| language: ja | |
| license: cc-by-sa-4.0 | |
| datasets: | |
| - wikipedia | |
| widget: | |
| - text: 仙台は「[MASK]の都」と呼ばれている。 | |
| # BERT base Japanese (character tokenization) | |
| This is a [BERT](https://github.com/google-research/bert) model pretrained on texts in the Japanese language. | |
| This version of the model processes input texts with word-level tokenization based on the IPA dictionary, followed by character-level tokenization. | |
| The codes for the pretraining are available at [cl-tohoku/bert-japanese](https://github.com/cl-tohoku/bert-japanese/tree/v1.0). | |
| ## Model architecture | |
| The model architecture is the same as the original BERT base model; 12 layers, 768 dimensions of hidden states, and 12 attention heads. | |
| ## Training Data | |
| The model is trained on Japanese Wikipedia as of September 1, 2019. | |
| To generate the training corpus, [WikiExtractor](https://github.com/attardi/wikiextractor) is used to extract plain texts from a dump file of Wikipedia articles. | |
| The text files used for the training are 2.6GB in size, consisting of approximately 17M sentences. | |
| ## Tokenization | |
| The texts are first tokenized by [MeCab](https://taku910.github.io/mecab/) morphological parser with the IPA dictionary and then split into characters. | |
| The vocabulary size is 4000. | |
| ## Training | |
| The model is trained with the same configuration as the original BERT; 512 tokens per instance, 256 instances per batch, and 1M training steps. | |
| ## Licenses | |
| The pretrained models are distributed under the terms of the [Creative Commons Attribution-ShareAlike 3.0](https://creativecommons.org/licenses/by-sa/3.0/). | |
| ## Acknowledgments | |
| For training models, we used Cloud TPUs provided by [TensorFlow Research Cloud](https://www.tensorflow.org/tfrc/) program. | |