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#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;
}
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