pybytecode-v3-1.5b / DATA-CARD-training-corpus.md
coolblaze03's picture
Add files using upload-large-folder tool
0b19a1b verified
|
Raw
History Blame Contribute Delete
7.89 kB

Data card β€” PyBytecode v2 / v3 training corpus

The corpus behind pybytecode-v2-1.5b and pybytecode-v3-1.5b. Written 2026-08-04; no data card existed before.

This corpus is not distributed. Section 5 states why, as a property of the artifact rather than an apology. The model weights are unaffected β€” see WEIGHTS-LICENSE-PROPOSAL.md.


1. What it is

Task Python 3.12 bytecode disassembly β†’ original source
Rows 48,196 (identical row set in v2 and v3)
Row shape {"input": <disassembly>, "output": <source>}
Source dataset codeparrot/github-code-clean (the dataset itself is Apache-2.0)
Shards used for training 0–5
Unit one top-level function plus its transitive helpers and imports
Python 3.12, optimize=0
Files data/foundry/pybytecode-v2_train.jsonl, -v3_train.jsonl, -v3-sft_train.jsonl

v3 differs from v2 in the input representation only. v2's rep.py omitted the exception table's end, so a bare try: body and a try/else: body that compile to the same instruction stream were byte-identical in the model's input. v3 emits EXC try=Ls..Le -> ... and the end label joins the label set, making the two distinguishable. 14,122 of 48,196 inputs changed; no row was added, removed or relabelled (data/foundry/pybytecode-artifacts/v3_build_report.json). Any v2β†’v3 delta is therefore attributable to the representation fix alone.

2. Licence filtering β€” what was dropped, and why

scripts/pybytecode/extract_v2.py filters per row on github-code-clean's license column and keeps seven permissive values:

mit   apache-2.0   bsd-2-clause   bsd-3-clause   isc   unlicense   cc0-1.0

Every GPL, LGPL, AGPL, MPL and EPL row is dropped before extraction, along with everything the column does not positively identify. The intent was to avoid training on reciprocally-licensed source; the filter is a hard gate, not a preference.

Rows are then dropped by a chain of quality gates, each counted rather than silently applied: unparseable; not stable under ast.unparse round-trip (canonicalise(canon) != canon); does not compile; disassembly or source over the size ceiling; duplicate of an already-kept unit (SHA-1 of the canonical source).

3. Decontamination against the test sets

Three layers, because one is never enough (scripts/pybytecode/build_final.py):

  1. Shard-disjoint β€” training from shards 0–5, held-out pool from shards 8–9. The held-out pool was never read during training extraction.
  2. Repo-disjoint β€” any repo appearing in training is removed from the held-out pool outright. A repo can span shards, so layer 1 does not imply this.
  3. Fingerprint-disjoint β€” an identifier-blind structural fingerprint (every Name/arg/ attribute β†’ placeholder, every literal β†’ its type name). This catches the same algorithm under renamed variables, which exact match misses. It caught 15 items exact match missed.

The CSN benchmarks apply the same identifier-blind fingerprint against this corpus. On the 600-row licensed rebuild it removed 3 rows.

4. Labelling

Labels are the canonical source itself, so the supervision is exact by construction. The grading tier attached to each unit was assigned by running an oracle, not by inspection:

  • tier A / behavioural β€” differential execution. Kills 100% of injected semantic bugs; the gold tier.
  • tier B / stub β€” stubbed execution. Kills 78.9%, so scores on it are an upper bound.
  • tier C / AST-exact β€” undercounts by roughly 2.4Γ—, so scores on it are a lower bound.

Only 5.43% of all real top-level Python functions survive to be behaviourally adjudicable. That ceiling is why the byte-identical recompile oracle exists: it needs no runnable environment and so has 100% coverage.

5. The corpus cannot be redistributed

Per-row attribution was not retained. extract_v2.py carried repo and license on every row through extraction, and build_final.py:118 writes only {"input", "expected"} when it emits the final splits. The intermediate pool that still held the metadata was written to /tmp and no longer exists.

The consequence is specific: the corpus is 48,196 excerpts of MIT-, BSD-, Apache-, ISC- and public-domain-licensed source, and every one of those licences except the two public-domain dedications requires the copyright notice to be reproduced with the copy. We cannot produce those notices, because we no longer know which row came from which repository. Redistributing the file would strip required notices from tens of thousands of copyright holders.

This is a limitation of the artifact, not of the licences: nothing about the corpus is unlicensed or reciprocally licensed. It is not fixable by adding a licence file, and it is not repaired by listing the source dataset β€” attribution under these licences is per-work, not per-collection.

It is fixable by rebuilding. Extraction is deterministic and the source dataset is public. Carrying repo, license and file path through build_final.py's writer β€” one line β€” produces an equivalent corpus that is redistributable with a NOTICES file. That is the recommended fix for a v4 and it does not require retraining anything to be useful.

6. Held-out evaluation sets built from the same corpus

data/foundry/pybytecode-v3-ood-{behavioural,stub,ast,doc}_test.jsonl are drawn from the held-out shards of this same corpus and inherit section 5 exactly β€” they carry no attribution and cannot be redistributed either.

They are named -ood- but they are not out-of-distribution: they are the same source and the same distribution as training, held out three ways. Matching all 974 canonicalised google-research-datasets/mbpp rows against them yields 0 matches in all four files, while the v1-era pybytecode-ood_test.jsonl matches at 400/400. Only that v1-era file is MBPP. Full evidence in LICENSING-DETERMINATION.md Β§4.

They remain sound generalisation tests, and the numbers measured on them stand. Only the label is wrong, and it should be corrected wherever it appears.

On the tier-A set specifically (n=279, the set behind the 91.04% and 97.49% figures): it is the complete behaviourally-adjudicable population of the held-out pool β€” the 400-row cap did not truncate it, whereas the stub and ast tiers both hit that cap. The pool was therefore larger than 400 units, but its exact size is not recoverable: build_final.py printed its census to stdout and no run log was kept. The framing "279 of 400 = 70% of the set" does not describe these files (the four tiers are largely disjoint populations β€” the 279 behavioural rows share 9 function names with the 400 stub rows and 8 with the 400 ast rows) and should not be used. Report the denominator as 279 with the sentence above, or rebuild the pool to recover the true rate.

7. Known confound, stated rather than engineered away

extract_v2.py carries from __future__ import annotations, and its compile() call inherits the flag, so the training bytecode has PEP-563 stringised annotations. Real .pyc files are not compiled that way. The benchmarks deliberately compile with dont_inherit=True, giving the model an input distribution it was not trained on for annotated functions. Any resulting handicap is a real property of the model and is counted against it.

8. Provenance summary

Field Value
Base model Qwen/Qwen2.5-Coder-1.5B-Instruct (Apache-2.0)
Rows 48,196
Method LoRA r=16, Ξ±=32, all attention + MLP projections, 1 epoch, lr 2e-4
Build scripts scripts/pybytecode/{extract_v2,build_final,build_v3,rep,gen,verify}.py
Grader hashes all six match grader.sha256 in data/models/models.jsonl
Redistributable No β€” Β§5