How to handle rare hieroglyphic characters and emojis in the tokenizer?

Rare hieroglyphic symbols and emojis often fall outside the standard tokenizer vocabulary, which can lead to them being split into multiple tokens or replaced with a special token (e.g., [UNK]). To handle such symbols correctly, the following approaches can be used:

• Using tokenizers that support Unicode and subword units: For example, Byte Pair Encoding (BPE) or WordPiece split words into subwords, which helps better handle rare symbols.
• Adding rare symbols to the vocabulary: If certain rare hieroglyphs or emojis frequently appear in the data, they can be added to the tokenizer's vocabulary.
• Using tokenizers that operate at the character or byte level: For instance, byte-level BPE tokenizers can process any symbols without needing to expand the vocabulary.

Example of using a Byte-level BPE tokenizer from the Hugging Face library:

from tokenizers import ByteLevelBPETokenizer

# Initialize the tokenizer
tokenizer = ByteLevelBPETokenizer()

# Tokenize a string with rare symbols and emojis
text = "测试 🐉🔥"
tokens = tokenizer.encode(text)
print(tokens.tokens)

Thus, the choice of tokenizer and vocabulary setup play a crucial role in correctly processing rare hieroglyphs and emojis.