C++ Quickstart

Start using the CTranslate2 library in your own C++ project.

1. Compile and Install CTranslate2

mkdir build && cd build
cmake ..
make -j4 install

It’s important that the library is getting installed into a directory that is on the CMAKE_PREFIX_PATH, otherwise you can install to a custom directory, e.g.:

export CTRANSLATE_INSTALL_PATH=$(pwd)/install
make -j4 install

See [installation guide][installation.md] for more info.

2. Add CTranslate2 to your CMakeLists.txt

cmake_minimum_required (VERSION 2.8.11)


add_executable (main main.cpp)
target_link_libraries(main CTranslate2::ctranslate2)

3. Have a model ready in the CTranslate2 format

ct2-transformers-converter --model Helsinki-NLP/opus-mt-en-de --output_dir opus-mt-en-de

4. Write the translation C++ code using the API

You will need to have your input string tokenised, which depends on what type of model you are using. Have a look at the guides to get tokens from your input string.

#include <iostream>
#include <vector>

#include "ctranslate2/translator.h"

int main(int argc, char* argv[]) {

    std::string model_path("opus-mt-en-de");
    const auto model = ctranslate2::models::Model::load(model_path);
    const ctranslate2::models::ModelLoader model_loader(model_path);
    ctranslate2::Translator translator(model_loader);

    std::vector<std::vector<std::string>> batch = {{"▁Hello", "▁World", "!", "</s>"}};
    auto translation = translator.translate_batch(batch);
    for (auto &token:  translation[0].output()) {
        std::cout << token << ' ';
    std::cout << std::endl;

5. Compile and run the example

cmake .

If you have installed the CTranslate lib to a custom path use: cmake -DCMAKE_PREFIX_PATH=$CTRANSLATE_INSTALL_PATH .

This code should print the output tokens:

▁Hall o ▁Welt

If that’s the case, you successfully converted and executed a translation model with CTranslate2! (De)tokenisation is handled outside of CTranslate2, so make sure to properly tokenise the input and detokenise the output.