per-module.

Phase 3: Learn from Past Optimizations

Read the optimization history to understand what techniques work and what's already done:

Read .claude/skills/lading-optimize-hunt/assets/db.yaml

For each entry, read its detail file (file: field, relative to .claude/skills/lading-optimize-hunt/) to extract:

Technique and measurements — which techniques yielded what % improvements
Lessons — what patterns were optimized and what the before/after looked like
Targets already covered — so you skip them

This history teaches you what to look for. Successful past techniques are strong signals for where to look next. The lessons field often suggests next targets explicitly.

Phase 4: Find Opportunities

Scan every benchmark-eligible source module for every known pattern below. This is an exhaustive cross-product — do not short-circuit after finding one hit.

Known Patterns

Name	Pattern	Technique
`vec-with-capacity`	`Vec::new()` + repeated push	`Vec::with_capacity(n)`
`string-with-capacity`	`String::new()` + repeated push	`String::with_capacity(n)`
`map-with-capacity`	`FxHashMap::default()` hot insert	`FxHashMap::with_capacity(n)`
`buffer-reuse`	`format!()` in hot loop	`write!()` to reused buffer
`slice-params`	`&Vec<T>` or `&String` parameter	`&[T]` or `&str` slice
`hoist-allocation`	Allocation in hot loop	Move allocation outside loop
`object-pool`	Repeated temp allocations	Object pool / buffer reuse
`borrow-not-clone`	Clone where borrow works	Use reference
`inline`	Hot cross-crate fn call	`#[inline]` attribute
`lazy-iterators`	Intermediate `.collect()` calls	Iterator chains without collect
`box-large-structs`	Large struct by value	Box or reference
`bounded-buffer`	Unbounded growth	Bounded buffer with `.clear()`
`scratch-buffer`	`encode_to_vec()` per call	Reusable `BytesMut` scratch buffer
`on-demand-serialization`	Deep clone of template in loop	Incremental mutation / COW

Procedure (must follow exactly)

Step 1 — Read source files. For each module's source file(s), Read the full file (excluding #[cfg(test)] blocks). Understand the data flow: what structs exist, how serialization works, where the hot path is, and what allocations occur.

Step 2 — Identify patterns. For each module, check whether any of the Known Patterns above apply. Record a hit matrix:

module × pattern → match count (0 = no hit)

Show the full matrix as a table. Every cell must have a value. Do NOT skip any combination.

Step 3 — Record opportunities. Each verified hot-path hit becomes an opportunity: (pattern, technique, target_function, file, module, allocations_from_profiling)

Phase 5: Filter

Remove any opportunity that:

Already in .claude/skills/lading-optimize-hunt/assets/db.yaml — same function + semantically equivalent technique already exists
No benchmark — module has no matching bench file in lading_payload/benches/

If zero survive, STOP: "No valid optimization targets found."

Phase 6: Rank

Sort by two dimensions:

Technique impact — techniques with measured history in .claude/skills/lading-optimize-hunt/assets/db.yaml rank higher (compute avg % improvement from measurements.benchmarks.macro). Unknown techniques rank last.
Allocation intensity — modules with higher allocation counts from profiling rank higher.

Sort by technique impact first, allocation intensity second. Tiebreaker: Prefer modules with no prior .claude/skills/lading-optimize-hunt/assets/db.yaml entries, then alphabetical file name.

Show sorted results in a table.

Phase 7: Return Result

Pick the top-ranked opportunity. Return as a fenced YAML code block. Do NOT write to disk. Do not include intermediate tables, matrices, or analysis.

pattern: "<description of the code pattern found>"
technique: "<pattern name / optimization technique to apply>"
target: "<Module::function>"
file: "<relative path to source file>"
bench: "<relative path to Criterion benchmark .rs file>"
fingerprint: "<relative path to fingerprint lading.yaml config, or null>"