02 First Run

We will create a minimal C++ program that uses LightlyEdge C++ SDK. We will use CMake to build it. CMake is a popular cross-platform tool that allows us to add the library easily to our C++ project.

Prerequisites

Verify CMake is installed with cmake --version. Minimum required version: 3.13. If not, install it.

Code Walkthrough

Our minimal program will instantiate a LightlyEdge object and exit. Code for this tutorial is provided in examples/02_first_run directory. Before starting this tutorial, copy the model file to examples/lightly_model.tar and verify that your project layout is as follows:

lightly_edge_sdk_cpp
├── ...
└── examples
    ├──02_first_run
    │  ├── CMakeLists.txt
    │  └── main.cpp
    └── lightly_model.tar

The 02_first_run subfolder in examples contains two files. There is CMakeLists.txt with build instructions:

# CMakeLists.txt
cmake_minimum_required(VERSION 3.13)
 
# Set the project name.
project(main)
 
# Add search paths for FindLightlyEdgeSDK.cmake module.
list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/../../dist/cmake/LightlyEdgeSDK")
 
# Specify source files to build an executable.
add_executable(main main.cpp)
 
# Specify the C++ standard.
target_compile_features(main PUBLIC cxx_std_11)
 
# Link LightlyEdge SDK.
find_package(LightlyEdgeSDK REQUIRED)
target_link_libraries(main LightlyEdgeSDK::lightly_edge)
 
if(WIN32)
  # Copy dlls from /bin to the executable folder after building the target.
  file(GLOB DLL_FILES "${CMAKE_SOURCE_DIR}/../lightly_edge_sdk_cpp/bin/*.dll"
    "${CMAKE_SOURCE_DIR}/../../bin/*.dll")
  add_custom_command(
    TARGET main
    POST_BUILD
    COMMAND ${CMAKE_COMMAND} -E copy_if_different ${DLL_FILES}
    $<TARGET_FILE_DIR:main>
    COMMENT
    "Copying .dll files from lightly_edge_sdk_cpp/bin to the executable output folder."
  )
endif()

The second file is main.cpp with the program logic. This code uses the TAR model to initialize a lightly_edge_sdk::LightlyEdge, which is the central object in LightlyEdge C++ SDK. It throws an exception if something goes wrong.

// main.cpp
#include <iostream>
#include "lightly_edge_sdk.h"
using namespace lightly_edge_sdk;
 
int main() {
    std::cout << "Initializing LightlyEdge..." << std::endl;
    lightly_edge_sdk::LightlyEdgeConfig config = lightly_edge_sdk::default_config();
    auto lightly_edge = LightlyEdge::new_from_tar("../lightly_model.tar", config);
    std::cout << "LightlyEdge successfully initialized!" << std::endl;
    return 0;
}

Build and Run

We are ready to build and run the program! Execute the following commands in a terminal:

# Enter the project folder.
cd 02_first_run
 
# Configure CMake. This will create a `build` subfolder.
cmake -B build
 
# Build using configuration from the `build` subfolder.
cmake --build build
 
# Run (Linux variant)
./build/main
# Or run (Windows variant)
.\build\[build_type]\main.exe
# where [build_type] is either Release or Debug.

If you see the following output, congratulations! Everything is set up correctly and you can start using LightlyEdge.

Initializing LightlyEdge...
LightlyEdge successfully initialized!

Note

If you see the following uncaught exception please check that you are in the correct directory and that lightly_model.tar is at the correct location:

IO Error: No such file or directory (os error 2): "../lightly_model.tar"

Next Steps

Next, we will use LightlyEdge for our first real-world application, Similarity Search.

Note that the code above uses exceptions, which should be handled in a real-world application. LightlyEdge also provides a no throw interface. For more details on the topic see Error Handling.

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