Update README.md

README.md

@@ -16,6 +16,10 @@ but it is presented in a more manageable format. Instead of using the Megatron f
 
 ## Format
 
+### `/data`
+
+The `/data` folder contains the original tokenised, packed, and preshuffled data.
+
 The dataset has 3 columns:
 - `uid`: a sequential identified for the sequence (not present in the original dataset)
 - `batch_idx`: the index of the batch to which a sequence belongs (not present in the original dataset).
@@ -35,6 +39,22 @@ Batches with `batch_idx` >= 1000 are only seen by later checkpoints.
 I did not create a separate file for these, but you can easily subset the first chunk (i.e., `data/train-001000.parquet`).
 
 
+### `idxmaps-npy`
+
+These are the files that are used to load the packed, tokenised, and preshuffled data starting
+from the [`EleutherAI/pythia_deduped_pile_idxmaps`](https://huggingface.co/datasets/EleutherAI/pythia_deduped_pile_idxmaps)
+using the [GPT2Dataset](https://github.com/EleutherAI/gpt-neox/blob/71df4d5017f9f4919566a11454fe3a507ffdc632/megatron/data/gpt2_dataset.py#L29)
+class implemented in the GPT-NeoX library.
+
+You can read this numpy file as follows:
+```python
+idx_file = np.load(<path_to_npy>, allow_pickle=True, mmap_mode="r")
+```
+
+Note: the dataset available under the `/data` folder is basically what you would get by combining the `pythia_deduped_pile_idxmaps`
+and these files.
+
+
 ## License
 
 For the license, refer to the original dataset ([EleutherAI/pile-deduped-pythia-preshuffled](https://huggingface.co/datasets/EleutherAI/pile-deduped-pythia-preshuffled)).