Extreme Software Optimization

The One Rule: Profile first. Prove behavior unchanged. One change at a time.

The Loop (Mandatory)

1. BASELINE    → hyperfine --warmup 3 --runs 10 'command'
2. PROFILE     → cargo flamegraph / py-spy / clinic flame
3. PROVE       → Golden outputs + isomorphism proof per change
4. IMPLEMENT   → Score ≥ 2.0 only, one lever per commit
5. VERIFY      → sha256sum -c golden_checksums.txt
6. REPEAT      → Re-profile (bottlenecks shift)

Opportunity Matrix

Hotspot	Impact (1-5)	Confidence (1-5)	Effort (1-5)	Score
func:line	×	×	÷	Impact×Conf/Effort

Rule: Only implement Score ≥ 2.0

Isomorphism Proof Template

For EVERY change, document:

## Change: [description]
- Ordering preserved:     [yes/no + why]
- Tie-breaking unchanged: [yes/no + why]
- Floating-point:         [identical/N/A]
- RNG seeds:              [unchanged/N/A]
- Golden outputs:         sha256sum -c golden_checksums.txt ✓

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Pattern Tiers (Quick Reference)

Tier 1: Low-Hanging Fruit

Pattern	When	Isomorphism
N+1 → Batch	Sequential fetches	Same results, fewer round-trips
Linear → HashMap	Keyed lookups	O(n)→O(1), order may change
Lazy eval	Maybe-unused values	Same final values
Memoization	Repeated pure calls	Cached = recomputed
Buffer reuse	Alloc per iteration	Zero-copy in loop

Tier 2: Algorithmic

Pattern	Change	Check
Binary search	O(n)→O(log n)	Sorted input
Two-pointer	O(n²)→O(n)	Structured input
Prefix sums	O(n)→O(1) query	Static data
Priority queue	O(n)→O(log n)	Top-k/scheduling

Tier 3: Data Structures

Structure	Use Case
HashMap	Point lookups
BTreeMap	Range queries
SmallVec	Usually-small collections
Arena	Many allocations, bulk free
Bloom filter	Membership pre-filter

Full catalog: TECHNIQUES.md

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Language Cheatsheet

Lang	CPU Profile	Trouble Spot Grep
Rust	cargo flamegraph	rg '\.clone\(\)' --type rust
Go	go tool pprof /debug/pprof/profile	rg 'interface\{\}' --type go
TS	clinic flame -- node app.js	rg 'JSON\.(parse|stringify)' --type ts
Python	py-spy record -o flame.svg -- python script.py	rg '\.iterrows\(\)' --type py

Full language guides: LANGUAGE-SPECIFIC.md

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Anti-Patterns (Never Do)

✗	Why
Optimize without profiling	Wastes effort on non-hotspots
Multiple changes per commit	Can't isolate regressions
Assume improvement	Must measure before/after
Change behavior "while we're here"	Breaks isomorphism guarantee
Skip golden output capture	No regression detection

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Checklist (Before Any Optimization)

• Baseline captured (p50/p95/p99, throughput, memory)
• Profiled: hotspot in top 5 by % time
• Opportunity score ≥ 2.0
• Golden outputs saved
• Isomorphism proof written
• Single lever only
• Rollback plan: git revert <sha>

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Tool Commands

# Benchmark
hyperfine --warmup 3 --runs 10 'command'

# Profile
cargo flamegraph                           # Rust CPU
heaptrack ./binary                         # Allocation
strace -c ./binary                         # Syscalls

# Verify
sha256sum golden_outputs/* > golden_checksums.txt
sha256sum -c golden_checksums.txt          # After changes

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References

Need	Reference
Complete technique catalog	TECHNIQUES.md
Step-by-step methodology	METHODOLOGY.md
Language-specific guides	LANGUAGE-SPECIFIC.md
Advanced (Round 2+)	ADVANCED.md

Iteration Rounds

• Round 1: Standard (N+1, indexes, batching, memoization)
• Round 2: Algorithmic (DP, convex, semirings) → ADVANCED.md
• Round 3: Exotic (suffix automata, link-cut trees)

Each round: fresh profile → new hotspots → new matrix.