---
license: apache-2.0
pretty_name: CSP-Atlas
size_categories:
  - 100K<n<1M
tags:
  - mechanistic-interpretability
  - code
  - python
  - sparse-transformer
  - circuits
  - concept-extraction
language:
  - code
---

# CSP-Atlas: Concept-Specific Neural Circuits in a Sparse Python Transformer

Frozen experimental artifacts for the paper *CSP-Atlas: Concept-Specific Neural Circuits in a Sparse Python Transformer* (Wilam, 2026). This repository holds the prompts, masks, and decomposition tables that the paper's figures and numbers are computed from; the model itself is `openai/circuit-sparsity` on the Hub.

- **Paper code:** <https://github.com/piotrwilam/AtlasCSP>
- **Model used:** [`openai/circuit-sparsity`](https://huggingface.co/openai/circuit-sparsity) — 8-layer sparse Python transformer, 2,048-dim MLP output per layer.
- **Concept space:** 106 Python concepts = 43 AST node types + 63 builtin objects.
- **Prompts:** 63,800 object prompts (1,276 pairs × 50 variations) + 2,848 checker + 2,861 token-checker.
- **Parameter sweep:** ε ∈ {0.001, 0.1, 0.5} × C ∈ {20%, 50%, 80%} = 9 settings.

All claims in the paper regenerate from these files via the released code (`pytest tests/test_paper_numbers.py`).

## Layout

```
CSP-Atlas/
├── 11A_object_prompts.parquet          # 63,800 object prompts (the (AST × builtin) × 50 grid)
├── 11B_checker_prompts.parquet         # 2,848 checker prompts (keyword present, concept absent)
├── token_checker_prompts.parquet       # 2,861 token-checker prompts (broader set, all keyword contexts)
│
├── 12_object_activations.h5            # Raw MLP-output activations, object prompts (optional — derivable)
├── 12_checker_activations.h5           # Raw MLP-output activations, checker prompts (optional)
│
├── 13_object_masks_eps{ε}_cons{C}.h5   # 9 files — binarised + marginalised universal masks per (ε, C)
├── 13_checker_masks_eps{ε}_cons{C}.h5  # 9 files — binarised checker masks per (ε, C)
├── token_checker_masks.h5              # Token-checker masks (single setting: ε=0.5, C=0.8)
│
├── 14_summary.csv                              # 9 rows — global concept/token fractions per (ε, C)
├── 14_target_checker_eps{ε}_cons{C}.csv        # 9 files — per-object × per-layer "co / sh / to" decomposition
│
├── relaxed_modularity_scores.csv       # §6.1 — significant-layer count per concept × trim level p ∈ {0, 0.05, 0.1, 0.25}
├── relaxed_modularity_detail.csv       # §6.1 — full per-layer Jaccard trim-mean values
│
├── token_independence_summary.csv      # Per-object: concept_fraction, token_fraction, A_size, A∩B, A\B, B\A
├── token_independence_detail.csv       # Per-object × per-layer breakdown
└── token_independence_no_keyword.csv   # The 48 tokenless concepts (no checker confound applies)
```

## File schemas

### HDF5 mask files (`13_*.h5`, `token_checker_masks.h5`, `universal_106x50.h5`)

Layer-major group layout. Datasets are boolean vectors of length 2,048 (one bit per MLP-output dimension):

```
/metadata
    .attrs: {epsilon, consistency_thresh, n_layers=8, n_pairs=1276}
    /ast_nodes        — array of 43 AST node names
    /builtin_objs     — array of 63 builtin object names
/universal_masks
    /layer_0/{concept_name}      — (2048,) bool
    /layer_1/{concept_name}      — (2048,) bool
    …
    /layer_7/{concept_name}      — (2048,) bool
/pair_masks
    /layer_0/{ast}__{builtin}    — (2048,) bool    (e.g. AnnAssign__abs)
    …
/metrics
    aggregate statistics per layer (sizes, intersection counts)
```

Concept names use the convention `ast__<NodeType>` or `builtin__<object>` (double underscore).

### Prompt parquets

`11A_object_prompts.parquet` (63,800 rows):

| column | type | meaning |
|---|---|---|
| `ast_node` | str | AST node type (e.g. `For`) |
| `builtin_obj` | str | Builtin name (e.g. `bytearray`) |
| `variation_id` | int | 0..49 (50 variations per pair) |
| `prompt_text` | str | The Python snippet |
| `sequence_loss` | float | Model's per-token loss on the snippet (used for filtering) |
| `token_length` | int | Tokenizer output length |
| `ast_verified` | bool | True if `ast.parse()` round-trips with the target node present |

`11B_checker_prompts.parquet` (2,848 rows) and `token_checker_prompts.parquet` (2,861 rows):

| column | type | meaning |
|---|---|---|
| `object` | str | Target concept (e.g. `ast__Break`) |
| `keyword` | str | The bare token under test (e.g. `break`) |
| `variation_id` | int | 0..49 |
| `prompt_text` | str | Python that contains the keyword but excludes the concept (string literal, comment, var name, …) |

### Decomposition CSVs (`14_target_checker_*.csv`)

One row per testable concept (58 of them), 8 layer columns (`L0`–`L7`). Each cell encodes the three-way decomposition as a string:

```
co / sh / to
```

— concept-only `|A \ B|`, shared `|A ∩ B|`, token-only `|B \ A|`. From these the concept fraction `co / (co + sh)` is recovered.

### Global summary (`14_summary.csv`)

One row per (ε, C) setting. Columns: `epsilon, consistency, n_testable, n_ast, n_builtin, mean_concept_fraction, mean_token_fraction, ast_concept_fraction, ast_token_fraction, blt_concept_fraction, blt_token_fraction, mean_A_size, mean_B_size`.

### Modularity (`relaxed_modularity_scores.csv`)

| column | meaning |
|---|---|
| (index) | concept name |
| `type` | `ast` or `builtin` |
| `p=0.0`, `p=0.05`, `p=0.1`, `p=0.25` | Number of layers (0–8) at which the concept's mean Jaccard to its k-nearest-neighbour shell, trimmed at trim level p, exceeds the permutation null at significance 0.05. The paper's §6.1 Break-at-top result is `p=0.0 == 3`. |

`relaxed_modularity_detail.csv` is the un-aggregated per-layer per-trim-level Jaccard means feeding the score table.

### Token-independence (`token_independence_*.csv`)

`summary.csv` is one row per testable object: `object, type, keyword, concept_fraction, token_fraction, A_size, A_and_B, A_only, B_only` (averaged across layers).

`detail.csv` breaks the same statistics out by `(object, layer)`.

`no_keyword.csv` is the 48 concepts (19 tokenless AST + 29 tokenless builtins) for which no checker confound applies — included so downstream users can see the full 106-concept universe.

## Quickstart

The dataset is normally accessed through the [AtlasCSP code repository](https://github.com/piotrwilam/AtlasCSP), which contains loaders that auto-download missing files from this Hub mirror:

```python
from csp_atlas.io import (
    load_universal_masks,        # 13_object_masks_*.h5
    load_pair_masks,             # 13_object_masks_*.h5
    load_concept_inventory,      # the 43 + 63 names
    load_summary,                # 14_summary.csv
    load_target_checker,         # 14_target_checker_*.csv
    load_modularity_scores,      # relaxed_modularity_scores.csv
    load_prompts,                # 11A / 11B / token_checker
)

# Universal mask set at the paper's reference setting:
masks = load_universal_masks(eps=0.5, cons=0.8)        # dict[concept] -> dict[layer] -> set[int]
ast, builtin = load_concept_inventory(eps=0.5, cons=0.8)  # 43, 63
prompts = load_prompts(kind="object")                  # the 63,800-row DataFrame
```

Direct download with `huggingface_hub`:

```python
from huggingface_hub import hf_hub_download
path = hf_hub_download(
    repo_id="piotrwilam/CSP-Atlas",
    filename="13_object_masks_eps0.5_cons0.8.h5",
    repo_type="dataset",
)
```

Or with `datasets` (parquets only):

```python
from datasets import load_dataset
ds = load_dataset("piotrwilam/CSP-Atlas", data_files="11A_object_prompts.parquet")
```

## Reproducing the paper

The paper's claims are locked in `tests/test_paper_numbers.py` in the code repo. With the dataset in place at `$CSP_ATLAS_DATA_ROOT` (or the default local mirror) and a uv venv:

```bash
git clone https://github.com/piotrwilam/AtlasCSP
cd AtlasCSP
uv sync
export CSP_ATLAS_DATA_ROOT=/path/to/CSP-Atlas
pytest tests/test_paper_numbers.py -v
python experiments/fig1_atomicity_dendrogram.py
```

The single dendrogram figure (Figure 1) is produced by `experiments/fig1_atomicity_dendrogram.py`, driven by `configs/paper/figure1_atomicity_dendrogram.yaml`.

## Generation pipeline

The four-stage extraction (`11_` → `12_` → `13_` → `14_`) is documented in [`circuits/README.md`](https://github.com/piotrwilam/AtlasCSP/blob/main/circuits/README.md) in the code repo:

| Stage | Step | Output |
|---|---|---|
| 11 | Prompt generation (`circuits/prompts/`) | `11A`, `11B`, `token_checker` parquets |
| 12 | Forward-pass extraction (`circuits/extraction/`) | `12_*_activations.h5` (last-token MLP outputs, 8 layers) |
| 13 | Binarisation + marginalisation | `13_object_masks_*.h5`, `13_checker_masks_*.h5` per (ε, C) |
| 14 | Decomposition vs checker masks | `14_summary.csv`, `14_target_checker_*.csv` |

The `relaxed_modularity_*.csv` and `token_independence_*.csv` are downstream analyses computed on stage 13/14 outputs.

## What is *not* in this repo

- **Model weights** — `openai/circuit-sparsity` is loaded from its own Hub repo at runtime; not duplicated here.
- **Pre-paper development snapshots** — checkpoints/, earlier 115-concept experiments, exploratory runs.
- **Figure PDFs** — the figure files for the paper live in the AtlasCSP code repo under `results/`.

## Citation

```bibtex
@article{Wilam2026CSPAtlas,
  title   = {CSP-Atlas: Concept-Specific Neural Circuits in a Sparse Python Transformer},
  author  = {Wilam, Piotr},
  year    = {2026},
  url     = {https://github.com/piotrwilam/AtlasCSP}
}
```

## License

Apache-2.0 — see `LICENSE`. The model `openai/circuit-sparsity` is distributed under its own licence on its own Hub repo and is not redistributed here.