XOR map · 4 inputs

L2.FM1.xor51-map4

Native verification status · ● solved

What this result establishes

4 fixed inputs. Every listed one-byte input is tested. This is the complete finite-map domain.

Placement: Placement uses published constructions, routing geometry, and size pressure. Different input sets and caps prevent a strict difficulty implication. How rank is interpreted.

Challenge

ladder rank: #9 (historical identifier L2)
family / transform: FiniteMap / XorMask
cases: 4 cases, 1 output byte each
finite-map inputs: 02 06 09 30
limits: program ≤ 1024 bytes, ≤ 2048 steps/case
task summary: Route four published inputs to distinct answers.
exact contract: Registry JSON · L2.FM1.xor51-map4

Harness documentation

Winning program

solutions/fm1/fm1-map4-codex.mal · 220 bytes · sha256 ebea036650ccb6391fb1bc29d63bd71d3e7e09b917238c955f8568219f0cb52a

(tBA@?>=65|W876543210/.-,+*)('&%$#"!~}|{zyxwvutsE10ihmONMMbgf_dcba`_^]\[ZYXWVOsSRoPONMLKJIHGFEDCOA@L>=<;:9870TA3210/.-,+*)('&%$#"!~}|{zyxwvutsrqponmlkjihgfedcba`_^]\[ZYXWVUTSRQPONMLKJIHGFEDCBA@?>=<;:9876543210/.-,+*)('&%

Solver

name: GPT-5.5 (Codex)
type: llm-agent
model: GPT-5.5
provider: OpenAI
harness: Codex CLI agent, MAL-51 internal match (iterative turns, native-evaluator feedback)
date: 2026-05-12
metric: 4/4 cases
attribution notes: Official match report records harness_name=codex, model_name=GPT-5.5 (provider/version/temperature unrecorded).

Task notes

Route four published inputs to distinct answers.

Earlier record notes

Retained for provenance; these notes may predate current calibration. See the verification scope and placement rationale above.

Four-input finite map; won in an internal two-agent evaluation.

From an internal two-agent evaluation, 2026-05-12. Claude's attempt produced a four-lane routing design, crazy(crazy(input,69),49), that put the correct first byte on all four lanes but let two lanes emit a second byte, failing the one-byte output rule. Codex's attempt fixed the termination conflict at the shared HALT cell. 220 bytes.

Verification transcript (native VM, 3 epochs)

Cases derive from the rung definition alone (seed-independent); 3 epochs ran identically, one shown.

epoch 0 · seed 0a1acd8f3bc6… · 4/4 cases

case	input	expected	observed	status
0	02	53	53	ok
1	06	57	57	ok
2	09	58	58	ok
3	30	61	61	ok

Reproduce

git clone https://github.com/oklo/malbolge-rungs
cargo run -p harness -- verify --rung L2.FM1.xor51-map4 --program solutions/fm1/fm1-map4-codex.mal --epochs 3 --verbose