Barycentric_coordinates_2/Triangle_coordinates_speed_test.cpp

#include <CGAL/Real_timer.h>
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Barycentric_coordinates_2/Triangle_coordinates_2.h>

// Construct an iterator that takes as input the current data type and pointer to the first element in the standard C++ array.
template<typename Scalar>
    class overwrite_iterator
{
private:
    Scalar* pointer;

public:
    explicit overwrite_iterator(Scalar* new_pointer) : pointer(new_pointer) { }

    // There are only two operations that we need to overload in order to use the class Triangle_coordinates_2.

    // This operation is intended to return the current coordinate value.
    inline Scalar& operator* () { return *pointer; }

    // This operation is intended to increase the index of the coordinate.
    inline void operator++ () { ++pointer; }
};

// Some convenient typedefs.
typedef CGAL::Real_timer Timer;

typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;

typedef Kernel::FT      Scalar;
typedef Kernel::Point_2 Point;

typedef overwrite_iterator<Scalar> Overwrite_iterator;

typedef CGAL::Barycentric_coordinates::Triangle_coordinates_2<Kernel> Triangle_coordinates;

using std::cout; using std::endl; using std::string;

int main()
{
    // Number of x and y coordinates together gives the number of points.
    const int number_of_x_coordinates = 100000;
    const int number_of_y_coordinates = 1000;

    // Number of runs to compute the arithmetic mean of the time.
    const int number_of_runs = 10;

    // Compute the uniform step size along x and y directions to change coordinates.
    const Scalar zero = Scalar(0);
    const Scalar one  = Scalar(1);
    const Scalar two  = Scalar(2);
    const Scalar x_step = one / Scalar(number_of_x_coordinates);
    const Scalar y_step = one / Scalar(number_of_y_coordinates);

    // Create a right triangle with a slight offset from zero.
    const Point  first_vertex(zero - x_step, zero - x_step);
    const Point second_vertex(two  + y_step, zero - x_step);
    const Point  third_vertex(zero - x_step, two  + y_step);

    // Instantiate the class Triangle_coordinates_2 for the right triangle defined above.
    Triangle_coordinates triangle_coordinates(first_vertex, second_vertex, third_vertex);

    // Create an instance of the standard C++ array to store coordinates.
    // It has the fixed size = 3 = number of vertices.
    Scalar coordinates [3] = {0, 0, 0};

    // Pass pointer to the first element of the array with coordinates in order to overwrite them.
    Overwrite_iterator it( &(coordinates[0]) );

    // Create a timer.
    Timer time_to_compute;

    double time = 0.0;
    for(int i = 0; i < number_of_runs; ++i) { // Number of runs

        time_to_compute.start(); // Start clock
        for(Scalar x = zero; x <= one; x += x_step) {
            for(Scalar y = zero; y <= one; y += y_step)
                triangle_coordinates(Point(x, y), it); // Compute 3 coordinate values for each generated point
        }
        time_to_compute.stop(); // Stop clock

        time += time_to_compute.time(); // Add time of the current run to the whole time

        time_to_compute.reset(); // Reset time
    }

    // Compute the arithmetic mean of all the runs.
    const double mean_time = time / number_of_runs;

    // Output the resulting time.
    cout.precision(10);
    cout << endl << "CPU time to compute triangle coordinates for "
         << number_of_x_coordinates * number_of_y_coordinates << " points = " << mean_time << " seconds.";
    cout << endl << endl;

    return EXIT_SUCCESS;
}