# FEVER Entity Retrieval Benchmark

Frozen benchmark for evaluating retrieval methods on the BEIR FEVER dataset (5.4M Wikipedia articles, 6,666 test queries). All data is pre-built so you can test a new method **without re-running BM25 or dense retrieval**.

## Files

### Core benchmark data (for testing new methods)

| File | Size | What it is |
|---|---|---|
| `beir_pool.json` | 31 MB | **BM25 top-100 candidate pool** (k1=1.2, b=0.75). 6,666 queries, each with 100 candidate docids + BM25 scores. Your method re-ranks these 100 docs. |
| `queries.jsonl` | 31 MB | 6,666 test queries (`{"_id": "...", "text": "..."}` per line) |
| `qrels/test.tsv` | 210 KB | TREC-style relevance judgments (`query-id \t doc-id \t relevance`) |
| `query_deltas.csv` | 2 MB | Per-query NDCG@10 for every Hadith variant (used for significance testing) |

### Evaluation scripts

| File | What it does |
|---|---|
| `fever_benchmark.py` | `FEVERBenchmark().evaluate(rankings) → {"ndcg@10": float, "recall@100": float}` |
| `setup_fever_benchmark.py` | Regenerate pool from scratch (downloads BEIR, builds index, runs BM25) |
| `beir_controlled_v3.py` | The definitive controlled ablation (6,666 queries, 0 errors) |
| `replay_verification.py` | Checksums `query_deltas.csv` against v3 aggregate results |

### Analysis scripts

| File | What it does |
|---|---|
| `significance_test.py` | Paired t-test + randomization test + Cohen's d |
| `export_per_query_v2.py` | Exports per-query NDCG to CSV with checkpoint resume |
| `significance_report.md` | Full significance report generated from the data |

### Reference results

| File | What it contains |
|---|---|
| `beir_controlled_v3_results.txt` | Final aggregate scores (all variants) |
| `benchmark_manifest.md` | Frozen configuration: dataset hashes, Pyserini version, BM25 params |

## Baseline Scores

| System | NDCG@10 |
|---|---|
| BM25 (k1=1.2, b=0.75) | **0.5214** |
| MiniLM Dense | **0.6497** |
| Dense + Muttafaq (best Hadith) | ~0.6461 |

## How to test a new method

### Quick start (using the frozen pool)

```python
import json
from huggingface_hub import hf_hub_download
from fever_benchmark import FEVERBenchmark

# 1. Download the frozen BM25 pool
pool_path = hf_hub_download("Kim-el/fever-ner", "beir_pool.json")
with open(pool_path) as f:
    pool_data = json.load(f)

pool = pool_data["pool"]  # {qid: [[docid, bm25_score], ...]}
qids = pool_data["qids"]  # [qid1, qid2, ...]

# 2. Re-rank with your method
#    For each query, take the 100 candidate docs and assign your own scores.
my_rankings = {}
for qid in qids:
    candidates = pool[qid]  # [[docid, bm25_score], ...]
    
    # Replace this with YOUR scoring function:
    scored = []
    for docid, bm25_score in candidates:
        your_score = your_model.score(query_text=qid, docid=docid)
        scored.append((docid, your_score))
    
    # Sort descending by your score
    scored.sort(key=lambda x: -x[1])
    my_rankings[qid] = scored

# 3. Evaluate
bench = FEVERBenchmark()
results = bench.evaluate(my_rankings)
print(f"NDCG@10: {results['ndcg@10']:.4f}")   # Beat 0.6497?
print(f"Recall@100: {results['recall@100']:.4f}")
```

### If you need query text or relevance judgments

```python
# Download query text
queries_path = hf_hub_download("Kim-el/fever-ner", "queries.jsonl")
with open(queries_path) as f:
    queries = {json.loads(line)["_id"]: json.loads(line)["text"]
               for line in f}

# Download qrels
qrels_path = hf_hub_download("Kim-el/fever-ner", "qrels/test.tsv")
# TREC format: query-id \t doc-id \t relevance

# Get query text for a specific qid
query_text = queries[qid]

# Get ground truth for a specific qid
# (automatically loaded by FEVERBenchmark.evaluate())
```

### Using the evaluation class directly

```python
# The evaluate() method handles qrels loading and NDCG computation.
# Your input:  {qid: [(docid, score), ...]}  — sorted descending by score.
# Output:      {"ndcg@10": float, "recall@100": float, "queries_evaluated": int}
```

### Comparing against baselines

```python
bench.verify_reproduction({
    "BM25 (k1=1.2, b=0.75)": 0.5214,
    "MiniLM Dense": 0.6497,
    "Your Method": results["ndcg@10"],
})
```

## Reproducibility

To reproduce the exact BM25 pool from scratch:

```bash
pip install pyserini==0.14.0
python setup_fever_benchmark.py
```

This downloads BEIR FEVER (3.3 GB), builds the Pyserini Lucene index (~6 min), and runs BM25 retrieval (~7 min). Expected BM25 NDCG@10: **0.5214 ± 0.001**.

## Key Research Findings

From the controlled ablation (6,666 queries, 0 errors):

1. **MiniLM Dense improves BM25 by +24.6% relative** (+0.1283 NDCG@10)
2. **Hadith graph signals provide no benefit on top of dense retrieval** — all variants were statistically significant but negative (Cohen's d < 0.2)
3. **95.9% of queries are unchanged** by Hadith signals; when they fire, they hurt 2:1
4. **The conditional benefit of Hadith on weak lexical systems (+4-5% on FTS5 BM25) does NOT generalize to strong dense retrieval**

## Requirements

- Python 3.8+
- `pyserini>=0.14.0` (only needed for pool regeneration)
- Java 11+ (for Pyserini/Lucene)
- `huggingface_hub` (for downloading)

## License

Same as BEIR FEVER — research use.