Function main

example/random_walk.cpp:31–153

this example uses the random-number generation functions in Boost.Compute to calculate a large number of random "steps" and then plots the final random "walk" in a 2D image on the GPU and displays it with OpenCV

// to calculate a large number of random "steps" and then plots the final
// random "walk" in a 2D image on the GPU and displays it with OpenCV
int main()
{
    // number of random steps to take
    size_t steps = 250000;

    // height and width of image
    size_t height = 800;
    size_t width = 800;

    // get default device and setup context
    compute::device gpu = compute::system::default_device();
    compute::context context(gpu);
    compute::command_queue queue(context, gpu);

    using compute::int2_;

    // calaculate random values for each step
    compute::vector<float> random_values(steps, context);
    compute::default_random_engine random_engine(queue);
    compute::uniform_real_distribution<float> random_distribution(0.f, 4.f);

    random_distribution.generate(
        random_values.begin(), random_values.end(), random_engine, queue
    );

    // calaculate coordinates for each step
    compute::vector<int2_> coordinates(steps, context);

    // function to convert random values to random directions (in 2D)
    BOOST_COMPUTE_FUNCTION(int2_, take_step, (const float x),
    {
        if(x < 1.f){
            // move right
            return (int2)(1, 0);
        }
        if(x < 2.f){
            // move up
            return (int2)(0, 1);
        }
        if(x < 3.f){
            // move left
            return (int2)(-1, 0);
        }
        else {
            // move down
            return (int2)(0, -1);
        }
    });

    // transform the random values into random steps
    compute::transform(
        random_values.begin(), random_values.end(), coordinates.begin(), take_step, queue
    );

    // set staring position
    int2_ starting_position(width / 2, height / 2);
    compute::copy_n(&starting_position, 1, coordinates.begin(), queue);