lnd/simulation/run_gepa_code.py
Olaoluwa Osuntokun 820d06d016 simulation: searchers default to high effort, 900s reflections
In this commit, we retune the codex searcher defaults with exp-018's
measurements in hand: the gepa arm at xhigh lost four of thirteen
iterations to the 600s reflection timeout and took nine hours for 150
evals. The evolutionary loop supplies the search, so iteration
throughput beats per-proposal depth; the default effort drops back to
high with a 900s timeout for headroom on large seeds, and xhigh stays
one flag away via codex:<model>:xhigh for runs where a deep single
proposal is the point.
2026-07-27 10:53:04 -07:00

277 lines
13 KiB
Python

#!/usr/bin/env python3
"""Run GEPA over entire routing algorithms (code candidates).
The candidate is the full Go source of cmd/routesim/candidate_impl.go. The
seed is the in-tree simple router; the target to beat is lnd's production
stack, whose per-example scores are reported alongside for reference.
"""
import argparse
from pathlib import Path
from gepa.optimize_anything import (
OptimizeAnythingConfig,
optimize_adaptive_sequential,
optimize_anything,
)
from claude_lm import ClaudeLM
from codex_lm import CodexLM
from evaluate_code import REPO, batch_evaluate, evaluate
OBJECTIVE = """
Evolve a Lightning Network routing algorithm (Go source, the complete
contents of candidate_impl.go) that maximizes payment success rate in a
network simulator, with fewer retry attempts and lower fees as secondary
goals. You may redesign the algorithm entirely — probability models,
splitting strategies, exploration policies — as long as the
newCandidateRouter contract compiles and the code stays pure routing logic.
"""
BACKGROUND = """
Contract: package main must define
newCandidateRouter(view routing.SimNetworkView, source route.Vertex,
localBalances map[uint64]lnwire.MilliSatoshi, spec *routing.SimPaymentSpec)
(routing.SimRouter, error). The returned router implements
RequestRoute(amt, inFlightHtlcs) (*route.Route, error) — return an error to
terminally give up — and ReportAttempt(attemptID, rt, result) error, which
delivers per-attempt feedback (result.Failure nil = settled; otherwise
result.FailureSource names the failing node and the failure code tells you
why: TemporaryChannelFailure = liquidity miss, FeeInsufficient /
IncorrectCltvExpiry = your route's fees or cltv deltas violate the failing
node's advertised policy).
Environment truths worth exploiting:
- Hidden liquidity is drawn mostly from a BIMODAL distribution: channel
funds sit almost entirely on one side. A 50/50 assumption is usually
wrong; a failure at amount a on a channel is strong evidence the whole
channel is depleted in that direction, and a success means most capacity
is available.
- The gossip view exposes per-direction policies (fees, cltv delta,
min/max htlc) and channel capacities via ForEachNodeDirectedChannel;
InPolicy on a channel of node N is the policy the OTHER node announced
toward N (i.e. it governs edges INTO N).
- Route encoding: amount over channel i is TotalAmount for i=0, else
Hops[i-1].AmtToForward; fees accumulate backward from the target;
the final hop needs cltv delta 40.
- MPP: the runner keeps calling RequestRoute with the remaining amount;
spec.MaxParts caps concurrent shards; each successful shard reduces the
remaining amount.
- Payments per scenario batch run sequentially and liquidity persists, so
knowledge from earlier payments in the batch transfers.
- THE NETWORK KEEPS MOVING BETWEEN YOUR PAYMENTS: scenario files may
enable background traffic, where other participants' payments shift
hidden liquidity in the (virtual) minutes between your payments, and a
virtual clock, readable as view.Now(), advances between payments and
attempts. In such environments, what you learned about a channel k
payments ago may no longer hold. Whether and how to account for the
age of evidence is entirely your design choice.
- ATOMIC MPP ARENAS: scenarios may set atomic_mpp, which changes the
economics of probing. Successful shards do NOT settle immediately:
they HOLD liquidity along their path until the whole payment
completes (all shards settle together) or fails (all release; a
failed payment moves nothing and pays no fees, but reveals what it
learned). Consequences you must design for: (a) your own in-flight
shards reserve real liquidity, so sibling shards contend with what
you already hold — two shards cannot lean on the same corridor
twice; (b) background traffic keeps moving DURING your payment, one
slice per attempt, so every extra sequential probe lets the network
drift under your plan; (c) burning attempts to learn is no longer
free — an up-front route-set plan that fills spec.MaxParts quickly
commits before the world moves, while a long probe ladder watches
its knowledge go stale mid-payment. Reactive halving was bred for
the old economics; this arena was built to reward deliberate
simultaneous commitment.
The current seed is a cheapest-path Dijkstra with failure blacklisting and
halving splits. Known weaknesses to consider: it ignores capacity when
choosing among paths (bigger channels succeed more often), it has no
notion of probability weighting fees vs reliability, it never retries a
blacklisted channel at lower amounts within a payment, and its shard
halving is crude.
Insights from prior successful runs (champions hb1/mx_c3, see
simulation/champions/), worth building on rather than rediscovering:
- An explicit BIMODAL PRIOR over amount/capacity works: near-certain for
tiny amounts (decaying exponential low mode), a logistic cliff as the
amount approaches capacity, floors/caps around [0.005, 0.985].
- Per-directed-channel liquidity BELIEFS work well: track lower-OK
(largest amount proven to pass) and upper-fail (smallest proven to
fail) bounds plus a confidence-weighted point estimate; return ~0.995
below lower-OK, ~0 above upper-fail, blend with the prior in between.
(Caveat: this insight was learned in environments with NO background
traffic, where old evidence never went stale. Its hard bounds may or
may not survive in a drifting network.)
- Retry-at-lower-amount on a failed channel (a lower-retry factor)
outperforms permanently blacklisting it.
- Time-decay of evidence has been tried under genuine liquidity drift
and came out a TIE with plain hard bounds, at every churn level
from none to roughly twenty times our default (exp-008, corrected
by exp-015). The evolved form that tied was confidence softening —
beliefs interpolate back toward the prior as they age, and bounds
expire — not lnd-style penalty fading. Read this as an open
question rather than a solved one: decay costs complexity and has
never yet bought anything measurable here, but nothing rules out a
form that does. If you spend the complexity, make it earn its
keep against a hard-bounds baseline.
- MPP splitting is where the least design space has been explored.
Prior winners split reactively: try an amount, and on failure carve
the next shard from a ladder of halves and evidence-derived sizes.
Nobody has yet evolved JOINT route-set planning: choosing a set of
routes AND their shard amounts together up front (min-cost-flow
style), so that parallel corridors of unequal capacity each carry a
shard sized to what they can bear. When single paths cannot carry
the payment, unequal splits chosen deliberately should beat halving
discovered by failure.
- Keep the implementation LEAN: past ~800 lines, edits stop compiling
and progress stalls. Prefer simplifying refactors over accretion.
"""
def main() -> None:
parser = argparse.ArgumentParser()
parser.add_argument("--corpus", default="corpus")
parser.add_argument("--name", default="router_code")
parser.add_argument("--max-evals", type=int, default=None)
parser.add_argument("--reflection-lm", default="codex:gpt-5.6-sol")
parser.add_argument("--max-concurrency", type=int, default=4)
parser.add_argument("--adaptive", action="store_true", default=True,
help="rotate gepa <-> meta_harness on plateaus")
parser.add_argument("--no-adaptive", dest="adaptive",
action="store_false")
parser.add_argument("--reflection-timeout", type=int, default=900,
help="seconds to allow one reflection call. Raise "
"it for large seeds, whose reflections are slow.")
parser.add_argument("--seed-file", default=None,
help="seed candidate .go file (default: the "
"in-tree candidate_impl.go). Use a prior "
"champion to continue evolving from it.")
args = parser.parse_args()
corpus = Path(args.corpus)
trainset = sorted(str(p) for p in (corpus / "train").glob("*.json"))
valset = sorted(str(p) for p in (corpus / "val").glob("*.json"))
testset = sorted(str(p) for p in (corpus / "test").glob("*.json"))
if not trainset or not valset:
raise SystemExit(f"no corpus at {corpus}; run gen_scenarios.py")
if args.seed_file:
seed = Path(args.seed_file).read_text()
else:
seed = (REPO / "cmd" / "routesim" / "candidate_impl.go").read_text()
max_evals = args.max_evals or 20 * len(valset)
# Every valid code candidate contains the package clause; the marker
# check turns a hijacked or chatty reply into one retry instead of a
# wasted optimizer iteration.
reflection_lm = args.reflection_lm
if reflection_lm.startswith("codex:"):
# codex:<model>[:<effort>] — e.g. codex:gpt-5.6-sol:xhigh.
# Searchers default to high effort with a 900s timeout after
# exp-018 measured xhigh at 600s losing roughly a third of its
# iterations to reflection timeouts; a large seed makes
# reflection slow, so the timeout knob matters more at higher
# effort.
spec = reflection_lm.split(":")
reflection_lm = CodexLM(
model=spec[1],
require_marker="package main",
timeout=args.reflection_timeout,
effort=spec[2] if len(spec) > 2 else "high",
)
elif reflection_lm.startswith("claude:"):
# claude:<model>[:<effort>] — e.g. claude:claude-opus-5:medium.
# Effort trades per-proposal deliberation for iteration
# throughput; the evolutionary loop supplies the search.
spec = reflection_lm.split(":")
reflection_lm = ClaudeLM(
model=spec[1],
require_marker="package main",
effort=spec[2] if len(spec) > 2 else None,
)
gepa_config = OptimizeAnythingConfig(
engine="gepa",
name=args.name,
max_evals=max_evals,
max_concurrency=args.max_concurrency,
run_dir=f"runs/{args.name}",
output_dir=f"outputs/{args.name}",
engine_config={
"reflection": {
"reflection_lm": reflection_lm,
"reflection_minibatch_size": 3,
},
"engine": {
"max_workers": args.max_concurrency,
"seed": 0,
# Hybrid frontier: per-example AND per-objective Pareto
# cells, fed by the evaluator's info["scores"] axes
# (success / retry_efficiency / fee_efficiency), so
# fee-efficient or low-retry specialists survive
# selection instead of being averaged away. "cartesian"
# would dissolve selection pressure at our corpus size.
"frontier_type": "hybrid",
# The evaluator is deterministic (verified), so identical
# (candidate, example) pairs are served from cache and
# do not consume budget. Report cache misses alongside
# eval counts when comparing runs.
"cache_evaluation": True,
# With caching on, max_evals counts only misses, so a
# converged search could spin; this is the enforceable
# cap. And an evaluator exception must cost a zero, not
# the run.
"max_candidate_proposals": 60,
"raise_on_exception": False,
},
},
)
if args.adaptive:
# Rotate between the gepa backend (codex reflection) and the
# meta_harness agentic proposer (claude CLI) whenever the score
# plateaus, all drawing from one shared eval budget.
meta_config = OptimizeAnythingConfig(
engine="meta_harness",
name=f"{args.name}_meta",
run_dir=f"runs/{args.name}_meta",
)
result = optimize_adaptive_sequential(
seed_candidate=seed,
evaluator=lambda cand, ex: evaluate(cand, ex),
batch_evaluator=batch_evaluate,
configs=[gepa_config, meta_config],
plateau_evals=len(valset) * 3,
dataset=trainset,
valset=valset,
test_set=testset,
objective=OBJECTIVE.strip(),
background=BACKGROUND.strip(),
name=args.name,
max_evals=max_evals,
max_concurrency=args.max_concurrency,
output_dir=f"outputs/{args.name}",
)
else:
result = optimize_anything(
seed_candidate=seed,
evaluator=lambda cand, ex: evaluate(cand, ex),
batch_evaluator=batch_evaluate,
dataset=trainset,
valset=valset,
test_set=testset,
objective=OBJECTIVE.strip(),
background=BACKGROUND.strip(),
config=gepa_config,
)
print("=== best candidate ===")
print(result.best_candidate)
print("best (val) score:", result.best_score)
print("held-out test:", result.metadata.get("test_score"),
"| seed held-out:", result.metadata.get("baseline_test_score"))
if __name__ == "__main__":
main()