Update dataset card body for conrnstack-samples (keep metadata)

README.md

@@ -278,3 +278,101 @@ configs:
   - split: train
     path: ruby-v1-pair-2M/train-*
 ---
+
+# conrnstack-samples
+
+`conrnstack-samples` is a compact, sampled version of CoRNStack for code-focused embedding training, reranker training, and retrieval experiments.
+
+Source dataset and paper:
+- CoRNStack collection: https://huggingface.co/collections/nomic-ai/cornstack
+- CoRNStack paper: https://huggingface.co/papers/2412.01007
+
+## Why this dataset
+
+CoRNStack is large. This dataset provides smaller, practical subsets for faster iteration and lower-cost experiments.
+
+Important notes:
+- This is a sampled dataset, not the full CoRNStack distribution.
+- If you need maximum coverage or full-scale training, use the original CoRNStack collection.
+
+## Config layout
+
+Each language is published as **two separate configs**:
+- `{lang}-v1-pair-2M`
+- `{lang}-v1-hard-negatives-100k`
+
+Each config uses split `train`.
+
+### `{lang}-v1-pair-2M`
+Fields:
+- `query`
+- `document`
+
+Target rows per language: ~2,000,000
+
+### `{lang}-v1-hard-negatives-100k`
+Fields:
+- `query`
+- `positive`
+- `negative_1`
+- `negative_2`
+- `negative_3`
+- `negative_4`
+- `negative_5`
+- `negative_6`
+- `negative_7`
+
+Target rows per language: ~100,000
+
+## Included configs
+
+| Config | Rows | Type |
+| --- | ---: | --- |
+| go-v1-pair-2M | 2,000,000 | pair |
+| go-v1-hard-negatives-100k | 100,000 | hard-negatives |
+| java-v1-pair-2M | 2,000,000 | pair |
+| java-v1-hard-negatives-100k | 100,000 | hard-negatives |
+| javascript-v1-pair-2M | 2,000,000 | pair |
+| javascript-v1-hard-negatives-100k | 100,000 | hard-negatives |
+| php-v1-pair-2M | 2,000,000 | pair |
+| php-v1-hard-negatives-100k | 100,000 | hard-negatives |
+| python-v1-pair-2M | 2,000,000 | pair |
+| python-v1-hard-negatives-100k | 100,000 | hard-negatives |
+| ruby-v1-pair-2M | 2,000,000 | pair |
+| ruby-v1-hard-negatives-100k | 100,000 | hard-negatives |
+
+## Quick usage
+
+```python
+from datasets import load_dataset
+
+pair_ds = load_dataset("hotchpotch/conrnstack-samples", "python-v1-pair-2M", split="train")
+hard_ds = load_dataset("hotchpotch/conrnstack-samples", "python-v1-hard-negatives-100k", split="train")
+
+print(pair_ds.column_names, len(pair_ds))
+print(hard_ds.column_names, len(hard_ds))
+```
+
+## Creation process (rough)
+
+For each language:
+1. Read CoRNStack shard files (`shard-*.jsonl.gz`).
+2. Count lines per shard and allocate per-shard targets.
+3. Build pair data via random line-index sampling with valid string `query`/`document`.
+4. Build hard-negative data from disjoint rows:
+   - valid string `query`/`document`
+   - `negatives` contains at least 7 unique non-empty strings
+   - sample 7 negatives per row
+   - cap output via reservoir sampling
+
+Default seed is fixed (`42`) for reproducibility under identical source snapshots and parameters.
+
+## License
+
+This dataset follows CoRNStack and is released under **Apache-2.0**.
+
+## Citation and attribution
+
+If you use this dataset, please cite and attribute CoRNStack:
+- Paper: https://huggingface.co/papers/2412.01007
+- Collection: https://huggingface.co/collections/nomic-ai/cornstack