Update README.md

README.md

@@ -1,4 +1,16 @@
 ---
+language:
+- en
+license: mit
+task_categories:
+- text-generation
+tags:
+- long-context
+- post-training
+- context-window-extension
+- packed-sequences
+- continual-training
+pretty_name: Mix-Context Post-Training 128K
 dataset_info:
   features:
   - name: input_ids
@@ -17,3 +29,107 @@ configs:
   - split: train
     path: data/train-*
 ---
+
+# Mix-Context Post-Training Dataset for 128K Context Extension
+
+## Overview
+
+**Mix-Context Post-Training 128K** is a dataset designed specifically for **post-training context window extension** of pretrained LLMs.
+
+It targets the stage *after base pretraining*, where a model is adapted to operate over **much longer contexts (up to 128K tokens)** while preserving short-context behavior. The dataset mixes short- and long-context packed sequences with a controlled length distribution to support:
+
+- Post-training context window extension
+- Length generalization / robustness evaluation
+- Continued training after positional / RoPE scaling methods
+
+If you use this dataset for post-training, context window extension, or evaluation, **please cite this dataset** (see Citation).
+
+---
+
+## Dataset Format
+
+Each example is a **packed sequence** ready for causal LM training:
+
+- `input_ids`: token IDs
+- `position_ids`: positional indices aligned to the packed sequence
+
+**Note:** This dataset does **not** include raw text. It contains tokenized, packed sequences produced by the preprocessing pipeline.
+
+---
+
+## Construction Summary (High-Level)
+
+This dataset is generated by:
+1. Downloading public corpora used for short- and long-context content
+2. Tokenizing with a specified tokenizer (default in scripts: `meta-llama/Meta-Llama-3-8B`)
+3. Filtering and bucketing by token length
+4. Packing sequences to target context windows
+5. Concatenating short- and long-context components into the final dataset
+
+### Tokenizer
+- Tokenizer name/path: `meta-llama/Meta-Llama-3-8B` (default; configurable in preprocessing)
+- Each text is encoded with explicit BOS/EOS:
+  - `BOS + text + EOS`
+- Length statistics and buckets are **tokenizer-dependent**
+
+### Short-Context Component
+- Source: FineWeb-Edu (`HuggingFaceFW/fineweb-edu`, `sample/10BT`)
+- Bucketed by token length (target sample sizes):
+  - 64–2,048: 8,000
+  - 2,048–4,096: 8,000
+  - 4,096–9,216: 16,000
+- Packed to **8K context** (short context length)
+
+### Long-Context Component
+- Source: RedPajama-Data-1T (`togethercomputer/RedPajama-Data-1T`)
+- Splits used:
+  - `arxiv`
+  - `wikipedia`
+  - `common_crawl` (subset used in preprocessing)
+- Documents are filtered before tokenization by raw byte length (approx):
+  - min: 32 KB
+  - max: 800 KB
+- After tokenization, long sequences are filtered and bucketed in token ranges:
+  - 8K–32K, 32K–64K, 64K–128K, 128K–200K
+- Packed to **128K context** (long context length)
+
+### Packing / Sequence Construction
+Packing concatenates tokenized samples sequentially until reaching `max_seq_len`:
+- `max_seq_len = 128K`
+- Short packing `context_len = 8K`
+- Long packing `context_len = 128K`
+
+---
+
+## Intended Use
+
+This dataset is intended for:
+- **Post-training context window extension** (e.g., extending an 8K/16K model to 128K)
+- Continued training after applying positional / RoPE scaling techniques
+- Long-context training ablations and evaluation
+
+This dataset is **not intended** to be a standalone base pretraining corpus.
+
+---
+
+## Limitations
+
+- Packing alters natural document boundaries
+- Tokenization, length distribution, and behavior depend on tokenizer choice/version
+- This artifact provides tokenized sequences, not raw text
+- Upstream corpora have their own limitations and licenses/terms
+
+---
+
+## Citation
+
+If you use this dataset, please cite:
+
+```bibtex
+@dataset{wang_chen_mix_context_post_training_128k_2026,
+  author       = {Qi Wang and Lizhang Chen},
+  title        = {Mix-Context Post-Training Dataset for 128K Context Extension},
+  year         = {2026},
+  publisher    = {Hugging Face},
+  url          = {https://huggingface.co/datasets/ghostcc3/mix-context-post-training-128k}
+}