mirror of https://github.com/lightningnetwork/lnd.git synced 2026-08-18 13:07:58 +02:00

Olaoluwa Osuntokun aecc30e4a9 simulation: add evolved router champions and lab notebook

In this commit, we check in the artifacts of the first evolution
campaign. The champions directory holds the three GEPA-evolved routers,
all validated on sealed test sets and out-of-distribution corpora
against both the lnd production stack and the hand-written seed:
hb1 (hard-regime specialist), hb2 (superseded OOD sibling), and mx_c3
(the generalist with the best combined average). All are exploit-clean
and independently rediscovered a bimodal liquidity prior with per-edge
liquidity bounds in place of time-decayed penalties.

The lab directory is the running notebook: dated experiment writeups
(exp-001 through exp-007) covering the parameter-tuning null result, the
seed-beats-lnd baseline, the simulator integrity audit, the breakthrough
run, and the follow-up that produced the generalist, plus an ideas
backlog with the engineering learnings.

2026-07-24 13:01:06 -07:00

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Ideas Backlog

Unordered, mined during work. Promote to experiments when picked up.

Simulator fidelity

Liquidity models from real lncli querymc data (dijkstrasden's BalanceHints idea) instead of synthetic distributions.
Mainnet describegraph snapshot corpus entries (loader exists; needs a snapshot file + bigger sim budget).
In-flight HTLC modeling: concurrent shards currently settle sequentially; real MPP races liquidity.
Time model: mission control decay currently only sees wall-clock of the batch; inject a virtual clock so half-life params matter across scenarios.
Non-strict forwarding / parallel channels between the same pair.

Optimization

Backend shootout on the identical evaluator (the point of the new optimize_anything API): best_of_n as the honesty baseline, meta_harness (agentic proposer reads frontier history), and the adaptive scheduler that rotates backends on plateaus — vs our pinned engine="gepa". Note the agentic backends shell out to the claude CLI headless.
Tune bimodal scale_msat relative to median channel size of the graph rather than as an absolute — likely the single biggest win for the bimodal estimator on non-mainnet-scale nets.
Multi-objective via info["scores"] (success / attempts / fees as separate axes) so the Pareto frontier keeps specialists.
Seedless code-mode run (seed_candidate=None): let GEPA invent a router from the contract description alone; compare against evolved seed lineage.
Tournament: evolve N routers on different liquidity regimes, then score cross-regime for a generalist.
Feed mission-control replay data from a real node as a validation scenario class (out-of-distribution check for evolved params).

Free-parameter tuning beyond pathfinding (roasbeef 2026-07-24)

The same harness pattern (evaluator + GEPA) applies to other magic numbers in lnd once a scoreable simulator exists for them:

Payment session knobs already covered: attempt cost, min probability, estimator params, shard minimum.
DefaultShardMinAmt, BlockPadding, max parts defaults.
Mission control: result decay, second-chance logic thresholds.
Sweeper/batching params (needs a fee-market sim), gossip rate limits (needs a gossip sim) — candidates for future simulators following the routesim recipe.

Learnings from the overnight runs (2026-07-24)

Giant-seed reflection is slow and fragile. Seeding code_mix1 from the 872-line hb1 champion makes every reflection prompt huge; codex reflection calls run many minutes and risk the 600s CodexLM timeout, which (like an eval timeout) can propagate and end the run. Prefer: seed from the SMALL original router (fast reflection) but ENRICH the background prompt with the discovered insight (the bimodal prior + per-edge liquidity bounds hb1 found). Tests whether the idea transfers without dragging the whole 872-line body through every prompt.
Reflection-timeout robustness: mirror the eval-timeout fix — a slow or failed reflection LM call should degrade to "no proposal this round" and let the run continue, not crash it. Needs handling at the gepa reflection layer (our CodexLM can't fix it alone since the protocol wants a candidate string back).
Code-evolution complexity wall: once a candidate grows past ~800 lines, LLM edits frequently fail to compile (code_hard1 iters 2-4+). Consider a "refactor/simplify" reflection instruction, or a size penalty in the objective, to keep candidates editable.

Engineering

Cache evals keyed by (candidate hash, example) to stretch budgets — GEPA re-evaluates the seed dozens of times.
Emit run.json lineage for the command-center dashboard directly from GEPA run_dir state after each run.
CI check: go build -overlay smoke with the in-tree candidate to keep the contract compiling.
lnd-side follow-up: whatever wins parameter mode becomes a proposed defaults change PR to lightningnetwork/lnd with the sim evidence.

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