alpha-evolve

Alpha-Evolve

Reference (read if you need the algorithm's details): AlphaEvolve — https://arxiv.org/abs/2506.13131 · OpenEvolve (open-source impl) — https://github.com/algorithmicsuperintelligence/openevolve

A population-based evolutionary loop over a program. The artifact is the editable model code; a child is one analysis-informed SEARCH/REPLACE diff to a parent, and the feedback signal is a cascade-evaluated training run (<metric>, smoke→full). Children are placed in a MAP-Elites archive across islands (complexity × diversity axes), so a child survives by being either better or more novel, not just better. The discipline this enforces: diversity is preserved, not collapsed — diverse high performers co-exist instead of one local optimum winning. You are the controller: sample a parent + inspirations, spawn parallel Mutators to propose and evaluate children, place them, migrate between islands, checkpoint. Loops to a fixed compute budget or until interrupted.

When to use

Use this for parallel, diversity-preserving search over a model/program where many variants explore at once and the archive keeps the illuminated frontier. Default to broad island coverage; if quality stalls, bias selection toward exploiting top elites; if coverage stalls, bias toward empty cells. Not for the sequential autoresearch loops (one change at a time), and not for fixing a known anomaly.

The cast (both in this folder): roles/Mutator.md produces + cascade-evaluates one child (the generation step); schemas/result.schema.json is the result a Mutator returns.

Setup

Resolve bindings interactively. If loop.run.yaml exists in the working dir, load it, confirm the values in one line, and skip to the loop. Otherwise: on Claude Code (the AskUserQuestion tool is available, <host> = claude-code) infer a likely value for each binding and present it as the recommended option; on other hosts (<host> = other) ask each as a quoted plain-text prompt. Then write loop.run.yaml (format: examples/run.example.yaml) and confirm the values before creating any other files. <host> also decides execution: Claude Code spawns real Agent Mutators in parallel (capped at <concurrency>); other hosts degrade to running a generation's children serially (identical algorithm).

Probe the box first (mandatory — measure, never assume <concurrency>). Record and report:

• CPU cores → <cores>: python3 -c "import os; print(os.cpu_count())".
• RAM → <ram_gb>: macOS sysctl -n hw.memsize; Linux grep MemTotal /proc/meminfo.
• Accelerator → <accelerator>/<vram>/<gpu_count>: nvidia-smi --query-gpu=name,memory.total,count --format=csv (NVIDIA); else macOS Apple GPU/MPS; else CPU-only.

binding	meaning	default	how to infer
<metric> + <metric_direction>	scalar to optimize; min/maximize	—	ask; scan eval output for the reported metric
<run_cmd> / <entrypoint>	command for one training run (the evaluator)	—	pyproject.toml/.venv/uv/README
<editable_files>	the program being evolved (e.g. model.py, config.yaml); never the harness or data	—	ask explicitly — this is the code that gets mutated; do not default it (multi-select on Claude Code)
<sandbox_root>	where lae/ is created	./sandbox	—
<gate> + <budget>	one full run's size: time/epochs + amount; the FIXED eval budget applied to every program	—	identify the duration key now (e.g. train.epochs) so the controller can override it
<total_budget>	total compute = number of full training runs (or wall-clock minutes); the single cost dial	—	ask
<concurrency>	parallel evaluations C	derived from the probe	CPU-only → max(1, <cores>//4); single GPU/MPS → 1 (ask if more fit <vram>); multi-GPU → <gpu_count> (pin one child/GPU)

num_generations is derived: ceil(<total_budget> / <concurrency>). The cascade is derived from <budget> (not asked): smoke = ~1 epoch / a small subset, full = <budget>, gate = child's smoke <metric> ≥ parent's smoke. <budget>/<metric>/eval split are FIXED — never mutation targets (a child may not "train longer" to look better); changing them means re-running the whole loop.

Advanced (opt-in). Ask one yes/no: "Use defaults for the evolutionary settings, or customize?" Defaults are faithful to AlphaEvolve/OpenEvolve — use them and ask nothing more. Only on "customize" ask for each (showing the default as recommended): num_islands (4), num_top (3), num_diverse (2), num_bins (10), migration_interval (5), diversity_reference_size (10), pop_per_island (40), seed (42). Axes are fixed: complexity × diversity. See examples/run.example.yaml for the shape.

Print the resolved bindings + the probe + derived num_generations, and do not create files or launch until the user confirms. Then initialise the sandbox (header rows only; programs/ is created as children are evaluated):

<sandbox_root>/lae/
├── archive.tsv     ← current elites = program database + checkpoint
├── history.tsv     ← append-only record of every child
├── leaderboard.md  ← rendered UI
└── programs/       ← one self-contained dir per program

The controller (loop)

You maintain num_islands MAP-Elites maps in archive.tsv, the append-only history.tsv, running per-axis percentile stats, and leaderboard.md. You are the sole writer of all shared logs — Mutators only return results, so there are no write races. Copy this checklist and tick items off:

• Setup done: probe recorded, bindings confirmed, sandbox initialised, num_generations derived.
• GEN 0 — in each island, create the baseline program (a copy of <editable_files>) + optionally a few stochastic variants; cascade-evaluate; place in the archive.
• Per generation: build EXACTLY <concurrency> tasks (round-robin island, seeded-rule parent, top num_top + num_diverse most-diverse inspirations); make each child dir by copying the parent program + harness.
• Run the C Mutators (spawn-or-degrade), each with roles/Mutator.md, parent code, inspirations, parent artifacts, its child dir, and the smoke/full budgets.
• For each returned child: append a history.tsv row; if evaluated, compute its niche → cell and place it in the island map iff <metric> is better (kept=y); record smoke_dropped/crash without placing.
• Re-render leaderboard.md; checkpoint (archive.tsv is the checkpoint); print a status line.
• Every migration_interval generations: ring-migrate top elites island k → k+1.
• Stop at <total_budget> (reserve a little for synthesis), then synthesize the final report.

Niche computation (you do this, from a child's sandbox):

• complexity = trainable param count (fallback: total LOC of the editable files + any files the child added), log10-scaled.
• diversity = average normalized edit distance of the program's concatenated code (editable + added files) to a random sample of diversity_reference_size programs from its island (vs the baseline if the island is near-empty). Higher = more novel.
• Normalize each axis with running ~5th/95th percentiles (not raw min/max, so one outlier can't collapse the range): scaled = clamp01((v − p5)/(p95 − p5)); bin = min(num_bins−1, int(scaled × num_bins)); cell = (complexity_bin, diversity_bin). Re-bin existing elites when a percentile shifts enough to move an edge (keep the higher <metric> on collisions; the archive is small).

The Mutator's prompt (the sampler): parent code + inspirations + the parent's rendered artifacts (<metric>, per-class accuracy, loss curve, stderr) + the instruction to return one SEARCH/REPLACE diff. Single harness model — no LLM ensemble. The Mutator applies its diff in the child dir, cascade-evaluates at the FIXED <budget> (the controller injects/caps the duration key on the run command), and returns a result validated against schemas/result.schema.json:

{"child_id": "g3-i1-a2", "parent_id": "g1-i1-a0", "approach_summary": "add BatchNorm after conv2",
 "sandbox_path": "<sandbox_root>/lae/programs/g3-i1-a2", "status": "evaluated",
 "smoke_metric": 0.61, "metric": 0.71}

status ∈ {evaluated, smoke_dropped, crash}; metric is null unless evaluated. Mutators compute nothing about the archive — the controller derives every niche from the sandbox.

Program sandboxes. A parallel population doesn't map onto branches, so every program is a self-contained, fully-runnable dir <sandbox_root>/lae/programs/<child_id>/; the archive references it by id. Build each child dir by copying real files (the parent's <editable_files>, then apply the diff, plus the harness/entrypoint code it imports) and evaluate from inside it (cd <child_dir> && <entrypoint>). Symlink only large read-only data, never the entrypoint or any imported .py: Python resolves a symlinked script's __file__ to the link target, so sys.path[0] becomes the original dir and the child's model.py/dataset.py are silently shadowed by the baselines — every architecture/data mutation becomes a no-op (tell-tale: identical loss curves across different "architectures"). Isolation sanity gate: the harness logs the param count / a code fingerprint; flag any child whose code changed but whose metric/loss curve is identical to its parent's (shadowed), and fix the sandbox before placing it. The repo working tree is never mutated.

Final synthesis. Report the global-best program + its lae/programs/<id>/ path, the illuminated complexity×diversity map (coverage + who won each region), per-island bests, and 2–3 notably diverse runners-up.

Ledger

All three logs live under <sandbox_root>/lae/, tab-separated, never commas in free text. The controller is the sole writer; resume from archive.tsv + history.tsv if interrupted.

archive.tsv — current elites + checkpoint. Header island cell metric child_id parent_id sandbox_path complexity diversity:

island	cell	metric	child_id	parent_id	sandbox_path	complexity	diversity
0	(2,7)	0.7100	g4-i0-a1	g2-i0-a3	lae/programs/g4-i0-a1	2.1M	0.71

history.tsv — every child, append-only. Header gen island parent_id child_id smoke_metric full_metric status kept cell:

gen	island	parent_id	child_id	smoke_metric	full_metric	status	kept	cell
4	0	g2-i0-a3	g4-i0-a1	0.61	0.71	evaluated	y	(2,7)
4	1	g2-i1-a0	g4-i1-a2	0.40	-	smoke_dropped	n	-

leaderboard.md — re-rendered each generation: global best + per-island coverage + the archive ranked by <metric>. Report the best program at stop (not the last), the archive coverage, and a few diverse runners-up. Leave lae/ untracked.

Constraints

• A child works only inside its own lae/programs/<child_id>/ dir — it may edit the copied <editable_files> and create new files there, but never modify any file outside it (the repo, the read-only harness, the data, other programs' dirs are ground truth or shared state).
• The controller is the sole writer of archive.tsv/history.tsv/leaderboard.md, so parallel Mutators never race on the logs.
• <concurrency> comes from the probe + the user's confirmation — never assume the box; pin one child per GPU on multi-GPU; if a run OOMs/thrashes, lower C and say so (don't rewrite a child's config to fit), because the box's limit is real and rewriting the child corrupts the comparison.
• <budget> (epochs/time), <metric>, and the eval/test split are FIXED and out-of-bounds for mutation. The controller injects <budget> on every run, overriding any duration the child set — so "train longer" / change-the-metric / change-the-test-set can never win. Evolve the model/optimizer/data pipeline, not the compute or the scoring; comparability across programs depends on it.
• Never symlink the entrypoint or any imported .py into a child dir (it shadows the child's code via sys.path[0]); copy harness code, symlink only data, and run the isolation sanity gate before placing a child — a shadowed result is a phantom.
• Do not install new packages or modify the evaluation harness — <metric> is ground truth.
• Do not pause to ask "should I continue?" Run until <total_budget> (reserving a little for synthesis) or interrupt; if coverage stalls bias toward empty cells, if quality stalls exploit top elites. A child that overruns its gate is killed and recorded as crash.