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tiktoken-go

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OpenAI's tiktoken in Go.

Tiktoken is a fast BPE tokeniser for use with OpenAI's models.

This is a port of the original tiktoken.

Usage

Install

go get github.com/pkoukk/tiktoken-go

Cache

Tiktoken-go has the same cache mechanism as the original Tiktoken library.

You can set the cache directory by using the environment variable TIKTOKEN_CACHE_DIR.

Once this variable is set, tiktoken-go will use this directory to cache the token dictionary.

If you don't set this environment variable, tiktoken-go will download the dictionary each time you initialize an encoding for the first time.

Alternative BPE loaders

If you don't want to use cache or download the dictionary each time, you can use alternative BPE loader.

Just call tiktoken.SetBpeLoader before calling tiktoken.GetEncoding or tiktoken.EncodingForModel.

BpeLoader is an interface, you can implement your own BPE loader by implementing this interface.

Offline BPE loader

The offline BPE loader loads the BPE dictionary from embed files, it helps if you don't want to download the dictionary at runtime.

Due to the size of the BPE dictionary, this loader is in other project.

Include if you require this loader: tiktoken_loader

Examples

Get Token By Encoding

package main

import (
    "fmt"
    "github.com/pkoukk/tiktoken-go"
)

func main()  {
	text := "Hello, world!"
	encoding := "cl100k_base"

	// if you don't want download dictionary at runtime, you can use offline loader
	// tiktoken.SetBpeLoader(tiktoken_loader.NewOfflineLoader())
	tke, err := tiktoken.GetEncoding(encoding)
	if err != nil {
		err = fmt.Errorf("getEncoding: %v", err)
		return
	}

	// encode
	token := tke.Encode(text, nil, nil)

	//tokens
	fmt.Println((token))
	// num_tokens
	fmt.Println(len(token))
}

Get Token By Model

package main

import (
    "fmt"
    "github.com/pkoukk/tiktoken-go"
)

func main()  {
	text := "Hello, world!"
	encoding := "gpt-3.5-turbo"

	tkm, err := tiktoken.EncodingForModel(encoding)
	if err != nil {
		err = fmt.Errorf("getEncoding: %v", err)
		return
	}

	// encode
	token := tkm.Encode(text, nil, nil)

	// tokens
	fmt.Println(token)
	// num_tokens
	fmt.Println(len(token))
}

Counting Tokens For Chat API Calls

Below is an example function for counting tokens for messages passed to gpt-3.5-turbo or gpt-4.

The following code was written based on openai-cookbook examples at Wednesday, 28 June 2023.

Please note that the token calculation method for the message may change at any time, so this code may not necessarily be applicable in the future.

If you need accurate calculation, please refer to the official documentation.

If you find that this code is no longer applicable, please feel free to submit a PR or Issue.

package main

import (
	"fmt"

	"github.com/pkoukk/tiktoken-go"
	"github.com/sashabaranov/go-openai"
)

// OpenAI Cookbook: https://github.com/openai/openai-cookbook/blob/main/examples/How_to_count_tokens_with_tiktoken.ipynb
func NumTokensFromMessages(messages []openai.ChatCompletionMessage, model string) (numTokens int) {
	tkm, err := tiktoken.EncodingForModel(model)
	if err != nil {
		err = fmt.Errorf("encoding for model: %v", err)
		log.Println(err)
		return
	}

	var tokensPerMessage, tokensPerName int
	switch model {
	case "gpt-3.5-turbo-0613",
		"gpt-3.5-turbo-16k-0613",
		"gpt-4-0314",
		"gpt-4-32k-0314",
		"gpt-4-0613",
		"gpt-4-32k-0613":
		tokensPerMessage = 3
		tokensPerName = 1
	case "gpt-3.5-turbo-0301":
		tokensPerMessage = 4 // every message follows <|start|>{role/name}\n{content}<|end|>\n
		tokensPerName = -1   // if there's a name, the role is omitted
	default:
		if strings.Contains(model, "gpt-3.5-turbo") {
			log.Println("warning: gpt-3.5-turbo may update over time. Returning num tokens assuming gpt-3.5-turbo-0613.")
			return NumTokensFromMessages(messages, "gpt-3.5-turbo-0613")
		} else if strings.Contains(model, "gpt-4") {
			log.Println("warning: gpt-4 may update over time. Returning num tokens assuming gpt-4-0613.")
			return NumTokensFromMessages(messages, "gpt-4-0613")
		} else {
			err = fmt.Errorf("num_tokens_from_messages() is not implemented for model %s. See https://github.com/openai/openai-python/blob/main/chatml.md for information on how messages are converted to tokens.", model)
			log.Println(err)
			return
		}
	}

	for _, message := range messages {
		numTokens += tokensPerMessage
		numTokens += len(tkm.Encode(message.Content, nil, nil))
		numTokens += len(tkm.Encode(message.Role, nil, nil))
		numTokens += len(tkm.Encode(message.Name, nil, nil))
		if message.Name != "" {
			numTokens += tokensPerName
		}
	}
	numTokens += 3 // every reply is primed with <|start|>assistant<|message|>
	return numTokens
}

Available Encodings

Available Models

Test

you can run test in test folder

compare with original tiktoken

get token by encoding

result

get token by model

result

Benchmark

you can run benchmark in test folder

Benchmark result

It looks like the performance is almost the same.

Maybe the difference is due to the difference in the performance of the machine.

Or maybe my benchmark method is not appropriate.

If you have better benchmark method or if you want add your benchmark result, please feel free to submit a PR.

For new o200k_base encoding, it seems slower than cl100k_base. tiktoken-go is slightly slower than tiktoken on the following benchmark.

License

MIT