FastBertTokenizer 0.5.18-alpha

FastBertTokenizer

A fast and memory-efficient library for WordPiece tokenization as it is used by BERT. Tokenization correctness and speed are automatically evaluated in extensive unit tests and benchmarks.

Goals

• Enabling you to run your AI workloads on .NET in production.
• Correctness - Results that are equivalent to HuggingFace Transformers' AutoTokenizer's in all practical cases.
• Speed - Tokenization should be as fast as reasonably possible.
• Ease of use - The API should be easy to understand and use.

Getting Started

dotnet new console
dotnet add package FastBertTokenizer

using FastBertTokenizer;

var tok = new BertTokenizer();
await tok.LoadFromHuggingFaceAsync("bert-base-uncased");
var (inputIds, attentionMask, tokenTypeIds) = tok.Encode("Lorem ipsum dolor sit amet.");
Console.WriteLine(string.Join(", ", inputIds.ToArray()));
var decoded = tok.Decode(inputIds.Span);
Console.WriteLine(decoded);

// Output:
// 101, 19544, 2213, 12997, 17421, 2079, 10626, 4133, 2572, 3388, 1012, 102
// [CLS] lorem ipsum dolor sit amet. [SEP]

example project

Comparison to BERTTokenizers

• about 1 order of magnitude faster
• allocates more than 1 order of magnitude less memory
• better whitespace handling
• handles unknown characters correctly
• does not throw if text is longer than maximum sequence length
• handles unicode control chars
• handles other alphabets such as greek and right-to-left languages

Note that while BERTTokenizers handles token type incorrectly, it does support input of two pieces of text that are tokenized with a separator in between. FastBertTokenizer currently does not support this.

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